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https://issues.apache.org/jira/browse/HDFS-1172?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon updated HDFS-1172:
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Attachment: hdfs-1172.txt
Here's a new patch against trunk for this issue.
A few things changed since Hairong's original patch:
- I removed the part of the test that changes the replication factor of a file
while it's under construction. This part of the test wasn't succeeding
reliably, since it was running into a different bug: HDFS-2283
- added the test code from HDFS-1197 which allows the DNs to artificially delay
blockReceived calls in the tests. This exposed some other bugs with the patch
- the new replicateLastBlock code needed to be called in a different place:
-- the original patch called this on every attempt of completeFile(), rather
than on only the final/successful attempt. This meant that, if the replicas
were very slow to check in, the targets would be added to pendingReplication
many times, yielding a pending replica count much larger than the actual
replication factor
-- the code needs to be called for all blocks, not just the last block in a file
I looped the new tests for a while and they pass reliably.
> Blocks in newly completed files are considered under-replicated too quickly
> ---------------------------------------------------------------------------
>
> Key: HDFS-1172
> URL: https://issues.apache.org/jira/browse/HDFS-1172
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Affects Versions: 0.21.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Fix For: 0.23.0
>
> Attachments: HDFS-1172.patch, hdfs-1172.txt,
> replicateBlocksFUC.patch, replicateBlocksFUC1.patch, replicateBlocksFUC1.patch
>
>
> I've seen this for a long time, and imagine it's a known issue, but couldn't
> find an existing JIRA. It often happens that we see the NN schedule
> replication on the last block of files very quickly after they're completed,
> before the other DNs in the pipeline have a chance to report the new block.
> This results in a lot of extra replication work on the cluster, as we
> replicate the block and then end up with multiple excess replicas which are
> very quickly deleted.
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