pubsub.run_in_thread throws exceptions in case of lost redis connection

I started the thread for keyspace events:

self._pubsub = self._redis.pubsub()
self._pubsub.psubscribe(**{'__keyspace@0__:*': self._redis_notification})
self._pubsub_thread = self._pubsub.run_in_thread(sleep_time=0.5)

If the connection broke with redis (redis process stopped), lot of exceptions appeared. And I do not know, how my main thread could handle this (or get notified about it).

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/local/lib/python3.4/dist-packages/redis/connection.py", line 129, in _read_from_socket
    raise socket.error(SERVER_CLOSED_CONNECTION_ERROR)
OSError: Connection closed by server.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.4/dist-packages/redis/client.py", line 2165, in _execute
    return command(*args)
  File "/usr/local/lib/python3.4/dist-packages/redis/connection.py", line 577, in read_response
    response = self._parser.read_response()
  File "/usr/local/lib/python3.4/dist-packages/redis/connection.py", line 238, in read_response
    response = self._buffer.readline()
  File "/usr/local/lib/python3.4/dist-packages/redis/connection.py", line 168, in readline
    self._read_from_socket()
  File "/usr/local/lib/python3.4/dist-packages/redis/connection.py", line 143, in _read_from_socket
    (e.args,))
redis.exceptions.ConnectionError: Error while reading from socket: ('Connection closed by server.',)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.4/dist-packages/redis/connection.py", line 439, in connect
    sock = self._connect()
  File "/usr/local/lib/python3.4/dist-packages/redis/connection.py", line 494, in _connect
    raise err
  File "/usr/local/lib/python3.4/dist-packages/redis/connection.py", line 482, in _connect
    sock.connect(socket_address)
ConnectionRefusedError: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.4/threading.py", line 920, in _bootstrap_inner
    self.run()
  File "/usr/local/lib/python3.4/dist-packages/redis/client.py", line 2345, in run
    timeout=sleep_time)
  File "/usr/local/lib/python3.4/dist-packages/redis/client.py", line 2260, in get_message
    response = self.parse_response(block=False, timeout=timeout)
  File "/usr/local/lib/python3.4/dist-packages/redis/client.py", line 2183, in parse_response
    return self._execute(connection, connection.read_response)
  File "/usr/local/lib/python3.4/dist-packages/redis/client.py", line 2172, in _execute
    connection.connect()
  File "/usr/local/lib/python3.4/dist-packages/redis/connection.py", line 442, in connect
    raise ConnectionError(self._error_message(e))
redis.exceptions.ConnectionError: Error 111 connecting to 172.18.0.4:6379. Connection refused.

[wiwat-tharateeraparb]

I have worked around this by polling the pubsub thread’s health e.g. self._pubsub_thread.is_alive() and stop the thread when it’s not alive anymore. But it will be awesome if we can register a callback or handler for run_in_thread’s exception.

[dmarsh19]

I am having similar issues. Its additionally problematic because ConnectionError exceptions bubble up all the way from SocketBuffer to PubSubWorkerThread.run() without being handled, which eventually kills the thread unnoticed. threading.excepthook() can be used in Python3.8 to catch exceptions as a workaround.