[GitHub] [incubator-ratis] GlenGeng commented on a change in pull request #161: RATIS-993. Preventing disruptions when a server rejoins the cluster

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

GlenGeng commented on a change in pull request #161:
URL: https://github.com/apache/incubator-ratis/pull/161#discussion_r466128412



##########
File path: ratis-server/src/main/java/org/apache/ratis/server/impl/ServerState.java
##########
@@ -221,10 +221,10 @@ boolean hasLeader() {
   /**
    * Become a candidate and start leader election
    */
-  long initElection() {
+  long initElection(boolean preVote) {

Review comment:
       If `preVote` is true, you will not change `currentTerm`, meanwhile change `voteFor`, which may violate the raft algorithm that one can only vote once in a specific term.

##########
File path: ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderElection.java
##########
@@ -188,89 +197,104 @@ private boolean shouldRun(long electionTerm) {
     return shouldRun() && server.getState().getCurrentTerm() == electionTerm;
   }
 
+  private ResultAndTerm submitRequestAndWaitResult(
+      final ServerState state, final RaftConfiguration conf, final long electionTerm, boolean preVote)
+      throws InterruptedException {
+    final ResultAndTerm r;
+    final Collection<RaftPeer> others = conf.getOtherPeers(server.getId());
+    if (others.isEmpty()) {
+      r = new ResultAndTerm(Result.PASSED, electionTerm);
+    } else {
+      TermIndex lastEntry = state.getLastEntry();
+      final Executor voteExecutor = new Executor(this, others.size());
+      try {
+        final int submitted = submitRequests(electionTerm, lastEntry, others, voteExecutor, preVote);
+        r = waitForResults(electionTerm, submitted, conf, voteExecutor, preVote);
+      } finally {
+        voteExecutor.shutdown();
+      }
+    }
+
+    return r;
+  }
+
   /**
    * After a peer changes its role to candidate, it invokes this method to
    * send out requestVote rpc to all other peers.
    */
-  private void askForVotes() throws InterruptedException, IOException {
+  private boolean askForVotes(boolean preVote) throws InterruptedException, IOException {

Review comment:
       `While (shouldRu())` may be omitted for preVote case, since it just need one round roc.




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