Re: Troubleshooting a brief spike in active sessions

From: Nikolay Samokhvalov <nik(at)postgres(dot)ai>
To: "Dirschel, Steve-CW" <Steve(dot)Dirschel(at)bestbuy(dot)com>
Cc: "pgsql-performance(at)lists(dot)postgresql(dot)org" <pgsql-performance(at)lists(dot)postgresql(dot)org>
Subject: Re: Troubleshooting a brief spike in active sessions
Date: 2026-01-09 22:27:17
Message-ID: CAM527d-Udxg5NSg_kEsEuTm-gB5GJ8z=84znpTQQT-tu2VQW_A@mail.gmail.com
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On Fri, Jan 9, 2026 at 1:41 PM Dirschel, Steve-CW <
Steve(dot)Dirschel(at)bestbuy(dot)com> wrote:
>
> Aurora Postgres version 17.4
>
> ...
>
> The app sessions will show as wait_event_type and wait_event as null
which I understand means they are on CPU
>
> ...

Not necessarily. It also might be an uninstrumented wait event.

Do the spikes of "CPU" AAS (I prefer to call them "CPU*") correspond well
to the spikes of high usage?

If you have N active sessions marked as CPU in ASH, does it match to the
CPU load of similar scale?

If the VM has much less than 400 vCPUs and you see overall CPU load far
from 100%, then we should suspect some missing wait event.

Nik

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