Re: Apache hangs after having 6 x SSE streams active

--00000000000014d7db0641d58a67
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

PerlInterpScope handler


use threads;
# in loop:
threads->yield();


?

On Thu, Oct 23, 2025, 08:43 Steven Haigh via modperl <
[email protected]> wrote:

> Hi all,
>
> I'm writing a web UI in perl + mod_perl that sends an SSE stream to the
> browser full of JSON formatted updates etc. The browser then renders
> that all via Javascript to the user.
>
> I've noticed that if I reload the page multiple times, or just navigate
> away, when there's ~6 existing SSE streams, apache will stop accepting
> new connections completely.
>
> I've hunted around via the normal search engines, turned up very little
> - and out of desperation, asked ChatGPT's Codex...
>
> It suggested the following apache config:
>
> LoadModule mpm_event_module modules/mod_mpm_event.so
> # Tune event MPM so we have headroom for long-lived SSE connections
> <IfModule mpm_event_module>
>      ServerLimit              4
>      StartServers             2
>      MinSpareThreads         50
>      MaxSpareThreads        150
>      ThreadsPerChild         64
>      MaxRequestWorkers      256
>      MaxConnectionsPerChild   0
> </IfModule>
>
> ## Load mod_perl
> LoadModule perl_module /usr/lib/apache2/modules/mod_perl.so
> PerlModule Apache2::Reload
> PerlInitHandler Apache2::Reload
> PerlOptions +Parent
> PerlSwitches -Mlib=3D/usr/local/apache2/htdocs-includes
> PerlInterpStart      20
> PerlInterpMinSpare   10
> PerlInterpMaxSpare   20
> PerlInterpMax        80
>
> Even with this however, when I hit 6 x concurrent SSE streams being
> served, Apache grinds to a halt and doesn't even load the
> /server-status/ page for troubleshooting.
>
> Once some of the 'dead' SSE streams fail and those connections
> terminated, apache starts behaving again.
>
> Has anyone come across this before and maybe knows a bit of additional
> knowledge as to why this is, and what I can do about it?
>
> Thanks.
>
> --
> Steven Haigh
>
> =F0=9F=93=A7 [email protected]
> =F0=9F=92=BB https://crc.id.au
>
>
>

--00000000000014d7db0641d58a67
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"auto">PerlInterpScope handler<div dir=3D"auto"><br></div><div d=
ir=3D"auto"><br></div><div dir=3D"auto">use threads;</div><div dir=3D"auto"=
># in loop:</div><div dir=3D"auto">threads-&gt;yield();</div><div dir=3D"au=
to"><br></div><div dir=3D"auto"><br></div><div dir=3D"auto">?</div></div><b=
r><div class=3D"gmail_quote gmail_quote_container"><div dir=3D"ltr" class=
=3D"gmail_attr">On Thu, Oct 23, 2025, 08:43 Steven Haigh via modperl &lt;<a=
 href=3D"mailto:[email protected]">[email protected]</a>&gt; wr=
ote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px=
 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi all,<br>
<br>
I&#39;m writing a web UI in perl + mod_perl that sends an SSE stream to the=
 <br>
browser full of JSON formatted updates etc. The browser then renders <br>
that all via Javascript to the user.<br>
<br>
I&#39;ve noticed that if I reload the page multiple times, or just navigate=
 <br>
away, when there&#39;s ~6 existing SSE streams, apache will stop accepting =
<br>
new connections completely.<br>
<br>
I&#39;ve hunted around via the normal search engines, turned up very little=
 <br>
- and out of desperation, asked ChatGPT&#39;s Codex...<br>
<br>
It suggested the following apache config:<br>
<br>
LoadModule mpm_event_module modules/mod_mpm_event.so<br>
# Tune event MPM so we have headroom for long-lived SSE connections<br>
&lt;IfModule mpm_event_module&gt;<br>
=C2=A0 =C2=A0 =C2=A0ServerLimit=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 4<br>
=C2=A0 =C2=A0 =C2=A0StartServers=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A02<br>
=C2=A0 =C2=A0 =C2=A0MinSpareThreads=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A050<br>
=C2=A0 =C2=A0 =C2=A0MaxSpareThreads=C2=A0 =C2=A0 =C2=A0 =C2=A0 150<br>
=C2=A0 =C2=A0 =C2=A0ThreadsPerChild=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A064<br>
=C2=A0 =C2=A0 =C2=A0MaxRequestWorkers=C2=A0 =C2=A0 =C2=A0 256<br>
=C2=A0 =C2=A0 =C2=A0MaxConnectionsPerChild=C2=A0 =C2=A00<br>
&lt;/IfModule&gt;<br>
<br>
## Load mod_perl<br>
LoadModule perl_module /usr/lib/apache2/modules/mod_perl.so<br>
PerlModule Apache2::Reload<br>
PerlInitHandler Apache2::Reload<br>
PerlOptions +Parent<br>
PerlSwitches -Mlib=3D/usr/local/apache2/htdocs-includes<br>
PerlInterpStart=C2=A0 =C2=A0 =C2=A0 20<br>
PerlInterpMinSpare=C2=A0 =C2=A010<br>
PerlInterpMaxSpare=C2=A0 =C2=A020<br>
PerlInterpMax=C2=A0 =C2=A0 =C2=A0 =C2=A0 80<br>
<br>
Even with this however, when I hit 6 x concurrent SSE streams being <br>
served, Apache grinds to a halt and doesn&#39;t even load the <br>
/server-status/ page for troubleshooting.<br>
<br>
Once some of the &#39;dead&#39; SSE streams fail and those connections <br>
terminated, apache starts behaving again.<br>
<br>
Has anyone come across this before and maybe knows a bit of additional <br>
knowledge as to why this is, and what I can do about it?<br>
<br>
Thanks.<br>
<br>
-- <br>
Steven Haigh<br>
<br>
=F0=9F=93=A7 <a href=3D"mailto:[email protected]" target=3D"_blank" rel=3D"n=
oreferrer">[email protected]</a><br>
=F0=9F=92=BB <a href=3D"https://crc.id.au" rel=3D"noreferrer noreferrer" ta=
rget=3D"_blank">https://crc.id.au</a><br>
<br>
<br>
</blockquote></div>

--00000000000014d7db0641d58a67--