The most likely cause for this is that something is triggering a graceful
restart of Apache. Most likely this could be your system logging system doing a
restart of Apache because of the need to rotate log files.
Apache actually has its own way of managing and rotating log files so that
there is no need to do a restart of Apache, but Linux systems totally ignore
that and do it their own way, which in the default configuration with mod_wsgi
can result in this error, since you get stale socket information in Apache
child worker process since the socket for the daemon process group gets changed
on each restart, yet Apache child worker processes when graceful restart is
used can hang around longer if keep alive connections are used for clients.
Seems it is missing from the main docs and only mention in change notes, but
you can try setting:
WSGISocketRotation Off
This will cause it to use the same socket name for daemon process groups across
restarts.
Make that change and see if things improve.
Also look at the Apache logs and see if you can confirm if anything is trigger
an Apache restart. You may need to have the Apache log level set to info rather
than err or warn to see information about restarts.
Graham
> On 29 Mar 2021, at 11:49 pm, ramiro rodriguez <[email protected]>
> wrote:
>
> Hi Graham and everyone,
>
> I have a problem with my mod_wsgi configuration. Sometimes, I think that when
> there is a lot of traffic on my website, the page breaks and says "Resource
> temporarily unavailable..."
>
> Timeout when reading response headers from daemon process
>
> (11)Resource temporarily unavailable: [client 181...] mod_wsgi (pid=4726):
> Unable to connect to WSGI daemon process 'FlaskApp' on
> '/run/httpd/wsgi.28794.0.1.sock' after multiple attempts as listener backlog
> limit was exceeded or the socket does not exist.
>
> The website makes aprox 12 requests every 2 minutes.
>
> This is my httpd.conf file
>
> <VirtualHost *:443>
>
> DocumentRoot "/var/www/FlaskApp/FlaskApp"
> ServerName 54.165.200.2000
>
> WSGIScriptAlias / /var/www/FlaskApp/flaskapp.wsgi
> WSGIDaemonProcess FlaskApp
> python-path=/var/www/FlaskApp/FlaskApp/venv/lib/python3.6/site packages
> processes=6 threads=5
> WSGIProcessGroup FlaskApp
> <Directory /var/www/FlaskApp/FlaskApp/>
> WSGIProcessGroup FlaskApp
> WSGIApplicationGroup %{GLOBAL}
> Order allow,deny
> Allow from all
> </Directory>
> Alias /static /var/www/FlaskApp/FlaskApp/static
> <Directory /var/www/FlaskApp/FlaskApp/static/>
> Order allow,deny
> Allow from all
> </Directory>
>
> What's causing the problem?
> Thanks!
>
>
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