HBASE-26649 Support meta replica LoadBalance mode for RegionLocator#getAllRegionLocations() (#4044)

Signed-off-by: Duo Zhang <zhangduo@apache.org>

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

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.apache.hadoop.hbase.client;
+package org.apache.hadoop.hbase;
 
 import org.apache.yetus.audience.InterfaceAudience;
 
@@ -33,7 +33,7 @@ import org.apache.yetus.audience.InterfaceAudience;
  * </ol>
  */
 @InterfaceAudience.Private
-enum CatalogReplicaMode {
+public enum CatalogReplicaMode {
   NONE {
     @Override
     public String toString() {

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

@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.hbase;
 
+import static org.apache.hadoop.hbase.client.RegionLocator.LOCATOR_META_REPLICAS_MODE;
 import static org.apache.hadoop.hbase.util.FutureUtils.addListener;
 
 import java.io.Closeable;
@@ -26,6 +27,7 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.stream.Collectors;
 import org.apache.hadoop.hbase.client.AdvancedScanResultConsumer;
 import org.apache.hadoop.hbase.client.AsyncTable;
@@ -416,10 +418,40 @@ public final class ClientMetaTableAccessor {
     Scan scan = new Scan();
     int scannerCaching = metaTable.getConfiguration().getInt(HConstants.HBASE_META_SCANNER_CACHING,
       HConstants.DEFAULT_HBASE_META_SCANNER_CACHING);
-    if (metaTable.getConfiguration().getBoolean(HConstants.USE_META_REPLICAS,
+    // Get the region locator's meta replica mode.
-      HConstants.DEFAULT_USE_META_REPLICAS)) {
+    CatalogReplicaMode metaReplicaMode = CatalogReplicaMode.fromString(metaTable.getConfiguration()
-      scan.setConsistency(Consistency.TIMELINE);
+      .get(LOCATOR_META_REPLICAS_MODE, CatalogReplicaMode.NONE.toString()));
+
+    switch (metaReplicaMode) {
+      case LOAD_BALANCE:
+        int numOfReplicas = 1;
+        try {
+          numOfReplicas = metaTable.getDescriptor().get().getRegionReplication();
+        } catch (Exception e) {
+          LOG.warn("Failed to get region replication for meta table");
+        }
+        if (numOfReplicas > 1) {
+          int replicaId = ThreadLocalRandom.current().nextInt(numOfReplicas);
+
+          // When the replicaId is 0, do not set to Consistency.TIMELINE
+          if (replicaId > 0) {
+            scan.setReplicaId(replicaId);
+            scan.setConsistency(Consistency.TIMELINE);
+          }
+        }
+        break;
+      case NONE:
+        // If user does not configure LOCATOR_META_REPLICAS_MODE, let's check the legacy config.
+        if (metaTable.getConfiguration().getBoolean(HConstants.USE_META_REPLICAS,
+          HConstants.DEFAULT_USE_META_REPLICAS)) {
+          scan.setConsistency(Consistency.TIMELINE);
+        }
+        break;
+
+      default:
+        // Do nothing
     }
+
     if (rowUpperLimit <= scannerCaching) {
       scan.setLimit(rowUpperLimit);
     }

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

@@ -50,6 +50,7 @@ import java.util.concurrent.ConcurrentSkipListMap;
 import java.util.concurrent.TimeUnit;
 import org.apache.commons.lang3.ObjectUtils;
 import org.apache.hadoop.hbase.CatalogFamilyFormat;
+import org.apache.hadoop.hbase.CatalogReplicaMode;
 import org.apache.hadoop.hbase.HBaseIOException;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.HRegionLocation;

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestAsyncNonMetaRegionLocator.java

@@ -36,6 +36,7 @@ import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.stream.IntStream;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.CatalogReplicaMode;
 import org.apache.hadoop.hbase.HBaseClassTestRule;
 import org.apache.hadoop.hbase.HBaseTestingUtil;
 import org.apache.hadoop.hbase.HRegionLocation;

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

@@ -43,6 +43,7 @@ import org.apache.hadoop.hbase.client.Connection;
 import org.apache.hadoop.hbase.client.ConnectionFactory;
 import org.apache.hadoop.hbase.client.Get;
 import org.apache.hadoop.hbase.client.RegionInfo;
+import org.apache.hadoop.hbase.client.RegionLocator;
 import org.apache.hadoop.hbase.client.Result;
 import org.apache.hadoop.hbase.client.Scan;
 import org.apache.hadoop.hbase.client.Table;
@@ -385,6 +386,12 @@ public class TestMetaRegionReplicaReplication {
     }
   }
 
+  private void PrimaryIncreaseReplicaIncrease(final long[] before, final long[] after) {
+    for (int i = 0; i < after.length; i++) {
+      assertTrue(after[i] > before[i]);
+    }
+  }
+
   private void primaryIncreaseReplicaNoChange(final long[] before, final long[] after) {
     // There are read requests increase for primary meta replica.
     assertTrue(after[RegionInfo.DEFAULT_REPLICA_ID] > before[RegionInfo.DEFAULT_REPLICA_ID]);
@@ -410,6 +417,7 @@ public class TestMetaRegionReplicaReplication {
     final Region[] metaRegions = getAllRegions(TableName.META_TABLE_NAME, numOfMetaReplica);
     long[] readReqsForMetaReplicas = new long[numOfMetaReplica];
     long[] readReqsForMetaReplicasAfterGet = new long[numOfMetaReplica];
+    long[] readReqsForMetaReplicasAfterGetAllLocations = new long[numOfMetaReplica];
     long[] readReqsForMetaReplicasAfterMove = new long[numOfMetaReplica];
     long[] readReqsForMetaReplicasAfterSecondMove = new long[numOfMetaReplica];
     long[] readReqsForMetaReplicasAfterThirdGet = new long[numOfMetaReplica];
@@ -459,6 +467,16 @@ public class TestMetaRegionReplicaReplication {
       // For rest of meta replicas, there are more reads against them.
       primaryNoChangeReplicaIncrease(readReqsForMetaReplicas, readReqsForMetaReplicasAfterGet);
 
+      RegionLocator locator = tableForGet.getRegionLocator();
+
+      for (int j = 0; j < numOfMetaReplica * 3; j ++) {
+        locator.getAllRegionLocations();
+      }
+
+      getMetaReplicaReadRequests(metaRegions, readReqsForMetaReplicasAfterGetAllLocations);
+      PrimaryIncreaseReplicaIncrease(readReqsForMetaReplicasAfterGet,
+        readReqsForMetaReplicasAfterGetAllLocations);
+
       // move one of regions so it meta cache may be invalid.
       HTU.moveRegionAndWait(userRegion.getRegionInfo(), destRs.getServerName());
 
@@ -468,7 +486,7 @@ public class TestMetaRegionReplicaReplication {
 
       // There are read requests increase for primary meta replica.
       // For rest of meta replicas, there is no change as regionMove will tell the new location
-      primaryIncreaseReplicaNoChange(readReqsForMetaReplicasAfterGet,
+      primaryIncreaseReplicaNoChange(readReqsForMetaReplicasAfterGetAllLocations,
         readReqsForMetaReplicasAfterMove);
       // Move region again.
       HTU.moveRegionAndWait(userRegion.getRegionInfo(), srcRs.getServerName());