2

According to Salesforce documentation.

You can add up to 50 jobs to the queue with System.enqueueJob in a single transaction. In asynchronous transactions (for example, from a batch Apex job), you can add only one job to the queue with System.enqueueJob. To check how many queueable jobs have been added in one transaction, call Limits.getQueueableJobs().

So I enabled Change Data Capture on an object Queue_Item__c. And added this:

trigger QueueItemCDC on Queue_Item__ChangeEvent (after insert) {

    System.debug('After Insert From CDC');
    QueueItemExecutor.execute();
}

public without sharing class QueueItemExecutor {

    public static void execute() {

        System.debug(Limits.getLimitQueueableJobs());
        System.debug(Limits.getQueueableJobs());
    }

}

But the result was surprising, I got this in debug.

19:17:47.0 (1436473)|USER_DEBUG|[7]|DEBUG|After Insert From CDC
19:17:47.0 (1660299)|USER_DEBUG|[9]|DEBUG|50
19:17:47.0 (1685315)|USER_DEBUG|[10]|DEBUG|0

So the limit is showing as 50 whereas documentation says, in Async transaction the limit should be max 1. Does anyone know why, as CDC is considered as Async why Sync limits are applied to it?

To verify I logged more Limits to check, I saw all limits are from Sync transactions .

19:33:06.0 (1938344)|USER_DEBUG|[7]|DEBUG|After Insert From CDC
19:33:06.0 (11884797)|USER_DEBUG|[9]|DEBUG|getLimitQueueableJobs 50
19:33:06.0 (11921914)|USER_DEBUG|[10]|DEBUG|getLimitFutureCalls 50
19:33:06.0 (11942764)|USER_DEBUG|[11]|DEBUG|getLimitSoslQueries 20
19:33:06.0 (11962850)|USER_DEBUG|[12]|DEBUG|getLimitQueries 100
19:33:06.0 (11981041)|USER_DEBUG|[13]|DEBUG|getLimitDmlRows 10000
19:33:06.0 (12002651)|USER_DEBUG|[14]|DEBUG|getLimitHeapSize 6000000
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1 Answer 1

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2

CDC events share a 1:1 relationship with transactions, so they need to have the smaller synchronous limits imposed upon them, otherwise they would likely consume too many system resources. Also remember that CDC triggers are guaranteed to run, which would be impossible to guarantee as asynchronous code only gets 250,000 executions per day, shared between Queueable, Batchable, and future methods.

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  • Thanks for the explanation. One doubt this 250,000 executions, is this same as DailyAsyncApexExecutions. Because when I check mine its showing 991,000
    – Nagendra Singh
    Mar 27, 2022 at 7:00
  • 1
    Got it just read the documentation, its 250,000 or the number of user licenses in your org multiplied by 200, whichever is greater, so may be our org has more licenses.
    – Nagendra Singh
    Mar 27, 2022 at 7:05
  • I do wonder if CDC is implemented using the same infrastructure as Platform Events. Though Platform Events have no guarantee of delivery, and this could mean CDC is also not guaranteed delivery. (The docs suggest CDC is implemented this way, so...)
    – Phil W
    Mar 27, 2022 at 7:52
  • @PhilW Yes, CDC is a channel that you subscribe to on Platform Events. Even though the delivery may not be guaranteed off-platform, it certainly should never fail for CDC triggers, as far as I'm aware.
    – sfdcfox
    Mar 27, 2022 at 11:06
  • In principle it could since it uses queue-based, non-database technology, so if there is a failure of a server node the messages will get lost.
    – Phil W
    Mar 27, 2022 at 12:55

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