MAPREDUCE-3970 ServiceOperations class

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1300901 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/service/ServiceOperations.java

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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.yarn.service;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.conf.Configuration;
+
+/**
+ * This class contains a set of methods to work with services, especially
+ * to walk them through their lifecycle.
+ */
+public final class ServiceOperations {
+  private static final Log LOG = LogFactory.getLog(AbstractService.class);
+
+  private ServiceOperations() {
+  }
+
+  /**
+   * Verify that that a service is in a given state.
+   * @param state the actual state a service is in
+   * @param expectedState the desired state
+   * @throws IllegalStateException if the service state is different from
+   * the desired state
+   */
+  public static void ensureCurrentState(Service.STATE state,
+                                        Service.STATE expectedState) {
+    if (state != expectedState) {
+      throw new IllegalStateException("For this operation, the " +
+                                          "current service state must be "
+                                          + expectedState
+                                          + " instead of " + state);
+    }
+  }
+
+  /**
+   * Initialize a service.
+   * <p/>
+   * The service state is checked <i>before</i> the operation begins.
+   * This process is <i>not</i> thread safe.
+   * @param service a service that must be in the state
+   *   {@link Service.STATE#NOTINITED}
+   * @param configuration the configuration to initialize the service with
+   * @throws RuntimeException on a state change failure
+   * @throws IllegalStateException if the service is in the wrong state
+   */
+
+  public static void init(Service service, Configuration configuration) {
+    Service.STATE state = service.getServiceState();
+    ensureCurrentState(state, Service.STATE.NOTINITED);
+    service.init(configuration);
+  }
+
+  /**
+   * Start a service.
+   * <p/>
+   * The service state is checked <i>before</i> the operation begins.
+   * This process is <i>not</i> thread safe.
+   * @param service a service that must be in the state 
+   *   {@link Service.STATE#INITED}
+   * @throws RuntimeException on a state change failure
+   * @throws IllegalStateException if the service is in the wrong state
+   */
+
+  public static void start(Service service) {
+    Service.STATE state = service.getServiceState();
+    ensureCurrentState(state, Service.STATE.INITED);
+    service.start();
+  }
+
+  /**
+   * Initialize then start a service.
+   * <p/>
+   * The service state is checked <i>before</i> the operation begins.
+   * This process is <i>not</i> thread safe.
+   * @param service a service that must be in the state 
+   *   {@link Service.STATE#NOTINITED}
+   * @param configuration the configuration to initialize the service with
+   * @throws RuntimeException on a state change failure
+   * @throws IllegalStateException if the service is in the wrong state
+   */
+  public static void deploy(Service service, Configuration configuration) {
+    init(service, configuration);
+    start(service);
+  }
+
+  /**
+   * Stop a service.
+   * <p/>Do nothing if the service is null or not
+   * in a state in which it can be/needs to be stopped.
+   * <p/>
+   * The service state is checked <i>before</i> the operation begins.
+   * This process is <i>not</i> thread safe.
+   * @param service a service or null
+   */
+  public static void stop(Service service) {
+    if (service != null) {
+      Service.STATE state = service.getServiceState();
+      if (state == Service.STATE.STARTED) {
+        service.stop();
+      }
+    }
+  }
+
+  /**
+   * Stop a service; if it is null do nothing. Exceptions are caught and
+   * logged at warn level. (but not Throwables). This operation is intended to
+   * be used in cleanup operations
+   *
+   * @param service a service; may be null
+   * @return any exception that was caught; null if none was.
+   */
+  public static Exception stopQuietly(Service service) {
+    try {
+      stop(service);
+    } catch (Exception e) {
+      LOG.warn("When stopping the service " + service.getName()
+                   + " : " + e,
+               e);
+      return e;
+    }
+    return null;
+  }
+}

hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/service/TestServiceOperations.java

@@ -0,0 +1,312 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+package org.apache.hadoop.yarn.service;
+
+import org.apache.hadoop.conf.Configuration;
+import org.junit.Test;
+
+/**
+ * These tests verify that the {@link ServiceOperations} methods
+ * do a best-effort attempt to make  the service state change operations 
+ * idempotent. That is still best effort -there is no thread safety, and
+ * a failure during a state change does not prevent the operation
+ * being called again.
+ */
+public class TestServiceOperations extends ServiceAssert {
+
+  @Test
+  public void testWalkthrough() throws Throwable {
+    BreakableService svc = new BreakableService();
+    assertServiceStateCreated(svc);
+    Configuration conf = new Configuration();
+    conf.set("test.walkthrough","t");
+    ServiceOperations.init(svc, conf);
+    assertServiceStateInited(svc);
+    assertStateCount(svc, Service.STATE.INITED, 1);
+    //check the configuration made it all the way through.
