XAUTOCLAIM

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Transfer ownership of pending stream entries

Transfers ownership of pending stream entries that match the given criteria.
It is like calling XPENDING and XCLAIM.
Internally it uses a SCAN-style walk, a simpler way to recover from failed deliveries.
Available since version 6.2.

Like XCLAIM, it works on stream <key> in consumer group <group>.
It transfers to <consumer> messages pending for at least <min-idle-time> milliseconds whose ID is at least <start>.

Example

Command>	XADD sensor1 * temp 10
Command>	XADD sensor1 * temp 20
Command>	XGROUP CREATE sensor1 CG 0
Command>	XREADGROUP GROUP CG C1 count 1 STREAMS sensor1 >
Result>	1) 1) "sensor1" 2) 1) 1) "1624776138517-0" 2) 1) "temp" 2) "10"
Command>	XREADGROUP GROUP CG C1 count 1 STREAMS sensor1 >
Result>	1) 1) "sensor1" 2) 1) 1) "1624776140772-0" 2) 1) "temp" 2) "20"
Command>	XAUTOCLAIM sensor1 CG C2 5000 0-0 Moves the 2 pending entries from C1 to C2.
Result>	1) "0-0" 2) 1) 1) "1624776138517-0" 2) 1) "temp" 2) "10" 2) 1) "1624776140772-0" 2) 1) "temp" 2) "20"
Command>	XPENDING sensor1 CG
Result>	1) (integer) 2 2) "1624776138517-0" 3) "1624776140772-0" 4) 1) 1) "C2" Now owned by C2. 2) "2"

<count> (default 100) is an upper limit on how many items to try to claim. Internally the command scans the consumer group's Pending Entry List (PEL) from <start> and picks entries whose idle time is at least <min-idle-time>. The maximum number of pending entries scanned is <count> times 10 (hard-coded). So fewer entries than requested may be claimed.
JUSTID changes the reply to an array of successfully claimed IDs only, without the message bodies. With this option the retry counter is not incremented.
The command returns claimed stream IDs and entries as arrays. If no PEL entries remain, it returns the special ID 0-0 to signal completion. You can still call XAUTOCLAIM after a 0-0 scan. If enough time has passed, previously pending entries may become claimable.
Only messages idle longer than <min-idle-time> are claimed, and idle time is reset. That way only one consumer can successfully claim a given pending message at a time, which reduces (but does not eliminate) double processing.
Claiming with XAUTOCLAIM also increments the delivery attempt count. Messages that cannot be processed (for example because the consumer always crashes) show a high delivery count that monitoring can detect.

Syntax

XAUTOCLAIM key group consumer min-idle-time start [COUNT count] [JUSTID]

Available since version 6.2.0.
Time complexity is O(1) if COUNT is small.

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