redis: BUSY Redis is busy running a script

TL;DR

A Lua script is hogging the single thread: Redis rejects other commands with BUSY until it finishes. If the script is not write-heavy, run SCRIPT KILL; otherwise wait it out, then rewrite the script to be short. BUSY clears once the script ends.

Error

redis: BUSY Redis is busy running a script

Steps

1. Check what is running: the BUSY error means a script is executing; identify it from your application logs or the slow log. Expected: the offending script named.
2. Kill it if safe: run SCRIPT KILL to abort a script that has not yet written. Expected: the script aborts and BUSY clears (kill fails if the script already wrote; then you must wait).
3. Wait it out if kill refuses: the script will finish; monitor until commands succeed again. Expected: normal operation resumes.
4. Rewrite the script: keep Lua scripts to milliseconds (small key counts, no unbounded loops), and move heavy work out of Redis. Expected: no script ever blocks the server noticeably.
5. Add a timeout mindset: scripts have no preemption, so treat every script as a critical section. Expected: future scripts are reviewed for runtime before deploy.

When to use

• Commands fail with BUSY during script execution
• After deploying a new Lua script
• Designing Redis-side logic

When not to use

• Slow non-script commands (command optimization)
• A script that already finished (the error is transient)

Tool compatibility

• Redis Lua scripting, SCRIPT KILL, slow log

Variant phrasings

redis script kill not working

Kill only works before the script writes; after a write you must wait.

lua script blocking redis

Rewrite it short; Redis scripts run atomically on the single thread.

Why it happens

Redis executes Lua scripts atomically on its single main thread with no preemption. A script that loops over millions of keys blocks every other client until it returns, and BUSY is the server telling everyone else to wait.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstwOtdgAG3Nx1SGarRlcXrQ

Resolved from the public thread: https://vectle.com/posts/pstwOtdgAG3Nx1SGarRlcXrQ

Thread query: redis: BUSY Redis is busy running a script

TL;DR: A Lua script is hogging the single thread: Redis rejects other commands with BUSY until it finishes. If the script is not write-heavy, run SCRIPT KILL; otherwise wait it out, then rewrite the script to be short. BUSY clears once the script ends.