Already spawned in {1}

Cylc Cylc Support
1

This warning appeared in my log:
2024-02-21T17:13:24Z WARNING - Task 20230410T0000Z/bk_ready already spawned in {1}
I cannot tie this to any bad behavior, but it’s a WARNING so cylc thinks something is wrong. Any idea what could be causing this?

2

Yeah the meaning of that isn’t exactly clear, sorry. It will be clearer come 8.3.0 (soon).

The curly brackets contain flow numbers. Cylc 8 can handle multiple flows through the graph, within the same run. See Concurrent Flows — Cylc 8.2.3 documentation .

Flow 1 is the original flow, that begins when you start the workflow. If you haven’t subsequently triggered other flows, that log message probably doesn’t indicate that anything is wrong

Consider this trigger construct, which says task c should trigger if either a or b succeeds:

a | b => c

So, if a succeeds (in flow 1, say), the scheduler will trigger c. But then say, sometime later b runs too, and succeeds. The scheduler will log that it’s not going to spawn c again, because it was already spawned in flow 1.

3

In this case (well, if the cause is as I described) it shouldn’t really be a warning. But it’s not trivial to distinguish that from cases that perhaps should be (e.g. if I try to trigger flow 1 again, over a part of the graph that was already traversed by flow 1).