[seam-dev] Seam Cron Concurrency

[Dave Oxley]

Hi Pete,

I have raised and am trying to implement SEAMCRON-33 which adds concurrency control to Seam Cron. The API's I was thinking of implement are:

    @AsyncRestriction(group = "test_group")
    public boolean canRun(StatusIndexes indexes) {
        HasLessThan max = new HasLessThan(MAX_CONCURRENT);
        max = indexes.iterateRunningProcesses(max);
        indexes.iterateWaitingToRunProcesses(max);
        return max.hasLess();
    }
StatusIndexes will be an interface providing various methods to interrogate the state of other jobs in the queue and true or false should be returned to run or not run another.

And reference the group with a new attribute on the Asynchronous annotation:
    @Asynchronous(group = "test_group")
    public void doWork() {
        ....
    }
or a scheduled annotation:
    public void every40Seconds(@Observes @Every(group = "test_group", nth = 40, value = Interval.SECOND) Trigger t) {
        ....
    }

I have a few questions:
1. Are you ok with the API changes? Do you have a better/different idea for the API changes?
2. @AsynRestriction is a new feature for asynchronous or scheduling methods. Therefore it doesn't really make sense to be a new spi. But then if I implement it in the QueuJ scheduling and asynchronous as a new feature it will just be an unimplemented feature for the Quartz provider. How would you want this handled? Just document that it only works for the QueuJ provider?
3. We will need to scan all classes on the classpath for methods marked with the @AsynRestriction annotation at startup. Is there a utility to do this or some example code?

Cheers,
Dave.
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