WUI: Runahead limit is showing for the "next" cycle but not the ones afterwards

Cylc Cylc Support
1

Looking at workflow that has tasks in a failed state, I was looking at the final cycle in the display and thought the runahead limit was not met. But, when looking at the “next” cycle, it shows the runahead limit has been met.

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Is this expected? The n-window is set to 3, so I’m guessing that the runahead limit being met only shows for tasks in the n=0 or n=1 window, not for greater N’s? If this is correct, my follow-up question is, should it show for all future N’s?

2

Hi @TomC

Yes, this is expected.

The web UI does not convey runahead limiting very helpfully yet. We have plans to fix that.

The nightly build of the User Guide explains the status quo better nightly_8.5: Runahead Limiting.

  • Tasks spawn into the n=0 window (i.e., they become “active”) when their prerequisites are met, or automatically out to the runahead limit if they have no task prerequisites.
  • Tasks in the n=0 window that are just beyond the runahead limit are marked with the little “target” badge and prevented from spawning any further.
    • These tasks are being actively held back by the runahead limit
  • Tasks at n>0 in the UI belong to the abstract future graph - the bigger the value of n the more you’ll see around the active tasks.
    • These tasks are beyond the runahead limit, but they are not actively held back by the limit because workflow activity has not reached that part of the graph yet.

Currently, the only way to see exactly which tasks are active is to set n-window extent to zero.

In future GUI updates we plan to make the distinction between n=0 and n>0 more obvious, and also show what cycles are beyond the runahead limit so you won’t have look for the one cycle that is at the limit. (Note the two concepts are different: the future graph includes any tasks downstream of active tasks in any cycle point, not just those beyond the runahead limit).