HBASE-21658 Addendum fix infinite wait when there are no meta locations yet

Author: Apache9

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

@@ -138,6 +138,9 @@ private Pair<RegionState.State, ServerName> getStateAndServerName(
 
   private void getMetaRegionLocation(CompletableFuture<RegionLocations> future,
       List<String> metaReplicaZNodes) {
+    if (metaReplicaZNodes.isEmpty()) {
+      future.completeExceptionally(new IOException("No meta znode available"));
+    }
     HRegionLocation[] locs = new HRegionLocation[metaReplicaZNodes.size()];
     MutableInt remaining = new MutableInt(locs.length);
     for (String metaReplicaZNode : metaReplicaZNodes) {

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

@@ -18,10 +18,13 @@
 package org.apache.hadoop.hbase.client;
 
 import static org.apache.hadoop.hbase.HConstants.META_REPLICAS_NUM;
+import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.fail;
 
 import java.io.IOException;
 import java.util.concurrent.ExecutionException;
@@ -115,4 +118,18 @@ public void testIndependentZKConnections() throws IOException {
       LOG.info("DONE!");
     }
   }
+
+  @Test
+  public void testNoMetaAvailable() throws InterruptedException {
+    Configuration conf = new Configuration(TEST_UTIL.getConfiguration());
+    conf.set("zookeeper.znode.metaserver", "whatever");
+    try (ZKAsyncRegistry registry = new ZKAsyncRegistry(conf)) {
+      try {
+        registry.getMetaRegionLocation().get();
+        fail("Should have failed since we set an incorrect meta znode prefix");
+      } catch (ExecutionException e) {
+        assertThat(e.getCause(), instanceOf(IOException.class));
+      }
+    }
+  }
 }