Update timer cycle definition to support cron expression

[korthout]

What should we do?

Update timer cycle definition to support cron expressions.

Inspiration can be retrieved from the docs (once those are completed).

• I can read about cycle timer definitions with cron expressions camunda-docs#1117

Why should we do it?

Camunda Platform 8.1 introduces the following

• feat(engine): support cron expression for timer cycle. camunda#9674

Note that we can define a CRON expression, but that the description specifies the ISO 8601 repeating intervals only:

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Related to https://github.com/camunda/product-hub/issues/300.

[pinussilvestrus]

Are there changes needed for the property itself, or are only documentation/description updates required?

[korthout]

@pinussilvestrus I don't think so. For the Cycle Type, the Value can simply be set to a cron expression (like in the example above).

[CatalinaMoisuc]

We decided to split it up:

• adapt the hint to highlight that you can use both CRON and ISO
• support both and validate both versions

@nikku mentioned that he can pick up the first part.

[nikku]

Split up validation into separate topic: #3084. That one goes beyond duration but shall cover different mentions of times, durations and intervals, as well as CRON expressions across our app(s).

[CatalinaMoisuc]

@barmac
As discussed, it makes sense to amend also the documentation with cron, even if the link is available for both 8.0 and 8.1.
This is the usual approach we use and we use linting to encourage the user to upgrade.

[CatalinaMoisuc]

@barmac
No urgency, but when you start working on this could you please also move the Product Hub epic in Implement and write an update that we are on it? Thanks

[barmac]

Do we want to update the description for C7 too? As noted in the Zeebe issue, C7 also supports cron expression and it's documented: https://docs.camunda.org/manual/7.17/reference/bpmn20/events/timer-events/#time-cycle

[nikku]

Yes, let us do it!

[barmac]

Draft:

[barmac]

The example comes from the docs: https://docs.camunda.io/docs/next/components/modeler/bpmn/timer-events/#time-cycle

[christian-konrad]

This looks fine! I assume this is parsed at Zeebe, and no additional flag necessary to pass so Zeebe knows what to expect?

[barmac]

I confirmed that a timer with exactly this expression is successfully deployed to zeebe@8.1.0-alpha5. No additional flags are required.

[barmac]

OK, so I will proceed with the contents as on the screenshot.

[barmac]

This will be implemented via bpmn-io/bpmn-js-properties-panel#772