NIFI-9217 - avoid deadlock on cluster operation (#5390)

nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/leader/election/CuratorLeaderElectionManager.java

@@ -64,10 +64,10 @@ public class CuratorLeaderElectionManager implements LeaderElectionManager {
 
     private volatile boolean stopped = true;
 
-    private final Map<String, LeaderRole> leaderRoles = new HashMap<>();
+    private final ConcurrentMap<String, LeaderRole> leaderRoles = new ConcurrentHashMap<>();
-    private final Map<String, RegisteredRole> registeredRoles = new HashMap<>();
+    private final ConcurrentMap<String, RegisteredRole> registeredRoles = new ConcurrentHashMap<>();
 
-    private final Map<String, TimedBuffer<TimestampedLong>> leaderChanges = new HashMap<>();
+    private final ConcurrentMap<String, TimedBuffer<TimestampedLong>> leaderChanges = new ConcurrentHashMap<>();
     private final TimedBuffer<TimestampedLongAggregation> pollTimes = new TimedBuffer<>(TimeUnit.SECONDS, 300, new CountSumMinMaxAccess());
     private final ConcurrentMap<String, String> lastKnownLeader = new ConcurrentHashMap<>();
 
@@ -221,16 +221,16 @@ public class CuratorLeaderElectionManager implements LeaderElectionManager {
         return "CuratorLeaderElectionManager[stopped=" + isStopped() + "]";
     }
 
-    private synchronized LeaderRole getLeaderRole(final String roleName) {
+    private LeaderRole getLeaderRole(final String roleName) {
         return leaderRoles.get(roleName);
     }
 
-    private synchronized void onLeaderChanged(final String roleName) {
+    private void onLeaderChanged(final String roleName) {
         final TimedBuffer<TimestampedLong> buffer = leaderChanges.computeIfAbsent(roleName, key -> new TimedBuffer<>(TimeUnit.HOURS, 24, new LongEntityAccess()));
         buffer.add(new TimestampedLong(1L));
     }
 
-    public synchronized Map<String, Integer> getLeadershipChangeCount(final long duration, final TimeUnit unit) {
+    public Map<String, Integer> getLeadershipChangeCount(final long duration, final TimeUnit unit) {
         final Map<String, Integer> leadershipChangesPerRole = new HashMap<>();
 
         for (final Map.Entry<String, TimedBuffer<TimestampedLong>> entry : leaderChanges.entrySet()) {
@@ -301,49 +301,58 @@ public class CuratorLeaderElectionManager implements LeaderElectionManager {
         return participantId;
     }
 
-    private synchronized void registerPollTime(final long nanos) {
+    private void registerPollTime(final long nanos) {
+        synchronized (pollTimes) {
             pollTimes.add(TimestampedLongAggregation.newValue(nanos));
         }
+    }
 
-    public synchronized long getAveragePollTime(final TimeUnit timeUnit) {
+    public long getAveragePollTime(final TimeUnit timeUnit) {
+        final long averageNanos;
+        synchronized (pollTimes) {
             final TimestampedLongAggregation.TimestampedAggregation aggregation = pollTimes.getAggregateValue(0L).getAggregation();
             if (aggregation == null || aggregation.getCount() == 0) {
                 return 0L;
             }
-
+            averageNanos = aggregation.getSum() / aggregation.getCount();
-        final long averageNanos = aggregation.getSum() / aggregation.getCount();
+        }
         return timeUnit.convert(averageNanos, TimeUnit.NANOSECONDS);
     }
 
-    public synchronized long getMinPollTime(final TimeUnit timeUnit) {
+    public long getMinPollTime(final TimeUnit timeUnit) {
+        final long minNanos;
+        synchronized (pollTimes) {
             final TimestampedLongAggregation.TimestampedAggregation aggregation = pollTimes.getAggregateValue(0L).getAggregation();
             if (aggregation == null) {
                 return 0L;
             }
-
+            minNanos = aggregation.getMin();
-        final long minNanos = aggregation.getMin();
+        }
         return timeUnit.convert(minNanos, TimeUnit.NANOSECONDS);
     }
 
-    public synchronized long getMaxPollTime(final TimeUnit timeUnit) {
+    public long getMaxPollTime(final TimeUnit timeUnit) {
+        final long maxNanos;
+        synchronized (pollTimes) {
             final TimestampedLongAggregation.TimestampedAggregation aggregation = pollTimes.getAggregateValue(0L).getAggregation();
             if (aggregation == null) {
                 return 0L;
             }
-
+            maxNanos = aggregation.getMax();
-        final long maxNanos = aggregation.getMax();
+        }
         return timeUnit.convert(maxNanos, TimeUnit.NANOSECONDS);
     }
 
     @Override
-    public synchronized long getPollCount() {
+    public long getPollCount() {
+        synchronized (pollTimes) {
             final TimestampedLongAggregation.TimestampedAggregation aggregation = pollTimes.getAggregateValue(0L).getAggregation();
             if (aggregation == null) {
                 return 0L;
             }
-
             return aggregation.getCount();
         }
+    }
 
     /**
      * Determines whether or not leader election has already begun for the role with the given name