HBASE-22707 [HBCK2] MasterRpcServices assigns method should try to reload regions from meta if the passed regions isn't found under AssignmentManager RegionsStateStore

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

@@ -59,6 +59,8 @@ import org.apache.hadoop.hbase.client.coprocessor.Batch;
 import org.apache.hadoop.hbase.exceptions.DeserializationException;
 import org.apache.hadoop.hbase.filter.Filter;
 import org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter;
+import org.apache.hadoop.hbase.filter.RowFilter;
+import org.apache.hadoop.hbase.filter.SubstringComparator;
 import org.apache.hadoop.hbase.ipc.CoprocessorRpcUtils;
 import org.apache.hadoop.hbase.ipc.ServerRpcController;
 import org.apache.hadoop.hbase.master.RegionState;
@@ -372,6 +374,25 @@ public class MetaTableAccessor {
     return get(getMetaHTable(connection), get);
   }
 
+  /**
+   * Scans META table for a row whose key contains the specified <B>regionEncodedName</B>,
+   * returning a single related <code>Result</code> instance if any row is found, null otherwise.
+   *
+   * @param connection the connection to query META table.
+   * @param regionEncodedName the region encoded name to look for at META.
+   * @return <code>Result</code> instance with the row related info in META, null otherwise.
+   * @throws IOException if any errors occur while querying META.
+   */
+  public static Result scanByRegionEncodedName(Connection connection,
+      String regionEncodedName) throws IOException {
+    RowFilter rowFilter = new RowFilter(CompareOperator.EQUAL,
+      new SubstringComparator(regionEncodedName));
+    Scan scan = getMetaScan(connection, 1);
+    scan.setFilter(rowFilter);
+    ResultScanner resultScanner = getMetaHTable(connection).getScanner(scan);
+    return resultScanner.next();
+  }
+
   /**
    * Get regions from the merge qualifier of the specified merged region
    * @return null if it doesn't contain merge qualifier, else two merge regions

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

@@ -2383,7 +2383,9 @@ public class MasterRpcServices extends RSRpcServices
         String encodedRegionName = Bytes.toString(rs.getValue().toByteArray());
         RegionState regionState = this.master.getAssignmentManager().getRegionStates().
             getRegionState(encodedRegionName);
-        ri = regionState == null? null: regionState.getRegion();
+        ri = regionState == null ?
+          this.master.getAssignmentManager().loadRegionFromMeta(encodedRegionName) :
+            regionState.getRegion();
         break;
       default:
         break;

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

@@ -1377,9 +1377,15 @@ public class AssignmentManager {
     }
   }
 
-  private void loadMeta() throws IOException {
-    // TODO: use a thread pool
-    regionStateStore.visitMeta(new RegionStateStore.RegionStateVisitor() {
+  /* AM internal RegionStateStore.RegionStateVisitor implementation. To be used when
+   * scanning META table for region rows, using RegionStateStore utility methods. RegionStateStore
+   * methods will convert Result into proper RegionInfo instances, but those would still need to be
+   * added into AssignmentManager.regionStates in-memory cache.
+   * RegionMetaLoadingVisitor.visitRegionState method provides the logic for adding RegionInfo
+   * instances as loaded from latest META scan into AssignmentManager.regionStates.
+   */
+  private class RegionMetaLoadingVisitor implements RegionStateStore.RegionStateVisitor  {
+
     @Override
     public void visitRegionState(Result result, final RegionInfo regionInfo, final State state,
       final ServerName regionLocation, final ServerName lastHost, final long openSeqNum) {
@@ -1420,8 +1426,33 @@ public class AssignmentManager {
         regionNode.getProcedure().stateLoaded(AssignmentManager.this, regionNode);
       }
     }
-    });
+  };
 
+  /**
+   * Query META if the given <code>RegionInfo</code> exists, adding to
+   * <code>AssignmentManager.regionStateStore</code> cache if the region is found in META.
+   * @param regionEncodedName encoded name for the region to be loaded from META into
+   *                          <code>AssignmentManager.regionStateStore</code> cache
+   * @return <code>RegionInfo</code> instance for the given region if it is present in META
+   *          and got successfully loaded into <code>AssignmentManager.regionStateStore</code>
+   *          cache, <b>null</b> otherwise.
+   * @throws UnknownRegionException if any errors occur while querying meta.
+   */
+  public RegionInfo loadRegionFromMeta(String regionEncodedName) throws UnknownRegionException {
+    try {
+      RegionMetaLoadingVisitor visitor = new RegionMetaLoadingVisitor();
+      regionStateStore.visitMetaForRegion(regionEncodedName, visitor);
+      return regionStates.getRegionState(regionEncodedName) == null ? null :
+        regionStates.getRegionState(regionEncodedName).getRegion();
+    } catch(IOException e) {
+      LOG.error("Error trying to load region {} from META", regionEncodedName, e);
+      throw new UnknownRegionException("Error while trying load region from meta");
+    }
+  }
+
+  private void loadMeta() throws IOException {
+    // TODO: use a thread pool
+    regionStateStore.visitMeta(new RegionMetaLoadingVisitor());
     // every assignment is blocked until meta is loaded.
     wakeMetaLoadedEvent();
   }

