YARN-5669. Add support for docker pull command (Contribtued by luhuichun)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/runtime/docker/DockerPullCommand.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.server.nodemanager.containermanager.linux.runtime.docker;
+
+/**
+ * Encapsulates the docker pull command and its command
+ * line arguments.
+ */
+public class DockerPullCommand extends DockerCommand {
+  private static final String PULL_COMMAND = "pull";
+
+  public DockerPullCommand(String imageName) {
+    super(PULL_COMMAND);
+    super.addCommandArguments(imageName);
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/test/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/runtime/docker/TestDockerPullCommand.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.server.nodemanager.containermanager.linux.runtime.docker;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests the docker pull command and its command
+ * line arguments.
+ */
+public class TestDockerPullCommand {
+  private DockerPullCommand dockerPullCommand;
+
+  private static final String IMAGE_NAME = "foo";
+
+  @Before
+  public void setup() {
+    dockerPullCommand = new DockerPullCommand(IMAGE_NAME);
+  }
+
+  @Test
+  public void testGetCommandOption() {
+    assertEquals("pull", dockerPullCommand.getCommandOption());
+  }
+
+  @Test
+  public void testGetCommandWithArguments() {
+    assertEquals("pull foo", dockerPullCommand.getCommandWithArguments());
+  }
+
+
+}