XINFO GROUPS

Introduction

In Dragonfly, as well as in Redis and Valkey, the XINFO GROUPS command provides information about consumer groups associated with a specific stream. This command is essential for monitoring and managing stream processing tasks, providing insights into consumer group configurations and activity.

Syntax

XINFO GROUPS key

• Time complexity: O(1)
• ACL categories: @read, @stream, @slow

Parameter Explanations

• key: The key of the stream for which consumer groups information is requested.

Return Values

• The command returns a list of dictionaries, each dictionary representing a consumer group and its details.
• The details include fields such as name, consumers, pending, last-delivered-id, etc.
  • name: the consumer group's name.
  • consumers: the number of consumers within the group.
  • pending: the length of the group's pending entries list (PEL), which are messages that were delivered but not yet acknowledged.
  • last-delivered-id: the ID of the last entry delivered to the group's consumer(s).
  • entries-read: number of entries read by the group's consumers.
  • lag: the number of entries that are yet to be delivered to the group's consumers.

Code Examples

Basic Example

Get information about consumer groups for a stream:

dragonfly$> XGROUP CREATE mystream mygroup $ MKSTREAM
OK

dragonfly$> XINFO GROUPS mystream
1)  1) "name"
    2) "mygroup"
    3) "consumers"
    4) (integer) 0
    5) "pending"
    6) (integer) 0
    7) "last-delivered-id"
    8) "0-0"
    9) "entries-read"
   10) (nil)
   11) "lag"
   12) (integer) 0

Monitor Multiple Consumer Groups

Creating and monitoring multiple consumer groups:

dragonfly$> XGROUP CREATE mystream group1 $ MKSTREAM
OK

dragonfly$> XGROUP CREATE mystream group2 $
OK

dragonfly$> XINFO GROUPS mystream
1)  1) "name"
    2) "group1"
    3) "consumers"
    4) (integer) 0
    5) "pending"
    6) (integer) 0
    7) "last-delivered-id"
    8) "0-0"
    9) "entries-read"
   10) (nil)
   11) "lag"
   12) (integer) 0
2)  1) "name"
    2) "group2"
    3) "consumers"
    4) (integer) 0
    5) "pending"
    6) (integer) 0
    7) "last-delivered-id"
    8) "0-0"
    9) "entries-read"
   10) (nil)
   11) "lag"
   12) (integer) 0

Best Practices

• Regularly use XINFO GROUPS to check on the health and status of consumer groups in your stream processing system.
• Ensure consumer groups are correctly created with unique and descriptive names to avoid confusion and ease monitoring and management.

Common Mistakes

• Assuming that XINFO GROUPS modifies consumer groups; it only retrieves information.

FAQs

What happens if the stream key does not exist?

If the stream key does not exist, XINFO GROUPS returns an error.

Can XINFO GROUPS be used on keys that are not streams?

No, XINFO GROUPS is specific to streams, and attempting to use it on a non-stream key will result in an error.