From 4df07b2b2f13306e65058804358eec6f556498ea Mon Sep 17 00:00:00 2001
From: Burmaja Milan <burmajam@gmail.com>
Date: Tue, 16 Jun 2026 17:40:29 +0100
Subject: [PATCH] Add configurable conn_max_idle_time to Finch pool

Co-Authored-By: Claude Sonnet 4.6
---
 CHANGELOG.md                        |  9 +++
 lib/graph_conn/supervisor.ex        | 16 +++++-
 mix.exs                             |  2 +-
 test/graph_conn/supervisor_test.exs | 86 +++++++++++++++++++++++++++++
 4 files changed, 110 insertions(+), 3 deletions(-)
 create mode 100644 test/graph_conn/supervisor_test.exs

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6f5f122..7574033 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,12 @@
+# 1.9.12
+
+## Enhancement
+
+- Add configurable `conn_max_idle_time` Finch pool option. Set
+  `config :graph_conn, conn_max_idle_time: ms` to proactively drop idle
+  HTTP connections before the upstream gateway closes them. Defaults to
+  `nil` (Finch default: `:infinity`, preserving existing behaviour).
+
 # 1.9.11
 
 ## Update
diff --git a/lib/graph_conn/supervisor.ex b/lib/graph_conn/supervisor.ex
index a1a81fe..11c97ed 100644
--- a/lib/graph_conn/supervisor.ex
+++ b/lib/graph_conn/supervisor.ex
@@ -35,7 +35,7 @@ defmodule GraphConn.Supervisor do
       {Finch,
        name: Module.concat(base_name, Finch),
        pools: %{
-         default: [{:size, 50}, {:count, 1} | _conn_opts()]
+         default: _pool_opts()
        }},
       {GraphConn.ConnectionManager, [base_name, config]}
     ]
@@ -44,6 +44,17 @@ defmodule GraphConn.Supervisor do
 
   defp _name(base_name), do: Module.concat(base_name, Supervisor)
 
+  defp _pool_opts do
+    base = [{:size, 50}, {:count, 1} | _conn_opts()]
+
+    :graph_conn
+    |> Application.get_env(:conn_max_idle_time)
+    |> case do
+      nil -> base
+      timeout -> [{:conn_max_idle_time, timeout} | base]
+    end
+  end
+
   defp _conn_opts do
     insecure? = Application.get_env(:graph_conn, :insecure) == true
     proxy = Application.get_env(:graph_conn, :proxy, false)
@@ -51,7 +62,8 @@ defmodule GraphConn.Supervisor do
     if ca_cert_file = Application.get_env(:graph_conn, :ca_cert),
       do: :public_key.cacerts_load(ca_cert_file)
 
-    case {insecure?, proxy} do
+    {insecure?, proxy}
+    |> case do
       {true, false} ->
         transport_opts = [verify: :verify_none]
         [conn_opts: [transport_opts: transport_opts]]
diff --git a/mix.exs b/mix.exs
index a6c7a0a..074d1eb 100644
--- a/mix.exs
+++ b/mix.exs
@@ -7,7 +7,7 @@ defmodule GraphConn.MixProject do
   def project do
     [
       app: :graph_conn,
-      version: "1.9.9",
+      version: "1.9.12",
       elixir: "~> 1.17",
       start_permanent: true,
       test_coverage: [tool: ExCoveralls],
diff --git a/test/graph_conn/supervisor_test.exs b/test/graph_conn/supervisor_test.exs
new file mode 100644
index 0000000..59f8cdf
--- /dev/null
+++ b/test/graph_conn/supervisor_test.exs
@@ -0,0 +1,86 @@
+defmodule GraphConn.SupervisorTest do
+  use ExUnit.Case, async: false
+
+  alias GraphConn.{Request, TestConn}
+
+  describe "Finch conn_max_idle_time" do
+    setup do
+      original = Application.get_env(:graph_conn, :conn_max_idle_time)
+      test_pid = self()
+
+      "supervisor-test-idle-#{inspect(self())}"
+      |> :telemetry.attach(
+        [:finch, :conn_max_idle_time_exceeded],
+        fn _, _, _, _ -> send(test_pid, :idle_exceeded) end,
+        nil
+      )
+
+      fn ->
+        :telemetry.detach("supervisor-test-idle-#{inspect(test_pid)}")
+
+        original
+        |> case do
+          nil -> Application.delete_env(:graph_conn, :conn_max_idle_time)
+          val -> Application.put_env(:graph_conn, :conn_max_idle_time, val)
+        end
+
+        TestConn
+        |> Module.concat(Supervisor)
+        |> Process.whereis()
+        |> case do
+          nil -> :ok
+          pid -> Process.exit(pid, :test_cleanup)
+        end
+      end
+      |> on_exit()
+
+      :ok
+    end
+
+    test "idle connection is discarded when conn_max_idle_time is configured" do
+      Application.put_env(:graph_conn, :conn_max_idle_time, 50)
+
+      config = Application.get_env(:graph_conn, TestConn)
+      assert {:ok, _pid} = _start_connection(config)
+      assert_receive {:conn_status_changed, :ready}
+
+      # Wait longer than the configured idle time so the connection ages
+      Process.sleep(100)
+
+      # Trigger a checkout — Finch discards the stale connection and emits the event
+      assert {:ok, _} = TestConn.execute(:action, %Request{path: "capabilities"})
+
+      assert_receive :idle_exceeded, 500
+      assert :ok = TestConn.stop()
+    end
+
+    test "idle connection is kept when conn_max_idle_time is not configured" do
+      Application.delete_env(:graph_conn, :conn_max_idle_time)
+
+      config = Application.get_env(:graph_conn, TestConn)
+      assert {:ok, _pid} = _start_connection(config)
+      assert_receive {:conn_status_changed, :ready}
+
+      Process.sleep(100)
+
+      assert {:ok, _} = TestConn.execute(:action, %Request{path: "capabilities"})
+
+      refute_receive :idle_exceeded, 200
+      assert :ok = TestConn.stop()
+    end
+  end
+
+  defp _start_connection(config) do
+    config
+    |> TestConn.start_supervisor(%{forward_to: self()})
+    |> case do
+      {:ok, pid} ->
+        assert Process.alive?(pid)
+        {:ok, pid}
+
+      {:error, {:already_started, pid}} ->
+        Process.exit(pid, :we_need_new_connection)
+        _start_connection(config)
+    end
+  end
+end