+    assertServiceConfigurationContains(svc, "test.walkthrough");
+    ServiceOperations.start(svc);
+    assertServiceStateStarted(svc);
+    assertStateCount(svc, Service.STATE.STARTED, 1);
+    ServiceOperations.stop(svc);
+    assertServiceStateStopped(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 1);
+  }
+
+  /**
+   * Call init twice -expect a failure, and expect the count
+   * of initialization attempts to still be 1: the state
+   * check was made before the subclass method was called.
+   * @throws Throwable if need be
+   */
+  @Test
+  public void testInitTwice() throws Throwable {
+    BreakableService svc = new BreakableService();
+    Configuration conf = new Configuration();
+    conf.set("test.init", "t");
+    ServiceOperations.init(svc, conf);
+    try {
+      ServiceOperations.init(svc, new Configuration());
+      fail("Expected a failure, got " + svc);
+    } catch (IllegalStateException e) {
+      //expected
+    }
+    assertStateCount(svc, Service.STATE.INITED, 1);
+    assertServiceConfigurationContains(svc, "test.init");
+  }
+
+  /**
+   * call start twice; expect failures and the start invoke count to 
+   * be exactly 1.
+   * @throws Throwable if necessary
+   */
+  @Test
+  public void testStartTwice() throws Throwable {
+    BreakableService svc = new BreakableService();
+    ServiceOperations.init(svc, new Configuration());
+    ServiceOperations.start(svc);
+    try {
+      ServiceOperations.start(svc);
+      fail("Expected a failure, got " + svc);
+    } catch (IllegalStateException e) {
+      //expected
+    }
+    assertStateCount(svc, Service.STATE.STARTED, 1);
+  }
+
+  /**
+   * Test that the deploy operation pushes a service into its started state
+   * @throws Throwable on any failure.
+   */
+  @Test
+  public void testDeploy() throws Throwable {
+    BreakableService svc = new BreakableService();
+    assertServiceStateCreated(svc);
+    ServiceOperations.deploy(svc, new Configuration());
+    assertServiceStateStarted(svc);
+    assertStateCount(svc, Service.STATE.INITED, 1);
+    assertStateCount(svc, Service.STATE.STARTED, 1);
+    ServiceOperations.stop(svc);
+    assertServiceStateStopped(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 1);
+  }
+
+  /**
+   * Demonstrate that the deploy operation fails when invoked twice,
+   * but the service method call counts are unchanged after the second call.
+   * @throws Throwable on any failure.
+   */
+  @Test
+  public void testDeployNotIdempotent() throws Throwable {
+    BreakableService svc = new BreakableService();
+    assertServiceStateCreated(svc);
+    ServiceOperations.deploy(svc, new Configuration());
+    try {
+      ServiceOperations.deploy(svc, new Configuration());
+      fail("Expected a failure, got " + svc);
+    } catch (IllegalStateException e) {
+      //expected
+    }
+    //verify state and values are unchanged
+    assertServiceStateStarted(svc);
+    assertStateCount(svc, Service.STATE.INITED, 1);
+    assertStateCount(svc, Service.STATE.STARTED, 1);
+    ServiceOperations.stop(svc);
+  }
+
+  /**
+   * Test that the deploy operation can fail part way through, in which
+   * case the service is in the state that it was in before the failing
+   * state method was called.
+   * @throws Throwable on any failure.
+   */
+  @Test
+  public void testDeployNotAtomic() throws Throwable {
+    //this instance is set to fail in the start() call.
+    BreakableService svc = new BreakableService(false, true, false);
+    try {
+      ServiceOperations.deploy(svc, new Configuration());
+      fail("Expected a failure, got " + svc);
+    } catch (BreakableService.BrokenLifecycleEvent expected) {
+      //expected
+    }
+    //now in the inited state
+    assertServiceStateInited(svc);
+    assertStateCount(svc, Service.STATE.INITED, 1);
+    assertStateCount(svc, Service.STATE.STARTED, 1);
+    //try again -expect a failure as the service is now inited.
+    try {
+      ServiceOperations.deploy(svc, new Configuration());
+      fail("Expected a failure, got " + svc);
+    } catch (IllegalStateException e) {
+      //expected
+    }
+  }
+  
+  /**
+   * verify that when a service is stopped more than once, no exception
+   * is thrown, and the counter is not incremented
+   * this is because the state change operations happen after the counter in
+   * the subclass is incremented, even though stop is meant to be a no-op
+   * @throws Throwable on a failure
+   */
+  @Test
+  public void testStopTwice() throws Throwable {
+    BreakableService svc = new BreakableService();
+    ServiceOperations.deploy(svc, new Configuration());
+    ServiceOperations.stop(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 1);
+    assertServiceStateStopped(svc);
+    ServiceOperations.stop(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 1);
+  }
+
+  /**
+   * verify that when a service that is not started is stopped, it's counter
+   * is not incremented -the stop() method was not invoked.
