Cron resource

A datetime-based resource type that understands cron syntax and emits regular new versions into a Concourse pipeline.

Example

---
resource_types:
- name: cron-resource
  type: docker-image
  source:
    repository: jpluscplusm/concourse-cron-resource

resources:
  - name: 10-min-trigger
    type: cron-resource
    source:
      expression: "*/10 * * * *"

Source configuration

A source block configuring this resource contains the following keys:

• expression: a string containing a 5- or 6- field cron expression.

Notes

FIXME:

• The period of per-resource or Concourse-wide checker interval can be unintuitive: "check_every simply sets a lower bound on the time between checks" (https://concourse-ci.org/checker.html#when-are-resources-checked). Document if/that we emit a version for each tick that the cron schedule implies, thus a longer check_every could result in multiple new versions when combined with a high-frequency schedule. The consumer should be careful to consume latest versus every version.
• Timezones
• Extended cron syntax, or not.