From fd0672fcffd519b306810e0562b96b9aabd11624 Mon Sep 17 00:00:00 2001
From: Lukasz Samson <lukaszsamson@gmail.com>
Date: Sun, 19 Jul 2026 12:57:49 +0200
Subject: [PATCH] Reject checkouts after deadline

---
 integration_test/cases/queue_test.exs     | 23 +++++++++++++++
 integration_test/ownership/owner_test.exs |  2 +-
 lib/db_connection/holder.ex               | 36 ++++++++++++++++-------
 3 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/integration_test/cases/queue_test.exs b/integration_test/cases/queue_test.exs
index 3e79b4f3..688c0b99 100644
--- a/integration_test/cases/queue_test.exs
+++ b/integration_test/cases/queue_test.exs
@@ -86,6 +86,29 @@ defmodule QueueTest do
     assert P.run(pool, fn _ -> :result end) == :result
   end
 
+  test "does not checkout a connection after its deadline" do
+    stack = [
+      {:ok, :state},
+      :ok,
+      fn opts ->
+        send(opts[:parent], :reconnected)
+        {:ok, :state}
+      end
+    ]
+
+    {:ok, agent} = A.start_link(stack)
+
+    opts = [agent: agent, parent: self()]
+    {:ok, pool} = P.start_link(opts)
+    deadline = System.monotonic_time(:millisecond) - 1
+
+    assert_raise DBConnection.ConnectionError, ~r/deadline reached/, fn ->
+      P.run(pool, fn _ -> flunk("checkout succeeded") end, deadline: deadline)
+    end
+
+    assert_receive :reconnected
+  end
+
   test "queue many async exits" do
     stack = [{:ok, :state}] ++ List.duplicate({:idle, :state}, 20)
     {:ok, agent} = A.start_link(stack)
diff --git a/integration_test/ownership/owner_test.exs b/integration_test/ownership/owner_test.exs
index 69bc0d6f..f0b86d79 100644
--- a/integration_test/ownership/owner_test.exs
+++ b/integration_test/ownership/owner_test.exs
@@ -132,7 +132,7 @@ defmodule OwnerTest do
                fn _ ->
                  assert_receive :reconnected
                end,
-               timeout: 0
+               timeout: 10
              )
            end) =~ ~r"timed out"
 
diff --git a/lib/db_connection/holder.ex b/lib/db_connection/holder.ex
index 3b9916d8..0d69a51d 100644
--- a/lib/db_connection/holder.ex
+++ b/lib/db_connection/holder.ex
@@ -321,7 +321,7 @@ defmodule DBConnection.Holder do
         pool_ref =
           pool_ref(pool: pool, reference: ref, deadline: deadline, holder: holder, lock: lock)
 
-        checkout_result(holder, pool_ref, checkin_time)
+        checkout_result(holder, pool_ref, checkin_time, timeout)
 
       {^lock, reply} ->
         Process.demonitor(lock, [:flush])
@@ -332,20 +332,34 @@ defmodule DBConnection.Holder do
     end
   end
 
-  defp checkout_result(holder, pool_ref, checkin_time) do
-    try do
-      :ets.lookup(holder, :conn)
-    rescue
-      ArgumentError ->
-        # Deadline could hit and be handled pool before using connection
-        msg = "connection not available because deadline reached while in queue"
-        {:error, DBConnection.ConnectionError.exception(msg)}
+  defp checkout_result(holder, pool_ref, checkin_time, timeout) do
+    if deadline_reached?(timeout) do
+      err = checkout_deadline_error()
+      disconnect(pool_ref, err)
+      {:error, err}
     else
-      [conn(module: mod, state: state)] ->
-        {:ok, pool_ref, mod, checkin_time, state}
+      try do
+        :ets.lookup(holder, :conn)
+      rescue
+        ArgumentError ->
+          # Deadline could hit and be handled by the pool before using the connection.
+          {:error, checkout_deadline_error()}
+      else
+        [conn(module: mod, state: state)] ->
+          {:ok, pool_ref, mod, checkin_time, state}
+      end
     end
   end
 
+  defp checkout_deadline_error do
+    DBConnection.ConnectionError.exception(
+      "connection not available because deadline reached while in queue"
+    )
+  end
+
+  defp deadline_reached?(nil), do: false
+  defp deadline_reached?(timeout), do: timeout <= System.monotonic_time(@time_unit)
+
   defp no_holder(holder, maybe_pid) do
     reason =
       case :ets.info(holder, :owner) do