fix(metrics): attach sentry.timestamp.sequence

lib/sentry/application.ex

@@ -5,6 +5,7 @@ defmodule Sentry.Application do
 
   alias Sentry.Config
   alias Sentry.LoggerUtils
+  alias Sentry.Metric
 
   @compile {:no_warn_undefined, [NimbleOwnership]}
 
@@ -82,6 +83,7 @@ defmodule Sentry.Application do
         [Sentry.Transport.SenderPool]
 
     cache_loaded_applications()
+    Metric.init_sequence()
 
     with {:ok, pid} <-
            Supervisor.start_link(children, strategy: :one_for_one, name: Sentry.Supervisor) do

lib/sentry/metric.ex

@@ -42,6 +42,8 @@ defmodule Sentry.Metric do
 
   @sdk_version Mix.Project.config()[:version]
 
+  @sequence_key {:sentry, :metric_sequence}
+
   @doc """
   Attaches default attributes to a metric.
 
@@ -64,7 +66,22 @@ defmodule Sentry.Metric do
       |> maybe_put_attr("server.address", Config.server_name())
 
     # Merge with user attributes (user attributes take precedence)
-    %{metric | attributes: Map.merge(default_attrs, metric.attributes)}
+    attributes =
+      default_attrs
+      |> Map.merge(metric.attributes)
+      |> Map.put("sentry.timestamp.sequence", next_sequence())
+
+    %{metric | attributes: attributes}
+  end
+
+  @doc false
+  @spec init_sequence() :: :ok
+  def init_sequence do
+    :persistent_term.put(@sequence_key, :atomics.new(1, signed: true))
+  end
+
+  defp next_sequence do
+    :atomics.add_get(:persistent_term.get(@sequence_key), 1, 1) - 1
   end
 
   defp maybe_put_attr(attrs, _key, nil), do: attrs

test/sentry/metric_sequence_test.exs

@@ -0,0 +1,37 @@
+defmodule Sentry.MetricSequenceTest do
+  use Sentry.Case, async: false
+
+  alias Sentry.Metric
+
+  setup do
+    Metric.init_sequence()
+    :ok
+  end
+
+  test "starts at 0 and increments by 1 for every metric captured" do
+    assert sequence_of(build(:counter)) == 0
+    assert sequence_of(build(:gauge)) == 1
+    assert sequence_of(build(:distribution)) == 2
+  end
+
+  test "cannot be overridden by a user-supplied attribute" do
+    assert sequence_of(build(:counter, %{"sentry.timestamp.sequence" => 999})) == 0
+  end
+
+  defp build(type, attributes \\ %{}) do
+    %Metric{
+      type: type,
+      name: "test.#{type}",
+      value: 1,
+      timestamp: 1_234_567_890.0,
+      attributes: attributes
+    }
+  end
+
+  defp sequence_of(metric) do
+    metric
+    |> Metric.attach_default_attributes()
+    |> Map.fetch!(:attributes)
+    |> Map.fetch!("sentry.timestamp.sequence")
+  end
+end