# Opentelemetry [![build](https://github.com/AestheticIntegration/ocaml-opentelemetry/actions/workflows/main.yml/badge.svg)](https://github.com/AestheticIntegration/ocaml-opentelemetry/actions/workflows/main.yml)

This project provides an API for instrumenting server software
using [opentelemetry](https://opentelemetry.io/docs), as well as
connectors to talk to opentelemetry software such as [jaeger](https://www.jaegertracing.io/).

- library `opentelemetry` should be used to instrument your code
  and possibly libraries. It doesn't communicate with anything except
  a backend (default: dummy backend)
- library `opentelemetry-client-ocurl` is a backend that communicates
  via http+protobuf with some collector (otelcol, datadog-agent, etc.)

## Features

- [x] basic traces
- [x] basic metrics
- [x] basic logs
- [ ] nice API
- [x] interface with `lwt`
- [x] sync collector relying on ocurl
  * [x] batching, perf, etc.
- [ ] async collector relying on ocurl-multi
- [ ] interface with `logs` (carry context around)

## Use

For now, instrument manually:

```ocaml
module Otel = Opentelemetry
let (let@) f x = f x

let foo () =
  let@ scope = Otel.Trace.with_  "foo"
      ~attrs:["hello", `String "world"] in
  do_work();
  Otel.Metrics.(
    emit [
      gauge ~name:"foo.x" [int 42];
    ]);
  do_more_work();
  ()

let main () =
  Otel.Globals.service_name := "my_service";
  Otel.GC_metrics.basic_setup();

  Opentelemetry_client_ocurl.with_setup () @@ fun () ->
  (* … *)
  foo ();
  (* … *)
``` 

## Configuration

The library is configurable via `Opentelemetry.Config`, via the standard
opentelemetry env variables, or with some custom environment variables.

- `OTEL_EXPORTER_OTLP_ENDPOINT` sets the http endpoint to send signals to
- `OTEL_OCAML_DEBUG=1` to print some debug messages from the opentelemetry library ide
- `OTEL_RESOURCE_ATTRIBUTES` sets a comma separated list of custom resource attributes

## Collector opentelemetry-client-ocurl

This is a synchronous collector that uses the http+protobuf format
to send signals (metrics, traces) to some other collector (eg. `otelcol`
or the datadog agent).

## License

MIT

## Semantic Conventions

Not supported yet.

- [ ] [metrics](https://opentelemetry.io/docs/reference/specification/metrics/semantic_conventions/)
- [ ] [traces](https://opentelemetry.io/docs/reference/specification/trace/semantic_conventions/)
- [ ] [resources](https://opentelemetry.io/docs/reference/specification/resource/semantic_conventions/)