HADOOP-14615. Add ServiceOperations.stopQuietly that accept slf4j logger API.

Contributed by Wenxin He.

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

@@ -25,6 +25,7 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience.Public;
 import org.apache.hadoop.classification.InterfaceStability.Evolving;
+import org.slf4j.Logger;
 
 /**
  * This class contains a set of methods to work with services, especially
@@ -87,6 +88,25 @@ public final class ServiceOperations {
     return null;
   }
 
+  /**
+   * 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 log the log to warn at
+   * @param service a service; may be null
+   * @return any exception that was caught; null if none was.
+   * @see ServiceOperations#stopQuietly(Service)
+   */
+  public static Exception stopQuietly(Logger log, Service service) {
+    try {
+      stop(service);
+    } catch (Exception e) {
+      log.warn("When stopping the service {} : {}", service.getName(), e, e);
+      return e;
+    }
+    return null;
+  }
 
   /**
    * Class to manage a list of {@link ServiceStateChangeListener} instances,

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

@@ -0,0 +1,65 @@
+/*
+ * 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.service;
+
+import org.apache.hadoop.test.GenericTestUtils.LogCapturer;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.runners.MockitoJUnitRunner;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.PrintWriter;
+
+import static org.apache.hadoop.test.GenericTestUtils.LogCapturer.captureLogs;
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.junit.Assert.assertThat;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Test miscellaneous service operations through mocked failures.
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class TestServiceOperations {
+
+  @Mock
+  private Service service;
+
+  @Mock
+  private RuntimeException e;
+
+  @Test
+  public void testStopQuietlyWhenServiceStopThrowsException() throws Exception {
+    Logger logger = LoggerFactory.getLogger(TestServiceOperations.class);
+    LogCapturer logCapturer = captureLogs(logger);
+    doThrow(e).when(service).stop();
+
+    ServiceOperations.stopQuietly(logger, service);
+
+    assertThat(logCapturer.getOutput(),
+        containsString("When stopping the service " + service.getName()
+            + " : " + e));
+    verify(e, times(1)).printStackTrace(Mockito.any(PrintWriter.class));
+  }
+
+}