https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=43989
Bug ID: 43989
Summary: Concurrent real-time holds queue updates can deadlock
and leave holds off the Holds queue
Initiative type: ---
Sponsorship ---
status:
Product: Koha
Version: Main
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P5 - low
Component: Hold requests
Assignee: [email protected]
Reporter: [email protected]
QA Contact: [email protected]
CC: [email protected], [email protected],
[email protected]
Target Milestone: ---
With RealTimeHoldsQueue enabled, a single action (e.g. a check-in) enqueues
several update_holds_queue_for_biblios jobs for the same biblio
(Koha::Item->store, the SIP/circ check-in code, hold changes). When the worker
runs these in parallel, update_queue_for_biblio deletes and re-inserts the same
tmp_holdsqueue/hold_fill_targets rows from two transactions at once. One fails
with "Deadlock found when trying to get lock", BatchUpdateBiblioHoldsQueue
rolls it back and records an error, and it is never retried.
If the failed update was the one carrying the newer state (e.g. the item is now
available), the hold stays off the Holds queue until something else touches the
biblio. Holds to pull still shows it, because it works out the list when the
page is loaded.
Since build_holds_queue.pl exits without --force while RealTimeHoldsQueue is
on, nothing catches these misses unless the cron is run with --force.
To reproduce: in two processes, begin a transaction and call
update_queue_for_biblio( { biblio_id => $id, delete => 1 } ) for a biblio with
a pending hold and an available item, with a short sleep before
CreatePicklistFromItemMap. The second process dies with a deadlock.
Seen in production at a ByWater partner: holds on Holds to pull were missing
from the Holds queue for months.
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