HBASE-26173 Return only a sub set of region servers as bootstrap nodes (

#3599)

Signed-off-by: Bharath Vissapragada <bharathv@apache.org>

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

@@ -41,6 +41,7 @@
 import java.util.TreeSet;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
@@ -320,6 +321,10 @@ public class RSRpcServices implements HBaseRPCErrorHandler,
    */
   private static final boolean DEFAULT_REJECT_BATCH_ROWS_OVER_THRESHOLD = false;
 
+  public static final String CLIENT_BOOTSTRAP_NODE_LIMIT = "hbase.client.bootstrap.node.limit";
+
+  public static final int DEFAULT_CLIENT_BOOTSTRAP_NODE_LIMIT = 10;
+
   // Request counter. (Includes requests that are not serviced by regions.)
   // Count only once for requests with multiple actions like multi/caching-scan/replayBatch
   final LongAdder requestCount = new LongAdder();
@@ -4124,8 +4129,12 @@ public GetMetaRegionLocationsResponse getMetaRegionLocations(RpcController contr
   @Override
   public final GetBootstrapNodesResponse getBootstrapNodes(RpcController controller,
     GetBootstrapNodesRequest request) throws ServiceException {
+    List<ServerName> bootstrapNodes = new ArrayList<>(regionServer.getRegionServers());
+    Collections.shuffle(bootstrapNodes, ThreadLocalRandom.current());
+    int maxNodeCount = regionServer.getConfiguration().getInt(CLIENT_BOOTSTRAP_NODE_LIMIT,
+      DEFAULT_CLIENT_BOOTSTRAP_NODE_LIMIT);
     GetBootstrapNodesResponse.Builder builder = GetBootstrapNodesResponse.newBuilder();
-    regionServer.getRegionServers().stream().map(ProtobufUtil::toServerName)
+    bootstrapNodes.stream().limit(maxNodeCount).map(ProtobufUtil::toServerName)
       .forEach(builder::addServerName);
     return builder.build();
   }

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

@@ -31,6 +31,7 @@
 import org.apache.hadoop.hbase.ServerName;
 import org.apache.hadoop.hbase.TableName;
 import org.apache.hadoop.hbase.master.HMaster;
+import org.apache.hadoop.hbase.regionserver.RSRpcServices;
 import org.apache.hadoop.hbase.testclassification.ClientTests;
 import org.apache.hadoop.hbase.testclassification.MediumTests;
 import org.junit.After;
@@ -78,6 +79,15 @@ public void tearDown() throws IOException {
     Closeables.close(registry, true);
   }
 
+  private void setMaxNodeCount(int count) {
+    UTIL.getMiniHBaseCluster().getMasterThreads().stream()
+      .map(t -> t.getMaster().getConfiguration())
+      .forEach(conf -> conf.setInt(RSRpcServices.CLIENT_BOOTSTRAP_NODE_LIMIT, count));
+    UTIL.getMiniHBaseCluster().getRegionServerThreads().stream()
+      .map(t -> t.getRegionServer().getConfiguration())
+      .forEach(conf -> conf.setInt(RSRpcServices.CLIENT_BOOTSTRAP_NODE_LIMIT, count));
+  }
+
   @Test
   public void testRegistryRPCs() throws Exception {
     HMaster activeMaster = UTIL.getHBaseCluster().getMaster();
@@ -99,5 +109,9 @@ public void testRegistryRPCs() throws Exception {
     Collections.sort(metaLocations);
     Collections.sort(actualMetaLocations);
     assertEquals(actualMetaLocations, metaLocations);
+
+    // test that the node count config works
+    setMaxNodeCount(1);
+    UTIL.waitFor(10000, () -> registry.getParsedServers().size() == 1);
   }
 }