Thank you Adrian for the reply, I did check the postgres processes running around the time when OOM was invoked, there were lots of high CPU consuming postgres processes running long running selects.
I am not sure of how to interpret the memory terms appearing in linux dmeg or /var/log/messages but I can see out of memory happened and Postmaster invoked OOM.
Regards
Vikas Sharma
On 2/12/19 8:20 AM, Vikas Sharma wrote:
> Hello All,
>
> I have a 4 node PostgreSQL 9.6 cluster with streaming replication. we
> encounter today the Out of Memory Error on the Master which resulted in
> All postres processes restarted and cluster recovered itself. Please
> let me know the best way to diagnose this issue.
For a start look back further in the Postgres log then the below. What
is shown below is the effects of the OOM killer. What you need to look
for is the statement that caused Postgres memory to increase to the
point that the OOM killer was invoked.
>
>
>
> The error seen in the postgresql log:
>
> 2019-02-12 10:55:17 GMT LOG: terminating any other active server processes
> 2019-02-12 10:55:17 GMT WARNING: terminating connection because of
> crash of another server process
> 2019-02-12 10:55:17 GMT DETAIL: The postmaster has commanded this
> server process to roll back the current transaction and exit, because
> another server process exited abnormally and possibly corrupted shared
> memory.
> 2019-02-12 10:55:17 GMT HINT: In a moment you should be able to
> reconnect to the database and repeat your command.
> 2019-02-12 10:55:17 GMT WARNING: terminating connection because of
> crash of another server process
> 2019-02-12 10:55:17 GMT DETAIL: The postmaster has commanded this
> server process to roll back the current transaction and exit, because
> another server process exited abnormally and possibly corrupted shared
> memory.
> 2019-02-12 10:55:17 GMT HINT: In a moment you should be able to
> reconnect to the database and repeat your command.
> 2019-02-12 10:55:17 GMT WARNING: terminating connection because of
> crash of another server process
> -----
>
> Error from dmesg on linux:
> -----------------------------------
> [4331093.885622] Out of memory: Kill process nnnnn (postmaster) score nn
> or sacrifice child
> [4331093.890225] Killed process nnnnn (postmaster) total-vm:18905944kB,
> anon-rss:1747460kB, file-rss:4kB, shmem-rss:838220kB
>
> Thanks & Best Regards
> Vikas Sharma
--
Adrian Klaver
adrian.klaver@aklaver.com