HBASE-20115 Reimplement serial replication based on the new replication storage layer

hbase-client/src/main/java/org/apache/hadoop/hbase/HTableDescriptor.java

@@ -538,6 +538,14 @@ public class HTableDescriptor implements TableDescriptor, Comparable<HTableDescr
             .collect(Collectors.toList());
   }
 
+  /**
+   * Return true if there are at least one cf whose replication scope is serial.
+   */
+  @Override
+  public boolean hasSerialReplicationScope() {
+    return delegatee.hasSerialReplicationScope();
+  }
+
   /**
    * Returns the configured replicas per region
    */

hbase-client/src/main/java/org/apache/hadoop/hbase/MetaTableAccessor.java

@@ -34,6 +34,8 @@ import java.util.SortedMap;
 import java.util.TreeMap;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.Cell.Type;
 import org.apache.hadoop.hbase.client.Connection;
@@ -56,6 +58,7 @@ import org.apache.hadoop.hbase.client.TableState;
 import org.apache.hadoop.hbase.exceptions.DeserializationException;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcChannel;
 import org.apache.hadoop.hbase.master.RegionState;
+import org.apache.hadoop.hbase.master.RegionState.State;
 import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
 import org.apache.hadoop.hbase.protobuf.generated.ClientProtos;
 import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.RegionSpecifier;
@@ -137,7 +140,7 @@ public class MetaTableAccessor {
   private static final Logger LOG = LoggerFactory.getLogger(MetaTableAccessor.class);
   private static final Logger METALOG = LoggerFactory.getLogger("org.apache.hadoop.hbase.META");
 
-  static final byte [] META_REGION_PREFIX;
+  private static final byte[] META_REGION_PREFIX;
   static {
     // Copy the prefix from FIRST_META_REGIONINFO into META_REGION_PREFIX.
     // FIRST_META_REGIONINFO == 'hbase:meta,,1'.  META_REGION_PREFIX == 'hbase:meta,'
@@ -147,6 +150,11 @@ public class MetaTableAccessor {
       META_REGION_PREFIX, 0, len);
   }
 
+  private static final byte[] REPLICATION_PARENT_QUALIFIER = Bytes.toBytes("parent");
+
+  private static final String REPLICATION_PARENT_SEPARATOR = "|";
+
+  private static final String REPLICATION_PARENT_SEPARATOR_REGEX = "\\|";
   /**
    * Lists all of the table regions currently in META.
    * Deprecated, keep there until some test use this.
@@ -838,7 +846,7 @@ public class MetaTableAccessor {
 
   /**
    * Returns the column qualifier for serialized region state
-   * @return HConstants.TABLE_STATE_QUALIFIER
+   * @return HConstants.STATE_QUALIFIER
    */
   private static byte[] getRegionStateColumn() {
     return HConstants.STATE_QUALIFIER;
@@ -1266,7 +1274,6 @@ public class MetaTableAccessor {
   ////////////////////////
   // Editing operations //
   ////////////////////////
-
   /**
    * Generates and returns a Put containing the region into for the catalog table
    */
@@ -1438,7 +1445,7 @@ public class MetaTableAccessor {
    * Adds daughter region infos to hbase:meta row for the specified region. Note that this does not
    * add its daughter's as different rows, but adds information about the daughters in the same row
    * as the parent. Use
-   * {@link #splitRegion(Connection, RegionInfo, RegionInfo, RegionInfo, ServerName,int)}
+   * {@link #splitRegion(Connection, RegionInfo, long, RegionInfo, RegionInfo, ServerName, int)}
    * if you want to do that.
    * @param connection connection we're using
    * @param regionInfo RegionInfo of parent region
@@ -1464,7 +1471,7 @@ public class MetaTableAccessor {
    * Adds a (single) hbase:meta row for the specified new region and its daughters. Note that this
    * does not add its daughter's as different rows, but adds information about the daughters
    * in the same row as the parent. Use
-   * {@link #splitRegion(Connection, RegionInfo, RegionInfo, RegionInfo, ServerName, int)}
+   * {@link #splitRegion(Connection, RegionInfo, long, RegionInfo, RegionInfo, ServerName, int)}
    * if you want to do that.
    * @param connection connection we're using
    * @param regionInfo region information
@@ -1519,20 +1526,37 @@ public class MetaTableAccessor {
   }
 
   /**
-   * Merge the two regions into one in an atomic operation. Deletes the two
+   * Merge the two regions into one in an atomic operation. Deletes the two merging regions in
-   * merging regions in hbase:meta and adds the merged region with the information of
+   * hbase:meta and adds the merged region with the information of two merging regions.
-   * two merging regions.
    * @param connection connection we're using
    * @param mergedRegion the merged region
    * @param regionA merge parent region A
+   * @param regionAOpenSeqNum the next open sequence id for region A, used by serial replication. -1
+   *          if not necessary.
    * @param regionB merge parent region B
+   * @param regionBOpenSeqNum the next open sequence id for region B, used by serial replication. -1
+   *          if not necessary.
    * @param sn the location of the region
    */
-  public static void mergeRegions(final Connection connection, RegionInfo mergedRegion,
+  public static void mergeRegions(Connection connection, RegionInfo mergedRegion,
-      RegionInfo regionA, RegionInfo regionB, ServerName sn, int regionReplication)
+      RegionInfo regionA, long regionAOpenSeqNum, RegionInfo regionB, long regionBOpenSeqNum,
-      throws IOException {
+      ServerName sn, int regionReplication) throws IOException {
     try (Table meta = getMetaHTable(connection)) {
       long time = EnvironmentEdgeManager.currentTime();
+      List<Mutation> mutations = new ArrayList<>();
+
+      List<RegionInfo> replicationParents = new ArrayList<>(2);
+      // Deletes for merging regions
+      mutations.add(makeDeleteFromRegionInfo(regionA, time));
+      if (regionAOpenSeqNum > 0) {
+        mutations.add(makePutForReplicationBarrier(regionA, regionAOpenSeqNum, time));
+        replicationParents.add(regionA);
+      }
+      mutations.add(makeDeleteFromRegionInfo(regionB, time));
+      if (regionBOpenSeqNum > 0) {
+        mutations.add(makePutForReplicationBarrier(regionB, regionBOpenSeqNum, time));
+        replicationParents.add(regionB);
+      }
 
       // Put for parent
       Put putOfMerged = makePutFromRegionInfo(mergedRegion, time);
@@ -1552,18 +1576,13 @@ public class MetaTableAccessor {
               .setType(Type.Put)
               .setValue(RegionInfo.toByteArray(regionB))
               .build());
-
       // Set initial state to CLOSED
       // NOTE: If initial state is not set to CLOSED then merged region gets added with the
       // default OFFLINE state. If Master gets restarted after this step, start up sequence of
       // master tries to assign this offline region. This is followed by re-assignments of the
       // merged region from resumed {@link MergeTableRegionsProcedure}
       addRegionStateToPut(putOfMerged, RegionState.State.CLOSED);
-
+      mutations.add(putOfMerged);
-      // Deletes for merging regions
-      Delete deleteA = makeDeleteFromRegionInfo(regionA, time);
-      Delete deleteB = makeDeleteFromRegionInfo(regionB, time);
-
       // The merged is a new region, openSeqNum = 1 is fine. ServerName may be null
       // if crash after merge happened but before we got to here.. means in-memory
       // locations of offlined merged, now-closed, regions is lost. Should be ok. We
@@ -1577,26 +1596,30 @@ public class MetaTableAccessor {
       for (int i = 1; i < regionReplication; i++) {
         addEmptyLocation(putOfMerged, i);
       }
-
+      // add parent reference for serial replication
-      byte[] tableRow = Bytes.toBytes(mergedRegion.getRegionNameAsString()
+      if (!replicationParents.isEmpty()) {
-        + HConstants.DELIMITER);
+        addReplicationParent(putOfMerged, replicationParents);
-      multiMutate(connection, meta, tableRow, putOfMerged, deleteA, deleteB);
+      }
+      byte[] tableRow = Bytes.toBytes(mergedRegion.getRegionNameAsString() + HConstants.DELIMITER);
+      multiMutate(connection, meta, tableRow, mutations);
     }
   }
 
   /**
-   * Splits the region into two in an atomic operation. Offlines the parent
+   * Splits the region into two in an atomic operation. Offlines the parent region with the
-   * region with the information that it is split into two, and also adds
+   * information that it is split into two, and also adds the daughter regions. Does not add the
-   * the daughter regions. Does not add the location information to the daughter
+   * location information to the daughter regions since they are not open yet.
-   * regions since they are not open yet.
    * @param connection connection we're using
    * @param parent the parent region which is split
+   * @param parentOpenSeqNum the next open sequence id for parent region, used by serial
+   *          replication. -1 if not necessary.
    * @param splitA Split daughter region A
    * @param splitB Split daughter region B
    * @param sn the location of the region
    */
-  public static void splitRegion(final Connection connection, RegionInfo parent, RegionInfo splitA,
+  public static void splitRegion(Connection connection, RegionInfo parent, long parentOpenSeqNum,
-      RegionInfo splitB, ServerName sn, int regionReplication) throws IOException {
+      RegionInfo splitA, RegionInfo splitB, ServerName sn, int regionReplication)
+      throws IOException {
     try (Table meta = getMetaHTable(connection)) {
       long time = EnvironmentEdgeManager.currentTime();
       // Put for parent
@@ -1608,7 +1631,11 @@ public class MetaTableAccessor {
       // Puts for daughters
       Put putA = makePutFromRegionInfo(splitA, time);
       Put putB = makePutFromRegionInfo(splitB, time);
-
+      if (parentOpenSeqNum > 0) {
+        addReplicationBarrier(putParent, parentOpenSeqNum);
+        addReplicationParent(putA, Collections.singletonList(parent));
+        addReplicationParent(putB, Collections.singletonList(parent));
+      }
       // Set initial state to CLOSED
       // NOTE: If initial state is not set to CLOSED then daughter regions get added with the
       // default OFFLINE state. If Master gets restarted after this step, start up sequence of
@@ -1668,20 +1695,15 @@ public class MetaTableAccessor {
   }
 
   private static void multiMutate(Connection connection, Table table, byte[] row,
-      Mutation... mutations)
+      Mutation... mutations) throws IOException {
-  throws IOException {
     multiMutate(connection, table, row, Arrays.asList(mutations));
   }
 
   /**
    * Performs an atomic multi-mutate operation against the given table.
    */
-  // Used by the RSGroup Coprocessor Endpoint. It had a copy/paste of the below. Need to reveal
+  private static void multiMutate(Connection connection, final Table table, byte[] row,
-  // this facility for CPEP use or at least those CPEPs that are on their way to becoming part of
+      final List<Mutation> mutations) throws IOException {
-  // core as is the intent for RSGroup eventually.
-  public static void multiMutate(Connection connection, final Table table, byte[] row,
-      final List<Mutation> mutations)
-  throws IOException {
     debugLogMutations(mutations);
     // TODO: Need rollback!!!!
     // TODO: Need Retry!!!
@@ -1782,9 +1804,7 @@ public class MetaTableAccessor {
    * @param regionInfo region to be deleted from META
    * @throws IOException
    */
-  public static void deleteRegion(Connection connection,
+  public static void deleteRegion(Connection connection, RegionInfo regionInfo) throws IOException {
-                                  RegionInfo regionInfo)
-    throws IOException {
     long time = EnvironmentEdgeManager.currentTime();
     Delete delete = new Delete(regionInfo.getRegionName());
     delete.addFamily(getCatalogFamily(), time);
@@ -1901,6 +1921,33 @@ public class MetaTableAccessor {
               .build());
   }
 