+   * @throws Throwable on a failure
+   */
+  @Test
+  public void testStopInit() throws Throwable {
+    BreakableService svc = new BreakableService();
+    ServiceOperations.stop(svc);
+    assertServiceStateCreated(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 0);
+    ServiceOperations.stop(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 0);
+  }
+
+
+  /**
+   * Show that if the service failed during an init
+   * operation, it stays in the created state, even after stopping it
+   * @throws Throwable
+   */
+
+  @Test
+  public void testStopFailedInit() throws Throwable {
+    BreakableService svc = new BreakableService(true, false, false);
+    assertServiceStateCreated(svc);
+    try {
+      ServiceOperations.init(svc, new Configuration());
+      fail("Expected a failure, got " + svc);
+    } catch (BreakableService.BrokenLifecycleEvent e) {
+      //expected
+    }
+    //the service state wasn't passed
+    assertServiceStateCreated(svc);
+    //the init state got invoked once
+    assertStateCount(svc, Service.STATE.INITED, 1);
+    //now try to stop
+    ServiceOperations.stop(svc);
+    //even after the stop operation, we haven't entered the state
+    assertServiceStateCreated(svc);
+  }
+
+
+  /**
+   * Show that if the service failed during an init
+   * operation, it stays in the created state, even after stopping it
+   * @throws Throwable
+   */
+
+  @Test
+  public void testStopFailedStart() throws Throwable {
+    BreakableService svc = new BreakableService(false, true, false);
+    ServiceOperations.init(svc, new Configuration());
+    assertServiceStateInited(svc);
+    try {
+      ServiceOperations.start(svc);
+      fail("Expected a failure, got " + svc);
+    } catch (BreakableService.BrokenLifecycleEvent e) {
+      //expected
+    }
+    //the service state wasn't passed
+    assertServiceStateInited(svc);
+    assertStateCount(svc, Service.STATE.INITED, 1);
+    //now try to stop
+    ServiceOperations.stop(svc);
+    //even after the stop operation, we haven't entered the state
+    assertServiceStateInited(svc);
+  }
+
+  /**
+   * verify that when a service is stopped more than once, no exception
+   * is thrown, and the counter is incremented
+   * this is because the state change operations happen after the counter in
+   * the subclass is incremented, even though stop is meant to be a no-op.
+   *
+   * The {@link ServiceOperations#stop(Service)} operation does not prevent
+   * this from happening
+   * @throws Throwable
+   */
+  @Test
+  public void testFailingStop() throws Throwable {
+    BreakableService svc = new BreakableService(false, false, true);
+    ServiceOperations.deploy(svc, new Configuration());
+    try {
+      ServiceOperations.stop(svc);
+      fail("Expected a failure, got " + svc);
+    } catch (BreakableService.BrokenLifecycleEvent e) {
+      //expected
+    }
+    assertStateCount(svc, Service.STATE.STOPPED, 1);
+    //now try to stop, this time doing it quietly
+    Exception exception = ServiceOperations.stopQuietly(svc);
+    assertTrue("Wrong exception type : " + exception,
+        exception instanceof BreakableService.BrokenLifecycleEvent);
+    assertStateCount(svc, Service.STATE.STOPPED, 2);
+  }
+
+
+  /**
+   * verify that when a service that is not started is stopped, its counter
+   * of stop calls is still incremented-and the service remains in its
+   * original state..
+   * @throws Throwable on a failure
+   */
+  @Test
+  public void testStopUnstarted() throws Throwable {
+    BreakableService svc = new BreakableService();
+
+    //invocation in NOTINITED state should be no-op
+    ServiceOperations.stop(svc);
+    assertServiceStateCreated(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 0);
+
+    //stop failed, now it can be initialised
+    ServiceOperations.init(svc, new Configuration());
+
+    //again, no-op
+    ServiceOperations.stop(svc);
+    assertServiceStateInited(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 0);
+
+    //once started, the service can be stopped reliably
+    ServiceOperations.start(svc);
+    ServiceOperations.stop(svc);
+    assertServiceStateStopped(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 1);
+
+    //now stop one more time
+    ServiceOperations.stop(svc);
+    assertStateCount(svc, Service.STATE.STOPPED, 1);
+  }
+}