banshee/services-collection/services/redis/ssh/clients

Redis clients, by SSH

Returns the clients connected to a Redis server, those blocked on a blocking command, and the connections it refused because maxclients was reached, read by redis-cli INFO on the Redis server over SSH. Three watches are offered, each one set on the probe. No password leaves banshee.

Versions

Redis 2.8 and later (rejected_connections), and Valkey. Generic: no folder of version.

How it works

The collector runs, on the server, LC_ALL=C redis-cli -p <port> INFO, as redis/ssh/memory does, the password, when there is one, going from its file on the server into REDISCLI_AUTH. It reads:

connected_clients:42
blocked_clients:0
rejected_connections:0

clients is connected_clients, redis-cli itself included; blocked is blocked_clients, the clients waiting on BLPOP, BRPOP and the like.
rejected is rejected_connections, the connections refused because maxclients was reached: it only grows until Redis restarts, and "Connections refused" raises when it grows. It is the sign that the limit is too low, more reliable than a count against maxclients, which old servers do not give.
A Redis that refuses the connection is critical: "Redis is not running". A refused account stops the collector misconfigured, as does any other answer than INFO.
Nothing is written: INFO only reads.

Prerequisites

The same as redis/ssh/memory: an SSH account without write rights, redis-cli in its path, the password, when Redis asks for one, in a file of that account, mode 0400 (redis:password-file), no sudo, and the fingerprint of the server's host key.

Variables

Name	Label	Says	Default
`redis:port`	Port	the port Redis listens on, on the server	`6379`
`redis:password-file`	Password file	the path, on the server, of the file that holds the password; empty: no password	—

Outputs

Name	Label	Unit	Per instance
`clients`	Clients connected	—	no
`blocked`	Clients blocked	—	no
`rejected`	Connections refused at maxclients since start	—	no

Watches

Name	Title	Kind	Defaults	Checked by default
`rejected`	Connections refused	increase, on `rejected`	critical beyond 0 in 1 h	yes
`many`	Many clients	above a threshold, on `clients`	no threshold: set one on the probe	no
`blocked`	Clients blocked	above a threshold, on `blocked`	warning above 10, for 3 runs	no

Limits

Redis is reached on the server itself (127.0.0.1), without TLS, as its default user only (see redis/ssh/memory).
A queue whose consumers wait with BLPOP keeps clients blocked by design: "Clients blocked" is unchecked for that reason.
Not checked against a Redis: the fields are those of the documentation of INFO (redis.io).