From 3517aacf1911bc93ec52044bbbb9b300eef4c5d6 Mon Sep 17 00:00:00 2001
From: Gonzalo <456459+grzuy@users.noreply.github.com>
Date: Mon, 9 Sep 2024 12:56:57 -0300
Subject: [PATCH] feat: Tower.Event similarity_id

---
 lib/tower/event.ex  |  8 ++++++++
 test/tower_test.exs | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/lib/tower/event.ex b/lib/tower/event.ex
index e73314c..671f8e6 100644
--- a/lib/tower/event.ex
+++ b/lib/tower/event.ex
@@ -8,6 +8,7 @@ defmodule Tower.Event do
 
   defstruct [
     :id,
+    :similarity_id,
     :datetime,
     :level,
     :kind,
@@ -31,6 +32,7 @@ defmodule Tower.Event do
   """
   @type t :: %__MODULE__{
           id: Uniq.UUID.t(),
+          similarity_id: non_neg_integer(),
           datetime: DateTime.t(),
           level: level(),
           kind: error_kind() | non_error_kind(),
@@ -41,6 +43,7 @@ defmodule Tower.Event do
           metadata: map()
         }
 
+  @similarity_source_attributes [:level, :kind, :reason, :stacktrace, :metadata]
   @logger_time_unit :microsecond
 
   @doc false
@@ -120,6 +123,7 @@ defmodule Tower.Event do
       |> Map.merge(map)
       |> Map.merge(attributes_from_options(options))
     )
+    |> put_similarity_id()
   end
 
   defp attributes_from_options(options) do
@@ -150,4 +154,8 @@ defmodule Tower.Event do
   defp plug_conn(options) do
     Keyword.get(options, :plug_conn, Keyword.get(options, :log_event)[:meta][:conn])
   end
+
+  defp put_similarity_id(%__MODULE__{} = event) do
+    struct!(event, similarity_id: :erlang.phash2(Map.take(event, @similarity_source_attributes)))
+  end
 end
diff --git a/test/tower_test.exs b/test/tower_test.exs
index 2611c75..2b77feb 100644
--- a/test/tower_test.exs
+++ b/test/tower_test.exs
@@ -552,6 +552,45 @@ defmodule TowerTest do
     assert datetime1 > datetime2
   end
 
+  test "protects reporters from repeated events" do
+    capture_log(fn ->
+      for _ <- 1..2 do
+        in_unlinked_process(fn ->
+          1 / 0
+        end)
+      end
+
+      in_unlinked_process(fn ->
+        raise "something else"
+      end)
+    end)
+
+    assert_eventually(
+      [
+        %{
+          similarity_id: other_similarity_id,
+          level: :error,
+          kind: :error,
+          reason: %RuntimeError{message: "something else"}
+        },
+        %{
+          similarity_id: similarity_id,
+          level: :error,
+          kind: :error,
+          reason: %ArithmeticError{message: "bad argument in arithmetic expression"}
+        },
+        %{
+          similarity_id: similarity_id,
+          level: :error,
+          kind: :error,
+          reason: %ArithmeticError{message: "bad argument in arithmetic expression"}
+        }
+      ] = reported_events()
+    )
+
+    assert similarity_id != other_similarity_id
+  end
+
   defp in_unlinked_process(fun) when is_function(fun, 0) do
     {:ok, pid} = Task.Supervisor.start_link()