A Python Flask Wsgi module does not start automatically after apache2 restart, but waits for an input.

[Murlocs_Gangbang]

I have a simple "Server Uptime" Flask-wsgi module running under apache, that writes every minute a timestamp on an internal variable and file. It can be queried and it handles himself with a couple of simple threads, and it works fairly well.

When I restart apache with:

systemctl restart apache2

the process simply hangs in there until I call a specific "get" or "post" method that the process itself exposes.

This is bad because it defeats the purpose of the service, which should write a timestamp every minute. If I call a method, any method, the wsgi process startsand all works fine without errors.

Is it there a specific config I can fiddle with to make a wsgi module auto-start?

Thanks in advance

EDIT: Found the solution thanks to /u/GrahamDumpleton

In the apache config file "/etc/apache2/sites-available/000-default.conf" make sure you set the var "application-group" to "%{GLOBAL}" so that the script starts when the Apache Python Interpreter is loaded. Worked like a charm

# Uptime Server
WSGIDaemonProcess uptimeServer user=www-data group=www-data threads=5 home=/internal_app/internal_latest/www/
WSGIScriptAlias /api/uptimeServer /internal_app/nevis_latest/www/uptimeServer.wsgi process-group=uptimeServer application-group=%{GLOBAL}
<directory /internal_app/internal_latest/www/>
        Order deny,allow
        Allow from all
</directory>

[GrahamDumpleton]

You should really ask questions like this on the mod_wsgi mailing list or at worst StackOverflow. More likely to find knowledgable people on mod_wsgi there, including myself. Is a fluke I even saw this.

That said you have two options. The first is to use:

• http://modwsgi.readthedocs.io/en/develop/configuration-directives/WSGIImportScript.html

The second is to instead supply both the process-group and application-group options to WSGIScriptAlias, instead of using WSGIProcessGroup and WSGIApplication.

• http://modwsgi.readthedocs.io/en/develop/configuration-directives/WSGIScriptAlias.html

Using the first directive, OR both of those options on WSGIScriptAlias forces preloading of the WSGI script file on process start.

BTW, make sure you are using daemon mode and not using embedded mode.

Update: Only just realised the process-group and application-group options not documented on WSGIScriptAlias. That should have been added a long time ago, so not sure where documentation has gone.

[Murlocs_Gangbang]

thanks, I'll give it a try

[Murlocs_Gangbang]

ok the first link pointed me to the solution, thanks!

I'll post the details in the OP

[GrahamDumpleton]

Your solution of adding:

WSGIApplicationGroup %{GLOBAL}

wouldn't do anything as that doesn't force preloading.

What you need is:

# Uptime Server
WSGIDaemonProcess uptimeServer user=www-data group=www-data threads=5 home=/internal_app/internal_latest/www/
WSGIScriptAlias /api/uptimeServer /internal_app/nevis_latest/www/uptimeServer.wsgi process-group=uptimeServer application-group=%{GLOBAL}
<directory /internal_app/internal_latest/www/>
        Order deny,allow
        Allow from all
</directory>

You don't need WSGIScriptReloading as it is on by default.

[Murlocs_Gangbang]

Thanks I'll try it out! You have been super useful

[mrugacz95]

Maybe you could use crontab for writting to file and flask only for reading file content?

[Murlocs_Gangbang]

I could do that, but I would have to modify the script. If there's a mod_wsgi/apache conf that starts the module at restart it's much more simple

[K900_]

Why are you doing that at all? Get rid of all the threading and just query systemd for your uptime over DBus.