Merge pull request #193 from mxsm/dledger-191

[ISSUE #191]Optimize DLedgerLeaderElector.maintainAsCandidate code

Author: tsunghanjacktsai

src/main/java/io/openmessaging/storage/dledger/DLedgerLeaderElector.java

@@ -396,6 +396,9 @@ private void maintainAsCandidate() throws Exception {
         long term;
         long ledgerEndTerm;
         long ledgerEndIndex;
+        if (!memberState.isCandidate()) {
+            return;
+        }
         synchronized (memberState) {
             if (!memberState.isCandidate()) {
                 return;
@@ -443,9 +446,6 @@ private void maintainAsCandidate() throws Exception {
                             case ACCEPT:
                                 acceptedNum.incrementAndGet();
                                 break;
-                            case REJECT_ALREADY_VOTED:
-                            case REJECT_TAKING_LEADERSHIP:
-                                break;
                             case REJECT_ALREADY_HAS_LEADER:
                                 alreadyHasLeader.compareAndSet(false, true);
                                 break;
@@ -462,6 +462,8 @@ private void maintainAsCandidate() throws Exception {
                             case REJECT_TERM_NOT_READY:
                                 notReadyTermNum.incrementAndGet();
                                 break;
+                            case REJECT_ALREADY_VOTED:
+                            case REJECT_TAKING_LEADERSHIP:
                             default:
                                 break;