HDFS-16444. Show start time of JournalNode on Web

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/server/JournalNode.java

@@ -45,6 +45,7 @@
 
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_JOURNALNODE_HTTP_BIND_HOST_KEY;
 import static org.apache.hadoop.util.ExitUtil.terminate;
+import static org.apache.hadoop.util.Time.now;
 import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Tool;
 import org.apache.hadoop.util.ToolRunner;
@@ -83,6 +84,7 @@ public class JournalNode implements Tool, Configurable, JournalNodeMXBean {
   private String httpServerURI;
   private final ArrayList<File> localDir = Lists.newArrayList();
   Tracer tracer;
+  private long startTime = 0;
 
   static {
     HdfsConfiguration.init();
@@ -241,6 +243,7 @@ public void start() throws IOException {
 
       rpcServer = new JournalNodeRpcServer(conf, this);
       rpcServer.start();
+      startTime = now();
     } catch (IOException ioe) {
       //Shutdown JournalNode of JournalNodeRpcServer fails to start
       LOG.error("Failed to start JournalNode.", ioe);
@@ -415,6 +418,11 @@ public String getVersion() {
     return VersionInfo.getVersion() + ", r" + VersionInfo.getRevision();
   }
 
+  @Override // JournalNodeMXBean
+  public long getJNStartedTimeInMillis() {
+    return this.startTime;
+  }
+
   /**
    * Register JournalNodeMXBean
    */

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/server/JournalNodeMXBean.java

@@ -57,4 +57,11 @@ public interface JournalNodeMXBean {
    * @return the version of Hadoop.
    */
   String getVersion();
+
+  /**
+   * Get the start time of the JournalNode.
+   *
+   * @return the start time of the JournalNode.
+   */
+  long getJNStartedTimeInMillis();
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/webapps/journal/journalnode.html

@@ -71,6 +71,7 @@
   <div class="page-header"><h1>JournalNode on <small>{HostAndPort}</small></h1></div>
   <table class="table table-bordered table-striped">
     <tr><th>Cluster ID:</th><td>{ClusterIds}</td></tr>
+    <tr><th>Started:</th><td>{JNStartedTimeInMillis|date_tostring}</td></tr>
     <tr><th>Version:</th><td>{Version}</td></tr>
   </table>
   {/jn}

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/qjournal/server/TestJournalNodeMXBean.java

@@ -104,6 +104,9 @@ public void testJournalNodeMXBean() throws Exception {
     String[] clusterId = (String[]) mbs.getAttribute(mxbeanName, "ClusterIds");
     assertEquals(jn.getClusterIds().size(), clusterId.length);
     assertEquals("mycluster", clusterId[0]);
+    long startTime = (long) mbs.getAttribute(mxbeanName, "JNStartedTimeInMillis");
+    assertTrue("JournalNode start time should not be 0", startTime > 0);
+    assertEquals(jn.getJNStartedTimeInMillis(), startTime);
     String version = (String) mbs.getAttribute(mxbeanName, "Version");
     assertEquals(jn.getVersion(), version);