LiveQueryServer crashes when configured to run with Redis cacheAdapter

[evtimmy]

Issue Description

Running ParseLiveQueryServer where a RedisCacheAdapter is also configured causes crash when ParseLiveQueryServer tries to use the cache adapter.

Steps to reproduce

1. Run parse-server with ParseLiveQueryServer enabled. The cache adapter I configured via config.json like so:

 "cacheAdapter": {
  "module": "../Adapters/Cache/RedisCacheAdapter.js",
  "options": {
    "url": {{ printf "redis://%s-redis-cache-app-server-master:6379" .Release.Name | quote }}
    "password": {{ $redisAppServerCachePassword | quote }}
  }
}

2. Subscribe a client to listen to a query
3. Update an object that the query matches

Actual Outcome

error: RedisCacheAdapter error on get {"error":{}}
error: RedisCacheAdapter error on get {"error":{}}
An uncaught exception occurred: The client is closedStack Trace:
Error: The client is closed
at Commander._RedisClient_sendCommand (/parse-server/node_modules/@redis/client/dist/lib/client/index.js:510:31)
at Commander.commandsExecutor (/parse-server/node_modules/@redis/client/dist/lib/client/index.js:190:154)
at BaseClass.<computed> [as set] (/parse-server/node_modules/@redis/client/dist/lib/commander.js:8:29)
at RedisCacheAdapter.put (/parse-server/lib/Adapters/Cache/RedisCacheAdapter.js:85:24)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

Expected Outcome

LiveQueryServer post update to client

Environment

Server

• Parse Server version: 7.4.0-alpha.5
• Local or remote host (AWS, Azure, Google Cloud, Heroku, Digital Ocean, etc): Azure

Client

• SDK (iOS, Android, JavaScript, PHP, Unity, etc): iOS/Android

Workaround:

disable the redis cache adapter.

[parse-github-assistant]

Thanks for opening this issue!

[evtimmy]

I did debug the initialization of the server and saw that ParseLiveQueryServer creates its own cacheController instance:

parse-server/src/LiveQuery/ParseLiveQueryServer.js

Line 62 in 91f9aca

this.cacheController = getCacheController(parseServerConfig);

but that instance connect() is never called. The regular ParseServer does call connect() on its own instance of the cache when initializing the startup promises.

This used to work in earlier versions of parse-server, before we switched to redis 4 client as redis 4 requires the async connect() to be explicitly called before using the client, whereas redis 3 automatically called connect() if the client was not connected.

One simple fix would be to add initialization await this.cacheController.connect() here:

parse-server/src/LiveQuery/ParseLiveQueryServer.js

Lines 84 to 94 in 91f9aca

	async connect() {
	if (this.subscriber.isOpen) {
	return;
	}
	if (typeof this.subscriber.connect === 'function') {
	await Promise.resolve(this.subscriber.connect());
	} else {
	this.subscriber.isOpen = true;
	}
	this._createSubscribers();
	}

I'm just not clear on why we check this.subscriber.isOpen and if this connect() may be called multiple times, or only on startup?

[Chilldev]

The crash is coming from:

parse-server/src/Adapters/PubSub/RedisPubSub.js

Lines 1 to 11 in 5ca0aa3

	import { createClient } from 'redis';
	function createPublisher({ redisURL, redisOptions = {} }): any {
	redisOptions.no_ready_check = true;
	return createClient({ url: redisURL, ...redisOptions });
	}
	function createSubscriber({ redisURL, redisOptions = {} }): any {
	redisOptions.no_ready_check = true;
	return createClient({ url: redisURL, ...redisOptions });
	}

Connections do not have an error handler.
In my case it was happening when redis crashed unexpectdly or was unreachable.

I am not sure if this issue is related:
redis/node-redis#2624

I created a patch to listen to connection errors and the server is no longer crashing.

import { logger } from '../../logger';

function createPublisher({ redisURL, redisOptions = {} }): any {
  redisOptions.no_ready_check = true;
  const client = createClient({ url: redisURL, ...redisOptions });
  client.on('error', (err) => {
    logger.error('RedisPubSub publisher client error', {
      error: err
    });
  });
  return client;
}

function createSubscriber({ redisURL, redisOptions = {} }): any {
  redisOptions.no_ready_check = true;
  const client = createClient({ url: redisURL, ...redisOptions });
  client.on('error', (err) => {
    logger.error('RedisPubSub subscriber client error', {
      error: err
    });
  });
  return client;
}