XINFO GROUPS

XINFO GROUPS

Introduction and Use Case(s)

XINFO GROUPS is a command used in Redis to retrieve information about the consumer groups associated with a specific stream. This command is particularly useful for monitoring and debugging purposes, providing insights into the state and status of each consumer group.

Typical scenarios where it is used include:

Monitoring consumer group activity and health.
Debugging issues related to message consumption in streams.
Auditing and gathering metrics on stream processing.

Syntax

XINFO GROUPS <key>

Parameter Explanations

<key>: The name of the stream for which you want to get information about the consumer groups.

Return Values

The command returns an array where each element is a dictionary with details about a consumer group. Possible fields in each group’s dictionary include:

name: The name of the consumer group.
consumers: The number of consumers in the group.
pending: The number of pending messages (messages that have been delivered but not yet acknowledged).
last-delivered-id: The ID of the last entry delivered to this group.
entries-read: (If available) Number of entries read by the group.
lag: (If available) The number of entries that are still waiting to be delivered to at least one consumer.

Example output:

1)  1) "name"
    2) "group1"
    3) "consumers"
    4) (integer) 2
    5) "pending"
    6) (integer) 5
    7) "last-delivered-id"
    8) "1526569495631-0"
2)  1) "name"
    2) "group2"
    3) "consumers"
    4) (integer) 1
    5) "pending"
    6) (integer) 0
    7) "last-delivered-id"
    8) "1526569495639-0"

Code Examples

dragonfly> XGROUP CREATE mystream mygroup $ MKSTREAM
OK
dragonfly> XADD mystream * field1 value1
"1638409437348-0"
dragonfly> XADD mystream * field1 value2
"1638409441234-0"
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"

Best Practices

Regularly monitor your consumer groups using XINFO GROUPS to ensure they are functioning correctly and to identify any potential bottlenecks or issues with message processing.
Use the information provided by XINFO GROUPS to balance load among consumers by adding or removing them as needed based on the pending messages and consumer count.

Common Mistakes

Forgetting to create a consumer group before attempting to use XINFO GROUPS. Ensure that you have created one using XGROUP CREATE.
Not specifying the correct stream key, leading to unexpected results or errors. Double-check that the key you provide exists and is indeed a stream.

FAQs

What does the “pending” field in the output signify?

The “pending” field indicates the number of messages that have been delivered to consumers but have not yet been acknowledged.

How can I reduce the lag shown by `XINFO GROUPS`?

Lag can be reduced by either increasing the number of consumers in the group or optimizing the processing logic of existing consumers so they can handle messages more quickly.