[](CODE_OF_CONDUCT.md)
# opentelemetry_xray
[OpenTelemetry](https://opentelemetry.io/) [AWS X-Ray](https://aws.amazon.com/xray/) support for Erlang/Elixir.
This library includes two modules:
* An id generator that creates X-Ray-compatible `trace_id` and `span_id`.
It implements the `otel_id_generator` protocol in the Erlang SDK.
* A propagator that reads and writes AWS X-Ray trace context headers.
It implements the `otel_propagator_text_map` protocol in the Erlang SDK.
It assumes that you are using the
[AWS Distro for OpenTelemetry Collector](https://aws-otel.github.io/docs/getting-started/collector),
a version of the [OpenTelemetry Collector](https://opentelemetry.io/docs/collector/)
which has support for AWS services such as X-Ray. It accepts standard
OpenTelemetry traces, converts them to X-Ray format, and sends them to AWS.
You can run the collector as a sidecar container in an ECS task or as a daemon
on an EC2 instance.
In AWS X-Ray, the `trace_id` is a 128-bit value. The first 32 bits are a Unix
`time_t` and the rest are a 96-bit random number. If you use the default
`trace_id`, then X-Ray will reject your traces. This library generates ids that
are compatible with X-Ray.
If your app is running behind an AWS Application Load Balancer, then the ALB
will pass a trace in the `X-Amzn-Trace-Id` header. This library includes a
propagator which reads the trace id from this header and uses it within your app.
It can then pass the same trace id to downstream apps via the header.
Links:
* Propagator: https://opentelemetry.io/docs/specs/otel/context/api-propagators/
* https://docs.aws.amazon.com/xray/latest/devguide/xray-concepts.html#xray-concepts-tracingheader
* https://aws-otel.github.io/docs/getting-started/x-ray#configuring-the-aws-x-ray-exporter
* https://davelucia.com/blog/observing-elixir-with-lightstep
* https://opentelemetry.io/docs/instrumentation/erlang/getting-started/
## Installation
Erlang:
Add `opentelemetry_xray` to the list of dependencies in `rebar.config`:
```erlang
{deps, [opentelemetry_xray]}.
```
Elixir:
Add `logger_formatter_json` to the list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:opentelemetry_xray, "~> 0.7"},
]
end
```
## Configuration
In `config/config.exs` or `config/prod.exs`, configure `opentelemetry` to use this library:
```elixir
config :opentelemetry,
id_generator: :opentelemetry_xray_id_generator,
propagators: [:opentelemetry_xray_propagator, :baggage]
```
See [phoenix_container_example](https://github.com/cogini/phoenix_container_example)
for a complete Elixir Phoenix app that uses this library.
