# Different clock triggers for different cycles?

**URL:** <https://cylc.discourse.group/t/different-clock-triggers-for-different-cycles/120>\
**Category:** Cylc Support\
**Created:** [August 9, 2019, 10:10pm UTC](https://cylc.discourse.group/t/different-clock-triggers-for-different-cycles/120 "2019-08-09T22:10:14Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![Tim\_Whitcomb](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/tim_whitcomb/32/58_2.png) [@Tim\_Whitcomb](https://cylc.discourse.group/u/Tim_Whitcomb)\
**Post date:** [August 9, 2019, 10:10pm UTC](https://cylc.discourse.group/t/different-clock-triggers-for-different-cycles/120/1 "2019-08-09T22:10:14Z")

</div>

(cylc 7.8.x)

I have a task that runs every 6 hours. At times 00Z and 12Z, I want it to have a 2-hour clock offset. At times 06Z and 18Z, I want it to have a 1.5-hour clock offset. Other than that, the task is identical (i.e. same task script, same resources required, etc.). All offsets are to make the task run prior to the cycle point wallclock, but that won’t strictly matter for this example. When I set up a suite that looks like:

```
[cylc]
    UTC mode = True

[scheduling]
    initial cycle point = now

    [[xtriggers]]
        clock_synoptic = wall_clock(-PT2H)
        clock_offtime = wall_clock(-PT1H30M)

    [[dependencies]]
        [[[T00,T12]]]
            graph = """ @clock_synoptic => foo """
        [[[T06,T18]]]
            graph = """ @clock_offtime => foo """

```

I get an error (when turning on debug options) along the lines of:

```
Traceback (most recent call last):
  File "/users/whitcomb/working_copies/cylc-working/bin/cylc-validate", line 153, in <module>
    main()
  File "/users/whitcomb/working_copies/cylc-working/bin/cylc-validate", line 90, in main
    output_fname=options.output, mem_log_func=profiler.log_memory)
  File "/users/whitcomb/working_copies/cylc-working/lib/cylc/config.py", line 558, in __init__
    self.load_graph()
  File "/users/whitcomb/working_copies/cylc-working/lib/cylc/config.py", line 2127, in load_graph
    old_xtrig.func_kwargs['offset'])
KeyError: 'offset'

```

While looking through the code to track this down, several questions arose:

1. (minor) Is it valid to not use keyword arguments for the `wall_clock` builtin xtrigger? The user manual says that it’s fine, but the checks in config.py (in `load_graph`) are explicitly looking only for an `offset` keyword argument and never checking for positional arguments (and in fact set an offset of zero when comparing with another clock trigger if keyword arguments are not used)

2. (major) From looking at the code, it seems like the error is coming from the second portion of the graph being parsed and the task `foo` checking for other clock triggers, and resetting the clock trigger to be the one with the larger offset. The error had to do with the absence of keyword args, but it looks like the intended behavior (even if that’s fixed) is not what I want here. Am I correct in that task `foo` in the above example will have its clock trigger over-ridden when the second part of the graph is parsed and that I can’t have different clock xtriggers for the same task in different (non-overlapping) cycles?

---

<div class="post-metadata">

**Author:** ![hilary.j.oliver](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/hilary.j.oliver/32/4_2.png) [@hilary.j.oliver](https://cylc.discourse.group/u/hilary.j.oliver)\
**Post date:** [August 11, 2019, 4:59am UTC](https://cylc.discourse.group/t/different-clock-triggers-for-different-cycles/120/2 "2019-08-11T04:59:03Z")

</div>

Hi Tim,

Thanks, you have definitely found a bug (damn it!).

1. (minor) - agreed, you should be able to use a positional or keyword arg for the clock offset. This should be easy to fix, I’ll check Monday.

2. (major) - the override is intended and correct for _single tasks_ with multiple clock triggers (we might as well only keep the one with the largest date-time value). However, the problem is that xtriggers, unlike task triggers, are not being tied to the cycling sequence, so your two `foo` instances are not being recognized as different with respect to xtriggers (oops, my fault I think). From a quick look this bug affects all xtriggers, not just clock triggers (in the general case, both `foo` instances would end up with both xtriggers).

I will get endeavor to get a fix for this up quickly … [https://github.com/cylc/cylc-flow/issues/3283](https://github.com/cylc/cylc-flow/issues/3283)

… in the meantime the workaround is to use a different logical task that inherits the original `foo` content:

```auto
...
    [[dependencies]]
        [[[T00,T12]]]
            graph = "@clock_synoptic => foo-a"
        [[[T06,T18]]]
            graph = "@clock_offtime => foo-b"
[runtime]
    [[foo]]
        # (original foo job config)
        ...
    [[foo-a, foo-b]]
        inherit = foo
...

```

Hilary

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<div class="post-metadata">

**Author:** ![Tim\_Whitcomb](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/tim_whitcomb/32/58_2.png) [@Tim\_Whitcomb](https://cylc.discourse.group/u/Tim_Whitcomb)\
**Post date:** [August 15, 2019, 12:33am UTC](https://cylc.discourse.group/t/different-clock-triggers-for-different-cycles/120/3 "2019-08-15T00:33:14Z")

</div>

Thanks! I see the PRs in progress and that looks good. This also opens up another snag that means that I might need to rename the tasks anyway: with the syntax as it currently stands, I don’t think I can have cycle-specific expiration times

With the new PRs in place, it looks like I can support cycle-specific wallclock offsets (great!) but I realized today that I’m still constrained with expirations to have the same expire offset across all cycles.

---

<div class="post-metadata">

**Author:** ![hilary.j.oliver](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/hilary.j.oliver/32/4_2.png) [@hilary.j.oliver](https://cylc.discourse.group/u/hilary.j.oliver)\
**Post date:** [August 15, 2019, 1:47am UTC](https://cylc.discourse.group/t/different-clock-triggers-for-different-cycles/120/4 "2019-08-15T01:47:13Z")

</div>

Yes, clock-expiration is currently considered a property of the task, whereas clock xtriggers are entities in the workflow that tasks can trigger off of (and tasks can thus - after the fix! - trigger off of different xtriggers in different cycle points).

We should probably re-implement clock-expiration as an xtrigger. I’ll put an issue up for consideration (however, this one might not happen quickly).

---

<div class="post-metadata">

**Author:** ![hilary.j.oliver](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/hilary.j.oliver/32/4_2.png) [@hilary.j.oliver](https://cylc.discourse.group/u/hilary.j.oliver)\
**Post date:** [August 15, 2019, 11:28am UTC](https://cylc.discourse.group/t/different-clock-triggers-for-different-cycles/120/5 "2019-08-15T11:28:55Z")

</div>

The xtrigger fix has passed review and been merged to master - it will be in the upcoming cylc-7.8.4 release. [https://github.com/cylc/cylc-flow/pull/3285](https://github.com/cylc/cylc-flow/pull/3285)