SIGHUP config reload

[reubano]

Is your feature request related to a problem? Please describe.

I'm frustrated when I need to reload sql_exporter without making an HTTP request

Describe the solution you'd like

SIGHUP based config reload (similar to Prometheus). E.g., killall -HUP sql_exporter

Describe alternatives you've considered

-web.enable-reload. But since I'm running sql_exporter in an unexposed Azure container, I can't make an HTTP call to the reload endpoint. I can, however, run az container exec which would allow me to call killall -HUP.

Additional context

HTTP flags are considered a security concern in Prometheus, so a SIGHUP based sql_exporter reload would likewise be considered more secure than an HTTP flag.

[reubano]

FYI, turns out I am able to curl localhost via the nginx container. This would still be a nice feature though for the security benefits.

[burningalchemist]

Hi @reubano, there are no security concerns specifically for this endpoint (I also previously elaborated on that front before, since sql_exporter is not Prometheus), as /reload is idempotent and read-only, there are no mutations involved. Also, sql_exporter is not supposed to run in public networks, similar to how databases usually are located within private networks.

But yeah, I'll put SIGHUP reload feature in the list of improvements, when I find some free time. It probably won't take much time. Thanks for your contributions as always! :)

[reubano]

@burningalchemist thanks! Since I confirmed that I can curl to localhost there's no urgency on my end. I'll report back once I have everything working.

[burningalchemist]

Hey @reubano, JFYI, I've merged the SIGHUP support, and it should appear in the next release. 🚀