banshee/services-collection/services/redis/ssh/persistence

Redis persistence, by SSH

Returns whether the last snapshot (RDB) of a Redis server was saved, how old the last one saved is, the changes not saved yet, and the state of its append-only file (AOF), read by redis-cli INFO on the Redis server over SSH. Four watches are offered, each one set on the probe. No password leaves banshee.

Versions

Redis 2.8 and later, 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 the section Persistence:

rdb_changes_since_last_save:12
rdb_last_save_time:1793062803
rdb_last_bgsave_status:ok
aof_enabled:1
aof_last_bgrewrite_status:ok
aof_last_write_status:ok

rdb is rdb_last_bgsave_status, ok or err: a snapshot that fails (a full disk, a refused fork) means a restart would lose what changed since the last one.
rdb-age is the time since rdb_last_save_time, in hours, against the poller's clock. Without any snapshot saved since it started, Redis gives its start time.
changes is rdb_changes_since_last_save, the changes a crash would lose without an append-only file.
aof is off when the append-only file is not enabled; err when its last write or its last rewrite failed; ok otherwise.
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
`rdb`	Last snapshot	—	no
`rdb-age`	Age of the last snapshot saved	h	no
`changes`	Changes not saved	—	no
`aof`	Append-only file	—	no

Watches

Name	Title	Kind	Defaults	Checked by default
`rdb-failed`	Snapshot failed	expected value, on `rdb`	critical when anything but `ok`	yes
`aof-failed`	Append-only file failing	expected value, on `aof`	critical when anything but `ok` or `off`	yes
`rdb-old`	Snapshot too old	above a threshold, on `rdb-age`	warning above 24 h	no
`changes`	Many changes not saved	above a threshold, on `changes`	no threshold: set one on the probe	no

A Redis whose snapshots are turned off (save "") never saves one: rdb-age grows from its start, which is why "Snapshot too old" is unchecked.

Limits

The age is counted against the poller's clock: a server whose clock drifts reads the age off by as much.
Redis is reached on the server itself (127.0.0.1), without TLS, as its default user only (see redis/ssh/memory).
Not checked against a Redis: the fields are those of the documentation of INFO (redis.io).