Revert "Revert "HBASE-16698 Performance issue: handlers stuck waiting for CountDownLatch inside WALKey#getWriteEntry under high writing workload""

This reverts commit 13baf4d37a.

This is a revert of a revert.

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

@@ -64,6 +64,7 @@ import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.LongAdder;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 import org.apache.commons.logging.Log;
@@ -197,6 +198,10 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
   public static final String LOAD_CFS_ON_DEMAND_CONFIG_KEY =
     "hbase.hregion.scan.loadColumnFamiliesOnDemand";
 
+  /** Config key for using mvcc pre-assign feature for put */
+  public static final String HREGION_MVCC_PRE_ASSIGN = "hbase.hregion.mvcc.preassign";
+  public static final boolean DEFAULT_HREGION_MVCC_PRE_ASSIGN = true;
+
   /**
    * This is the global default value for durability. All tables/mutations not
    * defining a durability or using USE_DEFAULT will default to this value.
@@ -585,6 +590,9 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
   // that has non-default scope
   private final NavigableMap<byte[], Integer> replicationScope = new TreeMap<byte[], Integer>(
       Bytes.BYTES_COMPARATOR);
+  // flag and lock for MVCC preassign
+  private final boolean mvccPreAssign;
+  private final ReentrantLock preAssignMvccLock;
 
   /**
    * HRegion constructor. This constructor should only be used for testing and
@@ -744,6 +752,14 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
           false :
           conf.getBoolean(HConstants.ENABLE_CLIENT_BACKPRESSURE,
               HConstants.DEFAULT_ENABLE_CLIENT_BACKPRESSURE);
+
+    // get mvcc pre-assign flag and lock
+    this.mvccPreAssign = conf.getBoolean(HREGION_MVCC_PRE_ASSIGN, DEFAULT_HREGION_MVCC_PRE_ASSIGN);
+    if (this.mvccPreAssign) {
+      this.preAssignMvccLock = new ReentrantLock();
+    } else {
+      this.preAssignMvccLock = null;
+    }
   }
 
   void setHTableSpecificConf() {
@@ -3214,36 +3230,61 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
       // STEP 4. Append the final edit to WAL and sync.
       Mutation mutation = batchOp.getMutation(firstIndex);
       WALKey walKey = null;
+      long txid;
       if (replay) {
         // use wal key from the original
         walKey = new ReplayHLogKey(this.getRegionInfo().getEncodedNameAsBytes(),
           this.htableDescriptor.getTableName(), WALKey.NO_SEQUENCE_ID, now,
           mutation.getClusterIds(), currentNonceGroup, currentNonce, mvcc);
         walKey.setOrigLogSeqNum(batchOp.getReplaySequenceId());
-      }
-      // Not sure what is going on here when replay is going on... does the below append get
-      // called for replayed edits? Am afraid to change it without test.
         if (!walEdit.isEmpty()) {
-        if (!replay) {
+          txid = this.wal.append(this.getRegionInfo(), walKey, walEdit, true);
+          if (txid != 0) {
+            sync(txid, durability);
+          }
+        }
+      } else {
+        try {
+          if (!walEdit.isEmpty()) {
+            try {
+              if (this.mvccPreAssign) {
+                preAssignMvccLock.lock();
+                writeEntry = mvcc.begin();
+              }
               // we use HLogKey here instead of WALKey directly to support legacy coprocessors.
               walKey = new HLogKey(this.getRegionInfo().getEncodedNameAsBytes(),
                   this.htableDescriptor.getTableName(), WALKey.NO_SEQUENCE_ID, now,
                   mutation.getClusterIds(), currentNonceGroup, currentNonce, mvcc,
                   this.getReplicationScope());
+              if (this.mvccPreAssign) {
+                walKey.setPreAssignedWriteEntry(writeEntry);
               }
               // TODO: Use the doAppend methods below... complicated by the replay stuff above.
-        try {
+              txid = this.wal.append(this.getRegionInfo(), walKey, walEdit, true);
-          long txid = this.wal.append(this.getRegionInfo(), walKey,
+            } finally {
-              walEdit, true);
+              if (mvccPreAssign) {
-          if (txid != 0) sync(txid, durability);
+                preAssignMvccLock.unlock();
+              }
+            }
+            if (txid != 0) {
+              sync(txid, durability);
+            }
+            if (writeEntry == null) {
+              // if MVCC not preassigned, wait here until assigned
               writeEntry = walKey.getWriteEntry();
+            }
+          }
         } catch (IOException ioe) {
-          if (walKey != null) mvcc.complete(walKey.getWriteEntry());
+          if (walKey != null && writeEntry == null) {
+            // the writeEntry is not preassigned and error occurred during append or sync
+            mvcc.complete(walKey.getWriteEntry());
+          }
           throw ioe;
         }
       }
       if (walKey == null) {
-        // If no walKey, then skipping WAL or some such. Being an mvcc transaction so sequenceid.
+        // If no walKey, then not in replay and skipping WAL or some such. Begin an MVCC transaction
+        // to get sequence id.
         writeEntry = mvcc.begin();
       }
 
