HADOOP-8208. Disallow self failover. Contributed by Eli Collins

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1306935 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -445,6 +445,8 @@ Release 0.23.2 - UNRELEASED
     HADOOP-8088. User-group mapping cache incorrectly does negative caching on
     transient failures (Khiwal Lee via bobby)
 
+    HADOOP-8208. Disallow self failover. (eli)
+
 Release 0.23.1 - 2012-02-17 
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/FailoverController.java

@@ -54,16 +54,23 @@ public class FailoverController {
    * allow it to become active, eg because it triggers a log roll
    * so the standby can learn about new blocks and leave safemode.
    *
+   * @param from currently active service
    * @param target service to make active
    * @param forceActive ignore toSvc if it reports that it is not ready
    * @throws FailoverFailedException if we should avoid failover
    */
-  private static void preFailoverChecks(HAServiceTarget target,
+  private static void preFailoverChecks(HAServiceTarget from,
+                                        HAServiceTarget target,
                                         boolean forceActive)
       throws FailoverFailedException {
     HAServiceStatus toSvcStatus;
     HAServiceProtocol toSvc;
 
+    if (from.getAddress().equals(target.getAddress())) {
+      throw new FailoverFailedException(
+          "Can't failover a service to itself");
+    }
+
     try {
       toSvc = target.getProxy();
       toSvcStatus = toSvc.getServiceStatus();
@@ -146,7 +153,7 @@ public class FailoverController {
       throws FailoverFailedException {
     Preconditions.checkArgument(fromSvc.getFencer() != null,
         "failover requires a fencer");
-    preFailoverChecks(toSvc, forceActive);
+    preFailoverChecks(fromSvc, toSvc, forceActive);
 
     // Try to make fromSvc standby
     boolean tryFence = true;

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/ha/TestFailoverController.java

@@ -377,4 +377,31 @@ public class TestFailoverController {
     assertEquals(HAServiceState.STANDBY, svc1.state);
     assertEquals(HAServiceState.STANDBY, svc2.state);
   }
+
+  @Test
+  public void testSelfFailoverFails() throws Exception {
+    DummyHAService svc1 = new DummyHAService(HAServiceState.ACTIVE, svc1Addr);
+    DummyHAService svc2 = new DummyHAService(HAServiceState.STANDBY, svc2Addr);
+    svc1.fencer = svc2.fencer = setupFencer(AlwaysSucceedFencer.class.getName());
+    AlwaysSucceedFencer.fenceCalled = 0;
+
+    try {
+      FailoverController.failover(svc1, svc1, false, false);
+      fail("Can't failover to yourself");
+    } catch (FailoverFailedException ffe) {
+      // Expected
+    }
+    assertEquals(0, TestNodeFencer.AlwaysSucceedFencer.fenceCalled);
+    assertEquals(HAServiceState.ACTIVE, svc1.state);
+
+    try {
+      FailoverController.failover(svc2, svc2, false, false);
+      fail("Can't failover to yourself");
+    } catch (FailoverFailedException ffe) {
+      // Expected
+    }
+    assertEquals(0, TestNodeFencer.AlwaysSucceedFencer.fenceCalled);
+    assertEquals(HAServiceState.STANDBY, svc2.state);
+  }
+
 }