redis-observability

Redis 可觀測性指南 — 應監控哪些指標（記憶體、連線數、命中率、每秒操作數、被拒絕的連線數）、應使用哪些內建指令…

Redis Observability

What to watch, what to run, and what to alert on. Covers the metrics every Redis deployment should monitor and the built-in commands for ad-hoc diagnosis.

When to apply

Setting up monitoring or alerts for a Redis instance.
Diagnosing a Redis performance regression (high latency, memory pressure, connection storms).
Profiling a slow FT.SEARCH or pipeline.
Wiring Redis metrics into Prometheus, Datadog, CloudWatch, or similar.

1. Monitor these metrics

These come from INFO and should be exported to your monitoring system.

Metric	What it tells you	Alert when
`used_memory`	Current memory usage	> 80% of `maxmemory`
`connected_clients`	Open connections	Sudden spikes or drops
`blocked_clients`	Clients waiting on blocking ops	> 0 sustained
`instantaneous_ops_per_sec`	Current throughput	Significant drops
`keyspace_hits` / `keyspace_misses`	Cache hit ratio	Hit ratio < 80%
`rejected_connections`	Hit `maxclients` cap	> 0
`rdb_last_save_time`	Last persistence snapshot	Too old vs. RPO

info = redis.info()
hit_ratio = info["keyspace_hits"] / max(1, info["keyspace_hits"] + info["keyspace_misses"])
print(f"Memory:    {info['used_memory_human']}")
print(f"Clients:   {info['connected_clients']}")
print(f"Ops/sec:   {info['instantaneous_ops_per_sec']}")
print(f"Hit ratio: {hit_ratio:.1%}")

See references/metrics.md.

2. Built-in commands for debugging

Reach for these when something looks off.

Topic	Command
Slow commands	`SLOWLOG GET 10` / `SLOWLOG LEN` / `SLOWLOG RESET`
Server snapshot	`INFO all` (or `INFO memory` / `INFO stats` / `INFO clients` / `INFO replication`)
Memory diagnostics	`MEMORY DOCTOR` / `MEMORY STATS` / `MEMORY USAGE <key>`
Connections	`CLIENT LIST` / `CLIENT INFO`
RQE / Search	`FT.INFO <idx>` / `FT.PROFILE <idx> SEARCH QUERY "..."`

The two most useful for incident triage:

SLOWLOG GET to find queries that exceeded the slowlog-log-slower-than threshold (10ms by default). The output shows the exact command and duration in microseconds.
MEMORY DOCTOR for memory pressure — it returns a one-paragraph summary of what's unusual about memory usage right now.

for entry in redis.slowlog_get(10):
    print(f"{entry['duration']}μs  {entry['command']}")

See references/commands.md.

3. Redis Insight

For interactive use (running queries, browsing keys, profiling indexes), Redis Insight is the official GUI. It surfaces the same SLOWLOG / INFO / FT.PROFILE data visually and includes Redis Copilot for natural-language queries. Useful during development and incident response; not a replacement for exporting metrics to your monitoring system.