[RFE] add ability to pull metrics from unix socket in redis pmda

[jainnikhil30]

Currently redis pmda looks for a $host:$port combination for pulling the redis metrics. But it is possible that redis is using unix socket and not port like following:

redis 29103 1 0 04:05 ? 00:00:11 /usr/bin/redis-server unixsocket:/run/redis/redis.sock

With this redis pmda is not able to fetch the redis metrics. It should be able to fetch the metrics using redis.sock as well.

redis-cli -s /run/redis/redis.sock INFO
#Server
redis_version:6.2.16
redis_git_sha1:00000000
redis_git_dirty:0
redis_build_id:85a2e85bf3a77649
redis_mode:standalone
os:Linux 5.14.0-529.el9.x86_64 x86_64

[hhorak]

@jainnikhil30 Can you share some more info about what is your use case to get the data from the socket directly?

[natoscott]

@hhorak this is a mode in which redis/valkey can be run where it communicates only locally (security, efficiency) - currently the PMDA makes assumptions and is unaware of this feature.

Longer term, it would be good to rewrite this PMDA as a new (python/C) valkey PMDA, and allow Redis metrics support as a backwards-compatibility option in the updated code.