+  private static void addReplicationParent(Put put, List<RegionInfo> parents) throws IOException {
+    byte[] value = parents.stream().map(RegionReplicaUtil::getRegionInfoForDefaultReplica)
+      .map(RegionInfo::getRegionNameAsString).collect(Collectors
+        .collectingAndThen(Collectors.joining(REPLICATION_PARENT_SEPARATOR), Bytes::toBytes));
+    put.add(CellBuilderFactory.create(CellBuilderType.SHALLOW_COPY).setRow(put.getRow())
+      .setFamily(HConstants.REPLICATION_BARRIER_FAMILY).setQualifier(REPLICATION_PARENT_QUALIFIER)
+      .setTimestamp(put.getTimeStamp()).setType(Type.Put).setValue(value).build());
+  }
+
+  private static Put makePutForReplicationBarrier(RegionInfo regionInfo, long openSeqNum, long ts)
+      throws IOException {
+    Put put = new Put(regionInfo.getRegionName(), ts);
+    addReplicationBarrier(put, openSeqNum);
+    return put;
+  }
+
+  public static void addReplicationBarrier(Put put, long openSeqNum) throws IOException {
+    put.add(CellBuilderFactory.create(CellBuilderType.SHALLOW_COPY)
+      .setRow(put.getRow())
+      .setFamily(HConstants.REPLICATION_BARRIER_FAMILY)
+      .setQualifier(HConstants.SEQNUM_QUALIFIER)
+      .setTimestamp(put.getTimeStamp())
+      .setType(Type.Put)
+      .setValue(Bytes.toBytes(openSeqNum))
+      .build());
+  }
+
   private static Put addEmptyLocation(Put p, int replicaId) throws IOException {
     CellBuilder builder = CellBuilderFactory.create(CellBuilderType.SHALLOW_COPY);
     return p.add(builder.clear()
@@ -1926,6 +1973,92 @@ public class MetaTableAccessor {
                 .build());
   }
 
+  public static final class ReplicationBarrierResult {
+    private final long[] barriers;
+    private final RegionState.State state;
+    private final List<byte[]> parentRegionNames;
+
+    public ReplicationBarrierResult(long[] barriers, State state, List<byte[]> parentRegionNames) {
+      this.barriers = barriers;
+      this.state = state;
+      this.parentRegionNames = parentRegionNames;
+    }
+
+    public long[] getBarriers() {
+      return barriers;
+    }
+
+    public RegionState.State getState() {
+      return state;
+    }
+
+    public List<byte[]> getParentRegionNames() {
+      return parentRegionNames;
+    }
+  }
+
+  private static long getReplicationBarrier(Cell c) {
+    return Bytes.toLong(c.getValueArray(), c.getValueOffset(), c.getValueLength());
+  }
+
+  private static long[] getReplicationBarriers(Result result) {
+    return result.getColumnCells(HConstants.REPLICATION_BARRIER_FAMILY, HConstants.SEQNUM_QUALIFIER)
+      .stream().mapToLong(MetaTableAccessor::getReplicationBarrier).sorted().distinct().toArray();
+  }
+
+  private static ReplicationBarrierResult getReplicationBarrierResult(Result result) {
+    long[] barriers = getReplicationBarriers(result);
+    byte[] stateBytes = result.getValue(getCatalogFamily(), getRegionStateColumn());
+    RegionState.State state =
+      stateBytes != null ? RegionState.State.valueOf(Bytes.toString(stateBytes)) : null;
+    byte[] parentRegionsBytes =
+      result.getValue(HConstants.REPLICATION_BARRIER_FAMILY, REPLICATION_PARENT_QUALIFIER);
+    List<byte[]> parentRegionNames =
+      parentRegionsBytes != null
+        ? Stream.of(Bytes.toString(parentRegionsBytes).split(REPLICATION_PARENT_SEPARATOR_REGEX))
+          .map(Bytes::toBytes).collect(Collectors.toList())
+        : Collections.emptyList();
+    return new ReplicationBarrierResult(barriers, state, parentRegionNames);
+  }
+
+  public static ReplicationBarrierResult getReplicationBarrierResult(Connection conn,
+      TableName tableName, byte[] row, byte[] encodedRegionName) throws IOException {
+    byte[] metaStartKey = RegionInfo.createRegionName(tableName, row, HConstants.NINES, false);
+    byte[] metaStopKey =
+      RegionInfo.createRegionName(tableName, HConstants.EMPTY_START_ROW, "", false);
+    Scan scan = new Scan().withStartRow(metaStartKey).withStopRow(metaStopKey)
+      .addColumn(getCatalogFamily(), getRegionStateColumn())
+      .addFamily(HConstants.REPLICATION_BARRIER_FAMILY).readAllVersions().setReversed(true)
+      .setCaching(10);
+    try (Table table = getMetaHTable(conn); ResultScanner scanner = table.getScanner(scan)) {
+      for (Result result;;) {
+        result = scanner.next();
+        if (result == null) {
+          return new ReplicationBarrierResult(new long[0], null, Collections.emptyList());
+        }
+        byte[] regionName = result.getRow();
+        // TODO: we may look up a region which has already been split or merged so we need to check
+        // whether the encoded name matches. Need to find a way to quit earlier when there is no
+        // record for the given region, for now it will scan to the end of the table.
+        if (!Bytes.equals(encodedRegionName,
+          Bytes.toBytes(RegionInfo.encodeRegionName(regionName)))) {
+          continue;
+        }
+        return getReplicationBarrierResult(result);
+      }
+    }
+  }
+
+  public static long[] getReplicationBarrier(Connection conn, byte[] regionName)
+      throws IOException {
+    try (Table table = getMetaHTable(conn)) {
+      Result result = table.get(new Get(regionName)
+        .addColumn(HConstants.REPLICATION_BARRIER_FAMILY, HConstants.SEQNUM_QUALIFIER)
+        .readAllVersions());
+      return getReplicationBarriers(result);
+    }
+  }
+
   private static void debugLogMutations(List<? extends Mutation> mutations) throws IOException {
     if (!METALOG.isDebugEnabled()) {
       return;

hbase-client/src/main/java/org/apache/hadoop/hbase/client/TableDescriptor.java

@@ -244,6 +244,11 @@ public interface TableDescriptor {
    */
   boolean hasRegionMemStoreReplication();
 
+  /**
+   * @return true if there are at least one cf whose replication scope is serial.
+   */
+  boolean hasSerialReplicationScope();
+
   /**
    * Check if the compaction enable flag of the table is true. If flag is false
    * then no minor/major compactions will be done in real.
@@ -292,7 +297,8 @@ public interface TableDescriptor {
     boolean hasDisabled = false;
 
     for (ColumnFamilyDescriptor cf : getColumnFamilies()) {
-      if (cf.getScope() != HConstants.REPLICATION_SCOPE_GLOBAL) {
+      if (cf.getScope() != HConstants.REPLICATION_SCOPE_GLOBAL &&
+        cf.getScope() != HConstants.REPLICATION_SCOPE_SERIAL) {
         hasDisabled = true;
       } else {
         hasEnabled = true;

hbase-client/src/main/java/org/apache/hadoop/hbase/client/TableDescriptorBuilder.java

@@ -1127,6 +1127,15 @@ public class TableDescriptorBuilder {
       return families.values().toArray(new ColumnFamilyDescriptor[families.size()]);
     }
 
+    /**
+     * Return true if there are at least one cf whose replication scope is serial.
+     */
+    @Override
+    public boolean hasSerialReplicationScope() {
+      return families.values().stream()
+        .anyMatch(column -> column.getScope() == HConstants.REPLICATION_SCOPE_SERIAL);
+    }
+
     /**
      * Returns the configured replicas per region
      */

hbase-common/src/main/java/org/apache/hadoop/hbase/HConstants.java

@@ -535,6 +535,12 @@ public final class HConstants {
   /** The serialized table state qualifier */
   public static final byte[] TABLE_STATE_QUALIFIER = Bytes.toBytes("state");
 
+  /** The replication barrier family as a string*/
+  public static final String REPLICATION_BARRIER_FAMILY_STR = "rep_barrier";
+
+  /** The replication barrier family */
+  public static final byte[] REPLICATION_BARRIER_FAMILY =
+      Bytes.toBytes(REPLICATION_BARRIER_FAMILY_STR);
 
   /**
    * The meta table version column qualifier.
@@ -675,6 +681,12 @@ public final class HConstants {
    */
   public static final int REPLICATION_SCOPE_GLOBAL = 1;
 
+  /**
+   * Scope tag for serially scoped data
+   * This data will be replicated to all peers by the order of sequence id.
+   */
+  public static final int REPLICATION_SCOPE_SERIAL = 2;
+
   /**
    * Default cluster ID, cannot be used to identify a cluster so a key with
    * this value means it wasn't meant for replication.

hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterFileSystem.java

@@ -208,7 +208,16 @@ public class MasterFileSystem {
   /**
    * @return HBase root log dir.
    */
-  public Path getWALRootDir() { return this.walRootDir; }
+  public Path getWALRootDir() {
+    return this.walRootDir;
+  }
+
+  /**
+   * @return the directory for a give {@code region}.
+   */
+  public Path getRegionDir(RegionInfo region) {
+    return FSUtils.getRegionDir(FSUtils.getTableDir(getRootDir(), region.getTable()), region);
+  }
 
   /**
    * @return HBase temp dir.

hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/AssignmentManager.java

@@ -1571,8 +1571,7 @@ public class AssignmentManager implements ServerListener {
   }
 
   public void markRegionAsSplit(final RegionInfo parent, final ServerName serverName,
-      final RegionInfo daughterA, final RegionInfo daughterB)
+      final RegionInfo daughterA, final RegionInfo daughterB) throws IOException {
-  throws IOException {
     // Update hbase:meta. Parent will be marked offline and split up in hbase:meta.
     // The parent stays in regionStates until cleared when removed by CatalogJanitor.
     // Update its state in regionStates to it shows as offline and split when read

hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/RegionStateStore.java

@@ -1,5 +1,4 @@
 /**
- *
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
@@ -16,7 +15,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package org.apache.hadoop.hbase.master.assignment;
 
 import java.io.IOException;
@@ -36,11 +34,13 @@ import org.apache.hadoop.hbase.client.RegionInfo;
 import org.apache.hadoop.hbase.client.Result;
 import org.apache.hadoop.hbase.client.Table;
 import org.apache.hadoop.hbase.client.TableDescriptor;
+import org.apache.hadoop.hbase.master.MasterFileSystem;
 import org.apache.hadoop.hbase.master.MasterServices;
 import org.apache.hadoop.hbase.master.RegionState.State;
 import org.apache.hadoop.hbase.procedure2.util.StringUtils;
 import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
+import org.apache.hadoop.hbase.wal.WALSplitter;
 import org.apache.hadoop.hbase.zookeeper.MetaTableLocator;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.zookeeper.KeeperException;
@@ -163,6 +163,11 @@ public class RegionStateStore {
       Preconditions.checkArgument(state == State.OPEN && regionLocation != null,
           "Open region should be on a server");
       MetaTableAccessor.addLocation(put, regionLocation, openSeqNum, replicaId);
+      // only update replication barrier for default replica
+      if (regionInfo.getReplicaId() == RegionInfo.DEFAULT_REPLICA_ID &&
+        hasSerialReplicationScope(regionInfo.getTable())) {
+        MetaTableAccessor.addReplicationBarrier(put, openSeqNum);
+      }
       info.append(", openSeqNum=").append(openSeqNum);
       info.append(", regionLocation=").append(regionLocation);
     } else if (regionLocation != null && !regionLocation.equals(lastHost)) {
@@ -205,24 +210,41 @@ public class RegionStateStore {
     }
   }
 
+  private long getOpenSeqNumForParentRegion(RegionInfo region) throws IOException {
+    MasterFileSystem mfs = master.getMasterFileSystem();
+    long maxSeqId =
+        WALSplitter.getMaxRegionSequenceId(mfs.getFileSystem(), mfs.getRegionDir(region));
+    return maxSeqId > 0 ? maxSeqId + 1 : HConstants.NO_SEQNUM;
+  }
+
   // ============================================================================================
   //  Update Region Splitting State helpers
   // ============================================================================================
-  public void splitRegion(final RegionInfo parent, final RegionInfo hriA,
+  public void splitRegion(RegionInfo parent, RegionInfo hriA, RegionInfo hriB,
-      final RegionInfo hriB, final ServerName serverName)  throws IOException {
+      ServerName serverName) throws IOException {
-    final TableDescriptor htd = getTableDescriptor(parent.getTable());
+    TableDescriptor htd = getTableDescriptor(parent.getTable());
-    MetaTableAccessor.splitRegion(master.getConnection(), parent, hriA, hriB, serverName,
+    long parentOpenSeqNum = HConstants.NO_SEQNUM;
-        getRegionReplication(htd));
+    if (htd.hasSerialReplicationScope()) {
+      parentOpenSeqNum = getOpenSeqNumForParentRegion(parent);
+    }
+    MetaTableAccessor.splitRegion(master.getConnection(), parent, parentOpenSeqNum, hriA, hriB,
+      serverName, getRegionReplication(htd));
   }
 
