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From: Akshay Joshi <[email protected]>
To: Yogesh Mahajan <[email protected]>
Cc: pgadmin-hackers <[email protected]>
Cc: Nikhil Mohite <[email protected]>
Subject: Re: Request for inputs on #6208 - MaxQueuePool Issue
Date: Wed, 9 Aug 2023 12:54:42 +0530
Message-ID: <CANxoLDfHoprxmZ0ej8e2D1EWjswt3mv4ewCsBUtwsdELFQ8qhw@mail.gmail.com> (raw)
In-Reply-To: <CAMa=N=NVxKMyofyEL-53i8DV1=6PmgEjmomrXs1hya7BB8kcyw@mail.gmail.com>
References: <CAMa=N=NVxKMyofyEL-53i8DV1=6PmgEjmomrXs1hya7BB8kcyw@mail.gmail.com>

Hi Yogesh

On Tue, Aug 8, 2023 at 1:48 PM Yogesh Mahajan <
[email protected]> wrote:

> Hi Hackers,
>
> For the #6208 <https://github.com/pgadmin-org/pgadmin4/issues/6208;, below
> are the observations about this issue -
>
> On each API request, an application db connection is created with state
> 'idle in transaction'. Connection state is changed to idle only after a
> successful response from the web server. If an exception occurs while
> processing a request which is not handled and response is not sent, the
> application db connection remains orphaned. This connection is only reset
> on application restart.
>
> Issue - In case of pgAdmin, if the user openes 15 query tool tabs & all
> of them have long running transactions like pg_sleep(), then opening new
> query tool/or any operation on pgAdmin which hits API request to backend
> will throw 'QueuePool Limit reached' error. (Because by default, SQLAlchemy
> allows 15 connections total: 5 connections in pool & 10 in overflow and
> pgAdmin uses default setting.) OR  if the user executes a query in the
> query tool & while query execution is in progress, hits F5(keyboard
> shortcut to execute query) 16 times continuously, then pgAdmin throws
> 'QueuePool Limit reached' error. After that, the query tool gives incorrect
> responses to the queries.
>
> Solutions -
> 1.Provide configurable settings for 'pool_size' & 'max_overflow'
> parameters for SQLAlchemy.
> 2.Disable pooling using NullPool.A Pool which does not pool connections.
> Instead it literally opens and closes the underlying DB-API connection per
> each connection open/close. Using NullPool may impact the performance.
>
> What approach should be followed to fix the issue?
>

    If NullPool *may* impact the performance then we should go with
Solution 1.

>
>
> @Nikhil Mohite <[email protected]> Please add if anything is
> missed.
>
> Thanks,
> Yogesh Mahajan
> EnterpriseDB
>

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