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https://issues.apache.org/jira/browse/HBASE-4222?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13088091#comment-13088091
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jirapos...@reviews.apache.org commented on HBASE-4222:
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bq. On 2011-08-19 18:58:21, Michael Stack wrote:
bq. >
Will post an update with a default setting of 2 in hbase-default.xml and some
fixes to TestLogRolling -- my additional test is not playing nicely with the
HBASE-4095 changes there at the moment.
bq. On 2011-08-19 18:58:21, Michael Stack wrote:
bq. > src/main/java/org/apache/hadoop/hbase/regionserver/LogRoller.java, line
87
bq. > <https://reviews.apache.org/r/1590/diff/1/?file=33750#file33750line87>
bq. >
bq. > How do you manually roll a log? I want that.
Probably wouldn't be too hard to add a RPC call and shell command to manually
trigger a roll. That would be nice to have, but I'll leave it for a separate
issue.
(Log message just means triggered by HLog.requestLogRoll(), meaning from an
IOException, or current log size, or replica count below threshold).
- Gary
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On 2011-08-19 18:33:11, Gary Helmling wrote:
bq.
bq. -----------------------------------------------------------
bq. This is an automatically generated e-mail. To reply, visit:
bq. https://reviews.apache.org/r/1590/
bq. -----------------------------------------------------------
bq.
bq. (Updated 2011-08-19 18:33:11)
bq.
bq.
bq. Review request for hbase.
bq.
bq.
bq. Summary
bq. -------
bq.
bq. This patch corrects a few problems, as I see it, with the current log
rolling process:
bq.
bq. 1) HLog.LogSyncer.run() now handles an IOException in the inner while
loop. Previously any IOException would cause the LogSyncer thread to exit,
even if the subsequent log roll succeeded. This would mean the region server
kept running without a LogSyncer thread
bq. 2) Log rolls triggered by IOExceptions were being skipped in the event
that there were no entries in the log. This would prevent the log from being
recovered in a timely manner.
bq. 3) minor - FailedLogCloseException was never actually being thrown out of
HLog.cleanupCurrentWriter(), resulting in inaccurate logging on RS abort
bq.
bq. The bigger change is the addition of a configuration property --
hbase.regionserver.logroll.errors.tolerated -- that is checked against a
counter of consecutive close errors to see whether or not an abort should be
triggered.
bq.
bq. Prior to this patch, we could readily trigger region server aborts by
rolling all the data nodes in a cluster while region servers were running.
This was equally true whether write activity was happening or not. (In fact I
think having concurrent write activity actually gave a better chance for the
log to be rolled prior to all DNs in the write pipeline going down and thus the
region server not aborting).
bq.
bq. With this change and hbase.regionserver.logroll.errors.tolerated=2, I can
roll DNs at will without causing any loss of service.
bq.
bq. I'd appreciate some scrutiny on any log rolling subtleties or interactions
I may be missing here. If there are alternate/better ways to handle this in
the DFSClient layer, I'd also appreciate any pointers to that.
bq.
bq.
bq. This addresses bug HBASE-4222.
bq. https://issues.apache.org/jira/browse/HBASE-4222
bq.
bq.
bq. Diffs
bq. -----
bq.
bq. src/main/java/org/apache/hadoop/hbase/regionserver/LogRoller.java
8e87c83
bq. src/main/java/org/apache/hadoop/hbase/regionserver/wal/HLog.java 887f736
bq.
src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestLogRolling.java
287f1fb
bq.
bq. Diff: https://reviews.apache.org/r/1590/diff
bq.
bq.
bq. Testing
bq. -------
bq.
bq. Added a new test for rolling data nodes under a running cluster:
TestLogRolling.testLogRollOnPipelineRestart().
bq.
bq. Tested patch on a running cluster with 3 slaves, rolling data nodes with
and without concurrent write activity.
bq.
bq.
bq. Thanks,
bq.
bq. Gary
bq.
bq.
> Make HLog more resilient to write pipeline failures
> ---------------------------------------------------
>
> Key: HBASE-4222
> URL: https://issues.apache.org/jira/browse/HBASE-4222
> Project: HBase
> Issue Type: Improvement
> Components: wal
> Reporter: Gary Helmling
> Assignee: Gary Helmling
> Fix For: 0.92.0
>
>
> The current implementation of HLog rolling to recover from transient errors
> in the write pipeline seems to have two problems:
> # When {{HLog.LogSyncer}} triggers an {{IOException}} during time-based sync
> operations, it triggers a log rolling request in the corresponding catch
> block, but only after escaping from the internal while loop. As a result,
> the {{LogSyncer}} thread will exit and never be restarted from what I can
> tell, even if the log rolling was successful.
> # Log rolling requests triggered by an {{IOException}} in {{sync()}} or
> {{append()}} never happen if no entries have yet been written to the log.
> This means that write errors are not immediately recovered, which extends the
> exposure to more errors occurring in the pipeline.
> In addition, it seems like we should be able to better handle transient
> problems, like a rolling restart of DataNodes while the HBase RegionServers
> are running. Currently this will reliably cause RegionServer aborts during
> log rolling: either an append or time-based sync triggers an initial
> {{IOException}}, initiating a log rolling request. However the log rolling
> then fails in closing the current writer ("All datanodes are bad"), causing a
> RegionServer abort. In this case, it seems like we should at least allow you
> an option to continue with the new writer and only abort on subsequent errors.
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