The queue with the most items waiting, or null with the reason why not.
Pure SQL: asking PHP which queues have work costs a kernel boot to be told "none". expire = 0
is the unclaimed condition, so an item under another invocation's lease is not waiting.
update_fetch_tasks has no worker plugin and drains inside hook_cron, so picking it boots a
kernel to learn nothing and starves the queues that do have one.
exclude stops the deepest queue starving the others; prefer keeps a repeating (mid-drain)
unit on the queue it started.
The queue with the most items waiting, or null with the reason why not.
Pure SQL: asking PHP which queues have work costs a kernel boot to be told "none".
expire = 0is the unclaimed condition, so an item under another invocation's lease is not waiting.update_fetch_taskshas no worker plugin and drains insidehook_cron, so picking it boots a kernel to learn nothing and starves the queues that do have one.excludestops the deepest queue starving the others;preferkeeps a repeating (mid-drain) unit on the queue it started.