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From: Edwin UY <[email protected]>
To: Tom Lane <[email protected]>
Cc: David G. Johnston <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: How to check if session is a hung thread/session
Date: Mon, 11 Nov 2024 19:45:29 +1300
Message-ID: <CA+wokJ8VFQ1AkaqaCuND9A-+Xgq1rhdXioXNzQm7CSGPA5x2EQ@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CA+wokJ_QejkPWUym3njMQCkeFQ_kRcRdah5S2eseocwsHLc-4w@mail.gmail.com>
	<CAKFQuwZunKoiM4AO0BBAbRc73_unJoMJA5WmPFWYnUWj+s0Q_Q@mail.gmail.com>
	<CA+wokJ96V5UuHhPStt+eMigkXsn7RJbMaiL-aK1K=S5aFQg66g@mail.gmail.com>
	<[email protected]>

Thanks Tom,

OK, I've decided to 'painfully' look at the PostgreSQL RDS logs and it is
showing something like below.
There seems to be a locking/deadlock issue of some sort somewhere.
I have checked the other days' log prior to the patching and these appear
to be a 'normal' occurrence for this database and it wasn't affecting the
application nonetheless.
After the patching, it starts affecting the application. Not sure what else
I can check on the Aurora PostgreSQL RDS end. I may request them to restart
the app server.

[25751]:LOG:  process 25751 still waiting for ShareLock on transaction
114953443 after 1000.054 ms
[25751]:DETAIL:  Process holding the lock: 22297. Wait queue: 25751.
[25751]:CONTEXT:  while locking tuple (1,17) in relation "[table_name]"
[25751]:STATEMENT:  [SQL_STATEMENT] for update
[25751]:LOG:  process 25751 acquired ShareLock on transaction 114953443
after 4756.967 ms
[25751]:CONTEXT:  while locking tuple (1,17) in relation " [table_name] "


On Mon, Nov 11, 2024 at 5:45 PM Tom Lane <[email protected]> wrote:

> Edwin UY <[email protected]> writes:
> > I thought it could be the backend has sent something back to the client
> but
> > it never received it and it just kept on doing the same at some
> intervals.
>
> Your pg_stat_activity output shows the backend is idle, meaning it's
> waiting for a client command.  While the session has been around for
> days, we can see the last client command was about 47 minutes ago,
> from your "now() - pg_stat_activity.query_start AS duration" column.
> I see no reason to think there is anything interesting here at all,
> except for a client that is sitting doing nothing for long periods.
>
>                         regards, tom lane
>

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