This error occurs when using XREADGROUP on a Redis Stream consumer group that has not been created yet. Create the consumer group first with XGROUP CREATE before reading messages.
The NOGROUP error indicates that you are attempting to read from a Redis Stream using a consumer group that does not exist. This is a common issue when using Redis Streams for pub/sub messaging patterns. The error can occur if the consumer group was never created, if the stream itself does not exist, or if there is a mismatch between the group name you are trying to access and the one that actually exists in Redis.
Before using XREADGROUP, create the consumer group using the XGROUP CREATE command. The MKSTREAM flag ensures the stream is created if it does not already exist:
XGROUP CREATE mystream mygroup $ MKSTREAMReplace mystream with your stream key and mygroup with your desired consumer group name. The $ means new messages only; use 0 to read from the beginning.
Check that the consumer group was created successfully using XINFO GROUPS:
XINFO GROUPS mystreamThis displays all consumer groups for the stream. Confirm your group name is in the list.
For production applications, implement error handling to auto-create the group on startup:
import redis
r = redis.Redis()
try:
r.xgroup_create('mystream', 'mygroup', id='$', mkstream=True)
except redis.exceptions.ResponseError as e:
if 'BUSYGROUP' in str(e):
pass # Group already exists, that's fine
else:
raiseThis catches the BUSYGROUP error (which means the group already exists) and continues safely.
Ensure you are using the correct stream key and group name consistently across your codebase. Redis is case-sensitive, so mygroup and MyGroup are different. Use XINFO GROUPS or XINFO STREAM to verify which streams and groups actually exist.
Consumer groups with the same name on different streams are independent and do not share state. If you delete a stream, its consumer groups are automatically removed. Some client libraries (like older versions of go-redis and ioredis) have had bugs in their XREADGROUP implementation that caused incorrect key hashing, leading to the NOGROUP error on the wrong shard. Update your client library to the latest version if you encounter this. For frameworks like Symfony using Redis as a message transport, enable auto_setup in the configuration to automatically create streams and consumer groups.
ERR Unbalanced XREAD list of streams
How to fix "ERR Unbalanced XREAD list" in Redis
ERR syntax error
How to fix "ERR syntax error" in Redis
ConnectionError: Error while reading from socket
ConnectionError: Error while reading from socket in redis-py
ERR unknown command
How to fix ERR unknown command in Redis
Command timed out
How to fix 'Command timed out' in ioredis