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

@@ -96,6 +96,23 @@ public class RegionStateStore {
     });
   }
 
+  /**
+   * Queries META table for the passed region encoded name,
+   * delegating action upon results to the <code>RegionStateVisitor</code>
+   * passed as second parameter.
+   * @param regionEncodedName encoded name for the Region we want to query META for.
+   * @param visitor The <code>RegionStateVisitor</code> instance to react over the query results.
+   * @throws IOException If some error occurs while querying META or parsing results.
+   */
+  public void visitMetaForRegion(final String regionEncodedName, final RegionStateVisitor visitor)
+      throws IOException {
+    Result result = MetaTableAccessor.
+      scanByRegionEncodedName(master.getConnection(), regionEncodedName);
+    if (result != null) {
+      visitMetaEntry(visitor, result);
+    }
+  }
+
   private void visitMetaEntry(final RegionStateVisitor visitor, final Result result)
       throws IOException {
     final RegionLocations rl = MetaTableAccessor.getRegionLocations(result);

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

@@ -47,6 +47,7 @@ import org.apache.hadoop.hbase.ipc.DelegatingRpcScheduler;
 import org.apache.hadoop.hbase.ipc.PriorityFunction;
 import org.apache.hadoop.hbase.ipc.RpcScheduler;
 import org.apache.hadoop.hbase.master.HMaster;
+import org.apache.hadoop.hbase.regionserver.HRegion;
 import org.apache.hadoop.hbase.regionserver.HRegionServer;
 import org.apache.hadoop.hbase.regionserver.RSRpcServices;
 import org.apache.hadoop.hbase.regionserver.SimpleRpcSchedulerFactory;
@@ -866,7 +867,8 @@ public class TestMetaTableAccessor {
       List<RegionInfo> regionInfos = Lists.newArrayList(parent);
       MetaTableAccessor.addRegionsToMeta(connection, regionInfos, 3);
 
-      MetaTableAccessor.splitRegion(connection, parent, -1L, 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,
@@ -890,5 +892,28 @@ public class TestMetaTableAccessor {
       }
     }
   }
+
+  @Test
+  public void testScanByRegionEncodedNameExistingRegion() throws Exception {
+    final TableName tableName = TableName.valueOf("testScanByRegionEncodedNameExistingRegion");
+    UTIL.createTable(tableName, "cf");
+    final List<HRegion> regions = UTIL.getHBaseCluster().getRegions(tableName);
+    final String encodedName = regions.get(0).getRegionInfo().getEncodedName();
+    final Result result = MetaTableAccessor.scanByRegionEncodedName(UTIL.getConnection(),
+      encodedName);
+    assertNotNull(result);
+    assertTrue(result.advance());
+    final String resultingRowKey = CellUtil.getCellKeyAsString(result.current());
+    assertTrue(resultingRowKey.contains(encodedName));
+    UTIL.deleteTable(tableName);
+  }
+
+  @Test
+  public void testScanByRegionEncodedNameNonExistingRegion() throws Exception {
+    final String encodedName = "nonexistingregion";
+    final Result result = MetaTableAccessor.scanByRegionEncodedName(UTIL.getConnection(),
+      encodedName);
+    assertNull(result);
+  }
 }
 

hbase-server/src/test/java/org/apache/hadoop/hbase/master/assignment/TestAssignmentManager.java

