clean up tag map memory leak and add a mem leak regression test

salt/netapi/rest_tornado/saltnado.py

@@ -361,6 +361,9 @@ class EventListener:
             return
         if not future.done():
             future.set_exception(TimeoutException())
+        # We need to remove it from the map even if we didn't explicitly time it out
+        # Otherwise, we get a memory leak in the tag_map
+        if future in self.tag_map[(tag, matcher)] and future.done():
             self.tag_map[(tag, matcher)].remove(future)
         if len(self.tag_map[(tag, matcher)]) == 0:
             del self.tag_map[(tag, matcher)]

tests/pytests/integration/netapi/rest_tornado/test_minions_api_handler.py

@@ -98,3 +98,16 @@ async def test_post_with_incorrect_client(http_client):
             body=salt.utils.json.dumps(low),
         )
     assert exc.value.code == 400
+
+
+@pytest.mark.slow_test
+async def test_mem_leak_in_event_listener(http_client, salt_minion, app):
+    for i in range(10):
+        await http_client.fetch(
+            "/minions/{}".format(salt_minion.id),
+            method="GET",
+            follow_redirects=False,
+        )
+    assert len(app.event_listener.tag_map) == 0
+    assert len(app.event_listener.timeout_map) == 0
+    assert len(app.event_listener.request_map) == 0