FCALL

Invokes a function.

Browse all commands · Upstream source documentation

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

Syntax

FCALL function numkeys [key [key ...]] [arg [arg ...]]

ffkv behavior and limits

Sandboxed Lua 5.1 is bounded to 1 million instructions, 32 MiB Lua memory, 64 nesting levels, 8 MiB scripts/bridge values/replies, 10,000 bridge calls and 16 MiB cumulative bridge arguments. Writes before runtime errors commit. The volatile SHA cache holds 256 scripts/16 MiB with FIFO eviction; durable function libraries cap at 256 and one 16 MiB encoded WAL frame.

Source: README.md:426–449; tests/bdd/features/scripting.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: Depends on the function that is executed.

Upstream arity: -3 (includes the command name; a negative number is a minimum).

Command flags: NOSCRIPT, SKIP_MONITOR, MAY_REPLICATE, NO_MANDATORY_KEYS, SCRIPT_RUNNER, STALE.

ACL categories: SCRIPTING.

Argument structure

Argument	Type	Constraints / metadata
function	string	Required
numkeys	integer	Required
key	key	optional; multiple; key_spec_index: 0
arg	string	optional; multiple

Key specifications

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

[
  {
    "notes": "We cannot tell how the keys will be used so we assume the worst, RW and UPDATE",
    "flags": [
      "RW",
      "ACCESS",
      "UPDATE"
    ],
    "begin_search": {
      "index": {
        "pos": 2
      }
    },
    "find_keys": {
      "keynum": {
        "keynumidx": 0,
        "firstkey": 1,
        "step": 1
      }
    }
  }
]

Additional pinned upstream metadata

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

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

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.

• Dynamic Lua and function keys cannot diverge from their authoritative cluster owner — tests/bdd/features/cluster.feature:1279; command tag and invocation observed.
• Named callbacks share local helpers and expose registration metadata — tests/bdd/features/scripting.feature:123; command tag and invocation observed.
• Invalid replacement cannot discard the previous library — tests/bdd/features/scripting.feature:177; invocation observed.
• Function containers restore with append replace and flush policies — tests/bdd/features/scripting.feature:211; invocation observed.
• Libraries survive crash recovery but invalid containers cannot alter them — tests/bdd/features/scripting.feature:302; command tag and invocation observed.
• An executing readonly function is observable and can actually be interrupted — tests/bdd/features/scripting.feature:508; invocation observed.
• A function that has written cannot be killed and retains its completed effects — tests/bdd/features/scripting.feature:538; command tag and invocation observed.
• Replace policy cannot steal functions owned by a different library — tests/bdd/features/scripting.feature:568; invocation observed.
• Each outer Lua invocation owns a fresh import session rather than borrowing network layouts — tests/bdd/features/scripting.feature:623; command tag and invocation observed.
• Library source and optional metadata roundtrip through WITHCODE — tests/bdd/features/scripting.feature:684; invocation observed.
• Invalid counted script keys fail during EXEC without discarding adjacent writes (Scenario Outline) — tests/bdd/features/transactions.feature:289; 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.

Function containers restore with append replace and flush policies — tests/bdd/features/scripting.feature:247 (I execute:)

[
  "FCALL",
  "other",
  "0"
]

Next source assertion: the reply equals:

"extra"

Invalid replacement cannot discard the previous library — tests/bdd/features/scripting.feature:188 (I execute:)

[
  "FCALL",
  "answer",
  "0"
]

Next source assertion: the reply equals:

42

An executing readonly function is observable and can actually be interrupted — tests/bdd/features/scripting.feature:528 (I execute:)

[
  "FCALL",
  "healthy",
  "0"
]

Next source assertion: the reply equals:

"alive"