Fail gracefully if OpenTelemetry collector is not available?

[thomasjm]

I have a complex Haskell repo, with a stack.yaml and lots of sub-projects. I'd like an easy way to enable this plugin for all of them at once, but that seems to mean editing all the .cabal files to add -fplugin OpenTelemetry.Plugin, which is a little unwieldy. It would be nice to find a simple way to turn the plugin on across the whole project.

FWIW, I tried just passing the necessary args all in stack.yaml's ghc-options like this:

ghc-options:
  "$locals": >-
    -plugin-package opentelemetry-plugin -fplugin OpenTelemetry.Plugin

but I wasn't able to get this to work. The approach I'm currently going with is to define a cabal flag -fopentelemetry in every .cabal file, which passes the necessary GHC options. Then I can flip it on for all projects in stack.yaml as follows. This requires some boilerplate in every .cabal file though.

configure-options:
  "$locals":
  - -fopentelemetry

This made me I wonder, maybe I could just leave the plugin enabled all the time? AFAIK the overhead is negligible, and the build still works--the only problem is that I get a bunch of HttpExceptionRequest Request { ... } errors in the logs if I'm not running a collector. So I was thinking the plugin could just check if a collector is available at the beginning of the compilation run, and if not, just do nothing?

[Gabriella439]

It's probably not a good idea to fail silently, or at least not by default, but maybe this behavior could be toggled by an environment variable?

[thomasjm]

What about only running if OTEL_EXPORTER_OTLP_ENDPOINT is defined?

Currently it tries to connect to the default port of 4318 even if I don't define any OTEL_* variables.