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ASF GitHub Bot commented on CURATOR-358: ---------------------------------------- Github user dragonsinth commented on a diff in the pull request: https://github.com/apache/curator/pull/173#discussion_r88817351 --- Diff: curator-recipes/src/main/java/org/apache/curator/framework/recipes/leader/LeaderSelector.java --- @@ -341,11 +342,41 @@ public Participant getLeader() throws Exception static Participant getLeader(CuratorFramework client, Collection<String> participantNodes) throws Exception { + Participant result = null; + if ( participantNodes.size() > 0 ) { - return participantForPath(client, participantNodes.iterator().next(), true); + Iterator<String> iter = participantNodes.iterator(); + while ( iter.hasNext() ) + { + + try + { + result = participantForPath(client, iter.next(), true); --- End diff -- can probably just return here right? > Receiving KeeperException with NoNode when LeaderLatch#getLeader() > ------------------------------------------------------------------ > > Key: CURATOR-358 > URL: https://issues.apache.org/jira/browse/CURATOR-358 > Project: Apache Curator > Issue Type: Bug > Components: Recipes > Affects Versions: 2.10.0 > Reporter: Satish Duggana > Priority: Critical > > org.apache.curator.framework.recipes.leader.LeaderLatch#getLeader() throws > KeeperException with Code#NONODE intermittently as mentioned in the stack > trace below. It may be possible participant's ephemeral ZK node is removed > because its connection/session is closed. > You can see the below code at > https://github.com/apache/curator/blob/master/curator-recipes/src/main/java/org/apache/curator/framework/recipes/leader/LeaderLatch.java#L451 > public Participant getLeader() throws Exception > { > Collection<String> participantNodes = > LockInternals.getParticipantNodes(client, latchPath, LOCK_NAME, sorter); > return LeaderSelector.getLeader(client, participantNodes); > } > I guess it hits a race condition where a participant node is retrieved but > when it invokes LeaderSelector#getLeader() it would have been removed because > of session timeout and it throws KeeperException with NoNode code. It does > not retry as the RetryLoop retries only for connection/session timeouts. But > in this case, NoNode should have been retried. I could not find any APIs on > CuratorClient to configure the kind of KeeperException codes to be retried. > It may be good to have a way to take what kind of errors should be retried in > org.apache.curator.framework.CuratorFrameworkFactory.Builder APIs. > Intermittent Exception found with the stack trace: > 2016-11-15 06:09:33.954 o.a.s.d.nimbus [ERROR] Error when processing event > org.apache.storm.shade.org.apache.zookeeper.KeeperException$NoNodeException: > KeeperErrorCode = NoNode for > /storm/leader-lock/_c_97c09eed-5bba-4ac8-a05f-abdc4e8e95cf-latch-0000000002 > at > org.apache.storm.shade.org.apache.zookeeper.KeeperException.create(KeeperException.java:111) > at > org.apache.storm.shade.org.apache.zookeeper.KeeperException.create(KeeperException.java:51) > at > org.apache.storm.shade.org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1155) > at > org.apache.storm.shade.org.apache.curator.framework.imps.GetDataBuilderImpl$4.call(GetDataBuilderImpl.java:304) > at > org.apache.storm.shade.org.apache.curator.framework.imps.GetDataBuilderImpl$4.call(GetDataBuilderImpl.java:293) > at > org.apache.storm.shade.org.apache.curator.RetryLoop.callWithRetry(RetryLoop.java:108) > at > org.apache.storm.shade.org.apache.curator.framework.imps.GetDataBuilderImpl.pathInForeground(GetDataBuilderImpl.java:290) > at > org.apache.storm.shade.org.apache.curator.framework.imps.GetDataBuilderImpl.forPath(GetDataBuilderImpl.java:281) > at > org.apache.storm.shade.org.apache.curator.framework.imps.GetDataBuilderImpl.forPath(GetDataBuilderImpl.java:42) > at > org.apache.storm.shade.org.apache.curator.framework.recipes.leader.LeaderSelector.participantForPath(LeaderSelector.java:375) > at > org.apache.storm.shade.org.apache.curator.framework.recipes.leader.LeaderSelector.getLeader(LeaderSelector.java:346) > at > org.apache.storm.shade.org.apache.curator.framework.recipes.leader.LeaderLatch.getLeader(LeaderLatch.java:454) -- This message was sent by Atlassian JIRA (v6.3.4#6332)