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Posted to commits@cassandra.apache.org by "Jaydeepkumar Chovatia (JIRA)" <ji...@apache.org> on 2018/03/06 05:48:00 UTC
[jira] [Commented] (CASSANDRA-13740) Orphan hint file gets created
while node is being removed from cluster
[ https://issues.apache.org/jira/browse/CASSANDRA-13740?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16387326#comment-16387326 ]
Jaydeepkumar Chovatia commented on CASSANDRA-13740:
---------------------------------------------------
Hi [~iamaleksey]
A gentle ping. If you have some time then can you please help me close this?
Jaydeep
> Orphan hint file gets created while node is being removed from cluster
> ----------------------------------------------------------------------
>
> Key: CASSANDRA-13740
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13740
> Project: Cassandra
> Issue Type: Bug
> Components: Core, Hints
> Reporter: Jaydeepkumar Chovatia
> Assignee: Jaydeepkumar Chovatia
> Priority: Minor
> Fix For: 3.0.x, 3.11.x
>
> Attachments: 13740-3.0.15.txt, gossip_hang_test.py
>
>
> I have found this new issue during my test, whenever node is being removed then hint file for that node gets written and stays inside the hint directory forever. I debugged the code and found that it is due to the race condition between [HintsWriteExecutor.java::flush | https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/hints/HintsWriteExecutor.java#L195] and [HintsWriteExecutor.java::closeWriter | https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/hints/HintsWriteExecutor.java#L106]
> .
>
> *Time t1* Node is down, as a result Hints are being written by [HintsWriteExecutor.java::flush | https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/hints/HintsWriteExecutor.java#L195]
> *Time t2* Node is removed from cluster as a result it calls [HintsService.java-exciseStore | https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/hints/HintsService.java#L327] which removes hint files for the node being removed
> *Time t3* Mutation stage keeps pumping Hints through [HintService.java::write | https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/hints/HintsService.java#L145] which again calls [HintsWriteExecutor.java::flush | https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/hints/HintsWriteExecutor.java#L215] and new orphan file gets created
> I was writing a new dtest for {CASSANDRA-13562, CASSANDRA-13308} and that helped me reproduce this new bug. I will submit patch for this new dtest later.
> I also tried following to check how this orphan hint file responds:
> 1. I tried {{nodetool truncatehints <node>}} but it fails as node is no longer part of the ring
> 2. I then tried {{nodetool truncatehints}}, that still doesn’t remove hint file because it is not yet included in the [dispatchDequeue | https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/hints/HintsStore.java#L53]
> Reproducible steps:
> Please find dTest python file {{gossip_hang_test.py}} attached which reproduces this bug.
> Solution:
> This is due to race condition as mentioned above. Since {{HintsWriteExecutor.java}} creates thread pool with only 1 worker, so solution becomes little simple. Whenever we [HintService.java::excise | https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/hints/HintsService.java#L303] a host, just store it in-memory, and check for already evicted host inside [HintsWriteExecutor.java::flush | https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/hints/HintsWriteExecutor.java#L215]. If already evicted host is found then ignore hints.
> Jaydeep
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