How to fix NOSCRIPT No matching script in Redis

Check if the script hash exists in Redis cache. Replace SHA1_HASH with the actual SHA1 hash of your Lua script.

# Check if script is loaded
redis-cli SCRIPT EXISTS SHA1_HASH

# Returns 1 if script exists, 0 if not found

If the command returns 0, the script isn't cached and needs to be loaded.

If the script doesn't exist, load it into Redis cache. This will return the SHA1 hash of the script.

redis-cli SCRIPT LOAD "return redis.call('get', KEYS[1])"

Save the returned SHA1 hash. You'll use this hash with EVALSHA commands.

Most modern Redis client libraries have built-in support for handling NOSCRIPT errors. Use the library's Script wrapper if available.

For example, in redis-py:

from redis import Redis
from redis.commands.core import Script

redis = Redis()

# Use the Script object which automatically handles NOSCRIPT
script = redis.register_script("return redis.call('get', KEYS[1])")
result = script(keys=['my-key'])

The Script object will:
1. Try EVALSHA first (fast)
2. Catch NOSCRIPT error if returned
3. Load script with SCRIPT LOAD
4. Retry with EVALSHA

This pattern is reliable and handles all edge cases.

For mission-critical scripts, use EVAL instead of EVALSHA. This trades bandwidth for reliability since the full script source is sent each time, but the script is always available.

redis-cli EVAL "return redis.call('get', KEYS[1])" 1 my-key

EVAL automatically caches the script, so subsequent EVALSHA calls will work. Use this approach when you need guaranteed script execution.

When using pipelined commands with scripts, pre-load all scripts at application startup. This prevents NOSCRIPT errors in pipelines where errors can't be retried.

import redis

redis_client = redis.Redis()

# Pre-load scripts at startup
script_hashes = {}
scripts = {
    'get_and_increment': "return redis.call('incr', KEYS[1])",
    'atomic_swap': "return {redis.call('get', KEYS[1]), redis.call('set', KEYS[1], ARGV[1])}"
}

for name, source in scripts.items():
    script_hashes[name] = redis_client.script_load(source)

# Now use in pipelines
pipe = redis_client.pipeline()
pipe.evalsha(script_hashes['get_and_increment'], 1, 'counter')
pipe.evalsha(script_hashes['atomic_swap'], 1, 'value', 'new_value')
results = pipe.execute()

This ensures scripts are available before any pipeline execution attempts them.