HDFS-16461. Expose JournalNode storage info in the jmx metrics

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

@@ -423,6 +423,14 @@ public long getJNStartedTimeInMillis() {
     return this.startTime;
   }
 
+  @Override
+  // JournalNodeMXBean
+  public List<String> getStorageInfos() {
+    return journalsById.values().stream()
+        .map(journal -> journal.getStorage().toMapString())
+        .collect(Collectors.toList());
+  }
+
   /**
    * Register JournalNodeMXBean
    */

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

@@ -64,4 +64,13 @@ public interface JournalNodeMXBean {
    * @return the start time of the JournalNode.
    */
   long getJNStartedTimeInMillis();
+
+  /**
+   * Get the list of the storage infos of JournalNode's journals. Storage infos
+   * include layout version, namespace id, cluster id and creation time of the
+   * File system state.
+   *
+   * @return the list of storage infos associated with journals.
+   */
+  List<String> getStorageInfos();
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/common/StorageInfo.java

@@ -21,6 +21,7 @@
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.RandomAccessFile;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.Properties;
 import java.util.SortedSet;
@@ -112,6 +113,20 @@ public String toString() {
     .append(";nsid=").append(namespaceID).append(";c=").append(cTime);
     return sb.toString();
   }
+
+  /**
+   * Returns string representation of Storage info attributes stored in Map.
+   *
+   * @return string representation of storage info attributes.
+   */
+  public String toMapString() {
+    Map<String, Object> storageInfo = new HashMap<>();
+    storageInfo.put("LayoutVersion", layoutVersion);
+    storageInfo.put("ClusterId", clusterID);
+    storageInfo.put("NamespaceId", namespaceID);
+    storageInfo.put("CreationTime", cTime);
+    return storageInfo.toString();
+  }
 
   public String toColonSeparatedString() {
     return Joiner.on(":").join(

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

@@ -44,6 +44,7 @@ public class TestJournalNodeMXBean {
 
   private static final String NAMESERVICE = "ns1";
   private static final int NUM_JN = 1;
+  private static final int NS_ID = 12345;
 
   private MiniJournalCluster jCluster;
   private JournalNode jn;
@@ -80,9 +81,8 @@ public void testJournalNodeMXBean() throws Exception {
     assertFalse(journalStatus.contains(NAMESERVICE));
 
     // format the journal ns1
-    final NamespaceInfo FAKE_NSINFO = new NamespaceInfo(12345, "mycluster",
-        "my-bp", 0L);
-    jn.getOrCreateJournal(NAMESERVICE).format(FAKE_NSINFO, false);
+    final NamespaceInfo fakeNsInfo = new NamespaceInfo(NS_ID, "mycluster", "my-bp", 0L);
+    jn.getOrCreateJournal(NAMESERVICE).format(fakeNsInfo, false);
 
     // check again after format
     // getJournalsStatus
@@ -109,6 +109,11 @@ public void testJournalNodeMXBean() throws Exception {
     assertEquals(jn.getJNStartedTimeInMillis(), startTime);
     String version = (String) mbs.getAttribute(mxbeanName, "Version");
     assertEquals(jn.getVersion(), version);
+    String[] journalStorageInfos = (String[]) mbs.getAttribute(mxbeanName, "StorageInfos");
+    assertEquals(jn.getStorageInfos().size(), journalStorageInfos.length);
+    assertTrue(journalStorageInfos[1].contains("ClusterId=mycluster"));
+    assertTrue(journalStorageInfos[1].contains("CreationTime=0"));
+    assertTrue(journalStorageInfos[1].contains("NamespaceId=" + NS_ID));
 
     // restart journal node without formatting
     jCluster = new MiniJournalCluster.Builder(new Configuration()).format(false)