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https://issues.apache.org/jira/browse/HDFS-6681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16396099#comment-16396099
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Zsolt Venczel commented on HDFS-6681:
-------------------------------------
I had verified that the test was indeed flaky without the patch (failed 3 times
from 1000) but after applying the patch it got stable (no failures from 1000
run).
+1 from me.
> TestRBWBlockInvalidation#testBlockInvalidationWhenRBWReplicaMissedInDN is
> flaky and sometimes gets stuck in infinite loops
> --------------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-6681
> URL: https://issues.apache.org/jira/browse/HDFS-6681
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.4.1
> Environment: Java(TM) SE Runtime Environment (build 1.6.0_31-b04)
> Java HotSpot(TM) 64-Bit Server VM (build 20.6-b01, mixed mode)
> Linux [hostname] 2.6.32-279.14.1.el6.x86_64 #1 SMP Mon Oct 15 13:44:51 EDT
> 2012 x86_64 x86_64 x86_64 GNU/Linux
> Reporter: Ratandeep Ratti
> Assignee: Ratandeep Ratti
> Priority: Major
> Labels: BB2015-05-TBR, flaky-test
> Attachments: HDFS-6681.001.patch, HDFS-6681.patch
>
>
> This testcase has 3 infinite loops which break only on certain conditions
> being satisfied.
> 1st loop checks if there should be a single live replica. It assumes this to
> be true since it has just corrupted a block on one of the datanodes (testcase
> has replication factor as 2). One scenario in which this loop will never
> break is if the Namenode invalidates the corrupt replica, schedules a
> replication command, and the new copied replica is added all before this
> testcase has the chance to check the live-replica count.
> 2nd loop checks there should be 2 live replicas. It assumes this to be true
> (in some time) since the first loop has broken implying there is a single
> replica and now it is only a matter of time when the Namenode schedules a
> replication command to copy a replica to another datanode. One scenario in
> which this loop will never break is when the Namenode tries to schedule a new
> replica on the same node on which we actually corrupted the block. That dst.
> datanode will not copy the block, complaining that it already has the
> (corrupted) replica in the create state. The situation that results is that
> Namenode has scheduled a copy to a datanode, the block is now in the
> namenode's pending replication queue, this block will never be removed from
> the pending replication queue because the namenode will never receive a
> report from the datanodes that the block is 'added'.
> Note: The block can be transferred from the 'pending replication' to "needed
> replication" queue once the pending timeout (5 minutes) expires. The Namenode
> then actively tries to schedule a replication for blocks in 'needed
> replication' queue. This can cause the 2nd loop to break but the time in
> which this process gets kicked in is more than 5 minutes.
> 3rd loop: This loops checks if there are no corrupt replicas. I don't see a
> scenario in which this loop can go on for ever, since once the live replica
> count goes back to normal (2), the corrupted block will be removed
> I guess increasing the heart beat interval time, so that the testcase has
> enough time to check condition in loop 1 before a datanode reports a
> successful copy should help avoid race condition in loop1. Regarding loop2 I
> guess we can reduce the timeout after which the block is transferred from the
> pending replication to the needed replication queue.
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