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XINFO STREAM

Introduction​

In Dragonfly, as well as in Redis and Valkey, the XINFO STREAM command provides information about a specific stream. This command can be used to monitor and debug streams, as it helps you understand the structure and state of a stream.

Syntax​

XINFO STREAM key [FULL [COUNT count]]
  • Time complexity: O(1)
  • ACL categories: @read, @stream, @slow

Parameter Explanations​

  • key: The key of the stream for which information is to be retrieved.
  • FULL (optional): If specified, the command returns additional details about the stream.
  • COUNT count (optional): If FULL is specified, this parameter limits the number of returned stream and PEL entries returned. COUNT is default to 10. Setting COUNT to 0 returns all entries, which should be used with caution as it increases execution time for large streams.

Return Values​

  • The command returns a list of information about the specified stream's state and entries.

Code Examples​

Retrieve Stream Information​

Get information about a stream:

dragonfly$> XADD mystream * sensor-id 1234 temperature 19.8
"1632494980015-0"

dragonfly$> XINFO STREAM mystream
 1) "length"
 2) (integer) 1
 3) "radix-tree-keys"
 4) (integer) 1
 5) "radix-tree-nodes"
 6) (integer) 2
 7) "groups"
 8) (integer) 0
 9) "last-generated-id"
10) "1632494980015-0"
11) "first-entry"
12) 1) "1632494980015-0"
    2) 1) "sensor-id"
       2) "1234"
       3) "temperature"
       4) "19.8"
13) "last-entry"
14) 1) "1632494980015-0"
    2) 1) "sensor-id"
       2) "1234"
       3) "temperature"
       4) "19.8"

Best Practices​

  • Regularly use XINFO STREAM to monitor the health and performance of streams.
  • Analyze the output to optimize memory and understand stream usage patterns.

Common Mistakes​

  • Forgetting that XINFO STREAM only queries data and does not modify the stream content.
  • Not grasping the meaning of each output field; ensure you understand terms like radix-tree-keys and last-generated-id in the context of streams.

FAQs​

What does radix-tree-keys signify?​

radix-tree-keys indicates the number of entries in the underlying radix tree data structure for streams.

How do I interpret first-entry and last-entry?​

first-entry and last-entry give you the stream's start and end records, which helps to identify the pattern of data.