HDFS-15032. Properly handle InvocationTargetExceptions in the proxy created by ProxyCombiner. This fixes a bug encountered by the HDFS balancer when used with Observer Nodes. Contributed by Erik Krogen.

(cherry picked from c174d50b30)
(cherry picked from 3402c87353)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/ProxyCombiner.java

@@ -17,9 +17,11 @@
  */
 package org.apache.hadoop.ipc;
 
+import com.google.common.base.Joiner;
 import java.io.Closeable;
 import java.io.IOException;
 import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Proxy;
 
@@ -74,7 +76,8 @@ public final class ProxyCombiner {
           + combinedProxyInterface + " do not cover method " + m);
     }
 
-    InvocationHandler handler = new CombinedProxyInvocationHandler(proxies);
+    InvocationHandler handler =
+        new CombinedProxyInvocationHandler(combinedProxyInterface, proxies);
     return (T) Proxy.newProxyInstance(combinedProxyInterface.getClassLoader(),
         new Class[] {combinedProxyInterface}, handler);
   }
@@ -82,9 +85,12 @@ public final class ProxyCombiner {
   private static final class CombinedProxyInvocationHandler
       implements RpcInvocationHandler {
 
+    private final Class<?> proxyInterface;
     private final Object[] proxies;
 
-    private CombinedProxyInvocationHandler(Object[] proxies) {
+    private CombinedProxyInvocationHandler(Class<?> proxyInterface,
+        Object[] proxies) {
+      this.proxyInterface = proxyInterface;
       this.proxies = proxies;
     }
 
@@ -97,6 +103,8 @@ public final class ProxyCombiner {
           return method.invoke(underlyingProxy, args);
         } catch (IllegalAccessException|IllegalArgumentException e) {
           lastException = e;
+        } catch (InvocationTargetException ite) {
+          throw ite.getCause();
         }
       }
       // This shouldn't happen since the method coverage was verified in build()
@@ -116,6 +124,12 @@ public final class ProxyCombiner {
       return RPC.getConnectionIdForProxy(proxies[0]);
     }
 
+    @Override
+    public String toString() {
+      return "CombinedProxy[" + proxyInterface.getSimpleName() + "]["
+          + Joiner.on(",").join(proxies) + "]";
+    }
+
     @Override
     public void close() throws IOException {
       MultipleIOException.Builder exceptionBuilder =

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/balancer/TestBalancerWithHANameNodes.java

@@ -125,10 +125,25 @@ public class TestBalancerWithHANameNodes {
   /**
    * Test Balancer with ObserverNodes.
    */
-  @Test(timeout = 60000)
+  @Test(timeout = 120000)
   public void testBalancerWithObserver() throws Exception {
+    testBalancerWithObserver(false);
+  }
+
+  /**
+   * Test Balancer with ObserverNodes when one has failed.
+   */
+  @Test(timeout = 180000)
+  public void testBalancerWithObserverWithFailedNode() throws Exception {
+    testBalancerWithObserver(true);
+  }
+
+  private void testBalancerWithObserver(boolean withObserverFailure)
+      throws Exception {
     final Configuration conf = new HdfsConfiguration();
     TestBalancer.initConf(conf);
+    // Avoid the same FS being reused between tests
+    conf.setBoolean("fs.hdfs.impl.disable.cache", true);
 
     MiniQJMHACluster qjmhaCluster = null;
     try {
@@ -142,6 +157,10 @@ public class TestBalancerWithHANameNodes {
         namesystemSpies.add(
             NameNodeAdapter.spyOnNamesystem(cluster.getNameNode(i)));
       }
+      if (withObserverFailure) {
+        // First observer NN is at index 2
+        cluster.shutdownNameNode(2);
+      }
 
       DistributedFileSystem dfs = HATestUtil.configureObserverReadFs(
           cluster, conf, ObserverReadProxyProvider.class, true);
@@ -149,9 +168,10 @@ public class TestBalancerWithHANameNodes {
 
       doTest(conf);
       for (int i = 0; i < cluster.getNumNameNodes(); i++) {
-        // First observer node is at idx 2 so it should get both getBlocks calls
-        // all other NameNodes should see 0 getBlocks calls
-        int expectedCount = (i == 2) ? 2 : 0;
+        // First observer node is at idx 2, or 3 if 2 has been shut down
+        // It should get both getBlocks calls, all other NNs should see 0 calls
+        int expectedObserverIdx = withObserverFailure ? 3 : 2;
+        int expectedCount = (i == expectedObserverIdx) ? 2 : 0;
         verify(namesystemSpies.get(i), times(expectedCount))
             .getBlocks(any(), anyLong(), anyLong());
       }