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From Otis Gospodnetic <otis.gospodne...@gmail.com>
Subject Re: how to tell there is a OOM in regionserver
Date Tue, 02 Dec 2014 05:36:04 GMT
Hi Ming,

1) There typically is an OOM message from the JVM itself

2) I would monitor the server instead of relying on log messages mentioning
OOMs.  For example, in SPM <http://sematext.com/spm/> we have "hearbeat
alerts" that tell us when we stop hearing from RegionServers and other
types of servers.  It also helps when servers simply die for reasons other
than OOM.

3) You could (should?) monitor individual memory pools and possibly set
alerts or anomaly detection on those.  If you have that, if there was an
OOM, you will typically see one of the memory pools approach 100%
utilization.  I personally really like this report in SPM because it gives
a bit more insight than just "heap size/utilization".  So I'd point the
admin to this sort of monitoring report.

4) High GC counts/time, or jump in those metrics, and then typically also
jump in CPU usage is what often precedes OOMs.

Otis
--
Monitoring * Alerting * Anomaly Detection * Centralized Log Management
Solr & Elasticsearch Support * http://sematext.com/


On Tue, Dec 2, 2014 at 12:22 AM, Liu, Ming (HPIT-GADSC) <ming.liu2@hp.com>
wrote:

> Hi, all,
>
> Recently, one of our HBase 0.98.5 instance meet with issues: when run some
> specific workload, all region servers will suddenly shut down at same time,
> but master is still running. When I check the log, in master log, I can see
> messages like
> 2014-12-01 08:28:11,072 DEBUG [main-EventThread] master.ServerManager:
> Added=n008.cluster,60020,1417413986550 to dead servers, submitted shutdown
> handler to be executed meta=false
> And on n008, regionserver log file, there is no ERROR message, the last
> log entry looks very like a ZooKeeper startup message. The log just stopped
> with that last ZooKeeper startup message, and the Region Server process was
> gone when we check with 'jps'.
>
> We then increased the heap size of regionserver, and it work fine.
> RegionServer no longer disappear. So we doubt there was a Out Of Memory
> issue, so the region server processes are killed. But my questions are:
>
> 1.       What log message will indicate there is a OOM? Since the region
> server is 'kill -9', so I think there is no message can tell this.
>
> 2.       If there is no typical log message about OOM, then how can an
> admin make sure there is a region server OOM happened? We just guess, but
> can not make sure. We hope there is a method to tell OOM occured for sure.
>
> 3.       Does the Zookeeper message appears every time with RegionServer
> OOM (if it is a OOM). Or it is just a random event just in our system?
>
> So in sum, I want to know what is the typical clue that people can make
> sure there is a OOM issue in HBase region server?
>
> Thank you,
> Ming
>

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