[
https://issues.apache.org/jira/browse/HDFS-9752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15134625#comment-15134625
]
Xiaobing Zhou commented on HDFS-9752:
-------------------------------------
I agreed to avoid sleep in test with best efforts. Once my patch with sleep in
test is committed and failed quite often in jenkins.
[~arpitagarwal]'s proposal is good since pipelineRecoveryCount check is the key
point. The current test is based on exception check that might not be
deterministic due to sleep.
> Permanent write failures may happen to slow writers during datanode rolling
> upgrades
> ------------------------------------------------------------------------------------
>
> Key: HDFS-9752
> URL: https://issues.apache.org/jira/browse/HDFS-9752
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Kihwal Lee
> Assignee: Walter Su
> Priority: Critical
> Attachments: HDFS-9752.01.patch, HDFS-9752.02.patch, HdfsWriter.java
>
>
> When datanodes are being upgraded, an out-of-band ack is sent upstream and
> the client does a pipeline recovery. The client may hit this multiple times
> as more nodes get upgraded. This normally does not cause any issue, but if
> the client is holding the stream open without writing any data during this
> time, a permanent write failure can occur.
> This is because there is a limit of 5 recovery trials for the same packet,
> which is tracked by "last acked sequence number". Since the empty heartbeat
> packets for an idle output stream does not increment the sequence number, the
> write will fail after it seeing 5 pipeline breakages by datanode upgrades.
> This check/limit was added to avoid spinning until running out of nodes in
> the cluster due to a corruption or any other irrecoverable conditions. The
> datanode upgrade-restart should be excluded from the count.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
