Apache hangs after having 6 x SSE streams active

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=/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

📧 [email protected]
💻 https://crc.id.au