[GitHub] [ozone] Xushaohong commented on a diff in pull request #4128: HDDS-5686. Support transfer leadership

[GitBox <gi...@apache.org>]

Xushaohong commented on code in PR #4128:
URL: https://github.com/apache/ozone/pull/4128#discussion_r1064374439


##########
hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/ratis/RatisHelper.java:
##########
@@ -483,4 +488,81 @@ public static void debug(ByteBuf buf, String name, Logger log) {
     }
     log.debug("{}: {}\n  {}", name, buf, builder);
   }
+
+
+  /**
+   * Use raft client to send admin request, transfer the leadership.
+   * If not isRandom, then use host to match the target leader.
+   * 1. Set priority and send setConfiguration request
+   * 2. Trigger transferLeadership API.
+   *
+   * @param server        the Raft server
+   * @param groupId       the Raft group Id
+   * @param targetPeerId  the target expected leader
+
+   * @throws IOException
+   */
+  public static void transferRatisLeadership(RaftServer server,
+      RaftGroupId groupId, RaftPeerId targetPeerId)
+      throws IOException {
+    RaftGroup raftGroup = server.getDivision(groupId).getGroup();
+    RaftClient raftClient = createBackoffRaftClient(raftGroup);
+    if (!raftGroup.getPeers().stream().map(RaftPeer::getId)
+        .collect(Collectors.toSet()).contains(targetPeerId)) {
+      throw new IOException("Cannot choose the target leader. The expected " +
+          "leader RaftPeerId is " + targetPeerId + " and the peers are " +
+          raftGroup.getPeers().stream().map(RaftPeer::getId)
+              .collect(Collectors.toList()) + ".");
+    }
+    LOG.info("Chosen the targetLeaderId {} to transfer leadership",
+        targetPeerId);
+
+    // Set priority
+    List<RaftPeer> peersWithNewPriorities = new ArrayList<>();
+    for (RaftPeer peer : raftGroup.getPeers()) {
+      peersWithNewPriorities.add(
+          RaftPeer.newBuilder(peer)
+              .setPriority(peer.getId().equals(targetPeerId) ? 2 : 1)

Review Comment:
   Yes, the SetConfiguration request will sync and renew the conf between RaftPeers including the priorities.



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