Add support for Latency monitor about redis_exporter

[kpachhai]

The LATENCY LATEST command reports the latest latency events logged. Each event has the following fields:
Event name.
Unix timestamp of the latest latency spike for the event.
Latest event latency in millisecond.
All time maximum latency for this event.

So, I think the best way to do it is to maybe expose couple of metrics based on this:
redis_latest_latency_spike{event="event_name"} Unix timestamp
redis_latest_latency_time{event="event_name"} Latency in millisecond
redis_max_latency{event="event_name"} All time maximum latency

[oliver006]

I've never used latency monitoring but from the docs (https://redis.io/topics/latency-monitor) it sounds like you need to enable it first and then a latency event needs to occur. Did you try with the instructions from the docs above? It worked for me using the latest exporter and Redis 3.2.8

[oliver006]

That's an interesting feature, didn't know about it!

However, I'm not sure how to translate it into metrics. Maybe the timestamp of when the latest event occurred so you can alert on it? Would that be useful?
Other thoughts?

[oliver006]

That should work (though we might not need "max" - that's something that Prometheus can calculate for us).

I'll be away from my laptop for the next ~ 10 days - feel free to go ahead and give it a shot if you're interested.

[kpachhai]

Sounds good. I'm currently working on this. Thanks.

[kpachhai]

I created a PR for this change. Please look into it when you have time. #87

[davidpapx]

Installed oliver006/redis_exporter:v0.13 with Redis 3.2.11, and the relevant metrics are not exposed (redis_latest_latency_spike). didn't find any issue in the exporter itself. what can be the reason?

[oliver006]

Closing this, please re-open if this is still an issue.