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PUBSUB

Provides information about the state of the Pub/Sub subsystem, including channels and subscribers.

Syntax​

PUBSUB subcommand [argument [argument ...]]

Subcommands​

  • CHANNELS: List all channels currently with at least one subscriber.
  • NUMSUB: Get the number of subscribers for one or more channels.
  • NUMPAT: Get the number of patterns currently subscribed to.

CHANNELS​

Syntax​

PUBSUB CHANNELS [pattern]

Parameters​

  • pattern: An optional pattern to filter the channel names. Can include the wildcard character * to match multiple channels.

Details​

  • Available since: 1.0.0
  • Time complexity: O(N) where N is the number of channels. The complexity depends on the number of active channels.

The CHANNELS subcommand lists all active channels that have at least one subscriber. If a pattern is provided, only channels matching the pattern will be listed.

Example​

PUBSUB CHANNELS news*

Returns channels like:

1) "news.sports"
2) "news.weather"

NUMSUB​

Syntax​

PUBSUB NUMSUB channel [channel ...]

Parameters​

  • channel: One or more channel names to get the subscriber count for.

Details​

  • Available since: 1.0.0
  • Time complexity: O(1) for each channel queried.

The NUMSUB subcommand returns the number of subscribers for each specified channel. The command returns an array where each entry consists of a channel name followed by the number of subscribers to that channel.

Example​

PUBSUB NUMSUB mychannel anotherchannel

Returns:

1) "mychannel"
2) (integer) 5
3) "anotherchannel"
4) (integer) 3

NUMPAT​

Syntax​

PUBSUB NUMPAT

Details​

  • Available since: 1.0.0
  • Time complexity: O(1).

The NUMPAT subcommand returns the number of patterns currently subscribed to. This provides insight into the number of pattern-based subscriptions.

Example​

PUBSUB NUMPAT

Returns:

(integer) 2

RESP2/RESP3 Reply​

  • CHANNELS: Array of channel names matching the pattern (if provided).
  • NUMSUB: Array of channel names with their respective subscriber counts.
  • NUMPAT: Integer representing the number of patterns subscribed to.

Notes​

  • The PUBSUB command is used for monitoring and managing the state of the Pub/Sub subsystem in Redis.
  • For more advanced monitoring, consider using Redis’s monitoring tools or client libraries with Pub/Sub support.