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https://issues.apache.org/jira/browse/CURATOR-525?focusedWorklogId=413662&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-413662
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ASF GitHub Bot logged work on CURATOR-525:
------------------------------------------

                Author: ASF GitHub Bot
            Created on: 01/Apr/20 01:39
            Start Date: 01/Apr/20 01:39
    Worklog Time Spent: 10m 
      Work Description: chuchao333 commented on pull request #357: 
[CURATOR-525] Fix for Zombie LOST Curator
URL: https://github.com/apache/curator/pull/357#discussion_r401308665
 
 

 ##########
 File path: 
curator-framework/src/main/java/org/apache/curator/framework/state/ConnectionStateManager.java
 ##########
 @@ -319,8 +319,18 @@ else if ( currentConnectionState == ConnectionState.LOST )
         {
             try
             {
-                // give ConnectionState.checkTimeouts() a chance to run, reset 
ensemble providers, etc.
-                client.getZookeeperClient().getZooKeeper();
+                if ( client.getZookeeperClient().isConnected() )
 
 Review comment:
   right now, the `checkSessionExperiation` is only called `if 
sessionExpirationPercent > 0`, we should also change that?
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 413662)
    Time Spent: 0.5h  (was: 20m)

> There is a race condition in Curator which might lead to fake SUSPENDED event 
> and ruin CuratorFrameworkImpl inner state 
> ------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CURATOR-525
>                 URL: https://issues.apache.org/jira/browse/CURATOR-525
>             Project: Apache Curator
>          Issue Type: Bug
>          Components: Framework
>    Affects Versions: 4.2.0
>            Reporter: Mikhail Valiev
>            Assignee: Jordan Zimmerman
>            Priority: Critical
>             Fix For: 5.0.0
>
>         Attachments: CuratorFrameworkTest.java, 
> background-thread-infinite-loop.png, curator-race-condition.png, 
> event-watcher-thread.png
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> This was originally found in the 2.11.1 version of Curator, but I tested the 
> latest release as well, and the issue is still there.
> The issue is tied to guaranteed deletes and how it loops infinitely, if 
> called when there is no connection:
> client.delete().guaranteed().forPath(ourPath); 
> [https://curator.apache.org/apidocs/org/apache/curator/framework/api/GuaranteeableDeletable.html]
> This schedules a background operation which attempts to remove the node in 
> infinite loop. Each time a background operation fails due to connection loss 
> it performs a check (validateConnection() function) to see if the main thread 
> is already aware of connection loss, and if it's not - raises the connection 
> loss event. The problem is that this peace of code is also executed by the 
> event watcher thread when connection events are happening - this leads to 
> race condition. So when connection is restored it's easily possible for the 
> main thread to raise RECONNECTED event and after that for background thread 
> to raise SUSPENDED event.
> We might get unlucky and get a "phantom" SUSPENDED event. It breaks Curator 
> inner Connection state and leads to curator behaving unpredictably
> Attached some illustrations and Unit test to reproduce the issue. (Put debug 
> point in validateConnection() )
> *Possible solution*: in CuratorFrameworkImpl class adjust the processEvent() 
> function and add the following:
> if(event.getType() == CuratorEventType.SYNC) {
> connectionStateManager.addStateChange(ConnectionState.RECONNECTED);
> }
> If this is a same state as before - it will be ignored, if background 
> operation succeeded, but we are in SUSPENDED state - this would repair the 
> Curator state and raise RECONNECTED event.
>  



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