HDDS-7602. Adding metrics to display Pipeline leader Id's.

hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/pipeline/PipelineManagerImpl.java

@@ -67,6 +67,8 @@
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 import java.util.stream.Collectors;
 
+import static org.apache.hadoop.hdds.scm.pipeline.RatisPipelineUtils.pipelineLeaderFormat;
+
 /**
  * SCM Pipeline Manager implementation.
  * All the write operations for pipelines must come via PipelineManager.
@@ -697,6 +699,12 @@ public Map<String, Integer> getPipelineInfo() throws NotLeaderException {
     return pipelineInfo;
   }
 
+  @Override
+  public Map<String, Map<String, Map<String, String>>> getPipelineLeaders() {
+    List<Pipeline> pipelines = getPipelines();
+    return pipelineLeaderFormat(pipelines);
+  }
+
   /**
    * Get SafeMode status.
    * @return boolean

hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/pipeline/PipelineManagerMXBean.java

@@ -36,4 +36,6 @@ public interface PipelineManagerMXBean {
    */
   Map<String, Integer> getPipelineInfo() throws NotLeaderException;
 
+  Map<String, Map<String, Map<String, String>>> getPipelineLeaders();
+
 }

hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/pipeline/RatisPipelineUtils.java

@@ -19,6 +19,9 @@
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Collectors;
 
 import org.apache.hadoop.hdds.client.RatisReplicationConfig;
@@ -117,4 +120,50 @@ static List<Pipeline> checkPipelineContainSameDatanodes(
                 p.sameDatanodes(pipeline)))
         .collect(Collectors.toList());
   }
+
+  /**
+   * Returns a map containing pipeline information which includes
+   * pipeline-id & the corresponding roles of all datanodes along with
+   * their respective datanode-id
+   * part of the pipeline.
+   *
+   * @param pipelines input pipeline
+   * @return map containing pipeline details
+   */
+  public static Map<String, Map<String, Map<String, String>>>
+                          pipelineLeaderFormat(List<Pipeline> pipelines) {
+    final Map<String, Map<String, Map<String, String>>> pipelineInfo =
+        new ConcurrentHashMap<>();
+
+    pipelines.forEach(pipeline -> {
+      String leaderNode = "";
+      List<DatanodeDetails> dataNodes = pipeline.getNodes();
+      UUID pipelineId = pipeline.getId().getId();
+
+      try {
+        leaderNode = pipeline.getLeaderNode().getHostName();
+      } catch (IOException ioEx) {
+        LOG.warn("Cannot get leader node for pipeline {}",
+            pipelineId, ioEx);
+      }
+
+      int numOfNodes = dataNodes.size();
+      Map<String, Map<String, String>> nodeInfo = new ConcurrentHashMap<>();
+      for (int cnt = 0; cnt < numOfNodes; cnt++) {
+        Map<String, String> info = new ConcurrentHashMap<>();
+        DatanodeDetails node = dataNodes.get(cnt);
+        String role =
+            node.getHostName().equals(leaderNode) ? "Leader" : "Follower";
+        String dataNodeUUID = node.getUuidString();
+        String hostName = node.getHostName();
+        info.put("Role", role);
+        info.put("UUID", dataNodeUUID);
+        info.put("HostName", hostName);
+        nodeInfo.put("DataNode-" + cnt, info);
+      }
+      pipelineInfo.put(pipelineId.toString(), nodeInfo);
+    });
+    return pipelineInfo;
+  }
+
 }

hadoop-hdds/server-scm/src/test/java/org/apache/hadoop/hdds/scm/pipeline/MockPipelineManager.java

@@ -296,6 +296,11 @@ public Map<String, Integer> getPipelineInfo() {
     return null;
   }
 
+  @Override
+  public Map<String, Map<String, Map<String, String>>> getPipelineLeaders() {
+    return null;
+  }
+
   @Override
   public void acquireReadLock() {