Make it possible to log when an error occurs

[janmeier]

We are creating a redis rate limiter, with an in-memory insurance limiter. We would like to be notified whenever a call to redis fails, so we can do something about it :)

The way I've done it for now is to subclass RateLimiterRedis:

class LenusRateLimiterRedis extends RateLimiterRedis {
  _handleError(err, funcName, resolve, reject, key) {
    errorTracker.capture('Error in redis rate limiter', { key, funcName }, err)
    super._handleError(err, funcName, resolve, reject, key)
  }
}

This works fine, but since _handleError is not part of the ts interface definition we won't be notified if the definition of _handleError changes.

My idea would be to either:

• Make _handleError (or a similar method) part of the public interface, so we can subclass is properly
• Add an onError callback to options
• Emit an error event

Whichever option you like most, I would be happy to implement it :)

[animir]

@janmeier Hi, this is an interesting case.
While I understand your requirement, there is another way of thinking about it. We should expect Redis isn't able to handle a request in only one case—a connection error.
You could use redisClient.on('error', (err) => {}) event to catch and log that error.
If you see some issues with the suggested approach, please describe your case in more detail so that we can discuss it.

[janmeier]

You could use redisClient.on('error', (err) => {}) event to catch and log that error.

That was my initial though, but it seems the connection error is not being emitted (at least not in ioredis). Related issues redis/ioredis#969 and redis/ioredis#1386

While I agree in principle that we could just handle this on the redis level, there have been no maintainer responses to those issues as far as I can see :/

[animir]

@janmeier I understand your pain. Have you considered using node-redis package? Another option would be to PING Redis server once in a while and log error.

[animir]

@janmeier Hi, have you found a suitable solution for this?

[shameersheik]

Some of the errors didnot trigger redisClient.on('error', (err) => {}) in ioredis but triggered

reconnectOnError: function (err) {
          logger.info(`Got an error when redis tried to connect: ${err.stack}`);
          return true;
        },