Redis standalone client fails eagerly when disconnected

[KarelCemus]

Fixes #147

@tzimisce012 I figured out the solution to track the connection status. Since this PR the standalone client fails eagerly when the connection is not established. Would you be kind to test it? Does it resolve the issue you've opened?

[tzimisce012]

I'll check this today

[tzimisce012]

This works as expected. Now I am having the following issue. I don't know if this would be related with this PR. When you have a connection with Redis but it is not responding (a lot of requests, maybe), Redis might take 15 minutes to finally answer. In this case, it would be cool to have a timeout when we are doing a getOrElseUpdate. If you have connection with Redis, but the answer takes more than X seconds, use the "default" behavior.

[KarelCemus]

15 minutes? That looks more like a serious bug ... what takes that long? The get part, the OrElse, or the Update part? Is it possible there is lack of threads due to too many blocking requests?

It doesn't seem right to implement some other timeout without knowing the cause of this long response time

[tzimisce012]

Well, imagine that my server is getting a big overload. In my case, a simple ssh took 30 minutes. It is not just a bug on redis or the implementation, it is a problem on the server that contains the instance of redis. It was having problems to make the get but potentially it could give problems when making the set too.

Of course, I will have to do a fine tune on my server too 😄

[KarelCemus]

Alright, then what about a general request timeout?

[tzimisce012]

yes, I was wondering if it is a good idea to have a configurable value when making an redis command. Something like "I want to try to get a value from redis but if this value is not returned in less than 250ms I will get a TimeoutException". Right now the behavior is "I want to try to get a value from redis and I will wait unlimited amount of time if I have connection with Redis".