fix #4547: preventing a cancelled leader elector

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### 6.3-SNAPSHOT
 
 #### Bugs
+Fix #4547: preventing timing issues with leader election cancel
 
 #### Improvements
 

kubernetes-client-api/src/main/java/io/fabric8/kubernetes/client/extended/leaderelection/LeaderElector.java

@@ -50,6 +50,7 @@ public class LeaderElector {
   private final AtomicReference<LeaderElectionRecord> observedRecord = new AtomicReference<>();
   private final AtomicReference<LocalDateTime> observedTime = new AtomicReference<>();
   private final Executor executor;
+  private boolean stopped;
 
   public LeaderElector(KubernetesClient kubernetesClient, LeaderElectionConfig leaderElectionConfig, Executor executor) {
     this.kubernetesClient = kubernetesClient;
@@ -110,7 +111,8 @@ public CompletableFuture<?> start() {
     return result;
   }
 
-  private void stopLeading() {
+  private synchronized void stopLeading() {
+    stopped = true;
     LeaderElectionRecord current = observedRecord.get();
     if (current == null || !isLeader(current)) {
       return; // not leading
@@ -182,7 +184,10 @@ private CompletableFuture<Void> renewWithTimeout() {
     }, () -> leaderElectionConfig.getRetryPeriod().toMillis(), executor);
   }
 
-  boolean tryAcquireOrRenew() throws LockException {
+  synchronized boolean tryAcquireOrRenew() throws LockException {
+    if (stopped) {
+      return false;
+    }
     final Lock lock = leaderElectionConfig.getLock();
     final ZonedDateTime now = now();
     final LeaderElectionRecord oldLeaderElectionRecord = lock.get(kubernetesClient);

kubernetes-client-api/src/test/java/io/fabric8/kubernetes/client/extended/leaderelection/LeaderElectorTest.java

@@ -134,6 +134,8 @@ void shouldReleaseWhenCanceled() throws Exception {
     Awaitility.await().atMost(10, TimeUnit.SECONDS).until(() -> Utils.isNullOrEmpty(activeLer.get().getHolderIdentity()));
     assertEquals(0, activeLer.get().getLeaderTransitions());
 
+    // create a new elector, they are no good after a single use
+    leaderElector = new LeaderElector(mock(NamespacedKubernetesClient.class), lec, CommonThreadPool.get());
     // the leader is now empty/null, we should be able to re-acquire
     assertTrue(leaderElector.tryAcquireOrRenew());