   // ============================================================================================
   //  Update Region Merging State helpers
   // ============================================================================================
-  public void mergeRegions(final RegionInfo parent, final RegionInfo hriA, final RegionInfo hriB,
+  public void mergeRegions(RegionInfo child, RegionInfo hriA, RegionInfo hriB,
-      final ServerName serverName) throws IOException {
+      ServerName serverName) throws IOException {
-    final TableDescriptor htd = getTableDescriptor(parent.getTable());
+    TableDescriptor htd = getTableDescriptor(child.getTable());
-    MetaTableAccessor.mergeRegions(master.getConnection(), parent, hriA, hriB, serverName,
+    long regionAOpenSeqNum = -1L;
-      getRegionReplication(htd));
+    long regionBOpenSeqNum = -1L;
+    if (htd.hasSerialReplicationScope()) {
+      regionAOpenSeqNum = getOpenSeqNumForParentRegion(hriA);
+      regionBOpenSeqNum = getOpenSeqNumForParentRegion(hriB);
+    }
+    MetaTableAccessor.mergeRegions(master.getConnection(), child, hriA, regionAOpenSeqNum, hriB,
+      regionBOpenSeqNum, serverName, getRegionReplication(htd));
   }
 
   // ============================================================================================
@@ -239,11 +261,19 @@ public class RegionStateStore {
   // ==========================================================================
   //  Table Descriptors helpers
   // ==========================================================================
-  private int getRegionReplication(final TableDescriptor htd) {
+  private boolean hasSerialReplicationScope(TableName tableName) throws IOException {
-    return (htd != null) ? htd.getRegionReplication() : 1;
+    return hasSerialReplicationScope(getTableDescriptor(tableName));
   }
 
-  private TableDescriptor getTableDescriptor(final TableName tableName) throws IOException {
+  private boolean hasSerialReplicationScope(TableDescriptor htd) {
+    return htd != null ? htd.hasSerialReplicationScope() : false;
+  }
+
+  private int getRegionReplication(TableDescriptor htd) {
+    return htd != null ? htd.getRegionReplication() : 1;
+  }
+
+  private TableDescriptor getTableDescriptor(TableName tableName) throws IOException {
     return master.getTableDescriptors().get(tableName);
   }
 

hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/SplitTableRegionProcedure.java

@@ -253,7 +253,7 @@ public class SplitTableRegionProcedure
           setNextState(SplitTableRegionState.SPLIT_TABLE_REGION_UPDATE_META);
           break;
         case SPLIT_TABLE_REGION_UPDATE_META:
-          updateMetaForDaughterRegions(env);
+          updateMeta(env);
           setNextState(SplitTableRegionState.SPLIT_TABLE_REGION_PRE_OPERATION_AFTER_META);
           break;
         case SPLIT_TABLE_REGION_PRE_OPERATION_AFTER_META:
@@ -762,7 +762,7 @@ public class SplitTableRegionProcedure
    * Add daughter regions to META
    * @param env MasterProcedureEnv
    */
-  private void updateMetaForDaughterRegions(final MasterProcedureEnv env) throws IOException {
+  private void updateMeta(final MasterProcedureEnv env) throws IOException {
     env.getAssignmentManager().markRegionAsSplit(getParentRegion(), getParentRegionServerName(env),
       daughter_1_RI, daughter_2_RI);
   }

hbase-server/src/main/java/org/apache/hadoop/hbase/master/procedure/AbstractStateMachineTableProcedure.java

@@ -15,7 +15,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package org.apache.hadoop.hbase.master.procedure;
 
 import java.io.IOException;
@@ -31,15 +30,12 @@ import org.apache.hadoop.hbase.client.DoNotRetryRegionException;
 import org.apache.hadoop.hbase.client.RegionInfo;
 import org.apache.hadoop.hbase.client.RegionOfflineException;
 import org.apache.hadoop.hbase.client.TableState;
-import org.apache.hadoop.hbase.master.MasterFileSystem;
 import org.apache.hadoop.hbase.master.MasterServices;
 import org.apache.hadoop.hbase.master.RegionState;
 import org.apache.hadoop.hbase.master.TableStateManager;
 import org.apache.hadoop.hbase.master.assignment.RegionStates;
 import org.apache.hadoop.hbase.procedure2.StateMachineProcedure;
 import org.apache.hadoop.hbase.security.User;
-import org.apache.hadoop.hbase.util.FSUtils;
-import org.apache.hadoop.hbase.util.ServerRegionReplicaUtil;
 import org.apache.yetus.audience.InterfaceAudience;
 
 /**
@@ -131,9 +127,7 @@ public abstract class AbstractStateMachineTableProcedure<TState>
   }
 
   protected final Path getRegionDir(MasterProcedureEnv env, RegionInfo region) throws IOException {
-    MasterFileSystem mfs = env.getMasterServices().getMasterFileSystem();
+    return env.getMasterServices().getMasterFileSystem().getRegionDir(region);
-    Path tableDir = FSUtils.getTableDir(mfs.getRootDir(), getTableName());
-    return new Path(tableDir, ServerRegionReplicaUtil.getRegionInfoForFs(region).getEncodedName());
   }
 
   /**

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionFileSystem.java

@@ -1,5 +1,4 @@
 /**
- *
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
@@ -16,7 +15,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package org.apache.hadoop.hbase.regionserver;
 
 import java.io.FileNotFoundException;
@@ -25,6 +23,7 @@ import java.io.InterruptedIOException;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.UUID;
 import org.apache.hadoop.conf.Configuration;
@@ -84,6 +83,7 @@ public class HRegionFileSystem {
   private final Configuration conf;
   private final Path tableDir;
   private final FileSystem fs;
+  private final Path regionDir;
 
   /**
    * In order to handle NN connectivity hiccups, one need to retry non-idempotent operation at the
@@ -105,9 +105,10 @@ public class HRegionFileSystem {
       final RegionInfo regionInfo) {
     this.fs = fs;
     this.conf = conf;
-    this.tableDir = tableDir;
+    this.tableDir = Objects.requireNonNull(tableDir, "tableDir is null");
-    this.regionInfo = regionInfo;
+    this.regionInfo = Objects.requireNonNull(regionInfo, "regionInfo is null");
     this.regionInfoForFs = ServerRegionReplicaUtil.getRegionInfoForFs(regionInfo);
+    this.regionDir = FSUtils.getRegionDir(tableDir, regionInfo);
     this.hdfsClientRetriesNumber = conf.getInt("hdfs.client.retries.number",
       DEFAULT_HDFS_CLIENT_RETRIES_NUMBER);
     this.baseSleepBeforeRetries = conf.getInt("hdfs.client.sleep.before.retries",
@@ -135,7 +136,7 @@ public class HRegionFileSystem {
 
   /** @return {@link Path} to the region directory. */
   public Path getRegionDir() {
-    return new Path(this.tableDir, this.regionInfoForFs.getEncodedName());
+    return regionDir;
   }
 
   // ===========================================================================

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/NamespaceTableCfWALEntryFilter.java

@@ -21,16 +21,13 @@ package org.apache.hadoop.hbase.replication;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
 import org.apache.hadoop.hbase.TableName;
-import org.apache.yetus.audience.InterfaceAudience;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import org.apache.hadoop.hbase.wal.WALEdit;
 import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.hadoop.hbase.wal.WAL.Entry;
+import org.apache.hadoop.hbase.wal.WALEdit;
+import org.apache.yetus.audience.InterfaceAudience;
 
 /**
  * Filter a WAL Entry by the peer config: replicate_all flag, namespaces config, table-cfs config,
@@ -47,7 +44,6 @@ import org.apache.hadoop.hbase.wal.WAL.Entry;
 @InterfaceAudience.Private
 public class NamespaceTableCfWALEntryFilter implements WALEntryFilter, WALCellFilter {
 
-  private static final Logger LOG = LoggerFactory.getLogger(NamespaceTableCfWALEntryFilter.class);
   private final ReplicationPeer peer;
   private BulkLoadCellFilter bulkLoadFilter = new BulkLoadCellFilter();
 

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/ScopeWALEntryFilter.java

@@ -15,17 +15,15 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package org.apache.hadoop.hbase.replication;
 
 import java.util.NavigableMap;
-
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
 import org.apache.hadoop.hbase.HConstants;
-import org.apache.yetus.audience.InterfaceAudience;
-import org.apache.hadoop.hbase.wal.WALEdit;
 import org.apache.hadoop.hbase.wal.WAL.Entry;
+import org.apache.hadoop.hbase.wal.WALEdit;
+import org.apache.yetus.audience.InterfaceAudience;
 
 import org.apache.hbase.thirdparty.com.google.common.base.Predicate;
 
@@ -35,7 +33,7 @@ import org.apache.hbase.thirdparty.com.google.common.base.Predicate;
 @InterfaceAudience.Private
 public class ScopeWALEntryFilter implements WALEntryFilter, WALCellFilter {
 
-  BulkLoadCellFilter bulkLoadFilter = new BulkLoadCellFilter();
+  private final BulkLoadCellFilter bulkLoadFilter = new BulkLoadCellFilter();
 
   @Override
   public Entry filter(Entry entry) {

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/RecoveredReplicationSource.java

@@ -194,4 +194,9 @@ public class RecoveredReplicationSource extends ReplicationSource {
   public ServerName getServerWALsBelongTo() {
     return this.replicationQueueInfo.getDeadRegionServers().get(0);
   }
+
+  @Override
+  public boolean isRecovered() {
+    return true;
+  }
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/RecoveredReplicationSourceShipper.java

@@ -1,5 +1,4 @@
-/*
+/**
- *
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
@@ -20,12 +19,10 @@ package org.apache.hadoop.hbase.replication.regionserver;
 
 import java.io.IOException;
 import java.util.concurrent.PriorityBlockingQueue;
-
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.replication.ReplicationException;
 import org.apache.hadoop.hbase.replication.ReplicationQueueStorage;
-import org.apache.hadoop.hbase.replication.regionserver.ReplicationSourceWALReader.WALEntryBatch;
 import org.apache.hadoop.hbase.util.Threads;
 import org.apache.yetus.audience.InterfaceAudience;
 import org.slf4j.Logger;
@@ -127,13 +124,6 @@ public class RecoveredReplicationSourceShipper extends ReplicationSourceShipper
     return startPosition;
   }
 
-  @Override
-  protected void updateLogPosition(long lastReadPosition) {
-    source.getSourceManager().logPositionAndCleanOldLogs(currentPath, source.getQueueId(),
-      lastReadPosition, true);
-    lastLoggedPosition = lastReadPosition;
-  }
-
   private void terminate(String reason, Exception cause) {
     if (cause == null) {
       LOG.info("Closing worker for wal group " + this.walGroupId + " because: " + reason);

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/RecoveredReplicationSourceWALReader.java

@@ -35,6 +35,7 @@ import org.apache.hadoop.hbase.replication.WALEntryFilter;
 @InterfaceAudience.Private
 @InterfaceStability.Evolving
 public class RecoveredReplicationSourceWALReader extends ReplicationSourceWALReader {
+
   private static final Logger LOG =
     LoggerFactory.getLogger(RecoveredReplicationSourceWALReader.class);
 
@@ -45,13 +46,11 @@ public class RecoveredReplicationSourceWALReader extends ReplicationSourceWALRea
   }
 
   @Override
-  protected void handleEmptyWALEntryBatch(WALEntryBatch batch, Path currentPath)
+  protected void handleEmptyWALEntryBatch(Path currentPath) throws InterruptedException {
-      throws InterruptedException {
     LOG.trace("Didn't read any new entries from WAL");
     // we're done with queue recovery, shut ourself down
     setReaderRunning(false);
     // shuts down shipper thread immediately
-    entryBatchQueue.put(batch != null ? batch
+    entryBatchQueue.put(new WALEntryBatch(replicationBatchCountCapacity, currentPath));
-        : new WALEntryBatch(replicationBatchCountCapacity, currentPath));
   }
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/ReplicationSource.java

@@ -607,4 +607,12 @@ public class ReplicationSource implements ReplicationSourceInterface {
   public ServerName getServerWALsBelongTo() {
     return server.getServerName();
   }
+
+  Server getServer() {
+    return server;
+  }
+
+  ReplicationQueueStorage getQueueStorage() {
+    return queueStorage;
+  }
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/ReplicationSourceInterface.java

