Add Cron Monitoring for the Scheduler Component

[cleptric]

Symfony 6.3 added a new Scheduler Component, something we should add support for, for Cron Monitoring.

https://symfony.com/blog/new-in-symfony-6-3-scheduler-component

[Mika56]

Hello,

I am interested in using and implementing this feature as well.

Scheduler seems to have everything we need to implement this, the most important being that Scheduler dispatches events before and after running crons.

Questions that come to mind are:

• How/when are crons definitions sent to Sentry? I think it could be either:
  • A dedicated sentry:crons:sync-definitions command
  • Anytime a Messenger worker is started (my preference)
• How do we set checkinMargin, maxRuntime, failureIssueThreshold, recoveryThreshold? I suggest we add a #[Sentry\Cron] attribute or similar

[cleptric]

Our SDK has a baseline of PHP 7.2. If we conditionally can make this work, I'm ok with adding the Cron's configuration via attributes. I'm aware that the scheduler component is only available from PHP 8.1 and up.

[Mika56]

Doctrine annotations can be used as a fallback, but it is not a dependency.

Attributes are "compatible" with PHP 7, in a sense that the compiler just ignores it. Scheduler has indeed been introduced in Symfony 6.3, which requires PHP 8.1+. We could throw an exception for this feature when PHP_VERSION<8.1 just in case.

[cleptric]

We rather don’t want to throw exceptions but instead fail silently and emit a debug log entry.