stephenmoloney/apollo-tracing-elixir

Apollo Tracing middleware for Absinthe

ApolloTracing (for Elixir)

This package is used to collect and expose trace data in the Apollo Tracing format.

It relies on instrumenting a GraphQL schema to collect resolver timings, and exposes trace data for an individual request under extensions as part of the GraphQL response.

The extension format is work in progress, and we're collaborating with others in the GraphQL community to make it broadly available, and to build awesome tools on top of it.

One use of Apollo Tracing is to add support for Apollo Optics to more GraphQL servers.

Installation

Add :apollo_tracing to your deps

def deps do
  [
    {:apollo_tracing, "~> 0.2.0"}
  ]
end

Usage

To add tracing to your graphql schema, add ApolloTracing.Middleware as the first middleware of your middleware stack:

def middleware(middlewares, field, object) do
  [ApolloTracing.Middleware | ...your other middlewares]
end

If you have no custom middleware callback, you can simply add use ApolloTracing to your schema file:

def MyApp.Schema do
  use Absinthe.Schema
  use ApolloTracing
end

Note that you don't have to add tracing to all fields in your schema, like we did above. You could selectively add tracing information to the fields of your choice:

field :selected_field, :string do
  middleware ApolloTracing.Middleware # Has to be the first middleware
  resolve fn _, _ -> {:ok, "this field is now added to be traced"} end
end

After adding the middleware, then you want to modify Absinthe pipeline to ApolloTracing's custom pipeline before executing queries.

Modifying pipeline with Plug

To add the pipeline to your Absinthe.Plug endpoint, you can simpley use the :pipeline option:

forward "/graphql", Absinthe.Plug,
  schema: MyApp.Schema,
  pipeline: {ApolloTracing.Pipeline, :plug}

If you have your own pipeline function, you can use ApolloTracing.Pipeline.add_phases(pipeline) function to added the phases to your pipeline before passing it to Absinthe.Plug.

def my_pipeline_creator(config, pipeline_opts) do
  config.schema_mod
  |> Absinthe.Pipeline.for_document(pipeline_opts)
  |> add_my_phases() # w.e your custom phases are
  |> ApolloTracing.Pipeline.add_phases() # Add apollo at the end
end

Adding pipeline to Absinthe.run

When you want to just call run a query with tracing, but without going through a Plug endpoint, you can build the pipeline with ApolloTracing.Pipeline.default(schema, opts) and pass that to Absinthe.Pipeline.run

def custom_absinthe_runner(query, opts \\ []) do
  pipeline = ApolloTracing.Pipeline.default(YourSchema, opts)
  case Absinthe.Pipeline.run(query, pipeline) do
    {:ok, %{result: result}, _} -> {:ok, result}
    {:error, err, _} -> {:ok, err}
  end
end

"""
  query {
    fielda
    fieldb
  }
"""
|> custom_absinthe_runner()