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https://issues.apache.org/jira/browse/ZOOKEEPER-3037?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mate Szalay-Beko updated ZOOKEEPER-3037:
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Affects Version/s: 3.5.0
3.4.0
(was: 3.5.3)
(was: 3.4.12)
> Add JvmPauseMonitor to ZooKeeper
> --------------------------------
>
> Key: ZOOKEEPER-3037
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3037
> Project: ZooKeeper
> Issue Type: Improvement
> Components: contrib
> Affects Versions: 3.4.0, 3.5.0
> Reporter: Norbert Kalmár
> Assignee: Norbert Kalmár
> Priority: Minor
> Labels: pull-request-available
> Fix For: 3.6.0
>
> Time Spent: 2.5h
> Remaining Estimate: 0h
>
> After a ZK crash, or client timeout sometimes it's hard to determine from the
> logs what happened. Knowing if ZK was responsive at the time would help a
> lot. For example, ZK might spend a lot of time waiting on GC (there is still
> some misconception that ZK is a storage).
> To help detect this, HADOOP already has a great tool called JVM Pause
> Monitor. (As the name suggest, it can be also used for monitoring, but it
> also helps post-mortem in a lot of cases). Basically it has a daemon that
> sleeps for one second, and if the sleep time exceeds the 1s by more than the
> threshold (1s: INFO, 10s: WARN by default - this can be configurable in our
> case, see below), it will alert/make a log entry. It can also monitor the
> time GC took.
> The class implementing this is in HADOOP-common, but ZK should not depend on
> this package. Since this is a straightforward implementation, and in the past
> five years the few commits it had is nothing really serious, I think we could
> just copy this class in ZooKeeper, and introduce it as a configurable
> feature, by default it can be off.
> The class:
> https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/JvmPauseMonitor.java
> Task:
> - Create a class in ZK (under zookeeper/server/util/) called JvmPauseMonitor.
> - Make feature configurable, by default: OFF
> - Make sleep time and threshold time configurable
> - Update documentation
> - Add [current size of the heap OR % of heap used] in the log entry whenever
> sleep threshold had exceeded by a lot (10s)
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