[PR #9756/44d809f backport][3.11] Avoid tracking connections per host when there is no limit per host (#9758)

Author: bdraco

CHANGES/9756.misc.rst

@@ -0,0 +1 @@
+Improved performance of :py:class:`aiohttp.BaseConnector` when there is no ``limit_per_host`` -- by :user:`bdraco`.

aiohttp/connector.py

@@ -531,7 +531,8 @@ async def connect(
 
             placeholder = cast(ResponseHandler, _TransportPlaceholder())
             self._acquired.add(placeholder)
-            self._acquired_per_host[key].add(placeholder)
+            if self._limit_per_host:
+                self._acquired_per_host[key].add(placeholder)
 
             try:
                 # Traces are done inside the try block to ensure that the
@@ -557,11 +558,12 @@ async def connect(
         # be no awaits after the proto is added to the acquired set
         # to ensure that the connection is not left in the acquired set
         # on cancellation.
-        acquired_per_host = self._acquired_per_host[key]
         self._acquired.remove(placeholder)
-        acquired_per_host.remove(placeholder)
         self._acquired.add(proto)
-        acquired_per_host.add(proto)
+        if self._limit_per_host:
+            acquired_per_host = self._acquired_per_host[key]
+            acquired_per_host.remove(placeholder)
+            acquired_per_host.add(proto)
         return Connection(self, key, proto, self._loop)
 
     async def _wait_for_available_connection(
@@ -626,7 +628,8 @@ async def _get(
                     # The very last connection was reclaimed: drop the key
                     del self._conns[key]
                 self._acquired.add(proto)
-                self._acquired_per_host[key].add(proto)
+                if self._limit_per_host:
+                    self._acquired_per_host[key].add(proto)
                 if traces:
                     for trace in traces:
                         try:
@@ -680,7 +683,7 @@ def _release_acquired(self, key: "ConnectionKey", proto: ResponseHandler) -> Non
             return
 
         self._acquired.discard(proto)
-        if conns := self._acquired_per_host.get(key):
+        if self._limit_per_host and (conns := self._acquired_per_host.get(key)):
             conns.discard(proto)
             if not conns:
                 del self._acquired_per_host[key]

tests/test_connector.py

@@ -375,7 +375,7 @@ async def test_get_expired_ssl(loop: asyncio.AbstractEventLoop) -> None:
 
 async def test_release_acquired(loop, key) -> None:
     proto = mock.Mock()
-    conn = aiohttp.BaseConnector(loop=loop, limit=5)
+    conn = aiohttp.BaseConnector(loop=loop, limit=5, limit_per_host=10)
     conn._release_waiter = mock.Mock()
 
     conn._acquired.add(proto)
@@ -562,7 +562,7 @@ async def test_release_close(loop, key) -> None:
 async def test__release_acquired_per_host1(
     loop: asyncio.AbstractEventLoop, key: ConnectionKey
 ) -> None:
-    conn = aiohttp.BaseConnector()
+    conn = aiohttp.BaseConnector(limit_per_host=10)
     conn._release_acquired(key, create_mocked_conn(loop))
     assert len(conn._acquired_per_host) == 0
 
@@ -572,7 +572,7 @@ async def test__release_acquired_per_host1(
 async def test__release_acquired_per_host2(
     loop: asyncio.AbstractEventLoop, key: ConnectionKey
 ) -> None:
-    conn = aiohttp.BaseConnector()
+    conn = aiohttp.BaseConnector(limit_per_host=10)
     handler = create_mocked_conn(loop)
     conn._acquired_per_host[key].add(handler)
     conn._release_acquired(key, handler)
@@ -584,7 +584,7 @@ async def test__release_acquired_per_host2(
 async def test__release_acquired_per_host3(
     loop: asyncio.AbstractEventLoop, key: ConnectionKey
 ) -> None:
-    conn = aiohttp.BaseConnector()
+    conn = aiohttp.BaseConnector(limit_per_host=10)
     handler = create_mocked_conn(loop)
     handler2 = create_mocked_conn(loop)
     conn._acquired_per_host[key].add(handler)
@@ -2466,7 +2466,7 @@ async def test_connect_with_limit(
         "GET", URL("http://localhost:80"), loop=loop, response_class=mock.Mock()
     )
 
-    conn = aiohttp.BaseConnector(loop=loop, limit=1)
+    conn = aiohttp.BaseConnector(loop=loop, limit=1, limit_per_host=10)
     conn._conns[key] = deque([(proto, loop.time())])
     conn._create_connection = mock.Mock()
     conn._create_connection.return_value = loop.create_future()
@@ -2663,7 +2663,7 @@ async def f():
         connection2 = await conn.connect(req, None, ClientTimeout())
         acquired = True
         assert 1 == len(conn._acquired)
-        assert 1 == len(conn._acquired_per_host[key])
+        assert not conn._acquired_per_host
         connection2.release()
 
     task = loop.create_task(f())
@@ -2810,7 +2810,7 @@ async def test_connect_waiters_cleanup_key_error(loop) -> None:
 
     req = ClientRequest("GET", URL("http://host:80"), loop=loop)
 
-    conn = aiohttp.BaseConnector(loop=loop, limit=1)
+    conn = aiohttp.BaseConnector(loop=loop, limit=1, limit_per_host=10)
     conn._available_connections = mock.Mock(return_value=0)
 
     t = loop.create_task(conn.connect(req, None, ClientTimeout()))
@@ -2901,7 +2901,7 @@ async def test_force_close_and_explicit_keep_alive(loop) -> None:
 
 
 async def test_error_on_connection(loop, key) -> None:
-    conn = aiohttp.BaseConnector(limit=1, loop=loop)
+    conn = aiohttp.BaseConnector(limit=1, loop=loop, limit_per_host=10)
 
     req = mock.Mock()
     req.connection_key = key
@@ -2969,7 +2969,7 @@ async def create_connection(req, traces=None):
 
 
 async def test_error_on_connection_with_cancelled_waiter(loop, key) -> None:
-    conn = aiohttp.BaseConnector(limit=1, loop=loop)
+    conn = aiohttp.BaseConnector(limit=1, loop=loop, limit_per_host=10)
 
     req = mock.Mock()
     req.connection_key = key