Docker question: connecting to opentelemetry outside of container network

[vasigorc]

Hello team!

In order to seamlessly run the multitude of apps that we have at work, we created a single docker-compose file. We want to observe one of the apps within that file. Opentelemetry collector is not part of the docker-compose file (it runs as part of another docker-compose environment along with elasticsearch, kibana, etc.) and is available at localhost:4317.

In the dockerfile of the app in question I've added this line:

ENV OTEL_EXPORTER_OTLP_ENDPOINT=http://host.docker.internal:4317

based on the recommendation here. This however failed:

[error] [otel.javaagent 2022-05-24 17:29:22:959 +0000] [OkHttp http://host.docker.internal:4317/...] ERROR io.opentelemetry.exporter.internal.grpc.OkHttpGrpcExporter - Failed to export metrics. The request could not be executed. Full error message: timeout

I was wondering if anyone has encountered the problem of connecting to the otel collector on a host from within a dockerized application and maybe they know about a solution. Is there a way to fix this without baking the entire observability app stack into our business app stack?

[vasigorc]

It just started working with the same config 🤷‍♂️ I am on Mac, but for a Linux environment this may need to be added to the observed docker-compose service:

    extra_hosts:
      - "host.docker.internal:host-gateway"

Resolving this.