@@ -166,4 +166,11 @@ public interface ReplicationSourceInterface {
    * @return the server name which all WALs belong to
    */
   ServerName getServerWALsBelongTo();
+
+  /**
+   * @return whether this is a replication source for recovery.
+   */
+  default boolean isRecovered() {
+    return false;
+  }
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/ReplicationSourceManager.java

@@ -480,10 +480,10 @@ public class ReplicationSourceManager implements ReplicationListener {
    * @param queueRecovered indicates if this queue comes from another region server
    */
   public void logPositionAndCleanOldLogs(Path log, String queueId, long position,
-      boolean queueRecovered) {
+      Map<String, Long> lastSeqIds, boolean queueRecovered) {
     String fileName = log.getName();
     abortWhenFail(() -> this.queueStorage.setWALPosition(server.getServerName(), queueId, fileName,
-      position, null));
+      position, lastSeqIds));
     cleanOldLogs(fileName, queueId, queueRecovered);
   }
 

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/ReplicationSourceShipper.java

@@ -1,5 +1,4 @@
-/*
+/**
- *
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
@@ -20,13 +19,13 @@ package org.apache.hadoop.hbase.replication.regionserver;
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.PriorityBlockingQueue;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
 import org.apache.hadoop.hbase.replication.ReplicationEndpoint;
-import org.apache.hadoop.hbase.replication.regionserver.ReplicationSourceWALReader.WALEntryBatch;
 import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
 import org.apache.hadoop.hbase.util.Threads;
 import org.apache.hadoop.hbase.wal.WAL.Entry;
@@ -128,7 +127,7 @@ public class ReplicationSourceShipper extends Thread {
     int sleepMultiplier = 0;
     if (entries.isEmpty()) {
       if (lastLoggedPosition != lastReadPosition) {
-        updateLogPosition(lastReadPosition);
+        updateLogPosition(lastReadPosition, entryBatch.getLastSeqIds());
         // if there was nothing to ship and it's not an error
         // set "ageOfLastShippedOp" to <now> to indicate that we're current
         source.getSourceMetrics().setAgeOfLastShippedOp(EnvironmentEdgeManager.currentTime(),
@@ -174,7 +173,7 @@ public class ReplicationSourceShipper extends Thread {
             cleanUpHFileRefs(entries.get(i).getEdit());
           }
           // Log and clean up WAL logs
-          updateLogPosition(lastReadPosition);
+          updateLogPosition(lastReadPosition, entryBatch.getLastSeqIds());
         }
 
         source.postShipEdits(entries, currentSize);
@@ -222,9 +221,9 @@ public class ReplicationSourceShipper extends Thread {
     }
   }
 
-  protected void updateLogPosition(long lastReadPosition) {
+  private void updateLogPosition(long lastReadPosition, Map<String, Long> lastSeqIds) {
     source.getSourceManager().logPositionAndCleanOldLogs(currentPath, source.getQueueId(),
-      lastReadPosition, false);
+      lastReadPosition, lastSeqIds, source.isRecovered());
     lastLoggedPosition = lastReadPosition;
   }
 

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/ReplicationSourceWALActionListener.java

@@ -20,7 +20,6 @@ package org.apache.hadoop.hbase.replication.regionserver;
 import java.io.IOException;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
-import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
 import org.apache.hadoop.hbase.regionserver.wal.WALActionsListener;
 import org.apache.hadoop.hbase.replication.ReplicationUtils;
@@ -31,8 +30,6 @@ import org.apache.yetus.audience.InterfaceAudience;
 
 import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
 
-import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos;
-
 /**
  * Used to receive new wals.
  */
@@ -68,31 +65,25 @@ class ReplicationSourceWALActionListener implements WALActionsListener {
    * compaction WAL edits and if the scope is local.
    * @param logKey Key that may get scoped according to its edits
    * @param logEdit Edits used to lookup the scopes
-   * @throws IOException If failed to parse the WALEdit
    */
   @VisibleForTesting
-  static void scopeWALEdits(WALKey logKey, WALEdit logEdit, Configuration conf) throws IOException {
+  static void scopeWALEdits(WALKey logKey, WALEdit logEdit, Configuration conf) {
-    boolean replicationForBulkLoadEnabled =
+    // For bulk load replication we need meta family to know the file we want to replicate.
-        ReplicationUtils.isReplicationForBulkLoadDataEnabled(conf);
+    if (ReplicationUtils.isReplicationForBulkLoadDataEnabled(conf)) {
-    boolean foundOtherEdits = false;
+      return;
-    for (Cell cell : logEdit.getCells()) {
-      if (!CellUtil.matchingFamily(cell, WALEdit.METAFAMILY)) {
-        foundOtherEdits = true;
-        break;
     }
+    WALKeyImpl keyImpl = (WALKeyImpl) logKey;
+    // For serial replication we need to count all the sequence ids even for markers, so here we
+    // always need to retain the replication scopes to let the replication wal reader to know that
+    // we need serial replication. The ScopeWALEntryFilter will help filtering out the cell for
+    // WALEdit.METAFAMILY.
+    if (keyImpl.hasSerialReplicationScope()) {
+      return;
     }
-
+    // For replay, or if all the cells are markers, do not need to store replication scope.
-    if (!foundOtherEdits && logEdit.getCells().size() > 0) {
+    if (logEdit.isReplay() ||
-      WALProtos.RegionEventDescriptor maybeEvent =
+      logEdit.getCells().stream().allMatch(c -> CellUtil.matchingFamily(c, WALEdit.METAFAMILY))) {
-          WALEdit.getRegionEventDescriptor(logEdit.getCells().get(0));
+      keyImpl.clearReplicationScope();
-      if (maybeEvent != null &&
-        (maybeEvent.getEventType() == WALProtos.RegionEventDescriptor.EventType.REGION_CLOSE)) {
-        // In serially replication, we use scopes when reading close marker.
-        foundOtherEdits = true;
-      }
-    }
-    if ((!replicationForBulkLoadEnabled && !foundOtherEdits) || logEdit.isReplay()) {
-      ((WALKeyImpl) logKey).serializeReplicationScope(false);
     }
   }
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/ReplicationSourceWALReader.java

@@ -20,7 +20,6 @@ package org.apache.hadoop.hbase.replication.regionserver;
 
 import java.io.EOFException;
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
@@ -33,6 +32,7 @@ import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.replication.WALEntryFilter;
+import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.hadoop.hbase.util.Pair;
 import org.apache.hadoop.hbase.util.Threads;
 import org.apache.hadoop.hbase.wal.WAL.Entry;
@@ -46,8 +46,8 @@ import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos.BulkLoadDescr
 import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos.StoreDescriptor;
 
 /**
- * Reads and filters WAL entries, groups the filtered entries into batches, and puts the batches onto a queue
+ * Reads and filters WAL entries, groups the filtered entries into batches, and puts the batches
- *
+ * onto a queue
  */
 @InterfaceAudience.Private
 @InterfaceStability.Evolving
@@ -77,6 +77,8 @@ public class ReplicationSourceWALReader extends Thread {
   private AtomicLong totalBufferUsed;
   private long totalBufferQuota;
 
+  private final SerialReplicationChecker serialReplicationChecker;
+
   /**
    * Creates a reader worker for a given WAL queue. Reads WAL entries off a given queue, batches the
    * entries, and puts them on a batch queue.
@@ -111,6 +113,7 @@ public class ReplicationSourceWALReader extends Thread {
         this.conf.getInt("replication.source.maxretriesmultiplier", 300); // 5 minutes @ 1 sec per
     this.eofAutoRecovery = conf.getBoolean("replication.source.eof.autorecovery", false);
     this.entryBatchQueue = new LinkedBlockingQueue<>(batchCount);
+    this.serialReplicationChecker = new SerialReplicationChecker(conf, source);
     LOG.info("peerClusterZnode=" + source.getQueueId()
         + ", ReplicationSourceWALReaderThread : " + source.getPeerId()
         + " inited, replicationBatchSizeCapacity=" + replicationBatchSizeCapacity
@@ -131,15 +134,14 @@ public class ReplicationSourceWALReader extends Thread {
             continue;
           }
           WALEntryBatch batch = readWALEntries(entryStream);
-          if (batch != null && batch.getNbEntries() > 0) {
+          if (batch != null) {
-            if (LOG.isTraceEnabled()) {
+            // need to propagate the batch even it has no entries since it may carry the last
-              LOG.trace(String.format("Read %s WAL entries eligible for replication",
+            // sequence id information for serial replication.
-                batch.getNbEntries()));
+            LOG.trace("Read {} WAL entries eligible for replication", batch.getNbEntries());
-            }
             entryBatchQueue.put(batch);
             sleepMultiplier = 1;
           } else { // got no entries and didn't advance position in WAL
-            handleEmptyWALEntryBatch(batch, entryStream.getCurrentPath());
+            handleEmptyWALEntryBatch(entryStream.getCurrentPath());
           }
           currentPosition = entryStream.getPosition();
           entryStream.reset(); // reuse stream
@@ -160,34 +162,66 @@ public class ReplicationSourceWALReader extends Thread {
     }
   }
 
-  private WALEntryBatch readWALEntries(WALEntryStream entryStream) throws IOException {
+  private WALEntryBatch readWALEntries(WALEntryStream entryStream)
-    WALEntryBatch batch = null;
+      throws IOException, InterruptedException {
-    while (entryStream.hasNext()) {
+    if (!entryStream.hasNext()) {
-      if (batch == null) {
+      return null;
-        batch = new WALEntryBatch(replicationBatchCountCapacity, entryStream.getCurrentPath());
+    }
+    WALEntryBatch batch =
+      new WALEntryBatch(replicationBatchCountCapacity, entryStream.getCurrentPath());
+    do {
+      Entry entry = entryStream.peek();
+      batch.setLastWalPosition(entryStream.getPosition());
+      boolean hasSerialReplicationScope = entry.getKey().hasSerialReplicationScope();
+      // Used to locate the region record in meta table. In WAL we only have the table name and
+      // encoded region name which can not be mapping to region name without scanning all the
+      // records for a table, so we need a start key, just like what we have done at client side
+      // when locating a region. For the markers, we will use the start key of the region as the row
+      // key for the edit. And we need to do this before filtering since all the cells may be
+      // filtered out, especially that for the markers.
+      Cell firstCellInEdit = null;
+      if (hasSerialReplicationScope) {
+        assert !entry.getEdit().isEmpty() : "should not write empty edits";
+        firstCellInEdit = entry.getEdit().getCells().get(0);
       }
-      Entry entry = entryStream.next();
       entry = filterEntry(entry);
       if (entry != null) {
+        if (hasSerialReplicationScope) {
+          if (!serialReplicationChecker.canPush(entry, firstCellInEdit)) {
+            if (batch.getNbEntries() > 0) {
+              // we have something that can push, break
+              break;
+            } else {
+              serialReplicationChecker.waitUntilCanPush(entry, firstCellInEdit);
+            }
+          }
+          // arrive here means we can push the entry, record the last sequence id
+          batch.setLastSeqId(Bytes.toString(entry.getKey().getEncodedRegionName()),
+            entry.getKey().getSequenceId());
+        }
+        // actually remove the entry.
+        entryStream.next();
         WALEdit edit = entry.getEdit();
         if (edit != null && !edit.isEmpty()) {
           long entrySize = getEntrySize(entry);
           batch.addEntry(entry);
-          updateBatchStats(batch, entry, entryStream.getPosition(), entrySize);
+          updateBatchStats(batch, entry, entrySize);
           boolean totalBufferTooLarge = acquireBufferQuota(entrySize);
           // Stop if too many entries or too big
-          if (totalBufferTooLarge || batch.getHeapSize() >= replicationBatchSizeCapacity
+          if (totalBufferTooLarge || batch.getHeapSize() >= replicationBatchSizeCapacity ||
-              || batch.getNbEntries() >= replicationBatchCountCapacity) {
+            batch.getNbEntries() >= replicationBatchCountCapacity) {
             break;
           }
         }
+      } else {
+        // actually remove the entry.
+        entryStream.next();
       }
-    }
+    } while (entryStream.hasNext());
     return batch;
   }
 
