Bootstrap application

.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.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_tesla-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

README.md

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+# OpentelemetryTesla
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `opentelemetry_tesla` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:opentelemetry_tesla, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at [https://hexdocs.pm/opentelemetry_tesla](https://hexdocs.pm/opentelemetry_tesla).
+

lib/opentelemetry_tesla.ex

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+defmodule OpentelemetryTesla do
+  @tracer_id :opentelemetry_tesla
+
+  @doc """
+  Initializes and configures telemetry handlers.
+  """
+  @spec setup() :: :ok
+  def setup() do
+    {:ok, otel_tracer_vsn} = :application.get_key(@tracer_id, :vsn)
+    OpenTelemetry.register_tracer(@tracer_id, otel_tracer_vsn)
+
+    attach_request_start_handler()
+    attach_request_stop_handler()
+    # attach_request_exception_handler()
+    :ok
+  end
+
+  def attach_request_start_handler() do
+    :telemetry.attach(
+      "#{__MODULE__}.request_start",
+      [:tesla, :request, :start],
+      &handle_start/4,
+      %{}
+    )
+  end
+
+  def attach_request_stop_handler() do
+    :telemetry.attach(
+      "#{__MODULE__}.request_stop",
+      [:tesla, :request, :stop],
+      &handle_stop/4,
+      %{}
+    )
+  end
+
+  defp handle_start(_event, _measurements, _metadata, _config) do
+    OpentelemetryTelemetry.start_telemetry_span(
+      @tracer_id,
+      "External HTTP Request",
+      %{},
+      %{kind: :server}
+    )
+  end
+
+  defp handle_stop(_event, %{duration: measurement}, metadata, _config) do
+    headers_span_args =
+      metadata
+      |> Map.get(:env)
+      |> Map.get(:headers)
+      |> Enum.map(fn {key, value} -> {:"http.headers.#{key}", value} end)
+
+    span_args =
+      metadata
+      |> Map.get(:env)
+      |> Map.take([:method, :opts, :query, :status, :url])
+      |> Enum.map(fn {key, value} -> {:"http.#{key}", value} end)
+
+    ctx = OpentelemetryTelemetry.set_current_telemetry_span(@tracer_id, %{})
+
+    OpenTelemetry.Span.set_attributes(
+      ctx,
+      span_args ++ headers_span_args ++ [measurement: measurement / 1_000_000]
+    )
+
+    OpentelemetryTelemetry.end_telemetry_span(@tracer_id, %{})
+  end
+end

mix.exs

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+defmodule OpentelemetryTesla.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :opentelemetry_tesla,
+      version: "0.1.0",
+      elixir: "~> 1.12",
+      start_permanent: Mix.env() == :prod,
+      deps: deps(),
+      package: package()
+    ]
+  end
+
+  defp package do
+    [
+      maintainers: ["Ricardo Paiva"],
+      licenses: ["MIT"],
+      links: %{"GitHub" => "https://github.com/ricardoccpaiva/opentelemetry_tesla"}
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:telemetry, "~> 0.4"},
+      {:opentelemetry, "~> 1.0.0-rc.2"},
+      {:opentelemetry_telemetry, "~> 1.0.0-beta.2"},
+      {:tesla, "~> 1.4"}
+    ]
+  end
+end

mix.lock

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+%{
+  "mime": {:hex, :mime, "1.6.0", "dabde576a497cef4bbdd60aceee8160e02a6c89250d6c0b29e56c0dfb00db3d2", [:mix], [], "hexpm", "31a1a8613f8321143dde1dafc36006a17d28d02bdfecb9e95a880fa7aabd19a7"},
+  "opentelemetry": {:hex, :opentelemetry, "1.0.0-rc.2", "d3e1fd9debfd73e00b0241cac464be7cd6ca6ac2bd38ab2ebe0c92401c76a342", [:rebar3], [{:opentelemetry_api, "~> 1.0.0-rc.2", [hex: :opentelemetry_api, repo: "hexpm", optional: false]}], "hexpm", "2f810e2eed70a9ea0c9b6943969b59e37f96a2f9e10920045a6c7676c2ab8181"},
+  "opentelemetry_api": {:hex, :opentelemetry_api, "1.0.0-rc.2", "a0ec5b242bb7ce7563b4891e77dcfa529defc9e42c19a5a702574c5ac3d0c6e7", [:mix, :rebar3], [], "hexpm", "426a969c8ee2afa8ab55b58e6e40e81c1f934c064459a1acb530f54042f9a9a3"},
+  "opentelemetry_telemetry": {:hex, :opentelemetry_telemetry, "1.0.0-beta.2", "b840eee9e68307ad7fa4ee316da19db3f8e30763b87737d3304782ca3cc296a2", [:mix, :rebar3], [{:opentelemetry_api, "~> 1.0.0-rc.1", [hex: :opentelemetry_api, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: false]}, {:telemetry_registry, "~> 0.2.1", [hex: :telemetry_registry, repo: "hexpm", optional: false]}], "hexpm", "e8b12f42614d0aeb6a49001c75ca035544950f736fdbb240177838674f99e1e2"},
+  "telemetry": {:hex, :telemetry, "0.4.3", "a06428a514bdbc63293cd9a6263aad00ddeb66f608163bdec7c8995784080818", [:rebar3], [], "hexpm", "eb72b8365ffda5bed68a620d1da88525e326cb82a75ee61354fc24b844768041"},
+  "telemetry_registry": {:hex, :telemetry_registry, "0.2.1", "fe648a691f2128e4279d993cd010994c67f282354dc061e697bf070d4b87b480", [:mix, :rebar3], [{:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "4221cefbcadd0b3e7076960339223742d973f1371bc20f3826af640257bc3690"},
+  "tesla": {:hex, :tesla, "1.4.2", "54fc2c989b63c3c9ff675c2f193d824325a802e61575063363eaa97f471af2ed", [:mix], [{:castore, "~> 0.1", [hex: :castore, repo: "hexpm", optional: true]}, {:exjsx, ">= 3.0.0", [hex: :exjsx, repo: "hexpm", optional: true]}, {:finch, "~> 0.3", [hex: :finch, repo: "hexpm", optional: true]}, {:fuse, "~> 2.4", [hex: :fuse, repo: "hexpm", optional: true]}, {:gun, "~> 1.3", [hex: :gun, repo: "hexpm", optional: true]}, {:hackney, "~> 1.6", [hex: :hackney, repo: "hexpm", optional: true]}, {:ibrowse, "~> 4.4.0", [hex: :ibrowse, repo: "hexpm", optional: true]}, {:jason, ">= 1.0.0", [hex: :jason, repo: "hexpm", optional: true]}, {:mime, "~> 1.0", [hex: :mime, repo: "hexpm", optional: false]}, {:mint, "~> 1.0", [hex: :mint, repo: "hexpm", optional: true]}, {:poison, ">= 1.0.0", [hex: :poison, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: true]}], "hexpm", "aa3a4130a662a16471a6847fecd4772e2adaf9a4693488f022c612c0bb98c9fd"},
+}

test/opentelemetry_tesla_test.exs

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+defmodule OpentelemetryTeslaTest do
+  use ExUnit.Case
+  doctest OpentelemetryTesla
+
+  test "greets the world" do
+    assert OpentelemetryTesla.hello() == :world
+  end
+end

test/test_helper.exs

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+ExUnit.start()