fix(redis): subscriber watchdog

[LounisBou]

The Redis transport opens two connections from the same DSN, one for commands and one for the pub/sub subscription. The periodic ping only reached the command connection, so a half-open subscription socket went unnoticed: the hub kept answering publish requests while every subscriber stopped receiving anything.

The ping now runs on both connections. Paired with a non-zero readTimeout it turns a silent socket into a rejected promise, which reaches Hub::die and lets the supervisor restart the hub.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (ed9d6e4) to head (4bb152e).

Additional details and impacted files

@@             Coverage Diff             @@
##                main       #52   +/-   ##
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  Coverage     100.00%   100.00%           
- Complexity       164       166    +2     
===========================================
  Files             27        27           
  Lines            465       471    +6     
===========================================
+ Hits             465       471    +6     

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[bpolaszek]

AFAIK no other command can reach the subscribe connection as soon as subscribe() is called (blocking call).
Does that work for real?

[LounisBou]

AFAIK no other command can reach the subscribe connection as soon as subscribe() is called (blocking call).

It does, integration suite proves it. Why do you think it doesn't ? redis-react is asynchronous, so subscribe() just writes SUBSCRIBE and returns a promise, and the client keeps accepting commands on that connection.

Redis allows PING while subscribed and answers ["pong", ""].

[LounisBou]

I just re-check it on a real Redis

subscribe() is not blocking redis-react: it writes the command and returns a promise and a ping() in same tick.

Redis allows PING on a connection in subscribed state, while GET throws "ERR Can't execute 'get'".

It seems SUBSCRIBE / UNSUBSCRIBE / PING / QUIT / RESET are allowed.

[LounisBou]

Found documentation on it for ping: https://redis.io/docs/latest/commands/ping/

If the client is subscribed to a channel or a pattern, it will instead return a multi-bulk string with PONG in the first position and an empty bulk string in the second position, unless an argument is provided, in which case it returns a copy of the argument.

[bpolaszek]

LGTM :-)

[LounisBou]

@bpolaszek, thanks ! Can you make a new release with this please ?

[bpolaszek]

Consider it done ✅ https://github.com/bpolaszek/freddie/releases/tag/0.5.1