-  protected void handleEmptyWALEntryBatch(WALEntryBatch batch, Path currentPath)
+  protected void handleEmptyWALEntryBatch(Path currentPath) throws InterruptedException {
-      throws InterruptedException {
     LOG.trace("Didn't read any new entries from WAL");
     Thread.sleep(sleepForRetries);
   }
@@ -214,7 +248,7 @@ public class ReplicationSourceWALReader extends Thread {
     // if we've read some WAL entries, get the Path we read from
     WALEntryBatch batchQueueHead = entryBatchQueue.peek();
     if (batchQueueHead != null) {
-      return batchQueueHead.lastWalPath;
+      return batchQueueHead.getLastWalPath();
     }
     // otherwise, we must be currently reading from the head of the log queue
     return logQueue.peek();
@@ -253,16 +287,13 @@ public class ReplicationSourceWALReader extends Thread {
     return edit.heapSize() + calculateTotalSizeOfStoreFiles(edit);
   }
 
-  private void updateBatchStats(WALEntryBatch batch, Entry entry, long entryPosition, long entrySize) {
+  private void updateBatchStats(WALEntryBatch batch, Entry entry, long entrySize) {
     WALEdit edit = entry.getEdit();
-    if (edit != null && !edit.isEmpty()) {
     batch.incrementHeapSize(entrySize);
     Pair<Integer, Integer> nbRowsAndHFiles = countDistinctRowKeysAndHFiles(edit);
     batch.incrementNbRowKeys(nbRowsAndHFiles.getFirst());
     batch.incrementNbHFiles(nbRowsAndHFiles.getSecond());
   }
-    batch.lastWalPosition = entryPosition;
-  }
 
   /**
    * Count the number of different row keys in the given edit because of mini-batching. We assume
@@ -355,101 +386,4 @@ public class ReplicationSourceWALReader extends Thread {
   public void setReaderRunning(boolean readerRunning) {
     this.isReaderRunning = readerRunning;
   }
-
-  /**
-   * Holds a batch of WAL entries to replicate, along with some statistics
-   *
-   */
-  static class WALEntryBatch {
-    private List<Entry> walEntries;
-    // last WAL that was read
-    private Path lastWalPath;
-    // position in WAL of last entry in this batch
-    private long lastWalPosition = 0;
-    // number of distinct row keys in this batch
-    private int nbRowKeys = 0;
-    // number of HFiles
-    private int nbHFiles = 0;
-    // heap size of data we need to replicate
-    private long heapSize = 0;
-
-    /**
-     * @param walEntries
-     * @param lastWalPath Path of the WAL the last entry in this batch was read from
-     * @param lastWalPosition Position in the WAL the last entry in this batch was read from
-     */
-    WALEntryBatch(int maxNbEntries, Path lastWalPath) {
-      this.walEntries = new ArrayList<>(maxNbEntries);
-      this.lastWalPath = lastWalPath;
-    }
-
-    public void addEntry(Entry entry) {
-      walEntries.add(entry);
-    }
-
-    /**
-     * @return the WAL Entries.
-     */
-    public List<Entry> getWalEntries() {
-      return walEntries;
-    }
-
-    /**
-     * @return the path of the last WAL that was read.
-     */
-    public Path getLastWalPath() {
-      return lastWalPath;
-    }
-
-    /**
-     * @return the position in the last WAL that was read.
-     */
-    public long getLastWalPosition() {
-      return lastWalPosition;
-    }
-
-    public int getNbEntries() {
-      return walEntries.size();
-    }
-
-    /**
-     * @return the number of distinct row keys in this batch
-     */
-    public int getNbRowKeys() {
-      return nbRowKeys;
-    }
-
-    /**
-     * @return the number of HFiles in this batch
-     */
-    public int getNbHFiles() {
-      return nbHFiles;
-    }
-
-    /**
-     * @return total number of operations in this batch
-     */
-    public int getNbOperations() {
-      return getNbRowKeys() + getNbHFiles();
-    }
-
-    /**
-     * @return the heap size of this batch
-     */
-    public long getHeapSize() {
-      return heapSize;
-    }
-
-    private void incrementNbRowKeys(int increment) {
-      nbRowKeys += increment;
-    }
-
-    private void incrementNbHFiles(int increment) {
-      nbHFiles += increment;
-    }
-
-    private void incrementHeapSize(long increment) {
-      heapSize += increment;
-    }
-  }
 }

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/SerialReplicationChecker.java

@@ -0,0 +1,255 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hbase.replication.regionserver;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.concurrent.TimeUnit;
+import org.apache.commons.lang3.mutable.MutableLong;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.Cell;
+import org.apache.hadoop.hbase.CellUtil;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.MetaTableAccessor;
+import org.apache.hadoop.hbase.MetaTableAccessor.ReplicationBarrierResult;
+import org.apache.hadoop.hbase.client.Connection;
+import org.apache.hadoop.hbase.client.RegionInfo;
+import org.apache.hadoop.hbase.master.RegionState;
+import org.apache.hadoop.hbase.replication.ReplicationException;
+import org.apache.hadoop.hbase.replication.ReplicationQueueStorage;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.hbase.wal.WAL.Entry;
+import org.apache.yetus.audience.InterfaceAudience;
+
+import org.apache.hbase.thirdparty.com.google.common.cache.Cache;
+import org.apache.hbase.thirdparty.com.google.common.cache.CacheBuilder;
+import org.apache.hbase.thirdparty.com.google.common.cache.CacheLoader;
+import org.apache.hbase.thirdparty.com.google.common.cache.LoadingCache;
+
+/**
+ * <p>
+ * Helper class to determine whether we can push a given WAL entry without breaking the replication
+ * order. The class is designed to per {@link ReplicationSourceWALReader}, so not thread safe.
+ * </p>
+ * <p>
+ * We record all the open sequence number for a region in a special family in meta, which is called
+ * 'barrier', so there will be a sequence of open sequence number (b1, b2, b3, ...). We call [bn,
+ * bn+1) a range, and it is obvious that a region will always be on the same RS within a range.
+ * <p>
+ * When split and merge, we will also record the parent for the generated region(s) in the special
+ * family in meta. And also, we will write an extra 'open sequence number' for the parent region(s),
+ * which is the max sequence id of the region plus one.
+ * </p>
+ * </p>
+ * <p>
+ * For each peer, we record the last pushed sequence id for each region. It is managed by the
+ * replication storage.
+ * </p>
+ * <p>
+ * The algorithm works like this:
+ * <ol>
+ * <li>Locate the sequence id we want to push in the barriers</li>
+ * <li>If it is before the first barrier, we are safe to push. This usually because we enable serial
+ * replication for this table after we create the table and write data into the table.</li>
+ * <li>In general, if the previous range is finished, then we are safe to push. The way to determine
+ * whether a range is finish is straight-forward: check whether the last pushed sequence id is equal
+ * to the end barrier of the range minus 1. There are several exceptions:
+ * <ul>
+ * <li>If it is in the first range, we need to check whether there are parent regions. If so, we
+ * need to make sure that the data for parent regions have all been pushed.</li>
+ * <li>If it is in the last range, we need to check the region state. If state is OPENING, then we
+ * are not safe to push. This is because that, before we call reportRIT to master which update the
+ * open sequence number into meta table, we will write a open region event marker to WAL first, and
+ * its sequence id is greater than the newest open sequence number(which has not been updated to
+ * meta table yet so we do not know). For this scenario, the WAL entry for this open region event
+ * marker actually belongs to the range after the 'last' range, so we are not safe to push it.
+ * Otherwise the last pushed sequence id will be updated to this value and then we think the
+ * previous range has already been finished, but this is not true.</li>
+ * <li>Notice that the above two exceptions are not conflicts, since the first range can also be the
+ * last range if we only have one range.</li>
+ * </ul>
+ * </li>
+ * </ol>
+ * </p>
+ * <p>
+ * And for performance reason, we do not want to check meta for every WAL entry, so we introduce two
+ * in memory maps. The idea is simple:
+ * <ul>
+ * <li>If a range can be pushed, then put its end barrier into the {@code canPushUnder} map.</li>
+ * <li>Before accessing meta, first check the sequence id stored in the {@code canPushUnder} map. If
+ * the sequence id of WAL entry is less the one stored in {@code canPushUnder} map, then we are safe
+ * to push.</li>
+ * </ul>
+ * And for the last range, we do not have an end barrier, so we use the continuity of sequence id to
+ * determine whether we can push. The rule is:
+ * <ul>
+ * <li>When an entry is able to push, then put its sequence id into the {@code pushed} map.</li>
+ * <li>Check if the sequence id of WAL entry equals to the one stored in the {@code pushed} map plus
+ * one. If so, we are safe to push, and also update the {@code pushed} map with the sequence id of
+ * the WAL entry.</li>
+ * </ul>
+ * </p>
+ */
+@InterfaceAudience.Private
+class SerialReplicationChecker {
+
+  public static final String REPLICATION_SERIALLY_WAITING_KEY =
+    "hbase.serial.replication.waiting.ms";
+  public static final long REPLICATION_SERIALLY_WAITING_DEFAULT = 10000;
+
+  private final String peerId;
+
+  private final ReplicationQueueStorage storage;
+
+  private final Connection conn;
+
+  private final long waitTimeMs;
+
+  private final LoadingCache<String, MutableLong> pushed = CacheBuilder.newBuilder()
+    .expireAfterAccess(1, TimeUnit.DAYS).build(new CacheLoader<String, MutableLong>() {
+
+      @Override
+      public MutableLong load(String key) throws Exception {
+        return new MutableLong(HConstants.NO_SEQNUM);
+      }
+    });
+
+  // Use guava cache to set ttl for each key
+  private final Cache<String, Long> canPushUnder =
+    CacheBuilder.newBuilder().expireAfterAccess(1, TimeUnit.DAYS).build();
+
+  public SerialReplicationChecker(Configuration conf, ReplicationSource source) {
+    this.peerId = source.getPeerId();
+    this.storage = source.getQueueStorage();
+    this.conn = source.getServer().getConnection();
+    this.waitTimeMs =
+      conf.getLong(REPLICATION_SERIALLY_WAITING_KEY, REPLICATION_SERIALLY_WAITING_DEFAULT);
+  }
+
+  private boolean isRangeFinished(long endBarrier, String encodedRegionName) throws IOException {
+    long pushedSeqId;
+    try {
+      pushedSeqId = storage.getLastSequenceId(encodedRegionName, peerId);
+    } catch (ReplicationException e) {
+      throw new IOException(
+        "Failed to get pushed sequence id for " + encodedRegionName + ", peer " + peerId, e);
+    }
+    // endBarrier is the open sequence number. When opening a region, the open sequence number will
+    // be set to the old max sequence id plus one, so here we need to minus one.
+    return pushedSeqId >= endBarrier - 1;
+  }
+
+  private boolean isParentFinished(byte[] regionName) throws IOException {
+    long[] barriers = MetaTableAccessor.getReplicationBarrier(conn, regionName);
+    if (barriers.length == 0) {
+      return true;
+    }
+    return isRangeFinished(barriers[barriers.length - 1], RegionInfo.encodeRegionName(regionName));
+  }
+
+  // We may write a open region marker to WAL before we write the open sequence number to meta, so
+  // if a region is in OPENING state and we are in the last range, it is not safe to say we can push
+  // even if the previous range is finished.
+  private boolean isLastRangeAndOpening(ReplicationBarrierResult barrierResult, int index) {
+    return index == barrierResult.getBarriers().length &&
+      barrierResult.getState() == RegionState.State.OPENING;
+  }
+
+  private void recordCanPush(String encodedNameAsString, long seqId, long[] barriers, int index) {
+    if (barriers.length > index) {
+      canPushUnder.put(encodedNameAsString, barriers[index]);
+    }
+    pushed.getUnchecked(encodedNameAsString).setValue(seqId);
+  }
+
+  private boolean canPush(Entry entry, byte[] row) throws IOException {
+    String encodedNameAsString = Bytes.toString(entry.getKey().getEncodedRegionName());
+    long seqId = entry.getKey().getSequenceId();
+    ReplicationBarrierResult barrierResult = MetaTableAccessor.getReplicationBarrierResult(conn,
+      entry.getKey().getTableName(), row, entry.getKey().getEncodedRegionName());
+    long[] barriers = barrierResult.getBarriers();
+    int index = Arrays.binarySearch(barriers, seqId);
+    if (index == -1) {
+      // This means we are in the range before the first record openSeqNum, this usually because the
+      // wal is written before we enable serial replication for this table, just return true since
+      // we can not guarantee the order.
+      pushed.getUnchecked(encodedNameAsString).setValue(seqId);
+      return true;
+    }
+    // The sequence id range is left closed and right open, so either we decrease the missed insert
+    // point to make the index start from 0, or increase the hit insert point to make the index
+    // start from 1. Here we choose the latter one.
+    if (index < 0) {
+      index = -index - 1;
+    } else {
+      index++;
+    }
+    if (index == 1) {
+      // we are in the first range, check whether we have parents
+      for (byte[] regionName : barrierResult.getParentRegionNames()) {
+        if (!isParentFinished(regionName)) {
+          return false;
+        }
+      }
+      if (isLastRangeAndOpening(barrierResult, index)) {
+        return false;
+      }
+      recordCanPush(encodedNameAsString, seqId, barriers, 1);
+      return true;
+    }
+    // check whether the previous range is finished
+    if (!isRangeFinished(barriers[index - 1], encodedNameAsString)) {
+      return false;
+    }
+    if (isLastRangeAndOpening(barrierResult, index)) {
+      return false;
+    }
+    recordCanPush(encodedNameAsString, seqId, barriers, index);
+    return true;
+  }
+
+  public boolean canPush(Entry entry, Cell firstCellInEdit) throws IOException {
+    String encodedNameAsString = Bytes.toString(entry.getKey().getEncodedRegionName());
+    long seqId = entry.getKey().getSequenceId();
+    Long canReplicateUnderSeqId = canPushUnder.getIfPresent(encodedNameAsString);
+    if (canReplicateUnderSeqId != null) {
+      if (seqId < canReplicateUnderSeqId.longValue()) {
+        return true;
+      }
+      // we are already beyond the last safe point, remove
+      canPushUnder.invalidate(encodedNameAsString);
+    }
+    // This is for the case where the region is currently opened on us, if the sequence id is
+    // continuous then we are safe to replicate. If there is a breakpoint, then maybe the region
+    // has been moved to another RS and then back, so we need to check the barrier.
+    MutableLong previousPushedSeqId = pushed.getUnchecked(encodedNameAsString);
+    if (seqId == previousPushedSeqId.longValue() + 1) {
+      previousPushedSeqId.increment();
+      return true;
+    }
+    return canPush(entry, CellUtil.cloneRow(firstCellInEdit));
+  }
+
+  public void waitUntilCanPush(Entry entry, Cell firstCellInEdit)
+      throws IOException, InterruptedException {
+    byte[] row = CellUtil.cloneRow(firstCellInEdit);
+    while (!canPush(entry, row)) {
+      Thread.sleep(waitTimeMs);
+    }
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/WALEntryBatch.java

