Setup Jaeger and Elixir to have tracing locally

Based on the presentation from https://github.com/kamilkowalski/opentelemetry-demo

This is a simple example on how to setup a tracing environment on your Elixir project to help you during development.

What do you need in Elixir?

Add a new application for the SSL certificate checks and add de dependencies in your mix.exs

#...
def application do
    [
      extra_applications: [
        # ...
        :tls_certificate_check
      ]
    ]
end
#...
defp deps do
    [
        {:opentelemetry_api, "~> 1.0"},
        {:opentelemetry, "~> 1.0"},
        {:opentelemetry_exporter, "~> 1.0"},
        {:tls_certificate_check, "~> 1.13"},
    #...
    ]
end

On your config.exs configuration

config :opentelemetry, :resource, service: %{name:"app_name"}

config :opentelemetry,
       :processors,
       otel_batch_processor: %{
         exporter: {:opentelemetry_exporter, %{endpoints: [{:http, 'localhost', 55681, []}]}}
       }

And then instrument the areas of the code you want to measure. I suggest that the span has the Module name, the function and the arity.

    require OpenTelemetry.Tracer, as: Tracer

    Tracer.with_span "#{__MODULE__}.function/arity" do
    end

You can add more metadata to each trace to the active trace using OpenTelemetry.Tracer.set_attribute/2 or OpenTelemetry.Tracer.set_attributes/1, check https://hexdocs.pm/opentelemetry_api/OpenTelemetry.Tracer.html for more information.

Setup Jaeger

Finally, docker compose up -d and access http://localhost:16686

Jaeger was chosen due to the fact that it's contained in a single image with no configuration file but you can check out other services like Tempo from Gragana, Elastic APM from Elastic or OpenZipkin.

Demonstration

In this demo app, try it out by running iex -S mix and call OpentelemetrySetup.Demo.call().

In the code you can see that we instrument multiple functions and that we add an attribute to the last span to see what args were received by the function.