分析慢日志
使用 Redis 慢日志查找阻塞服务器的命令，解读日志条目，并调整用于捕获这些命令的阈值
分析慢日志 是 CoddyKit 上的免费 Redis Caching & Messaging (Pub/Sub, Streams) 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Redis Caching & Messaging (Pub/Sub, Streams) 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Redis Caching & Messaging (Pub/Sub, Streams) 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Redis Is Single-Threaded
Command execution in Redis is effectively single-threaded. One slow command blocks every other client. The slow log records commands whose execution time exceeds a threshold, so you can hunt down these blockers.
What It Measures
The slow log times only command execution, not network or I/O wait. So a logged entry means Redis itself spent that long, usually on an expensive operation over many elements.
Configuring the Threshold
slowlog-log-slower-than sets the threshold in microseconds. A value of 10000 logs commands slower than 10ms. Set it to 0 to log everything (for debugging) or -1 to disable.
CONFIG SET slowlog-log-slower-than 10000Limiting Log Size
slowlog-max-len caps how many entries are retained; older ones are evicted. This keeps memory bounded.
CONFIG SET slowlog-max-len 128Reading the Log
SLOWLOG GET returns recent entries; pass a count to limit them. Each entry has an ID, timestamp, microsecond duration, the command and arguments, and the client address.
SLOWLOG GET 10Interpreting an Entry
Look at the command and its duration. A KEYS * or a large SMEMBERS over a million-element set will show big durations, pinpointing the culprit and the calling client.
# 1) id 14
# 2) timestamp 1716900000
# 3) microseconds 23000
# 4) ["KEYS", "*"]Length and Reset
SLOWLOG LEN gives the current entry count, and SLOWLOG RESET clears the log, handy before reproducing an issue.
SLOWLOG LEN
SLOWLOG RESETCommon Offenders
Frequent slow-log culprits:
KEYSon large keyspaces (useSCAN)- Big
SMEMBERS/HGETALL/LRANGE 0 -1 - Unbounded
SORT - Large
DEL(useUNLINK)
SCAN 0 MATCH user:* COUNT 100
UNLINK biglistFrom Detection to Fix
Once the slow log names a command, fix it: paginate with cursors, model data to avoid huge single keys, or move heavy work off the hot path. Re-check the log to confirm the durations drop.
Continuous Monitoring
Sample the slow log periodically from a monitoring job and alert when slow commands appear, so you catch regressions before users feel them.
redis-cli SLOWLOG GET 5Threshold Tuning
Start with a moderate threshold (e.g. 10ms) in production. Lower it temporarily when investigating, then restore it, because logging everything adds a tiny per-command cost.
Quick Check
Test your understanding of the slow log.
Recap
You learned to use the slow log: configure slowlog-log-slower-than and slowlog-max-len, read entries with SLOWLOG GET, interpret durations, and fix common offenders like KEYS and huge single-key reads. Monitor it continuously to catch performance regressions early.
常见问题解答
「分析慢日志」课时是免费的吗？
是的 — 「分析慢日志」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Redis Caching & Messaging (Pub/Sub, Streams) 课程的其余内容，请升级到 CoddyKit PRO。 Redis Caching & Messaging (Pub/Sub, Streams) 课程共包含 4 节课。
「分析慢日志」这节课中我会学到什么？
使用 Redis 慢日志查找阻塞服务器的命令，解读日志条目，并调整用于捕获这些命令的阈值 你通过在浏览器中直接运行的动手代码来练习 Redis Caching & Messaging (Pub/Sub, Streams)，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Redis Caching & Messaging (Pub/Sub, Streams) 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Redis Caching & Messaging (Pub/Sub, Streams) 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「分析慢日志」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Redis Caching & Messaging (Pub/Sub, Streams) 课中编写并运行代码吗？
能。每节 Redis Caching & Messaging (Pub/Sub, Streams) 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。