Merge pull request rails#50190 from jhawthorn/retry_checkout_after_reap

Retry new connection on checkout after reap

Author: jhawthorn

activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb

@@ -668,7 +668,13 @@ def acquire_connection(checkout_timeout)
             conn
           else
             reap
-            @available.poll(checkout_timeout)
+            # Retry after reaping, which may return an available connection,
+            # remove an inactive connection, or both
+            if conn = @available.poll || try_to_checkout_new_connection
+              conn
+            else
+              @available.poll(checkout_timeout)
+            end
           end
         rescue ConnectionTimeoutError => ex
           raise ex.set_pool(self)

activerecord/test/cases/connection_pool_test.rb

@@ -216,6 +216,30 @@ def test_reap_inactive
         @pool.connections.each { |conn| conn.close if conn.in_use? }
       end
 
+      def test_inactive_are_returned_from_dead_thread
+        ready = Concurrent::CountDownLatch.new
+        @pool.instance_variable_set(:@size, 1)
+
+        child = new_thread do
+          @pool.checkout
+          ready.count_down
+          stop_thread
+        end
+
+        pass_to(child) until ready.wait(0)
+
+        assert_equal 1, active_connections(@pool).size
+
+        child.terminate
+        child.join
+
+        @pool.checkout
+
+        assert_equal 1, active_connections(@pool).size
+      ensure
+        @pool.connections.each { |conn| conn.close if conn.in_use? }
+      end
+
       def test_idle_timeout_configuration
         @pool.disconnect!