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From: Marco Torres <mtors25@gmail.com>
Date: Mon, 16 Jun 2025 10:41:44 -0600
Message-ID: <CAG2LZV7pSbd7Snx_foov-tkXw050sD54EiPv0x0C4J9VFxWG9g@mail.gmail.com>
Subject: Re: Getting error "too many clients already" despite having a db
 connection limit set
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: adolfo flores <adolfoflores2211@gmail.com>, pgsql-general@lists.postgresql.org
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You might want to explore pgpool and pgbouncer. Depending in your use case
you might want to glue them togeter.

On Mon, Jun 16, 2025, 10:39=E2=80=AFAM Tom Lane <tgl@sss.pgh.pa.us> wrote:

> adolfo flores <adolfoflores2211@gmail.com> writes:
> > I hope you can help me with an issue we're experiencing. We have an app
> > running on Kubernetes that opens a huge number of connections within a
> > couple of seconds.
>
> You need to fix that app to be less unfriendly, or maybe put it behind
> a connection pooler.
>
> > Is it expected behavior to reach the max_connections limit when that ap=
p
> > opens many connections in a short period of time, even if a connection
> > limit is set for that database and everything else uses no more than 10=
%
> of
> > the max_connections?
>
> It takes a finite amount of time for a new backend process to figure
> out which database it's supposed to connect to and then detect whether
> the per-DB connection limit is exceeded.  In the meantime, that
> session does count against the global limit, so yeah this isn't
> surprising if the connection arrival rate is high enough.
>
>                         regards, tom lane
>
>
>

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<p dir=3D"ltr">You might want to explore pgpool and pgbouncer. Depending in=
 your use case you might want to glue them togeter.</p>
<br><div class=3D"gmail_quote gmail_quote_container"><div dir=3D"ltr" class=
=3D"gmail_attr">On Mon, Jun 16, 2025, 10:39=E2=80=AFAM Tom Lane &lt;<a href=
=3D"mailto:tgl@sss.pgh.pa.us">tgl@sss.pgh.pa.us</a>&gt; wrote:<br></div><bl=
ockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #=
ccc solid;padding-left:1ex">adolfo flores &lt;<a href=3D"mailto:adolfoflore=
s2211@gmail.com" target=3D"_blank" rel=3D"noreferrer">adolfoflores2211@gmai=
l.com</a>&gt; writes:<br>
&gt; I hope you can help me with an issue we&#39;re experiencing. We have a=
n app<br>
&gt; running on Kubernetes that opens a huge number of connections within a=
<br>
&gt; couple of seconds.<br>
<br>
You need to fix that app to be less unfriendly, or maybe put it behind<br>
a connection pooler.<br>
<br>
&gt; Is it expected behavior to reach the max_connections limit when that a=
pp<br>
&gt; opens many connections in a short period of time, even if a connection=
<br>
&gt; limit is set for that database and everything else uses no more than 1=
0% of<br>
&gt; the max_connections?<br>
<br>
It takes a finite amount of time for a new backend process to figure<br>
out which database it&#39;s supposed to connect to and then detect whether<=
br>
the per-DB connection limit is exceeded.=C2=A0 In the meantime, that<br>
session does count against the global limit, so yeah this isn&#39;t<br>
surprising if the connection arrival rate is high enough.<br>
<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 regards, tom lane<br>
<br>
<br>
</blockquote></div>

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