Support LLEN

[berglh]

I'm using Redis as a message queue for elasticsearch.

Logstash output and input plugins actually support writing messages to a single list/key or a channel. Currently, redisbeat is unable to send the length LLEN of a list/key as a statistic as far as I can see, and the INFO keyspace stats don't really tell me how deep the queue of the list/key actually is.

I want to get this statistic:

host:6379> LLEN "logstash"
(integer) 63846

Keyspace looks like this though:

host:6379> INFO keyspace
# Keyspace
db0:keys=1,expires=0,avg_ttl=0

This is about the only thing left in my stack that I can't monitor with metricbeat that I'm interested in. This would be a pretty useful feature considering the function of other Elastic programs.

[chrsblck]

@berglh Thanks for the info. This does seem like a useful addition. Any chance you want to take a stab at it?

Also, it might be a worthwhile to add support for all LEN commands:

• HLEN
• HSTRLEN
• LLEN
• STRLEN

Thoughts about these other commands?

Would you be interested in trying to implement this?

[berglh]

@chrsblck I'll see how long it annoys me for and may have a stab at it. I wouldn't hold your breath because I have some other priorities at the moment, I do have a interest in getting it to work.

Also, it might be a worthwhile to add support for all LEN commands:

It's a good idea, but I'm not entirely convinced of their usefulness with respect to monitoring the metrics of a redis instance. They seem to me to be useful commands for applications using redis as a message queue that want to easily get properties of a string.

Having said that; STRLEN and HLEN would probably be very easy to implement alongside LEN, and if someone really wanted HSTRLEN, it would be just another function that would use the output of HLEN to determine the number of fields anyways.