Norbert Kalmar created ZOOKEEPER-3037:
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Summary: 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: 3.4.12, 3.5.3
Reporter: Norbert Kalmar
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 contrib called JvmPauseMonitor.
- Make feature configurable, by default: OFF
- ?Make sleep time and threshold time configurable?
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