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From Benoit Perroud <>
Subject Re: HA NameNode switching without reason
Date Fri, 24 Jul 2015 19:05:20 GMT
This is probably not the best place to ask such questions as they are not
specifically related to Ambari but HDFS.

There are lots of scenarios when a NN can switch, and there is always a
good reason for that :)

Some of them can be:
- if you're running a older version of hadoop/hdp (2.1), slow block reports
or slow fsimage transfer can lead to NN switch,
- you rpc pool is too small (NN server thread)
- you're hit by the futex lock bug (!topic/mechanical-sympathy/QbmpZxp6C64)
and might to upgrade your kernel(s).

2015-07-23 17:51 GMT+02:00 Loïc Chanel <>:

> Hi,
> I am using a high-availability cluster with 3 JournalNodes and 2 NameNodes
> on 2 out of 3 of these hosts, and the NameNode switched his host 3 times in
> less than 24 hours without apparent reason.
> This can't be a network problem, as the logs indicate clearly that the
> NameNode can't send logs to the JournalNode running on the exact same host,
> while calling it using its IP, and this doesn't seem to be a CPU or RAM
> problem as the command sar does not return any abnormality, and Ganglia
> graphics show that the JVM has way more memory than it needs to have.
> Do any of you have an idea about where the problem might come from ?
> Thanks in advance,
> Loïc
> Engineering student at TELECOM Nancy
> Trainee at Worldline - Villeurbanne

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