@@ -0,0 +1,138 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hbase.replication.regionserver;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.wal.WAL.Entry;
+import org.apache.yetus.audience.InterfaceAudience;
+
+/**
+ * Holds a batch of WAL entries to replicate, along with some statistics
+ */
+@InterfaceAudience.Private
+class WALEntryBatch {
+  private List<Entry> walEntries;
+  // last WAL that was read
+  private Path lastWalPath;
+  // position in WAL of last entry in this batch
+  private long lastWalPosition = 0;
+  // number of distinct row keys in this batch
+  private int nbRowKeys = 0;
+  // number of HFiles
+  private int nbHFiles = 0;
+  // heap size of data we need to replicate
+  private long heapSize = 0;
+  // save the last sequenceid for each region if the table has serial-replication scope
+  private Map<String, Long> lastSeqIds = new HashMap<>();
+
+  /**
+   * @param lastWalPath Path of the WAL the last entry in this batch was read from
+   */
+  WALEntryBatch(int maxNbEntries, Path lastWalPath) {
+    this.walEntries = new ArrayList<>(maxNbEntries);
+    this.lastWalPath = lastWalPath;
+  }
+
+  public void addEntry(Entry entry) {
+    walEntries.add(entry);
+  }
+
+  /**
+   * @return the WAL Entries.
+   */
+  public List<Entry> getWalEntries() {
+    return walEntries;
+  }
+
+  /**
+   * @return the path of the last WAL that was read.
+   */
+  public Path getLastWalPath() {
+    return lastWalPath;
+  }
+
+  /**
+   * @return the position in the last WAL that was read.
+   */
+  public long getLastWalPosition() {
+    return lastWalPosition;
+  }
+
+  public void setLastWalPosition(long lastWalPosition) {
+    this.lastWalPosition = lastWalPosition;
+  }
+
+  public int getNbEntries() {
+    return walEntries.size();
+  }
+
+  /**
+   * @return the number of distinct row keys in this batch
+   */
+  public int getNbRowKeys() {
+    return nbRowKeys;
+  }
+
+  /**
+   * @return the number of HFiles in this batch
+   */
+  public int getNbHFiles() {
+    return nbHFiles;
+  }
+
+  /**
+   * @return total number of operations in this batch
+   */
+  public int getNbOperations() {
+    return getNbRowKeys() + getNbHFiles();
+  }
+
+  /**
+   * @return the heap size of this batch
+   */
+  public long getHeapSize() {
+    return heapSize;
+  }
+
+  /**
+   * @return the last sequenceid for each region if the table has serial-replication scope
+   */
+  public Map<String, Long> getLastSeqIds() {
+    return lastSeqIds;
+  }
+
+  public void incrementNbRowKeys(int increment) {
+    nbRowKeys += increment;
+  }
+
+  public void incrementNbHFiles(int increment) {
+    nbHFiles += increment;
+  }
+
+  public void incrementHeapSize(long increment) {
+    heapSize += increment;
+  }
+
+  public void setLastSeqId(String region, long sequenceId) {
+    lastSeqIds.put(region, sequenceId);
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/WALEntryStream.java

@@ -21,29 +21,26 @@ package org.apache.hadoop.hbase.replication.regionserver;
 import java.io.Closeable;
 import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.util.NoSuchElementException;
 import java.util.OptionalLong;
 import java.util.concurrent.PriorityBlockingQueue;
-
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.ServerName;
-import org.apache.yetus.audience.InterfaceAudience;
-import org.apache.yetus.audience.InterfaceStability;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 import org.apache.hadoop.hbase.regionserver.wal.ProtobufLogReader;
 import org.apache.hadoop.hbase.util.CancelableProgressable;
 import org.apache.hadoop.hbase.util.FSUtils;
 import org.apache.hadoop.hbase.util.LeaseNotRecoveredException;
-import org.apache.hadoop.hbase.wal.AbstractFSWALProvider;
 import org.apache.hadoop.hbase.wal.WAL.Entry;
 import org.apache.hadoop.hbase.wal.WAL.Reader;
 import org.apache.hadoop.hbase.wal.WALFactory;
 import org.apache.hadoop.ipc.RemoteException;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.yetus.audience.InterfaceStability;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Streaming access to WAL entries. This class is given a queue of WAL {@link Path}, and continually
@@ -102,16 +99,18 @@ class WALEntryStream implements Closeable {
   }
 
   /**
-   * @return the next WAL entry in this stream
+   * Returns the next WAL entry in this stream but does not advance.
-   * @throws IOException
+   */
-   * @throws NoSuchElementException if no more entries in the stream.
+  public Entry peek() throws IOException {
+    return hasNext() ? currentEntry: null;
+  }
+
+  /**
+   * Returns the next WAL entry in this stream and advance the stream.
    */
   public Entry next() throws IOException {
-    if (!hasNext()) {
+    Entry save = peek();
-      throw new NoSuchElementException();
+    currentEntry = null;
-    }
-    Entry save = currentEntry;
-    currentEntry = null; // gets reloaded by hasNext()
     return save;
   }
 

hbase-server/src/main/java/org/apache/hadoop/hbase/util/FSTableDescriptors.java

@@ -170,6 +170,14 @@ public class FSTableDescriptors implements TableDescriptors {
         // Disable blooms for meta.  Needs work.  Seems to mess w/ getClosestOrBefore.
         .setBloomFilterType(BloomType.NONE)
         .build())
+      .setColumnFamily(ColumnFamilyDescriptorBuilder
+        .newBuilder(HConstants.REPLICATION_BARRIER_FAMILY)
+        .setMaxVersions(HConstants.ALL_VERSIONS)
+        .setInMemory(true)
+        .setScope(HConstants.REPLICATION_SCOPE_LOCAL)
+        // Disable blooms for meta.  Needs work.  Seems to mess w/ getClosestOrBefore.
+        .setBloomFilterType(BloomType.NONE)
+        .build())
       .setCoprocessor(CoprocessorDescriptorBuilder.newBuilder(
         MultiRowMutationEndpoint.class.getName())
         .setPriority(Coprocessor.PRIORITY_SYSTEM)

hbase-server/src/main/java/org/apache/hadoop/hbase/util/FSUtils.java

@@ -18,13 +18,7 @@
  */
 package org.apache.hadoop.hbase.util;
 
-import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
-import org.apache.hbase.thirdparty.com.google.common.base.Throwables;
-import org.apache.hbase.thirdparty.com.google.common.collect.Iterators;
-import org.apache.hbase.thirdparty.com.google.common.primitives.Ints;
-
 import edu.umd.cs.findbugs.annotations.CheckForNull;
-
 import java.io.ByteArrayInputStream;
 import java.io.DataInputStream;
 import java.io.EOFException;
@@ -54,7 +48,6 @@ import java.util.concurrent.FutureTask;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 import java.util.regex.Pattern;
-
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.BlockLocation;
 import org.apache.hadoop.fs.FSDataInputStream;
@@ -71,9 +64,7 @@ import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.HDFSBlocksDistribution;
 import org.apache.hadoop.hbase.HRegionInfo;
 import org.apache.hadoop.hbase.TableName;
-import org.apache.yetus.audience.InterfaceAudience;
+import org.apache.hadoop.hbase.client.RegionInfo;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 import org.apache.hadoop.hbase.exceptions.DeserializationException;
 import org.apache.hadoop.hbase.fs.HFileSystem;
 import org.apache.hadoop.hbase.io.HFileLink;
@@ -81,8 +72,6 @@ import org.apache.hadoop.hbase.master.HMaster;
 import org.apache.hadoop.hbase.regionserver.HRegion;
 import org.apache.hadoop.hbase.regionserver.StoreFileInfo;
 import org.apache.hadoop.hbase.security.AccessDeniedException;
-import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
-import org.apache.hadoop.hbase.shaded.protobuf.generated.FSProtos;
 import org.apache.hadoop.hbase.util.HBaseFsck.ErrorReporter;
 import org.apache.hadoop.hdfs.DFSClient;
 import org.apache.hadoop.hdfs.DFSHedgedReadMetrics;
@@ -94,6 +83,17 @@ import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.util.Progressable;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.util.StringUtils;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;
+import org.apache.hbase.thirdparty.com.google.common.base.Throwables;
+import org.apache.hbase.thirdparty.com.google.common.collect.Iterators;
+import org.apache.hbase.thirdparty.com.google.common.primitives.Ints;
+
+import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.FSProtos;
 
 /**
  * Utility methods for interacting with the underlying file system.
@@ -1028,6 +1028,10 @@ public abstract class FSUtils extends CommonFSUtils {
     return regionDirs;
   }
 
+  public static Path getRegionDir(Path tableDir, RegionInfo region) {
+    return new Path(tableDir, ServerRegionReplicaUtil.getRegionInfoForFs(region).getEncodedName());
+  }
+
   /**
    * Filter for all dirs that are legal column family names.  This is generally used for colfam
    * dirs <hbase.rootdir>/<tabledir>/<regiondir>/<colfamdir>.

hbase-server/src/main/java/org/apache/hadoop/hbase/wal/WALKeyImpl.java

@@ -415,10 +415,16 @@ public class WALKeyImpl implements WALKey {
     this.replicationScope = replicationScope;
   }
 
-  public void serializeReplicationScope(boolean serialize) {
+  public void clearReplicationScope() {
-    if (!serialize) {
     setReplicationScope(null);
   }
+
+  public boolean hasSerialReplicationScope() {
+    if (replicationScope == null || replicationScope.isEmpty()) {
+      return false;
+    }
+    return replicationScope.values().stream()
+      .anyMatch(scope -> scope.intValue() == HConstants.REPLICATION_SCOPE_SERIAL);
   }
 
   /**

hbase-server/src/test/java/org/apache/hadoop/hbase/TestMetaTableAccessor.java

@@ -494,7 +494,7 @@ public class TestMetaTableAccessor {
       List<RegionInfo> regionInfos = Lists.newArrayList(parent);
       MetaTableAccessor.addRegionsToMeta(connection, regionInfos, 3);
 
