Metrics

[az-adhoc]

Hi! @sbidoul

First of all, congratulations on this project; it's very useful. We recently started using it and found it to be a very practical and elegant solution.

We noticed that we also need the kwkhtmltoimage functionality. We saw that there is already a pull request addressing this: #31

If it helps move this forward, we'd be happy to contribute to getting it integrated.

We also think it could be useful to expose a very simple Prometheus metric, which is something we currently miss.

Would you prefer that we submit a pull request adding the metrics, or would you rather we maintain that in a fork?

[sbidoul]

Hi @az-adhoc,

I'll welcome a PR adding a metrics endpoint if it's simple enough and does not add too much maintenance burden or operational risks.

What kind of metrics do you have in mind?

[az-adhoc]

Thanks for the quick reply.

I agree that adding metrics introduces some cost :-(, so my idea would be to keep it as simple as possible (ex. without dependencies).

What I had in mind was something like:

• kwkhtmltopdf_requests_total: Total HTTP requests received by kwkhtmltopdf.
• kwkhtmltopdf_exec_total: Total wkhtmltopdf exec.Command calls.

Optionally, the second metric could include a label (for example account) to identify who requested the render. This is useful in shared deployments like ours, but it could also be omitted if you think it adds too much complexity. (I really prefer to implement this for my own convenience, jaja.)

If this sounds reasonable to you, I can prepare a PR. Or you prefer to add some other metrics?

[sbidoul]

• kwkhtmltopdf_requests_total: Total HTTP requests received by kwkhtmltopdf.
• kwkhtmltopdf_exec_total: Total wkhtmltopdf exec.Command calls.

Are these not the same?

metric could include a label (for example account) to identify who requested the render

For easier review I suggest a PR with one or two simple metrics, then possibly add more in followups. With tests.