How to fix BUSY Redis is busy running a script in Redis

Connect to Redis and check the current status:

SCRIPT HELP
LOGGET

Or use a Redis client library to monitor script execution. The SLOWLOG GET command can show recent slow operations.

Use the SCRIPT KILL command to stop the Lua script that is blocking other clients:

SCRIPT KILL

This only works if the script hasn't performed any write operations. If it has, you may need to use SHUTDOWN NOSAVE instead.

If SCRIPT KILL returns an error (because the script performed writes), you must force shutdown:

SHUTDOWN NOSAVE

This terminates Redis immediately without saving the database. Use only when necessary, as unsaved data will be lost.

Once Redis recovers, investigate which Lua script caused the BUSY state:

1. Check application logs for script execution patterns
2. Use SLOWLOG GET to identify slow commands:

SLOWLOG GET 10

3. Review EVALSHA or EVAL calls that exceed reasonable execution time
4. Profile the script locally before deploying

Review and optimize the problematic script:

1. Avoid SCAN-like operations over large key sets
2. Use pipelining instead of sequential commands
3. Minimize conditional logic inside scripts
4. Use local variables instead of repeated Redis calls
5. Break long operations into smaller chunks

Example of optimized script:

-- Bad: inefficient loop
for i=1,1000000 do
  redis.call('INCR', 'counter:' .. i)
end

-- Better: use pipelining or batch operations
local keys = {}
for i=1,1000000 do
  table.insert(keys, 'counter:' .. i)
end
return redis.call('MGET', keys)

If you have legitimate long-running scripts, increase the lua-time-limit configuration:

CONFIG SET lua-time-limit 10000

This increases the limit to 10 seconds (in milliseconds). Make the change permanent in redis.conf:

lua-time-limit 10000

WARNING: Long-running scripts still block all other clients, so this should only be used as a temporary measure while optimizing scripts.

In your application code, implement timeouts and error handling:

// Node.js example with redis library
const client = redis.createClient();

try {
  const result = await client.evalsha(scriptSHA, 0, timeout);
} catch (error) {
  if (error.message.includes('BUSY')) {
    // Handle BUSY error: retry after delay, kill script, etc.
    await sleep(1000);
    // Attempt retry or fallback
  }
}

Add monitoring to track script execution times and alert on anomalies.