Tips for integrating OpenTelemetry when using mod_wsgi

[Andras Csizmadia]

Hi!

I'm currently evaluating the possibility to integrate the OpenTelemetry framework into our existing Flask applications which are served at the moment using Apache2+mod_wsgi for trace and metrics collection.

Does anyone have experience with this topic?

Especially I'm hesitant about how does the OpenTelemetry tracing and metrics SDK behave with the multi process / multi thread model of mod_wsgi and Apache2 with the mpm_event module.

The OpenTelemetry documentation have some reference about it needs special configuration when using the fork process model:

link 1 link 2

Since I'm using the worker process model I'm a bit unsure about that should I need to use some kind of post-init hook to create my span/metrics processors?

Does mod_wsgi provide this kind of event hook?

I'll try to gather information from the OpenTelemetry groups as well but I wanted to try the other way too.

Thank you!

[Graham Dumpleton]

When using mod_wsgi there is no fork of the process after you have loaded any Python code. Each process is initialised from scratch as a separate Python process and each loads Python code itself.

So you don't have to worry about in process forking issues, only that there are multiple process/thread reporting.

BTW, make sure you are using daemon mode, and disable ability for Python to be initialised in embedded mode for good measure.

Graham

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[Andras Csizmadia]

Thanks for the response!

I think in this case OTEL traces will work out of the box, I'll just have to deal with aggregation of the different per process metrics values.

Best regards,

Andrew