-      MetaTableAccessor.splitRegion(connection, parent, splitA, splitB, serverName0, 3);
+      MetaTableAccessor.splitRegion(connection, parent, -1L, splitA, splitB, serverName0, 3);
 
       assertEmptyMetaLocation(meta, splitA.getRegionName(), 1);
       assertEmptyMetaLocation(meta, splitA.getRegionName(), 2);
@@ -535,7 +535,8 @@ public class TestMetaTableAccessor {
       List<RegionInfo> regionInfos = Lists.newArrayList(parentA, parentB);
       MetaTableAccessor.addRegionsToMeta(connection, regionInfos, 3);
 
-      MetaTableAccessor.mergeRegions(connection, merged, parentA, parentB, serverName0, 3);
+      MetaTableAccessor.mergeRegions(connection, merged, parentA, -1L, parentB, -1L, serverName0,
+        3);
 
       assertEmptyMetaLocation(meta, merged.getRegionName(), 1);
       assertEmptyMetaLocation(meta, merged.getRegionName(), 2);
@@ -682,8 +683,8 @@ public class TestMetaTableAccessor {
       EnvironmentEdgeManager.injectEdge(edge);
       try {
         // now merge the regions, effectively deleting the rows for region a and b.
-        MetaTableAccessor.mergeRegions(connection, mergedRegionInfo, regionInfoA, regionInfoB, sn,
+        MetaTableAccessor.mergeRegions(connection, mergedRegionInfo, regionInfoA, -1L, regionInfoB,
-          1);
+          -1L, sn, 1);
       } finally {
         EnvironmentEdgeManager.reset();
       }
@@ -776,7 +777,8 @@ public class TestMetaTableAccessor {
       }
       SpyingRpcScheduler scheduler = (SpyingRpcScheduler) rs.getRpcServer().getScheduler();
       long prevCalls = scheduler.numPriorityCalls;
-      MetaTableAccessor.splitRegion(connection, parent, splitA, splitB, loc.getServerName(), 1);
+      MetaTableAccessor.splitRegion(connection, parent, -1L, splitA, splitB, loc.getServerName(),
+        1);
 
       assertTrue(prevCalls < scheduler.numPriorityCalls);
     }
@@ -813,7 +815,7 @@ public class TestMetaTableAccessor {
       List<RegionInfo> regionInfos = Lists.newArrayList(parent);
       MetaTableAccessor.addRegionsToMeta(connection, regionInfos, 3);
 
-      MetaTableAccessor.splitRegion(connection, parent, splitA, splitB, serverName0, 3);
+      MetaTableAccessor.splitRegion(connection, parent, -1L, splitA, splitB, serverName0, 3);
       Get get1 = new Get(splitA.getRegionName());
       Result resultA = meta.get(get1);
       Cell serverCellA = resultA.getColumnLatestCell(HConstants.CATALOG_FAMILY,

hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegionFileSystem.java

@@ -194,7 +194,7 @@ public class TestHRegionFileSystem {
 
   @Test
   public void testOnDiskRegionCreation() throws IOException {
-    Path rootDir = TEST_UTIL.getDataTestDirOnTestFS("testOnDiskRegionCreation");
+    Path rootDir = TEST_UTIL.getDataTestDirOnTestFS(name.getMethodName());
     FileSystem fs = TEST_UTIL.getTestFileSystem();
     Configuration conf = TEST_UTIL.getConfiguration();
 
@@ -226,7 +226,7 @@ public class TestHRegionFileSystem {
 
   @Test
   public void testNonIdempotentOpsWithRetries() throws IOException {
-    Path rootDir = TEST_UTIL.getDataTestDirOnTestFS("testOnDiskRegionCreation");
+    Path rootDir = TEST_UTIL.getDataTestDirOnTestFS(name.getMethodName());
     FileSystem fs = TEST_UTIL.getTestFileSystem();
     Configuration conf = TEST_UTIL.getConfiguration();
 
@@ -235,19 +235,15 @@ public class TestHRegionFileSystem {
     HRegionFileSystem regionFs = HRegionFileSystem.createRegionOnFileSystem(conf, fs, rootDir, hri);
     assertTrue(fs.exists(regionFs.getRegionDir()));
 
-    regionFs = new HRegionFileSystem(conf, new MockFileSystemForCreate(),
+    regionFs = new HRegionFileSystem(conf, new MockFileSystemForCreate(), rootDir, hri);
-        null, null);
-    // HRegionFileSystem.createRegionOnFileSystem(conf, new MockFileSystemForCreate(), rootDir,
-    // hri);
     boolean result = regionFs.createDir(new Path("/foo/bar"));
     assertTrue("Couldn't create the directory", result);
 
-
+    regionFs = new HRegionFileSystem(conf, new MockFileSystem(), rootDir, hri);
-    regionFs = new HRegionFileSystem(conf, new MockFileSystem(), null, null);
     result = regionFs.rename(new Path("/foo/bar"), new Path("/foo/bar2"));
     assertTrue("Couldn't rename the directory", result);
 
-    regionFs = new HRegionFileSystem(conf, new MockFileSystem(), null, null);
+    regionFs = new HRegionFileSystem(conf, new MockFileSystem(), rootDir, hri);
     result = regionFs.deleteDir(new Path("/foo/bar"));
     assertTrue("Couldn't delete the directory", result);
     fs.delete(rootDir, true);

hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestRegionServerMetrics.java

@@ -348,7 +348,7 @@ public class TestRegionServerMetrics {
     TEST_UTIL.getAdmin().flush(tableName);
 
     metricsRegionServer.getRegionServerWrapper().forceRecompute();
-    assertGauge("storeCount", TABLES_ON_MASTER? 1: 4);
+    assertGauge("storeCount", TABLES_ON_MASTER ? 1 : 5);
     assertGauge("storeFileCount", 1);
   }
 

hbase-server/src/test/java/org/apache/hadoop/hbase/replication/TestReplicationDroppedTables.java

@@ -20,8 +20,6 @@ package org.apache.hadoop.hbase.replication;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.fail;
 
-import java.util.ArrayList;
-import java.util.List;
 import org.apache.hadoop.hbase.HBaseClassTestRule;
 import org.apache.hadoop.hbase.HColumnDescriptor;
 import org.apache.hadoop.hbase.HConstants;
@@ -38,6 +36,7 @@ import org.apache.hadoop.hbase.client.ResultScanner;
 import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.client.Table;
 import org.apache.hadoop.hbase.testclassification.LargeTests;
+import org.apache.hadoop.hbase.testclassification.ReplicationTests;
 import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.hadoop.hbase.util.JVMClusterUtil;
 import org.junit.Before;
@@ -47,7 +46,7 @@ import org.junit.experimental.categories.Category;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-@Category(LargeTests.class)
+@Category({ ReplicationTests.class, LargeTests.class })
 public class TestReplicationDroppedTables extends TestReplicationBase {
 
   @ClassRule
@@ -56,9 +55,6 @@ public class TestReplicationDroppedTables extends TestReplicationBase {
 
   private static final Logger LOG = LoggerFactory.getLogger(TestReplicationDroppedTables.class);
 
-  /**
-   * @throws java.lang.Exception
-   */
   @Before
   public void setUp() throws Exception {
     // Starting and stopping replication can make us miss new logs,

hbase-server/src/test/java/org/apache/hadoop/hbase/replication/TestSerialReplication.java

@@ -0,0 +1,234 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hbase.replication;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.util.UUID;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.Waiter.ExplainingPredicate;
+import org.apache.hadoop.hbase.client.ColumnFamilyDescriptorBuilder;
+import org.apache.hadoop.hbase.client.Put;
+import org.apache.hadoop.hbase.client.RegionInfo;
+import org.apache.hadoop.hbase.client.Table;
+import org.apache.hadoop.hbase.client.TableDescriptorBuilder;
+import org.apache.hadoop.hbase.regionserver.HRegionServer;
+import org.apache.hadoop.hbase.testclassification.LargeTests;
+import org.apache.hadoop.hbase.testclassification.ReplicationTests;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.hbase.util.CommonFSUtils.StreamLacksCapabilityException;
+import org.apache.hadoop.hbase.wal.WAL;
+import org.apache.hadoop.hbase.wal.WAL.Entry;
+import org.apache.hadoop.hbase.wal.WALFactory;
+import org.apache.hadoop.hbase.wal.WALProvider;
+import org.junit.After;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.junit.rules.TestName;
+
+@Category({ ReplicationTests.class, LargeTests.class })
+public class TestSerialReplication {
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+    HBaseClassTestRule.forClass(TestSerialReplication.class);
+
+  private static final HBaseTestingUtility UTIL = new HBaseTestingUtility();
+
+  private static String PEER_ID = "1";
+
+  private static byte[] CF = Bytes.toBytes("CF");
+
+  private static byte[] CQ = Bytes.toBytes("CQ");
+
+  private static FileSystem FS;
+
+  private static Path LOG_DIR;
+
+  private static WALProvider.Writer WRITER;
+
+  public static final class LocalReplicationEndpoint extends BaseReplicationEndpoint {
+
+    private static final UUID PEER_UUID = UUID.randomUUID();
+
+    @Override
+    public UUID getPeerUUID() {
+      return PEER_UUID;
+    }
+
+    @Override
+    public boolean replicate(ReplicateContext replicateContext) {
+      synchronized (WRITER) {
+        try {
+          for (Entry entry : replicateContext.getEntries()) {
+            WRITER.append(entry);
+          }
+          WRITER.sync(false);
+        } catch (IOException e) {
+          throw new UncheckedIOException(e);
+        }
+      }
+      return true;
+    }
+
+    @Override
+    public void start() {
+      startAsync();
+    }
+
+    @Override
+    public void stop() {
+      stopAsync();
+    }
+
+    @Override
+    protected void doStart() {
+      notifyStarted();
+    }
+
+    @Override
+    protected void doStop() {
+      notifyStopped();
+    }
+  }
+
+  @BeforeClass
+  public static void setUpBeforeClass() throws Exception {
+    UTIL.getConfiguration().setInt("replication.source.nb.capacity", 10);
+    UTIL.startMiniCluster(3);
+    LOG_DIR = UTIL.getDataTestDirOnTestFS("replicated");
+    FS = UTIL.getTestFileSystem();
+    FS.mkdirs(LOG_DIR);
+  }
+
+  @AfterClass
+  public static void tearDownAfterClass() throws Exception {
+    UTIL.shutdownMiniCluster();
+  }
+
+  @Rule
+  public final TestName name = new TestName();
+
+  private Path logPath;
+
+  @Before
+  public void setUp() throws IOException, StreamLacksCapabilityException {
+    UTIL.ensureSomeRegionServersAvailable(3);
+    logPath = new Path(LOG_DIR, name.getMethodName());
+    WRITER = WALFactory.createWALWriter(FS, logPath, UTIL.getConfiguration());
+    // add in disable state, so later when enabling it all sources will start push together.
+    UTIL.getAdmin().addReplicationPeer(PEER_ID,
+      ReplicationPeerConfig.newBuilder().setClusterKey("127.0.0.1:2181:/hbase")
+        .setReplicationEndpointImpl(LocalReplicationEndpoint.class.getName()).build(),
+      false);
+  }
+
+  @After
+  public void tearDown() throws IOException {
+    UTIL.getAdmin().removeReplicationPeer(PEER_ID);
+    if (WRITER != null) {
+      WRITER.close();
+      WRITER = null;
+    }
+  }
+
+  @Test
+  public void testRegionMove() throws Exception {
+    TableName tableName = TableName.valueOf(name.getMethodName());
+    UTIL.getAdmin().createTable(
+      TableDescriptorBuilder.newBuilder(tableName).addColumnFamily(ColumnFamilyDescriptorBuilder
+        .newBuilder(CF).setScope(HConstants.REPLICATION_SCOPE_SERIAL).build()).build());
+    UTIL.waitTableAvailable(tableName);
+    try (Table table = UTIL.getConnection().getTable(tableName)) {
+      for (int i = 0; i < 100; i++) {
+        table.put(new Put(Bytes.toBytes(i)).addColumn(CF, CQ, Bytes.toBytes(i)));
+      }
+    }
+    RegionInfo region = UTIL.getAdmin().getRegions(tableName).get(0);
+    HRegionServer rs = UTIL.getOtherRegionServer(UTIL.getRSForFirstRegionInTable(tableName));
+    UTIL.getAdmin().move(region.getEncodedNameAsBytes(),
+      Bytes.toBytes(rs.getServerName().getServerName()));
+    UTIL.waitFor(30000, new ExplainingPredicate<Exception>() {
+
+      @Override
+      public boolean evaluate() throws Exception {
+        return !rs.getRegions(tableName).isEmpty();
+      }
+
+      @Override
+      public String explainFailure() throws Exception {
+        return region + " is still not on " + rs;
+      }
+    });
+    try (Table table = UTIL.getConnection().getTable(tableName)) {
+      for (int i = 100; i < 200; i++) {
+        table.put(new Put(Bytes.toBytes(i)).addColumn(CF, CQ, Bytes.toBytes(i)));
+      }
+    }
+    UTIL.getAdmin().enableReplicationPeer(PEER_ID);
+    UTIL.waitFor(30000, new ExplainingPredicate<Exception>() {
+
+      @Override
+      public boolean evaluate() throws Exception {
+        try (WAL.Reader reader = WALFactory.createReader(FS, logPath, UTIL.getConfiguration())) {
+          int count = 0;
+          while (reader.next() != null) {
+            count++;
+          }
+          return count >= 200;
+        } catch (IOException e) {
+          return false;
+        }
+      }
+
+      @Override
+      public String explainFailure() throws Exception {
+        return "Not enough entries replicated";
+      }
+    });
+    try (WAL.Reader reader =
+      WALFactory.createReader(UTIL.getTestFileSystem(), logPath, UTIL.getConfiguration())) {
+      long seqId = -1L;
+      int count = 0;
+      for (Entry entry;;) {
+        entry = reader.next();
+        if (entry == null) {
+          break;
+        }
+        assertTrue(
+          "Sequence id go backwards from " + seqId + " to " + entry.getKey().getSequenceId(),
+          entry.getKey().getSequenceId() >= seqId);
+        count++;
+      }
+      assertEquals(200, count);
+    }
+  }
+}

