pyfagorass 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.SEARCHor 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 GETto find queries that exceeded theslowlog-log-slower-thanthreshold (10ms by default). The output shows the exact command and duration in microseconds.MEMORY DOCTORfor 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.