HADOOP-7925. Add interface and update CLI to query current state to HAServiceProtocol. Contributed by Eli Collins.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-1623@1220611 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.HDFS-1623.txt

@@ -18,3 +18,6 @@ HADOOP-7921. StandbyException should extend IOException (todd)
 
 HADOOP-7928. HA: Client failover policy is incorrectly trying to fail over all
              IOExceptions (atm)
+
+HADOOP-7925. Add interface and update CLI to query current state to
+             HAServiceProtocol (eli via todd)

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

@@ -24,6 +24,7 @@ import java.util.Map;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configured;
+import org.apache.hadoop.ha.HAServiceProtocol.HAServiceState;
 import org.apache.hadoop.ipc.RPC;
 import org.apache.hadoop.net.NetUtils;
 import org.apache.hadoop.util.Tool;
@@ -44,7 +45,9 @@ public class HAAdmin extends Configured implements Tool {
     .put("-transitionToActive",
         new UsageInfo("<host:port>", "Transitions the daemon into Active state"))
     .put("-transitionToStandby",
-        new UsageInfo("<host:port>", "Transitions the daemon into Passive state"))
+        new UsageInfo("<host:port>", "Transitions the daemon into Standby state"))
+    .put("-getServiceState",
+        new UsageInfo("<host:port>", "Returns the state of the daemon"))
     .put("-checkHealth",
         new UsageInfo("<host:port>",
             "Requests that the daemon perform a health check.\n" + 
@@ -123,6 +126,19 @@ public class HAAdmin extends Configured implements Tool {
     return 0;
   }
 
+  private int getServiceState(final String[] argv)
+      throws IOException, ServiceFailedException {
+    if (argv.length != 2) {
+      errOut.println("getServiceState: incorrect number of arguments");
+      printUsage(errOut, "-getServiceState");
+      return -1;
+    }
+
+    HAServiceProtocol proto = getProtocol(argv[1]);
+    out.println(proto.getServiceState());
+    return 0;
+  }
+
   /**
    * Return a proxy to the specified target host:port.
    */
@@ -155,6 +171,8 @@ public class HAAdmin extends Configured implements Tool {
       return transitionToActive(argv);
     } else if ("-transitionToStandby".equals(cmd)) {
       return transitionToStandby(argv);
+    } else if ("-getServiceState".equals(cmd)) {
+      return getServiceState(argv);
     } else if ("-checkHealth".equals(cmd)) {
       return checkHealth(argv);
     } else if ("-help".equals(cmd)) {

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

@@ -35,6 +35,24 @@ public interface HAServiceProtocol extends VersionedProtocol {
    */
   public static final long versionID = 1L;
 
+  /**
+   * An HA service may be in active or standby state.
+   */
+  public enum HAServiceState {
+    ACTIVE("active"),
+    STANDBY("standby");
+
+    private String name;
+
+    HAServiceState(String name) {
+      this.name = name;
+    }
+
+    public String toString() {
+      return name;
+    }
+  }
+
   /**
    * Monitor the health of service. This periodically called by the HA
    * frameworks to monitor the health of the service.
@@ -69,4 +87,9 @@ public interface HAServiceProtocol extends VersionedProtocol {
    *           if transition from active to standby fails.
    */
   public void transitionToStandby() throws ServiceFailedException;
+
+  /**
+   * Return the current state of the service.
+   */
+  public HAServiceState getServiceState();
 }

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

@@ -100,6 +100,12 @@ public class TestHAAdmin {
     Mockito.verify(mockProtocol).transitionToStandby();
   }
 
+  @Test
+  public void testGetServiceState() throws Exception {
+    assertEquals(0, runTool("-getServiceState", "xxx"));
+    Mockito.verify(mockProtocol).getServiceState();
+  }
+
   @Test
   public void testCheckHealth() throws Exception {
     assertEquals(0, runTool("-checkHealth", "xxx"));