Re: Dangling Client Backend Process

From: Rajeev rastogi <rajeev(dot)rastogi(at)huawei(dot)com>
To: Rajeev rastogi <rajeev(dot)rastogi(at)huawei(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Dangling Client Backend Process
Date: 2015-10-13 10:24:11
Message-ID: BF2827DCCE55594C8D7A8F7FFD3AB77159965D4C@szxeml521-mbs.china.huawei.com
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On 12th October 2015 20:45, Rajeev Rastogi Wrote:

>>> I observed one strange behavior today that if postmaster process gets crashed/killed, then it kill all background processes but not the client backend process.

>> This is a known behaviour and there was some discussion on this
>> topic [1] previously as well.

> Now as it is confirmed to be valid issue, I will spend some time on this to find if there is something more appropriate solution.

I checked the latest code and found Heikki has already added code for secure_read using the latch mechanism (using WaitLatchOrSocket). It currently waits for two events i.e. WL_LATCH_SET and WL_SOCKET_READABLE.
Commit id: 80788a431e9bff06314a054109fdea66ac538199

If we add the event WL_POSTMASTER_DEATH also, client backend process handling will become same as other backend process. So postmaster death can be detected in the same way.

But I am not sure if WL_POSTMASTER_DEATH event was not added intentionally for some reason. Please confirm.
Also is it OK to add this even handling in generic path of Libpq?

Please let me know if I am missing something?

Thanks and Regards,
Kumar Rajeev Rastogi

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