XACK(3valkey)

📦
version 9.0.6 · 2 versions
, in fedora 44

💖 XACK — the "okay we're DONE with this message bestie" command 💖

valkey command manual · section 3valkey · aka xack ✨

🌸 NAME 🌸

xack — returns the number of messages that were successfully acknowledged by the consumer group member of a stream. fr fr, that's the whole vibe. 🎀

🦋 SYNOPSIS 🦋

XACK key group ID [ID...]

💅 DESCRIPTION 💅

okay so. XACK removes one or multiple messages from the Pending Entries List — the PEL, bestie, say it with me — of a stream consumer group. 👑

A message is pending, and therefore sitting all cozy inside the PEL, when it was delivered to some consumer. That usually happens as a lil side effect of calling XREADGROUP, or when a consumer straight up took ownership of a message by calling XCLAIM. 🫶

So like: the pending message was delivered to some consumer, but the server is not yet sure it was processed at least once. Which means — plot twist — new calls to XREADGROUP that go grab the messages history for a consumer (for instance using an ID of 0) will return that same message again. 😭 And similarly, the pending message will be listed by the XPENDING command, which is the one that inspects the PEL. periodt.

Once a consumer successfully processes a message, it should call XACK so that message does not get processed again — and as a side effect, the PEL entry about that message is also purged, which releases memory from the Valkey server. slay, memory freed, we love to see it. ✨

🌈 REPLY 🌈

valkey-protocol(7) Integer reply: the command returns the number of messages successfully acknowledged.

heads up bestie 💀 certain message IDs may no longer be part of the PEL — for example because they have already been acknowledged — and XACK will not count them as successfully acknowledged. no cap.

⭐ COMPLEXITY ⭐

O(1) for each message ID processed. tiny. iconic. 🧚

🎀 ACL CATEGORIES 🎀

  • @fast
  • @stream
  • @write

💜 HISTORY 💜

  1. Available since: 5.0.0

🔥 EXAMPLES 🔥

127.0.0.1:6379> XACK mystream mygroup 1526569495631-0
(integer) 1

👑 SEE ALSO 👑

xadd(3valkey), xautoclaim(3valkey), xclaim(3valkey), xdel(3valkey), xgroup(3valkey), xgroup-create(3valkey), xgroup-createconsumer(3valkey), xgroup-delconsumer(3valkey), xgroup-destroy(3valkey), xgroup-help(3valkey), xgroup-setid(3valkey), xinfo(3valkey), xinfo-consumers(3valkey), xinfo-groups(3valkey), xinfo-help(3valkey), xinfo-stream(3valkey), xlen(3valkey), xpending(3valkey), xrange(3valkey), xread(3valkey), xreadgroup(3valkey), xrevrange(3valkey), xsetid(3valkey), xtrim(3valkey)

version 9.0.0 · dated 2025-10-21 · that's the whole page bestie, go ack some messages and hydrate 💖🦋🌸✨🫶

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