The queue with the most items waiting, or null with the reason why not.
Pure SQL: the only cron queue this site defines is
media_entity_thumbnail, and asking PHP which queues have work would cost a
kernel boot to be told "none", which is the answer every time until something
queues a thumbnail. expire = 0 is the unclaimed condition, so an item another
invocation still holds a lease on is not counted as waiting.
exclude is what stops the deepest queue starving the others: without it a
queue with a thousand items would be picked every round forever, and a second
queue would never be reached. prefer is the other direction -- a unit that is
repeating itself is mid-drain and must stay on the queue it started.
The queue with the most items waiting, or null with the reason why not.
Pure SQL: the only cron queue this site defines is media_entity_thumbnail, and asking PHP which queues have work would cost a kernel boot to be told "none", which is the answer every time until something queues a thumbnail.
expire = 0is the unclaimed condition, so an item another invocation still holds a lease on is not counted as waiting.excludeis what stops the deepest queue starving the others: without it a queue with a thousand items would be picked every round forever, and a second queue would never be reached.preferis the other direction -- a unit that is repeating itself is mid-drain and must stay on the queue it started.