redis by l3digitalnet/claude-code-plugins

Identity

Unit: redis-server.service
Config: /etc/redis/redis.conf
Logs: journalctl -u redis-server, /var/log/redis/redis-server.log
Data dir: /var/lib/redis/
Socket: /run/redis/redis-server.sock (if unixsocket enabled)
Distro install: apt install redis-server / dnf install redis

Key Operations

Operation	Command	Notes
Service status	`systemctl status redis-server`	Unit name is `redis` on RHEL
Connect (TCP)	`redis-cli -h 127.0.0.1 -p 6379`	Add `-a <password>` or use `AUTH` after connecting
Connect (socket)	`redis-cli -s /run/redis/redis-server.sock`	Faster; requires local access
Ping server	`redis-cli PING`	Returns `PONG`; use to verify connectivity
Set a key	`redis-cli SET mykey "value"`	Add `EX 60` for 60-second TTL
Get a key	`redis-cli GET mykey`	Returns `(nil)` if key doesn't exist
Delete a key	`redis-cli DEL mykey`	Accepts multiple keys; returns count deleted
List all keys (dev only)	`redis-cli KEYS '*'`	O(N) — blocks server; never use on prod
Safe key scan (prod)	`redis-cli --scan --pattern 'prefix:*'`	Uses SCAN internally; non-blocking
Check memory usage	`redis-cli INFO memory`	Look at `used_memory_human` and `maxmemory`
Memory per key	`redis-cli MEMORY USAGE mykey`	Returns bytes including overhead
Flush current database	`redis-cli FLUSHDB`	DESTRUCTIVE — deletes all keys in DB 0
Flush all databases	`redis-cli FLUSHALL`	DESTRUCTIVE — deletes every key in every DB
Full server info	`redis-cli INFO all`	Stats, replication, clients, memory, keyspace
Monitor live commands	`redis-cli MONITOR`	High overhead — only for short debugging sessions
Check slow log	`redis-cli SLOWLOG GET 10`	Last 10 slow commands; threshold set by `slowlog-log-slower-than`
Config get (runtime)	`redis-cli CONFIG GET maxmemory`	Read any directive without restarting
Config set (runtime)	`redis-cli CONFIG SET maxmemory 512mb`	Applies immediately; not persisted unless `CONFIG REWRITE` follows
Persist runtime config	`redis-cli CONFIG REWRITE`	Writes current runtime values back to redis.conf
Background save (RDB)	`redis-cli BGSAVE`	Fork-based; non-blocking for clients
Foreground save	`redis-cli SAVE`	Blocks all clients until complete — avoid in production
Replication info	`redis-cli INFO replication`	Role, replica count, replication offset, lag
Keyspace stats	`redis-cli INFO keyspace`	Per-database key counts, expires, avg TTL
Real-time stats	`redis-cli --stat`	One-line rolling stats every second

Expected Ports

6379/tcp — default Redis port
16379/tcp — cluster bus port (Redis Cluster only; always data-port + 10000)
Verify: ss -tlnp | grep redis
Firewall: Redis should not be exposed to the internet. Bind to 127.0.0.1 or use requirepass + firewall rules.

Health Checks

systemctl is-active redis-server → active
redis-cli PING → PONG
redis-cli INFO server | grep redis_version → version string present
redis-cli INFO memory | grep used_memory_human → reports current usage without OOM errors

Common Failures

Symptom	Likely cause	Check/Fix
`NOAUTH Authentication required`	Client not sending password	Pass `-a <password>` to redis-cli, or run `AUTH <password>` after connecting
`OOM command not allowed`	`maxmemory` reached with non-evicting policy	Set `maxmemory` and `maxmemory-policy` in redis.conf; `CONFIG SET` for immediate effect
`MISCONF Redis is configured to save RDB snapshots but it is currently not able to persist`	RDB write failed (usually disk full or permissions)	Check `df -h` on data dir; check `ls -la /var/lib/redis/`; verify redis user owns the dir
`KEYS` command slows/hangs prod	O(N) scan blocks entire server	Replace with `SCAN`; add `rename-command KEYS ""` in config to disable
Unexpected key eviction	Wrong `maxmemory-policy` for use case	Review policy: `allkeys-lru` evicts any key; `volatile-lru` only keys with TTL
Latency spikes every few minutes	Transparent huge pages (THP) enabled	`echo never > /sys/kernel/mm/transparent_hugepage/enabled`; make persistent via rc.local or systemd unit
`ERR max number of clients reached`	`maxclients` limit hit	`redis-cli INFO clients`; raise `maxclients` in config; check for connection leaks
AOF rewrite fails	`auto-aof-rewrite-percentage` triggered but fork fails	Check `vm.overcommit_memory` — must be 1: `sysctl vm.overcommit_memory=1`
Replica not connecting	`masterauth` not set on replica	Replica needs `masterauth <password>` matching master's `requirepass`

Pain Points

KEYS is O(N) and blocks: On a database with millions of keys, KEYS * can block Redis for seconds. Use SCAN with a cursor in production. Add rename-command KEYS "" to config to make it impossible to run accidentally.
maxmemory-policy default is noeviction: Without setting a policy, Redis returns errors when maxmemory is reached instead of evicting old data. For pure cache use cases, set allkeys-lru. For mixed persistence + cache, set volatile-lru and ensure cache keys have TTLs.
Persistence modes are mutually exclusive in impact: RDB gives point-in-time snapshots with low overhead but risks losing up to save interval of data. AOF logs every write for near-zero data loss but uses more disk. Running both provides the best durability but doubles I/O. Choose based on acceptable data loss window.
No authentication by default: Fresh installs have requirepass commented out. Anyone with network access to port 6379 has full access. Always set a password or bind exclusively to 127.0.0.1 before exposing any service on the same host.
vm.overcommit_memory must be 1 for BGSAVE: Linux's default overcommit behavior can cause BGSAVE (and AOF rewrites) to fail with "Cannot allocate memory" even when physical + swap is sufficient. Set sysctl -w vm.overcommit_memory=1 and persist in /etc/sysctl.conf.
ACL system replaces requirepass in Redis 6+: The ACL system (Redis 6+) allows per-user permissions and command restrictions. requirepass still works but sets the default user's password. For multi-tenant or security-sensitive deployments, use an aclfile with explicit user rules instead.

References

See references/ for:

redis.conf.annotated — complete config file with every directive explained
common-patterns.md — cache setup, queues, sessions, replication, Sentinel, and ACL examples
docs.md — official documentation links