Fix available connection calculation (#9623)

aiohttp/connector.py

@@ -475,14 +475,20 @@ def _available_connections(self, key: "ConnectionKey") -> int:
         available.
         """
         # check total available connections
-        if self._limit and (available := self._limit - len(self._acquired)) <= 0:
-            return available
+        # If there are no limits, this will always return 1
+        total_remain = 1
+
+        if self._limit and (total_remain := self._limit - len(self._acquired)) <= 0:
+            return total_remain
 
         # check limit per host
-        if self._limit_per_host and key in self._acquired_per_host:
-            return self._limit_per_host - len(self._acquired_per_host[key])
+        if host_remain := self._limit_per_host:
+            if acquired := self._acquired_per_host.get(key):
+                host_remain -= len(acquired)
+            if total_remain > host_remain:
+                return host_remain
 
-        return 1
+        return total_remain
 
     async def connect(
         self, req: ClientRequest, traces: List["Trace"], timeout: "ClientTimeout"

tests/test_connector.py

@@ -64,6 +64,12 @@ def key2() -> ConnectionKey:
     return ConnectionKey("localhost", 80, False, True, None, None, None)
 
 
+@pytest.fixture
+def other_host_key2() -> ConnectionKey:
+    # Connection key
+    return ConnectionKey("otherhost", 80, False, True, None, None, None)
+
+
 @pytest.fixture
 def ssl_key() -> ConnectionKey:
     # Connection key
@@ -3390,3 +3396,77 @@ def test_default_ssl_context_creation_without_ssl() -> None:
     with mock.patch.object(connector_module, "ssl", None):
         assert connector_module._make_ssl_context(False) is None
         assert connector_module._make_ssl_context(True) is None
+
+
+async def test_available_connections_with_limit_per_host(
+    key: ConnectionKey, other_host_key2: ConnectionKey
+) -> None:
+    """Verify expected values based on active connections with host limit."""
+    conn = aiohttp.BaseConnector(limit=3, limit_per_host=2)
+    assert conn._available_connections(key) == 2
+    assert conn._available_connections(other_host_key2) == 2
+    proto1 = create_mocked_conn()
+    connection1 = conn._acquired_connection(proto1, key)
+    assert conn._available_connections(key) == 1
+    assert conn._available_connections(other_host_key2) == 2
+    proto2 = create_mocked_conn()
+    connection2 = conn._acquired_connection(proto2, key)
+    assert conn._available_connections(key) == 0
+    assert conn._available_connections(other_host_key2) == 1
+    connection1.close()
+    assert conn._available_connections(key) == 1
+    assert conn._available_connections(other_host_key2) == 2
+    connection2.close()
+    other_proto1 = create_mocked_conn()
+    other_connection1 = conn._acquired_connection(other_proto1, other_host_key2)
+    assert conn._available_connections(key) == 2
+    assert conn._available_connections(other_host_key2) == 1
+    other_connection1.close()
+    assert conn._available_connections(key) == 2
+    assert conn._available_connections(other_host_key2) == 2
+
+
+@pytest.mark.parametrize("limit_per_host", [0, 10])
+async def test_available_connections_without_limit_per_host(
+    key: ConnectionKey, other_host_key2: ConnectionKey, limit_per_host: int
+) -> None:
+    """Verify expected values based on active connections with higher host limit."""
+    conn = aiohttp.BaseConnector(limit=3, limit_per_host=limit_per_host)
+    assert conn._available_connections(key) == 3
+    assert conn._available_connections(other_host_key2) == 3
+    proto1 = create_mocked_conn()
+    connection1 = conn._acquired_connection(proto1, key)
+    assert conn._available_connections(key) == 2
+    assert conn._available_connections(other_host_key2) == 2
+    proto2 = create_mocked_conn()
+    connection2 = conn._acquired_connection(proto2, key)
+    assert conn._available_connections(key) == 1
+    assert conn._available_connections(other_host_key2) == 1
+    connection1.close()
+    assert conn._available_connections(key) == 2
+    assert conn._available_connections(other_host_key2) == 2
+    connection2.close()
+    other_proto1 = create_mocked_conn()
+    other_connection1 = conn._acquired_connection(other_proto1, other_host_key2)
+    assert conn._available_connections(key) == 2
+    assert conn._available_connections(other_host_key2) == 2
+    other_connection1.close()
+    assert conn._available_connections(key) == 3
+    assert conn._available_connections(other_host_key2) == 3
+
+
+async def test_available_connections_no_limits(
+    key: ConnectionKey, other_host_key2: ConnectionKey
+) -> None:
+    """Verify expected values based on active connections with no limits."""
+    # No limits is a special case where available connections should always be 1.
+    conn = aiohttp.BaseConnector(limit=0, limit_per_host=0)
+    assert conn._available_connections(key) == 1
+    assert conn._available_connections(other_host_key2) == 1
+    proto1 = create_mocked_conn()
+    connection1 = conn._acquired_connection(proto1, key)
+    assert conn._available_connections(key) == 1
+    assert conn._available_connections(other_host_key2) == 1
+    connection1.close()
+    assert conn._available_connections(key) == 1
+    assert conn._available_connections(other_host_key2) == 1