PUBSUB SHARDNUMSUB

Returns the count of subscribers of shard channels.

Browse all commands · Upstream source documentation

Reference field	Value
Canonical name	PUBSUB SHARDNUMSUB
Catalog group	Pub/Sub commands
Upstream since	7.0.0 — upstream Redis/module version, not an ffkv release
Pinned catalog	Redis 8.10.0

Syntax

PUBSUB SHARDNUMSUB [shardchannel [shardchannel ...]]

ffkv behavior and limits

Pub/Sub is transient delivery, not durable leased jobs. Per client: 1,024 registrations, 8 MiB of names, 1,024-byte patterns, and 256 events/16 MiB of output. Overflow disconnects a slow subscriber; publications can fail the shared pattern-work budget.

Source: README.md:487–524; tests/bdd/features/pubsub.feature.

All requests share the 8 MiB framing/1,024-argument ingress limit; normal RESP replies have 64 MiB wire/logical budgets with bounded nesting/value counts. Management and Lua origins impose smaller budgets. These are not a process RSS cap. Catalog inclusion is not exhaustive option or wire-format parity. See limits and compatibility.

Upstream metadata

The following fields come from the pinned Redis metadata, not measured ffkv performance or an assertion that ffkv enforces every upstream flag. Running COMMAND INFO/COMMAND DOCS describe the current engine.

Upstream Redis complexity: O(N) for the SHARDNUMSUB subcommand, where N is the number of requested shard channels

Upstream arity: -2 (includes the command name; a negative number is a minimum).

Command flags: PUBSUB, LOADING, STALE.

Argument structure

Argument	Type	Constraints / metadata
shardchannel	string	optional; multiple

Additional pinned upstream metadata

{
  "group": "pubsub",
  "since": "7.0.0"
}

Metadata source · Local snapshot: src/command_metadata.json, key pubsub|shardnumsub.

BDD coverage and source examples

These are source observations, not a test run performed by this documentation build. A tag identifies scenario intent; an extracted vector identifies a command invocation, which may intentionally produce an error. Scenarios may require setup, multiple connections, persistence, cluster nodes or native-module fixtures.

• Shard channels are disjoint from regular channels even when their names match — tests/bdd/features/pubsub.feature:152; command tag and invocation observed.

Extracted command vectors

The following JSON arrays are the test harness’s argument vectors, not shell commands. Numeric arguments are converted by the harness; objects of the form {"base64":"…"} represent decoded binary bytes, not a literal JSON command argument. Preserve scenario setup and connection ordering. See the CLI guide for shell quoting and binary stdin. No reply is invented or inferred.

Shard channels are disjoint from regular channels even when their names match — tests/bdd/features/pubsub.feature:178 (I execute:)

[
  "PUBSUB",
  "SHARDNUMSUB",
  "{orders}:events",
  "absent"
]

Next source assertion: the reply equals:

["{orders}:events",1,"absent",0]