OpenTelemetryDecorator

A function decorator for OpenTelemetry traces.

Usage

The span name can be any string.

defmodule MyApp.Worker do
  use OpenTelemetryDecorator

  @decorate trace("my_app.worker.do_work")
  def do_work(arg1, arg2) do
    ...doing work
    do_more_work(arg1)
  end

  @decorate trace("MyApp::Worker::do_more_work")
  def do_more_work(arg1) do
    ...doing more work
  end
end

We use OpenTelemetry.Tracer.current_span_ctx() to automatically link new spans to the current trace (if it exists and is in the same process). So the above example will link the do_work and do_more_work spans for you by default.

You can provide span attributes by specifying a list of variable names as atoms.

This list can include...

Any variables (in the top level closure) available when the function exits:

defmodule MyApp.Math do
  use OpenTelemetryDecorator

  @decorate trace("my_app.math.add", [:a, :b, :sum])
  def add(a, b) do
    sum = a + b
    {:ok, thing1}
  end
end

The result of the function by including the atom :result:

defmodule MyApp.Math do
  use OpenTelemetryDecorator

  @decorate trace("my_app.math.add", [:result])
  def add(a, b) do
    sum = a + b
    {:ok, thing1}
  end
end

Map/struct properties using nested lists of atoms:

defmodule MyApp.Worker do
  use OpenTelemetryDecorator

  @decorate trace("my_app.worker.do_work", [[:arg1, :count], [:arg2, :count], :total])
  def do_work(arg1, arg2) do
    total = arg1.count + arg2.count
    {:ok, total}
  end
end

Installation

Add open_telemetry_decorator to your list of dependencies in mix.exs and do a mix deps.get:

def deps do
  [
    {:open_telemetry_decorator, "~> 0.1.0"}
  ]
end

Development

make check before you commit! If you'd prefer to do it manually:

• mix do deps.get, deps.unlock --unused, deps.clean --unused if you change dependencies
• mix compile --warnings-as-errors for a stricter compile
• mix coveralls.html to check for test coverage
• mix credo to suggest more idiomatic style for your code
• mix dialyzer to find problems typing might reveal… albeit slowly
• mix docs to generate documentation