Re: CLOSE_WAIT pileup and Application Timeout

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From: KK CHN <[email protected]>
To: Alvaro Herrera <[email protected]>
Cc: pgsql-general <[email protected]>
Subject: Re: CLOSE_WAIT pileup and Application Timeout
Date: Mon, 7 Oct 2024 17:00:47 +0530
Message-ID: <CAKgGyB8zMUzJSMQL8ryc-73aG3YEhWj4hGkqtOBT_yywesyCHQ@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CAKgGyB91QVCOFp+3vAcMDAauAPQ+TOVWrJxwcVAtYxaLxXaz4Q@mail.gmail.com>
	<[email protected]>

On Mon, Oct 7, 2024 at 12:07 AM Alvaro Herrera <[email protected]>
wrote:

> On 2024-Oct-04, KK CHN wrote:
>
> > The mobile tablets are installed with the android based vehicle
> > tracking app which updated every 30 seconds its location fitted inside
> the
> > vehicle ( lat long coordinates) to the PostgreSQL DB through the java
> > backend application to know the latest location of the vehicle and its
> > movement which will be rendered in a map based front end.
> >
> > The vehicles on the field communicate  via 443 to   8080 of the Wildfly
> > (version 27 ) deployed with the vehicle tracking application developed
> with
> > Java(version 17).
>
> It sounds like setting TCP keepalives in the connections between the
> Wildfly and the vehicles might help get the number of dead connections
> down to a reasonable level.  Then it's up to Wildfly to close the
> connections to Postgres in a timely fashion.  (It's not clear from your
> description how do vehicle connections to Wildfly relate to Postgres
> connections.)
>
>
Where do I have to introduce the TCP keepalives ? in the OS level or
application code level ?

[root@dbch wildfly-27.0.0.Final]# cat /proc/sys/net/ipv4/tcp_keepalive_time
7200
[root@dbch wildfly-27.0.0.Final]# cat /proc/sys/net/ipv4/tcp_keepalive_intvl
75
[root@dbch wildfly-27.0.0.Final]# cat
/proc/sys/net/ipv4/tcp_keepalive_probes
9
[root@dbch wildfly-27.0.0.Final]#

These are the default values in the OS level.   Do I need to reduce all the
above three values to  say 600, 20, 5  ?   Or need to be handled in the
application backend code ?

 Any hints much appreciated..

>
> I wonder if the connections from Wildfly to Postgres use SSL?  Because
> there are reported cases where TCP connections are kept and accumulate,
> causing problems -- but apparently SSL is a necessary piece for that to
> happen.
>
No SSL in between   Wildfly (8080 ) to    PGSQL(5432).  Both the machines
internal lan VMs  in the same network.    Only the devices on the field
(fitted on the  vehicles) communicate to the application backend via a
public URL :443  port  then  it connectes  to the 8080 of wildfly then the
java code connects the  database server running on 5432 on the internal LAN
network.

>

> --
> Álvaro Herrera               48°01'N 7°57'E  —
> https://www.EnterpriseDB.com/
> Thou shalt study thy libraries and strive not to reinvent them without
> cause, that thy code may be short and readable and thy days pleasant
> and productive. (7th Commandment for C Programmers)
>

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