Distribute daily cron schedules out over the hour
Problem to solve
When creating a pipeline schedule, currently there are some quick options. All of these kick-off at exactly 4 am which creates a relatively large load on our system at that time.
For example, if you choose daily at 4 am, then each job gets the cron value of 0 4 * * *.
| Cron example |
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This is actually our biggest reliable source of queue congestion on
.comand so I'm going to flag this as a ~S2 based upon https://gitlab.com/gitlab-org/gitlab-foss/blob/master/doc/development/contributing/issue_workflow.md#severity-labels
Intended users
| Managing persona | User persona |
|---|---|
| Our own systems administrators (Sidney (Systems Administrator)) have to better manage our load balancing. | Devon (DevOps Engineer) to setup scheduled automated pipelines |
Further details
Proposal
Spread the load out over the hour by randomizing the minute field and hide the filled-in cron text when using the daily/weekly/monthly options. So for example when a user selects "Daily at 4 am" the cron value set behind the scenes is a value ranging from 0 4 * * * to 59 4 * * * where the minute digit is chosen at random.
- Making the preset outcomes editable after being chosen
- The cron field stays editable
- Allowing for timezones to be randomized by the presets
- The timezone dropdown's information architecture is changed in the UI making it dependent on the presets
- The presets will randomize upon page load
- Every day: changes times
- Every week: changes day and times
- Every month: changes day and times
- Allowing for ranges to be defined in the cron syntax for hours only (borrowing from Jenkins)
- Hours: H (0-23)
- Potential to add others for bigger and smaller ranges (days of week and month, minutes)
- Upon loading the page, we generate one time for all options:
- Page load
- Generate Random Week day -> Wednesdays
- Generate Random Date -> 4th
- Generate Random Time -> 19h
- User then has the choice between Custom, Every day at 19h, Every Wednesday at 19h , Every month, 4th at 19h
| Mockup (Figma document) |
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Things to consider
Currently, the behavior is that picking "daily at 4 am" fills out the cron value for you, but leaves it visible and editable. This gives the user the easy opportunity to change it to 0 9 * * * if what they really want is to have the job run at 9 am every morning. By hiding it we lose that ability.