feat: setup code attributes in Elixir macros

apps/opentelemetry_api/lib/open_telemetry/attributes.ex

@@ -0,0 +1,74 @@
+defmodule OpenTelemetry.Attributes do
+  @moduledoc """
+  This module contains utility functions for span attributes.
+
+  Elixir has built in variables like `__ENV__` and `__CALLER__` that can be used to generate
+  span attributes like `code.function`, `code.lineno`, and `code.namespace` either during runtime
+  or compile time. This module provides a function to generate these attributes from a `t:Macro.Env`
+  struct.
+
+  For more information, view the [OpenTelemetry Semantic Conventions](OSC).
+
+  [OSC]: https://opentelemetry.io/docs/specs/semconv/attributes-registry
+  """
+
+  @code_filepath :"code.filepath"
+  @code_function :"code.function"
+  @code_lineno :"code.lineno"
+  @code_namespace :"code.namespace"
+
+  @doc """
+  A function used to generate attributes from a `t:Macro.Env` struct.
+
+  This function is used to generate span attributes like `code.function`, `code.lineno`, and
+  `code.namespace` from a `__CALLER__` variable during compile time or a `__ENV__` variable
+  run time.
+
+  ## Usage
+
+      # During run time
+      def my_function() do
+        OpenTelemetry.Attributes.from_macro_env(__ENV__)
+      end
+
+      iex> my_function()
+      %{code_function: "my_function/0", ...}
+
+      # During compile time in a macro
+      defmacro my_macro() do
+        attributes =
+          __CALLER__
+          |> OpenTelemetry.Attributes.from_macro_env()
+          |> Macro.escape()
+
+        quote do
+          unquote(attributes)
+        end
+      end
+
+      def my_other_function() do
+        my_macro()
+      end
+
+      iex> my_macro()
+      %{code_function: "my_other_function/0", ...}
+
+  """
+  @spec from_macro_env(Macro.Env.t()) :: OpenTelemetry.attributes_map()
+  def from_macro_env(%Macro.Env{} = env) do
+    function_arty =
+      case env.function do
+        {func_name, func_arity} -> "#{func_name}/#{func_arity}"
+        nil -> nil
+      end
+
+    %{
+      @code_function => function_arty,
+      @code_namespace => to_string(env.module),
+      @code_filepath => env.file,
+      @code_lineno => env.line
+    }
+    |> Enum.reject(fn {_k, v} -> is_nil(v) end)
+    |> Map.new()
+  end
+end

apps/opentelemetry_api/lib/open_telemetry/tracer.ex

@@ -22,11 +22,16 @@ defmodule OpenTelemetry.Tracer do
   The current active Span is used as the parent of the created Span.
   """
   defmacro start_span(name, opts \\ quote(do: %{})) do
-    quote bind_quoted: [name: name, start_opts: opts] do
+    attributes =
+      __CALLER__
+      |> OpenTelemetry.Attributes.from_macro_env()
+      |> Macro.escape()
+
+    quote bind_quoted: [name: name, start_opts: opts, attributes: attributes] do
       :otel_tracer.start_span(
         :opentelemetry.get_application_tracer(__MODULE__),
         name,
-        Map.new(start_opts)
+        OpenTelemetry.Tracer.merge_start_opts(start_opts, attributes)
       )
     end
   end
@@ -37,12 +42,17 @@ defmodule OpenTelemetry.Tracer do
   The current active Span is used as the parent of the created Span.
   """
   defmacro start_span(ctx, name, opts) do
-    quote bind_quoted: [ctx: ctx, name: name, start_opts: opts] do
+    attributes =
+      __CALLER__
+      |> OpenTelemetry.Attributes.from_macro_env()
+      |> Macro.escape()
+
+    quote bind_quoted: [ctx: ctx, name: name, start_opts: opts, attributes: attributes] do
       :otel_tracer.start_span(
         ctx,
         :opentelemetry.get_application_tracer(__MODULE__),
         name,
-        Map.new(start_opts)
+        OpenTelemetry.Tracer.merge_start_opts(start_opts, attributes)
       )
     end
   end
@@ -70,11 +80,16 @@ defmodule OpenTelemetry.Tracer do
   See `start_span/2` and `end_span/0`.
   """
   defmacro with_span(name, start_opts \\ quote(do: %{}), do: block) do
+    attributes =
+      __CALLER__
+      |> OpenTelemetry.Attributes.from_macro_env()
+      |> Macro.escape()
+
     quote do
       :otel_tracer.with_span(
         :opentelemetry.get_application_tracer(__MODULE__),
         unquote(name),
-        Map.new(unquote(start_opts)),
+        OpenTelemetry.Tracer.merge_start_opts(unquote(start_opts), unquote(attributes)),
         fn _ -> unquote(block) end
       )
     end
@@ -88,12 +103,17 @@ defmodule OpenTelemetry.Tracer do
   See `start_span/2` and `end_span/0`.
   """
   defmacro with_span(ctx, name, start_opts, do: block) do
+    attributes =
+      __CALLER__
+      |> OpenTelemetry.Attributes.from_macro_env()
+      |> Macro.escape()
+
     quote do
       :otel_tracer.with_span(
         unquote(ctx),
         :opentelemetry.get_application_tracer(__MODULE__),
         unquote(name),
-        Map.new(unquote(start_opts)),
+        OpenTelemetry.Tracer.merge_start_opts(unquote(start_opts), unquote(attributes)),
         fn _ -> unquote(block) end
       )
     end
@@ -221,4 +241,17 @@ defmodule OpenTelemetry.Tracer do
   def update_name(name) do
     :otel_span.update_name(:otel_tracer.current_span_ctx(), name)
   end
+
+  @doc false
+  @spec merge_start_opts(OpenTelemetry.Span.start_opts(), OpenTelemetry.attributes_map()) ::
+          OpenTelemetry.Span.start_opts()
+  def merge_start_opts(start_opts, builtin_attributes) do
+    start_opts
+    |> Map.new()
+    |> Map.update(:attributes, builtin_attributes, fn specified_attributes ->
+      specified_attributes
+      |> Map.new(fn {k, v} -> {to_string(k), v} end)
+      |> Map.merge(builtin_attributes)
+    end)
+  end
 end

apps/opentelemetry_api/test/open_telemetry_test.exs

@@ -144,4 +144,13 @@ defmodule OpenTelemetryTest do
     Ctx.detach(token)
     assert %{"a" => {"b", []}} = Baggage.get_all()
   end
+
+  test "from_macro_env/1" do
+    attributes = OpenTelemetry.Attributes.from_macro_env(__ENV__)
+
+    assert attributes[:"code.filepath"] =~ "open_telemetry_test.exs"
+    assert attributes[:"code.function"] =~ "from_macro_env/1"
+    assert attributes[:"code.lineno"] == 149
+    assert attributes[:"code.namespace"] == "Elixir.OpenTelemetryTest"
+  end
 end