hbase-server/src/test/java/org/apache/hadoop/hbase/replication/regionserver/TestReplicationSourceManager.java

@@ -321,7 +321,7 @@ public abstract class TestReplicationSourceManager {
     wal.rollWriter();
 
     manager.logPositionAndCleanOldLogs(manager.getSources().get(0).getCurrentPath(),
-        "1", 0, false);
+        "1", 0, null, false);
 
     wal.append(hri,
         new WALKeyImpl(hri.getEncodedNameAsBytes(), test, System.currentTimeMillis(), mvcc, scopes),

hbase-server/src/test/java/org/apache/hadoop/hbase/replication/regionserver/TestSerialReplicationChecker.java

@@ -0,0 +1,176 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hbase.replication.regionserver;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import java.io.IOException;
+import org.apache.hadoop.hbase.Cell;
+import org.apache.hadoop.hbase.Cell.Type;
+import org.apache.hadoop.hbase.CellBuilderFactory;
+import org.apache.hadoop.hbase.CellBuilderType;
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.Server;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.client.Put;
+import org.apache.hadoop.hbase.client.RegionInfo;
+import org.apache.hadoop.hbase.client.RegionInfoBuilder;
+import org.apache.hadoop.hbase.client.Table;
+import org.apache.hadoop.hbase.master.RegionState;
+import org.apache.hadoop.hbase.replication.ReplicationException;
+import org.apache.hadoop.hbase.replication.ReplicationQueueStorage;
+import org.apache.hadoop.hbase.replication.ReplicationStorageFactory;
+import org.apache.hadoop.hbase.testclassification.MediumTests;
+import org.apache.hadoop.hbase.testclassification.ReplicationTests;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
+import org.apache.hadoop.hbase.wal.WAL.Entry;
+import org.apache.hadoop.hbase.wal.WALKeyImpl;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.junit.rules.TestName;
+
+import org.apache.hbase.thirdparty.com.google.common.collect.ImmutableMap;
+
+@Category({ ReplicationTests.class, MediumTests.class })
+public class TestSerialReplicationChecker {
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+    HBaseClassTestRule.forClass(TestSerialReplicationChecker.class);
+
+  private static final HBaseTestingUtility UTIL = new HBaseTestingUtility();
+
+  private static String PEER_ID = "1";
+
+  private static ReplicationQueueStorage QUEUE_STORAGE;
+
+  private static String WAL_FILE_NAME = "test.wal";
+
+  private SerialReplicationChecker checker;
+
+  @Rule
+  public final TestName name = new TestName();
+
+  private TableName tableName;
+
+  @BeforeClass
+  public static void setUpBeforeClass() throws Exception {
+    UTIL.startMiniCluster(1);
+    QUEUE_STORAGE = ReplicationStorageFactory.getReplicationQueueStorage(UTIL.getZooKeeperWatcher(),
+      UTIL.getConfiguration());
+    QUEUE_STORAGE.addWAL(UTIL.getMiniHBaseCluster().getRegionServer(0).getServerName(), PEER_ID,
+      WAL_FILE_NAME);
+  }
+
+  @AfterClass
+  public static void tearDownAfterClass() throws Exception {
+    UTIL.shutdownMiniCluster();
+  }
+
+  @Before
+  public void setUp() throws IOException {
+    ReplicationSource source = mock(ReplicationSource.class);
+    when(source.getPeerId()).thenReturn(PEER_ID);
+    when(source.getQueueStorage()).thenReturn(QUEUE_STORAGE);
+    Server server = mock(Server.class);
+    when(server.getConnection()).thenReturn(UTIL.getConnection());
+    when(source.getServer()).thenReturn(server);
+    checker = new SerialReplicationChecker(UTIL.getConfiguration(), source);
+    tableName = TableName.valueOf(name.getMethodName());
+  }
+
+  private Entry createEntry(RegionInfo region, long seqId) {
+    WALKeyImpl key = mock(WALKeyImpl.class);
+    when(key.getTableName()).thenReturn(tableName);
+    when(key.getEncodedRegionName()).thenReturn(region.getEncodedNameAsBytes());
+    when(key.getSequenceId()).thenReturn(seqId);
+    Entry entry = mock(Entry.class);
+    when(entry.getKey()).thenReturn(key);
+    return entry;
+  }
+
+  private Cell createCell(RegionInfo region) {
+    return CellBuilderFactory.create(CellBuilderType.DEEP_COPY).setRow(region.getStartKey())
+      .setType(Type.Put).build();
+  }
+
+  @Test
+  public void testNoBarrierCanPush() throws IOException {
+    RegionInfo region = RegionInfoBuilder.newBuilder(tableName).build();
+    assertTrue(checker.canPush(createEntry(region, 100), createCell(region)));
+  }
+
+  private void addStateAndBarrier(RegionInfo region, RegionState.State state, long... barriers)
+      throws IOException {
+    Put put = new Put(region.getRegionName(), EnvironmentEdgeManager.currentTime());
+    put.addColumn(HConstants.CATALOG_FAMILY, HConstants.STATE_QUALIFIER,
+      Bytes.toBytes(state.name()));
+    for (int i = 0; i < barriers.length; i++) {
+      put.addColumn(HConstants.REPLICATION_BARRIER_FAMILY, HConstants.SEQNUM_QUALIFIER,
+        put.getTimeStamp() - i, Bytes.toBytes(barriers[i]));
+    }
+    try (Table table = UTIL.getConnection().getTable(TableName.META_TABLE_NAME)) {
+      table.put(put);
+    }
+  }
+
+  private void setState(RegionInfo region, RegionState.State state) throws IOException {
+    Put put = new Put(region.getRegionName(), EnvironmentEdgeManager.currentTime());
+    put.addColumn(HConstants.CATALOG_FAMILY, HConstants.STATE_QUALIFIER,
+      Bytes.toBytes(state.name()));
+    try (Table table = UTIL.getConnection().getTable(TableName.META_TABLE_NAME)) {
+      table.put(put);
+    }
+  }
+
+  private void updatePushedSeqId(RegionInfo region, long seqId) throws ReplicationException {
+    QUEUE_STORAGE.setWALPosition(UTIL.getMiniHBaseCluster().getRegionServer(0).getServerName(),
+      PEER_ID, WAL_FILE_NAME, 10, ImmutableMap.of(region.getEncodedName(), seqId));
+  }
+
+  @Test
+  public void testLastRegionAndOpeningCanNotPush() throws IOException, ReplicationException {
+    RegionInfo region = RegionInfoBuilder.newBuilder(tableName).build();
+    addStateAndBarrier(region, RegionState.State.OPEN, 10);
+    Cell cell = createCell(region);
+    // can push since we are in the first range
+    assertTrue(checker.canPush(createEntry(region, 100), cell));
+    setState(region, RegionState.State.OPENING);
+    // can not push since we are in the last range and the state is OPENING
+    assertFalse(checker.canPush(createEntry(region, 102), cell));
+    addStateAndBarrier(region, RegionState.State.OPEN, 50);
+    // can not push since the previous range has not been finished yet
+    assertFalse(checker.canPush(createEntry(region, 102), cell));
+    updatePushedSeqId(region, 49);
+    // can push since the previous range has been finished
+    assertTrue(checker.canPush(createEntry(region, 102), cell));
+    setState(region, RegionState.State.OPENING);
+    assertFalse(checker.canPush(createEntry(region, 104), cell));
+  }
+}

hbase-server/src/test/java/org/apache/hadoop/hbase/replication/regionserver/TestWALEntryStream.java

@@ -21,13 +21,13 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
 import static org.mockito.Mockito.when;
 
 import java.io.IOException;
 import java.util.NavigableMap;
-import java.util.NoSuchElementException;
 import java.util.OptionalLong;
 import java.util.TreeMap;
 import java.util.concurrent.PriorityBlockingQueue;
@@ -40,13 +40,13 @@ import org.apache.hadoop.hbase.HBaseClassTestRule;
 import org.apache.hadoop.hbase.HBaseTestingUtility;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.KeyValue;
+import org.apache.hadoop.hbase.Server;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.client.RegionInfo;
 import org.apache.hadoop.hbase.client.RegionInfoBuilder;
 import org.apache.hadoop.hbase.regionserver.MultiVersionConcurrencyControl;
 import org.apache.hadoop.hbase.regionserver.wal.WALActionsListener;
 import org.apache.hadoop.hbase.replication.WALEntryFilter;
-import org.apache.hadoop.hbase.replication.regionserver.ReplicationSourceWALReader.WALEntryBatch;
 import org.apache.hadoop.hbase.testclassification.LargeTests;
 import org.apache.hadoop.hbase.testclassification.ReplicationTests;
 import org.apache.hadoop.hbase.util.Bytes;
@@ -180,15 +180,12 @@ public class TestWALEntryStream {
         new WALEntryStream(walQueue, fs, conf, 0, log, null, new MetricsSource("1"))) {
       // There's one edit in the log, read it. Reading past it needs to throw exception
       assertTrue(entryStream.hasNext());
-      WAL.Entry entry = entryStream.next();
+      WAL.Entry entry = entryStream.peek();
+      assertSame(entry, entryStream.next());
       assertNotNull(entry);
       assertFalse(entryStream.hasNext());
-      try {
+      assertNull(entryStream.peek());
-        entry = entryStream.next();
+      assertNull(entryStream.next());
-        fail();
-      } catch (NoSuchElementException e) {
-        // expected
-      }
       oldPos = entryStream.getPosition();
     }
 
@@ -346,10 +343,12 @@ public class TestWALEntryStream {
     // start up a batcher
     ReplicationSourceManager mockSourceManager = Mockito.mock(ReplicationSourceManager.class);
     when(mockSourceManager.getTotalBufferUsed()).thenReturn(new AtomicLong(0));
+    Server mockServer= Mockito.mock(Server.class);
     ReplicationSource source = Mockito.mock(ReplicationSource.class);
     when(source.getSourceManager()).thenReturn(mockSourceManager);
     when(source.getSourceMetrics()).thenReturn(new MetricsSource("1"));
     when(source.getWALFileLengthProvider()).thenReturn(log);
+    when(source.getServer()).thenReturn(mockServer);
     ReplicationSourceWALReader batcher = new ReplicationSourceWALReader(fs, conf,
         walQueue, 0, getDummyFilter(), source);
     Path walPath = walQueue.peek();