fixing tcp_interface 100% cpu usage bug (#709)

meshtastic/tcp_interface.py

@@ -1,9 +1,11 @@
 """TCPInterface class for interfacing with http endpoint
 """
 # pylint: disable=R0917
+import contextlib
 import logging
 import socket
-from typing import Optional, cast
+import time
+from typing import Optional
 
 from meshtastic.stream_interface import StreamInterface
 
@@ -35,52 +37,63 @@
         self.socket: Optional[socket.socket] = None
 
         if connectNow:
-            logging.debug(f"Connecting to {hostname}") # type: ignore[str-bytes-safe]
-            server_address: tuple[str, int] = (hostname, portNumber)
-            sock: Optional[socket.socket] = socket.create_connection(server_address)
-            self.socket = sock
+            self.myConnect()
         else:
             self.socket = None
 
-        StreamInterface.__init__(
-            self, debugOut=debugOut, noProto=noProto, connectNow=connectNow, noNodes=noNodes
-        )
+        super().__init__(debugOut=debugOut, noProto=noProto, connectNow=connectNow, noNodes=noNodes)
 
     def _socket_shutdown(self) -> None:
         """Shutdown the socket.
         Note: Broke out this line so the exception could be unit tested.
         """
-        if self.socket:		#mian: please check that this should be "if self.socket:"
-            cast(socket.socket, self.socket).shutdown(socket.SHUT_RDWR)
+        if self.socket is not None:
+            self.socket.shutdown(socket.SHUT_RDWR)
 
     def myConnect(self) -> None:
         """Connect to socket"""
-        server_address: tuple[str, int] = (self.hostname, self.portNumber)
-        sock: Optional[socket.socket] = socket.create_connection(server_address)
-        self.socket = sock
+        logging.debug(f"Connecting to {self.hostname}") # type: ignore[str-bytes-safe]
+        server_address = (self.hostname, self.portNumber)
+        self.socket = socket.create_connection(server_address)
 
     def close(self) -> None:
         """Close a connection to the device"""
         logging.debug("Closing TCP stream")
-        StreamInterface.close(self)
+        super().close()
         # Sometimes the socket read might be blocked in the reader thread.
         # Therefore we force the shutdown by closing the socket here
-        self._wantExit: bool = True
-        if not self.socket is None:
-            try:
+        self._wantExit = True
+        if self.socket is not None:
+            with contextlib.suppress(Exception):  # Ignore errors in shutdown, because we might have a race with the server
                 self._socket_shutdown()
-            except:
-                pass  # Ignore errors in shutdown, because we might have a race with the server
             self.socket.close()
 
+        self.socket = None
+
     def _writeBytes(self, b: bytes) -> None:
         """Write an array of bytes to our stream and flush"""
-        if self.socket:
+        if self.socket is not None:
             self.socket.send(b)
 
     def _readBytes(self, length) -> Optional[bytes]:
         """Read an array of bytes from our stream"""
-        if self.socket:
-            return self.socket.recv(length)
-        else:
-            return None
+        if self.socket is not None:
+            data = self.socket.recv(length)
+            # empty byte indicates a disconnected socket,
+            # we need to handle it to avoid an infinite loop reading from null socket
+            if data == b'':
+                logging.debug("dead socket, re-connecting")
+                # cleanup and reconnect socket without breaking reader thread
+                with contextlib.suppress(Exception):
+                    self._socket_shutdown()
+                self.socket.close()
+                self.socket = None
+                time.sleep(1)
+                self.myConnect()
+                self._startConfig()
+                return None
+            return data
+
+        # no socket, break reader thread
+        self._wantExit = True
+        return None