[ratis] branch branch-2 updated: RATIS-1754. Set leader to null when stepping down (#792)

[sz...@apache.org]

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szetszwo pushed a commit to branch branch-2
in repository https://gitbox.apache.org/repos/asf/ratis.git


The following commit(s) were added to refs/heads/branch-2 by this push:
     new 21a90b314 RATIS-1754. Set leader to null when stepping down (#792)
21a90b314 is described below

commit 21a90b314b66a628768fdd9109c21efcc6fac9ba
Author: William Song <48...@users.noreply.github.com>
AuthorDate: Wed Dec 7 17:28:39 2022 +0800

    RATIS-1754. Set leader to null when stepping down (#792)
    
    (cherry picked from commit fda585051c2036acb91bd33c05d1fd28114ebf81)
---
 .../apache/ratis/server/impl/RaftServerImpl.java    |  1 +
 .../org/apache/ratis/server/impl/ServerState.java   | 21 +++++++++++----------
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java b/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
index 3d6fb517b..8e56ec935 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java
@@ -530,6 +530,7 @@ class RaftServerImpl implements RaftServer.Division,
       setRole(RaftPeerRole.FOLLOWER, reason);
       if (old == RaftPeerRole.LEADER) {
         role.shutdownLeaderState(false);
+        state.setLeader(null, reason);
       } else if (old == RaftPeerRole.CANDIDATE) {
         role.shutdownLeaderElection();
       } else if (old == RaftPeerRole.FOLLOWER) {
diff --git a/ratis-server/src/main/java/org/apache/ratis/server/impl/ServerState.java b/ratis-server/src/main/java/org/apache/ratis/server/impl/ServerState.java
index 4dba31756..b1422db4f 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/impl/ServerState.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/impl/ServerState.java
@@ -87,7 +87,7 @@ class ServerState implements Closeable {
    * The server ID of the leader for this term. Null means either there is
    * no leader for this term yet or this server does not know who it is yet.
    */
-  private volatile RaftPeerId leaderId;
+  private final AtomicReference<RaftPeerId> leaderId = new AtomicReference<>();
   /**
    * Candidate that this peer granted vote for in current term (or null if none)
    */
@@ -149,7 +149,6 @@ class ServerState implements Closeable {
     snapshotManager = new SnapshotManager(id, storage.getStorageDir(), stateMachine.getStateMachineStorage());
 
     // On start the leader is null, start the clock now
-    this.leaderId = null;
     this.lastNoLeaderTime = Timestamp.currentTime();
     this.noLeaderTimeout = RaftServerConfigKeys.Notification.noLeaderTimeout(prop);
 
@@ -256,7 +255,7 @@ class ServerState implements Closeable {
   }
 
   RaftPeerId getLeaderId() {
-    return leaderId;
+    return leaderId.get();
   }
 
   boolean hasLeader() {
@@ -298,7 +297,8 @@ class ServerState implements Closeable {
   }
 
   void setLeader(RaftPeerId newLeaderId, Object op) {
-    if (!Objects.equals(leaderId, newLeaderId)) {
+    final RaftPeerId oldLeaderId = leaderId.getAndSet(newLeaderId);
+    if (!Objects.equals(oldLeaderId, newLeaderId)) {
       String suffix;
       if (newLeaderId == null) {
         // reset the time stamp when a null leader is assigned
@@ -311,9 +311,8 @@ class ServerState implements Closeable {
         server.getStateMachine().event().notifyLeaderChanged(getMemberId(), newLeaderId);
       }
       LOG.info("{}: change Leader from {} to {} at term {} for {}{}",
-          getMemberId(), leaderId, newLeaderId, getCurrentTerm(), op, suffix);
-      leaderId = newLeaderId;
-      if (leaderId != null) {
+          getMemberId(), oldLeaderId, newLeaderId, getCurrentTerm(), op, suffix);
+      if (newLeaderId != null) {
         server.finishTransferLeadership();
         server.onGroupLeaderElected();
       }
@@ -376,13 +375,15 @@ class ServerState implements Closeable {
     final long current = currentTerm.get();
     if (leaderTerm < current) {
       return false;
-    } else if (leaderTerm > current || this.leaderId == null) {
+    }
+    final RaftPeerId curLeaderId = getLeaderId();
+    if (leaderTerm > current || curLeaderId == null) {
       // If the request indicates a term that is greater than the current term
       // or no leader has been set for the current term, make sure to update
       // leader and term later
       return true;
     }
-    return this.leaderId.equals(peerLeaderId);
+    return curLeaderId.equals(peerLeaderId);
   }
 
   static int compareLog(TermIndex lastEntry, TermIndex candidateLastEntry) {
@@ -406,7 +407,7 @@ class ServerState implements Closeable {
 
   @Override
   public String toString() {
-    return getMemberId() + ":t" + currentTerm + ", leader=" + leaderId
+    return getMemberId() + ":t" + currentTerm + ", leader=" + getLeaderId()
         + ", voted=" + votedFor + ", raftlog=" + log + ", conf=" + getRaftConf();
   }