XREAD

Returns messages from multiple streams with IDs greater than the ones requested. Blocks until a message is available otherwise.

Browse all commands · Upstream source documentation

Reference field	Value
Canonical name	XREAD
Catalog group	Stream commands
Upstream since	5.0.0 — upstream Redis/module version, not an ffkv release
Pinned catalog	Redis 8.10.0

Syntax

XREAD [COUNT count] [MAXCOUNT maxcount] [MAXSIZE maxsize]
  [BLOCK milliseconds] STREAMS key [key ...] id [id ...]

ffkv behavior and limits

Stream waits are bounded to 65,536 clients and 64 MiB of retained logical requests (also limited by the connection cap). Approximate MAXLEN trimming uses 100-entry granularity. EXEC/Lua reads never block. Physical index statistics describe ffkv, not Redis allocator internals.

Source: README.md:351–374; tests/bdd/features/streams.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 arity: -4 (includes the command name; a negative number is a minimum).

Command flags: BLOCKING, READONLY.

ACL categories: STREAM.

Argument structure

Argument	Type	Constraints / metadata
count	integer	optional; token: COUNT
maxcount	integer	optional; token: MAXCOUNT; since: 8.10.0
maxsize	integer	optional; token: MAXSIZE; since: 8.10.0
milliseconds	integer	optional; token: BLOCK
streams	block	token: STREAMS
↳ key	key	multiple; key_spec_index: 0
↳ ID	string	multiple

Key specifications

Upstream key discovery descriptors (indexes are relative to the full command vector):

[
  {
    "notes": "Incomplete because a stream key named STREAMS (or options before it) can shift the STREAMS keyword; fall back to xreadGetKeys",
    "flags": [
      "RO",
      "ACCESS",
      "INCOMPLETE"
    ],
    "begin_search": {
      "keyword": {
        "keyword": "STREAMS",
        "startfrom": 1
      }
    },
    "find_keys": {
      "range": {
        "lastkey": -1,
        "step": 1,
        "limit": 2
      }
    }
  }
]

Additional pinned upstream metadata

{
  "group": "stream",
  "since": "5.0.0",
  "history": [
    [
      "8.10.0",
      "Added the `MAXCOUNT` and `MAXSIZE` options."
    ]
  ]
}

Metadata source · Local snapshot: src/command_metadata.json, key xread.

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.

• A blocked read wakes with only entries newer than its requested ID — tests/bdd/features/streams.feature:94; 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.

A blocked read wakes with only entries newer than its requested ID — tests/bdd/features/streams.feature:100 (client “reader” sends:)

[
  "XREAD",
  "BLOCK",
  0,
  "STREAMS",
  "events",
  "1000-0"
]