@@ -18,12 +18,14 @@
 package org.apache.hadoop.hbase.master.assignment;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 import org.apache.hadoop.hbase.HBaseClassTestRule;
 import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.MetaTableAccessor;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.client.RegionInfo;
 import org.apache.hadoop.hbase.client.RegionInfoBuilder;
@@ -285,4 +287,43 @@ public class TestAssignmentManager extends TestAssignmentManagerBase {
     assertEquals(reopenFailedCount, reopenProcMetrics.getFailedCounter().getCount());
     assertCloseThenOpen();
   }
+
+  @Test
+  public void testLoadRegionFromMetaAfterRegionManuallyAdded() throws Exception {
+    try {
+      this.util.startMiniCluster();
+      final AssignmentManager am = this.util.getHBaseCluster().getMaster().getAssignmentManager();
+      final TableName tableName = TableName.
+        valueOf("testLoadRegionFromMetaAfterRegionManuallyAdded");
+      this.util.createTable(tableName, "f");
+      RegionInfo hri = createRegionInfo(tableName, 1);
+      assertNull("RegionInfo was just instantiated by the test, but "
+        + "shouldn't be in AM regionStates yet.", am.getRegionStates().getRegionState(hri));
+      MetaTableAccessor.addRegionToMeta(this.util.getConnection(), hri);
+      assertNull("RegionInfo was manually added in META, but "
+        + "shouldn't be in AM regionStates yet.", am.getRegionStates().getRegionState(hri));
+      hri = am.loadRegionFromMeta(hri.getEncodedName());
+      assertEquals(hri.getEncodedName(),
+        am.getRegionStates().getRegionState(hri).getRegion().getEncodedName());
+    }finally {
+      this.util.killMiniHBaseCluster();
+    }
+  }
+
+  @Test
+  public void testLoadRegionFromMetaRegionNotInMeta() throws Exception {
+    try {
+      this.util.startMiniCluster();
+      final AssignmentManager am = this.util.getHBaseCluster().getMaster().getAssignmentManager();
+      final TableName tableName = TableName.valueOf("testLoadRegionFromMetaRegionNotInMeta");
+      this.util.createTable(tableName, "f");
+      final RegionInfo hri = createRegionInfo(tableName, 1);
+      assertNull("RegionInfo was just instantiated by the test, but "
+        + "shouldn't be in AM regionStates yet.", am.getRegionStates().getRegionState(hri));
+      assertNull("RegionInfo was never added in META, should had returned null.",
+        am.loadRegionFromMeta(hri.getEncodedName()));
+    }finally {
+      this.util.killMiniHBaseCluster();
+    }
+  }
 }

hbase-server/src/test/java/org/apache/hadoop/hbase/master/assignment/TestRegionStateStore.java

@@ -0,0 +1,103 @@
+/**
+ * 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.master.assignment;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.ServerName;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.client.RegionInfo;
+import org.apache.hadoop.hbase.client.Result;
+import org.apache.hadoop.hbase.master.RegionState;
+import org.apache.hadoop.hbase.regionserver.HRegion;
+import org.apache.hadoop.hbase.testclassification.MasterTests;
+import org.apache.hadoop.hbase.testclassification.MediumTests;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+@Category({ MasterTests.class, MediumTests.class })
+public class TestRegionStateStore {
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+    HBaseClassTestRule.forClass(TestRegionStateStore.class);
+
+  private static final Logger LOG = LoggerFactory.getLogger(TestRegionStateStore.class);
+
+  protected HBaseTestingUtility util;
+
+  @Before
+  public void setup() throws Exception {
+    util = new HBaseTestingUtility();
+    util.startMiniCluster();
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    util.shutdownMiniCluster();
+  }
+
+  @Test
+  public void testVisitMetaForRegionExistingRegion() throws Exception {
+    final TableName tableName = TableName.valueOf("testVisitMetaForRegion");
+    util.createTable(tableName, "cf");
+    final List<HRegion> regions = util.getHBaseCluster().getRegions(tableName);
+    final String encodedName = regions.get(0).getRegionInfo().getEncodedName();
+    final RegionStateStore regionStateStore = util.getHBaseCluster().getMaster().
+      getAssignmentManager().getRegionStateStore();
+    final AtomicBoolean visitorCalled = new AtomicBoolean(false);
+    regionStateStore.visitMetaForRegion(encodedName, new RegionStateStore.RegionStateVisitor() {
+      @Override
+      public void visitRegionState(Result result, RegionInfo regionInfo, RegionState.State state,
+        ServerName regionLocation, ServerName lastHost, long openSeqNum) {
+        assertEquals(encodedName, regionInfo.getEncodedName());
+        visitorCalled.set(true);
+      }
+    });
+    assertTrue("Visitor has not been called.", visitorCalled.get());
+  }
+
+  @Test
+  public void testVisitMetaForRegionNonExistingRegion() throws Exception {
+    final String encodedName = "fakeencodedregionname";
+    final RegionStateStore regionStateStore = util.getHBaseCluster().getMaster().
+      getAssignmentManager().getRegionStateStore();
+    final AtomicBoolean visitorCalled = new AtomicBoolean(false);
+    regionStateStore.visitMetaForRegion(encodedName, new RegionStateStore.RegionStateVisitor() {
+      @Override
+      public void visitRegionState(Result result, RegionInfo regionInfo, RegionState.State state,
+        ServerName regionLocation, ServerName lastHost, long openSeqNum) {
+        visitorCalled.set(true);
+      }
+    });
+    assertFalse("Visitor has been called, but it shouldn't.", visitorCalled.get());
+  }
+
+}