Initial commit

.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+opentelemetry_absinthe-*.tar
+

README.md

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+# OpentelemetryAbsinthe
+
+OpentelemetryAbsinthe is a [OpenTelemetry](https://opentelemetry.io) instrumentation library for [Absinthe](https://github.com/absinthe-graphql/absinthe).

lib/helpers.ex

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+defmodule OpentelemetryAbsinthe.Helpers do
+  @moduledoc """
+  OpenTelemetry-friendly alternatives of Absinthe.Resolution.Helpers functions
+
+  Some of the standard absinthe resolution helpers, like `batch` or `async`,
+  are not "opentelemetry-friendly": the resolvers, when invoked, lose the active span
+  and break the trace propagation.
+
+  This module defines compatible alternatives that can be used in the same way,
+  but don't lose the trace information.
+  """
+
+  require OpenTelemetry.Tracer
+  alias Absinthe.Middleware.Batch
+
+  @doc """
+  Works like Absinthe.Resolution.Helpers.batch, but preserves the active span.
+
+  The function supplied to the `batch` helper is executed in a Task by Absinthe,
+  which means that the erlang opentelemetry SDK would lose track of the currently
+  active span, because they are kept in a pdict.
+
+  To work around this, you can just replace `batch` with `batch_keep_span`,
+  and the active span will be automatically passed and reset as the active one
+  inside the batch function.
+  """
+  @spec batch_keep_span(Batch.batch_fun(), any(), Batch.post_batch_fun()) ::
+          {:middleware, Batch, term}
+  @spec batch_keep_span(
+          Batch.batch_fun(),
+          any(),
+          Batch.post_batch_fun(),
+          opts :: [{:timeout, pos_integer}]
+        ) :: {:middleware, Batch, term}
+
+  def batch_keep_span(batch_key, batch_data, post_batch_fn) do
+    batch_keep_span(batch_key, batch_data, post_batch_fn, [])
+  end
+
+  def batch_keep_span({module, func}, batch_data, post_batch_fn, opts) do
+    batch_keep_span({module, func, []}, batch_data, post_batch_fn, opts)
+  end
+
+  def batch_keep_span({module, func, param}, batch_data, post_batch_fn, opts) do
+    span_ctx = OpenTelemetry.Tracer.current_span_ctx()
+    batch_key = {__MODULE__, :batch_fun_wrapper, {{module, func, param}, span_ctx}}
+    batch_config = {batch_key, batch_data, post_batch_fn, opts}
+    {:middleware, Absinthe.Middleware.Batch, batch_config}
+  end
+
+  # This is executed by the Absinthe.Middleware.Batch middleware in a Task
+  defp batch_fun_wrapper({{module, func, param}, span}, aggregate) do
+    OpenTelemetry.Tracer.set_span(span)
+    apply(module, func, [param, aggregate])
+  end
+end

lib/opentelemetry_absinthe.ex

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+defmodule OpentelemetryAbsinthe do
+  @moduledoc """
+  OpentelemetryAbsinthe is an opentelemetry instrumentation library for Absinthe
+  """
+end

mix.exs

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+defmodule OpentelemetryAbsinthe.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :opentelemetry_absinthe,
+      version: "0.1.0",
+      elixir: "~> 1.10",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  defp deps do
+    [
+      {:absinthe, ">= 1.4.0"},
+      {:opentelemetry_api, "~> 0.3.1"}
+    ]
+  end
+end

mix.lock

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+%{
+  "absinthe": {:hex, :absinthe, "1.5.1", "2f462f5849b2a4f72889d5a131ca6760b47ca8c5de2ba21c1dca3889634f2277", [:mix], [{:dataloader, "~> 1.0.0", [hex: :dataloader, repo: "hexpm", optional: true]}, {:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: true]}, {:nimble_parsec, "~> 0.5", [hex: :nimble_parsec, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "b264eeb69605c6012f563e240edcca3d8abc5a725cab6f58ad82510a0283618b"},
+  "nimble_parsec": {:hex, :nimble_parsec, "0.6.0", "32111b3bf39137144abd7ba1cce0914533b2d16ef35e8abc5ec8be6122944263", [:mix], [], "hexpm", "27eac315a94909d4dc68bc07a4a83e06c8379237c5ea528a9acff4ca1c873c52"},
+  "opentelemetry_api": {:hex, :opentelemetry_api, "0.3.2", "b474cd21af5855a6dfff0912f26c7c40fbf1fd05b045d8e29fd53edeb4c3ec99", [:mix, :rebar3], [], "hexpm", "39b0ef74906e5d001ad244307337d168c594c2a05b67beaddad48ceaebfee352"},
+  "telemetry": {:hex, :telemetry, "0.4.2", "2808c992455e08d6177322f14d3bdb6b625fbcfd233a73505870d8738a2f4599", [:rebar3], [], "hexpm", "2d1419bd9dda6a206d7b5852179511722e2b18812310d304620c7bd92a13fcef"},
+}