@@ -3266,7 +3307,9 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
       // STEP 6. Complete mvcc.
       if (replay) {
         this.mvcc.advanceTo(batchOp.getReplaySequenceId());
-      } else if (writeEntry != null/*Can be null if in replay mode*/) {
+      } else {
+        // writeEntry won't be empty if not in replay mode
+        assert writeEntry != null;
         mvcc.completeAndWait(writeEntry);
         writeEntry = null;
       }
@@ -7594,9 +7637,9 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver, Regi
   public static final long FIXED_OVERHEAD = ClassSize.align(
       ClassSize.OBJECT +
       ClassSize.ARRAY +
-      49 * ClassSize.REFERENCE + 2 * Bytes.SIZEOF_INT +
+      50 * ClassSize.REFERENCE + 2 * Bytes.SIZEOF_INT +
       (14 * Bytes.SIZEOF_LONG) +
-      5 * Bytes.SIZEOF_BOOLEAN);
+      6 * Bytes.SIZEOF_BOOLEAN);
 
   // woefully out of date - currently missing:
   // 1 x HashMap - coprocessorServiceHandlers

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

@@ -112,11 +112,16 @@ class FSWALEntry extends Entry {
     }
     stamped = true;
     long regionSequenceId = WALKey.NO_SEQUENCE_ID;
-    MultiVersionConcurrencyControl mvcc = getKey().getMvcc();
+    WALKey key = getKey();
-    MultiVersionConcurrencyControl.WriteEntry we = null;
+    MultiVersionConcurrencyControl.WriteEntry we = key.getPreAssignedWriteEntry();
-
+    boolean preAssigned = (we != null);
+    if (!preAssigned) {
+      MultiVersionConcurrencyControl mvcc = key.getMvcc();
       if (mvcc != null) {
         we = mvcc.begin();
+      }
+    }
+    if (we != null) {
       regionSequenceId = we.getWriteNumber();
     }
 
@@ -125,7 +130,9 @@ class FSWALEntry extends Entry {
         CellUtil.setSequenceId(c, regionSequenceId);
       }
     }
-    getKey().setWriteEntry(we);
+    if (!preAssigned) {
+      key.setWriteEntry(we);
+    }
     return regionSequenceId;
   }
 

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

@@ -42,6 +42,7 @@ import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos.FamilyScope;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.WALProtos.ScopeType;
 import org.apache.hadoop.hbase.regionserver.MultiVersionConcurrencyControl;
+import org.apache.hadoop.hbase.regionserver.MultiVersionConcurrencyControl.WriteEntry;
 import org.apache.hadoop.hbase.regionserver.SequenceId;
 // imports for things that haven't moved from regionserver.wal yet.
 import org.apache.hadoop.hbase.regionserver.wal.CompressionContext;
@@ -92,6 +93,10 @@ public class WALKey implements SequenceId, Comparable<WALKey> {
    */
   @InterfaceAudience.Private // For internal use only.
   public MultiVersionConcurrencyControl.WriteEntry getWriteEntry() throws InterruptedIOException {
+    if (this.preAssignedWriteEntry != null) {
+      // don't wait for seqNumAssignedLatch if writeEntry is preassigned
+      return this.preAssignedWriteEntry;
+    }
     try {
       this.sequenceIdAssignedLatch.await();
     } catch (InterruptedException ie) {
@@ -203,6 +208,7 @@ public class WALKey implements SequenceId, Comparable<WALKey> {
    * Set in a way visible to multiple threads; e.g. synchronized getter/setters.
    */
   private MultiVersionConcurrencyControl.WriteEntry writeEntry;
+  private MultiVersionConcurrencyControl.WriteEntry preAssignedWriteEntry = null;
   public static final List<UUID> EMPTY_UUIDS = Collections.unmodifiableList(new ArrayList<UUID>());
 
   // visible for deprecated HLogKey
@@ -731,4 +737,24 @@ public class WALKey implements SequenceId, Comparable<WALKey> {
       this.origLogSeqNum = walKey.getOrigSequenceNumber();
     }
   }
+
+  /**
+   * @return The preassigned writeEntry, if any
+   */
+  @InterfaceAudience.Private // For internal use only.
+  public MultiVersionConcurrencyControl.WriteEntry getPreAssignedWriteEntry() {
+    return this.preAssignedWriteEntry;
+  }
+
+  /**
+   * Preassign writeEntry
+   * @param writeEntry the entry to assign
+   */
+  @InterfaceAudience.Private // For internal use only.
+  public void setPreAssignedWriteEntry(WriteEntry writeEntry) {
+    if (writeEntry != null) {
+      this.preAssignedWriteEntry = writeEntry;
+      this.sequenceId = writeEntry.getWriteNumber();
+    }
+  }
 }

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

@@ -6290,8 +6290,11 @@ public class TestHRegion {
         @Override
         public Long answer(InvocationOnMock invocation) throws Throwable {
           WALKey key = invocation.getArgumentAt(1, WALKey.class);
-          MultiVersionConcurrencyControl.WriteEntry we = key.getMvcc().begin();
+          MultiVersionConcurrencyControl.WriteEntry we = key.getPreAssignedWriteEntry();
+          if (we == null) {
+            we = key.getMvcc().begin();
             key.setWriteEntry(we);
+          }
           return 1L;
         }