Avoid retrying open_connection on unrecoverable errors (#340)

* Avoid retrying open_connection on unrecoverable errors

- We can retry so hard that we block the event loop

Fixes
```
2022-04-16 22:18:51 WARNING (MainThread) [asyncio] Executing <Task finished name=Task-3576 coro=<open_connection() done, defined at /opt/homebrew/Cellar/python@3.9/3.9.12/Frameworks/Python.framework/Versions/3.9/lib/python3.9/asyncio/streams.py:25> exception=ConnectionRefusedError(61, "Connect call failed (192.168.107.200, 9999)") created at /opt/homebrew/Cellar/python@3.9/3.9.12/Frameworks/Python.framework/Versions/3.9/lib/python3.9/asyncio/tasks.py:460> took 1.001 seconds
```

* comment

kasa/protocol.py

@@ -11,6 +11,7 @@ http://www.apache.org/licenses/LICENSE-2.0
 """
 import asyncio
 import contextlib
+import errno
 import json
 import logging
 import struct
@@ -20,6 +21,7 @@ from typing import Dict, Generator, Optional, Union
 from .exceptions import SmartDeviceException
 
 _LOGGER = logging.getLogger(__name__)
+_NO_RETRY_ERRORS = {errno.EHOSTDOWN, errno.EHOSTUNREACH, errno.ECONNREFUSED}
 
 
 class TPLinkSmartHomeProtocol:
@@ -115,9 +117,30 @@ class TPLinkSmartHomeProtocol:
 
     async def _query(self, request: str, retry_count: int, timeout: int) -> Dict:
         """Try to query a device."""
+        #
+        # Most of the time we will already be connected if the device is online
+        # and the connect call will do nothing and return right away
+        #
+        # However, if we get an unrecoverable error (_NO_RETRY_ERRORS and ConnectionRefusedError)
+        # we do not want to keep trying since many connection open/close operations
+        # in the same time frame can block the event loop. This is especially
+        # import when there are multiple tplink devices being polled.
+        #
         for retry in range(retry_count + 1):
             try:
                 await self._connect(timeout)
+            except ConnectionRefusedError as ex:
+                await self.close()
+                raise SmartDeviceException(
+                    f"Unable to connect to the device: {self.host}: {ex}"
+                )
+            except OSError as ex:
+                await self.close()
+                if ex.errno in _NO_RETRY_ERRORS or retry >= retry_count:
+                    raise SmartDeviceException(
+                        f"Unable to connect to the device: {self.host}: {ex}"
+                    )
+                continue
             except Exception as ex:
                 await self.close()
                 if retry >= retry_count:

kasa/tests/test_protocol.py

@@ -1,3 +1,4 @@
+import errno
 import json
 import logging
 import struct
@@ -29,6 +30,39 @@ async def test_protocol_retries(mocker, retry_count):
     assert conn.call_count == retry_count + 1
 
 
+async def test_protocol_no_retry_on_unreachable(mocker):
+    conn = mocker.patch(
+        "asyncio.open_connection",
+        side_effect=OSError(errno.EHOSTUNREACH, "No route to host"),
+    )
+    with pytest.raises(SmartDeviceException):
+        await TPLinkSmartHomeProtocol("127.0.0.1").query({}, retry_count=5)
+
+    assert conn.call_count == 1
+
+
+async def test_protocol_no_retry_connection_refused(mocker):
+    conn = mocker.patch(
+        "asyncio.open_connection",
+        side_effect=ConnectionRefusedError,
+    )
+    with pytest.raises(SmartDeviceException):
+        await TPLinkSmartHomeProtocol("127.0.0.1").query({}, retry_count=5)
+
+    assert conn.call_count == 1
+
+
+async def test_protocol_retry_recoverable_error(mocker):
+    conn = mocker.patch(
+        "asyncio.open_connection",
+        side_effect=OSError(errno.ECONNRESET, "Connection reset by peer"),
+    )
+    with pytest.raises(SmartDeviceException):
+        await TPLinkSmartHomeProtocol("127.0.0.1").query({}, retry_count=5)
+
+    assert conn.call_count == 6
+
+
 @pytest.mark.skipif(sys.version_info < (3, 8), reason="3.8 is first one with asyncmock")
 @pytest.mark.parametrize("retry_count", [1, 3, 5])
 async def test_protocol_reconnect(mocker, retry_count):