feat: implement just cmds otel-stream, otel-stop, and otel-dev (#…

…2040)

Part 1 of #2020

This PR enables local testing of otel metric changes/additions. To use:

In tab 1, run `just otel-stream`.

In tab 2, run `just otel-dev`. You can pass in any args you'd run `ftl
dev` with (e.g. `--recreate`). If you set `--log-level=DEBUG`, you
should see `OTEL is enabled, exporting to localhost:4317` in your
output. Any signals you trigger to log at this point should appear in
the streaming output of tab 1.

When you're done, kill the `dev` command and then run `just otel-stop`
in any tab other than tab 1.

Justfile

@@ -173,4 +173,28 @@ debug *args:
   FTL_DEBUG=true just build ftl
   dlv --listen=:2345 --headless=true --api-version=2 --accept-multiclient exec "{{RELEASE}}/ftl" -- dev {{args}} &
   dlv_pid=$!
-  wait "$dlv_pid"
+  wait "$dlv_pid"
+
+# Run otel collector in a docker container to stream local (i.e. from ftl dev) signals to
+# the terminal tab where this is running. To start FTL, opepn another terminal tab and run
+# `just otel-dev` with any args you would pass to `ftl dev`. To stop the otel stream, run
+# `just otel-stop` in a third terminal tab.
+grpcPort := `cat docker-compose.yml | grep "OTLP gRPC" | sed 's/:.*//' | sed -r 's/ +- //'`
+otel-stream:
+  docker run \
+    -p {{grpcPort}}:{{grpcPort}} \
+    -p 55679:55679 \
+    otel/opentelemetry-collector:0.104.0
+
+# Stop the docker container running otel.
+otelContainerID := `docker ps -f ancestor=otel/opentelemetry-collector:0.104.0 | tail -1 | cut -d " " -f1`
+otel-stop:
+  docker stop "{{otelContainerID}}"
+
+# Run `ftl dev` with the given args after setting the necessary envar.
+otel-dev *args:
+  #!/bin/bash
+
+  gprcPort=$(cat docker-compose.yml | grep "OTLP gRPC" | sed 's/:.*//' | sed -r 's/ +- //')
+  export OTEL_EXPORTER_OTLP_ENDPOINT="localhost:${gprcPort}"
+  ftl dev {{args}}