How Can We Deploy Apex Classes That Are Scheduled?

Question

When deploying Apex classes that are scheduled, the main challenge is that Salesforce locks scheduled Apex jobs to the specific class they reference. This can cause deployment failures if you try to update a scheduled class without first unscheduling its jobs.

How can we effectively deploy updates to scheduled Apex classes without running into these issues?

Answer

One way to handle this is to manually abort scheduled jobs before deployment and reschedule them afterward. However, a more flexible approach is to use a dynamic dispatcher pattern, as presented by Dan Appleman in his Dreamforce 2013 session “Design Patterns for Asynchronous Apex.”

Using a Dispatcher Class to Avoid Deployment Issues

The idea is to have a ScheduledDispatcher class that remains locked but delegates execution to a separate ScheduleHandler class using Type.forName(). This allows us to update the handler class freely while keeping the dispatcher unchanged.

Implementation:

Step 1: Create the Dispatcher Class

global class ScheduledDispatcher implements Schedulable {
    public interface IScheduleDispatched { 
        void execute(SchedulableContext sc); 
    } 

    global void execute(SchedulableContext sc) {
        Type targetType = Type.forName('ScheduleHandler');   
        if (targetType != null) {
            IScheduleDispatched obj = (IScheduleDispatched) targetType.newInstance();
            obj.execute(sc);   
        } 
    } 
}

Explanation:

The ScheduledDispatcher implements the Schedulable interface, which Salesforce requires for scheduled jobs.
It defines an interface IScheduleDispatched, which enforces an execute() method.
The execute() method dynamically loads ScheduleHandler using Type.forName(), allowing us to update ScheduleHandler without modifying ScheduledDispatcher.
Since ScheduledDispatcher never changes, it avoids deployment failures.

Step 2: Create the Schedule Handler Class

public class ScheduleHandler implements ScheduledDispatcher.IScheduleDispatched {
    public void execute(SchedulableContext sc) {
        // Your scheduled logic here
    } 
}

Explanation:

The ScheduleHandler class implements the IScheduleDispatched interface, ensuring it has an execute() method. This class contains the actual scheduled job logic. Since it is dynamically loaded by ScheduledDispatcher, we can update it without worrying about deployment issues.

Alternative Approach: Unscheduling Before Deployment

If you don’t want to use the dynamic dispatch pattern, another approach is to unschedule all jobs referencing the Apex class before deployment and reschedule them afterward.

Step 1: Abort the Scheduled Job Before Deployment

List<CronTrigger> jobs = [SELECT Id FROM CronTrigger WHERE CronJobDetail.Name = 'Your_Scheduled_Job_Name'];
for (CronTrigger job : jobs) {
    System.abortJob(job.Id);
}

Explanation:

The System.abortJob(job.Id); call removes them from the scheduler, preventing deployment issues.
This SOQL query retrieves all scheduled jobs matching the given name.

Step 2: Reschedule the Job After Deployment

String cronExp = '0 0 12 * * ?'; // Runs daily at noon
System.schedule('Your_Scheduled_Job_Name', cronExp, new YourScheduledClass());

Explanation:

You must manually run this after deployment.
This schedules YourScheduledClass to run daily at 12:00 PM using a cron expression.

Which Approach Should You Use?

If your scheduled job logic changes frequently, use the dispatcher pattern. It avoids deployment issues without needing manual intervention.

If your job logic rarely changes, manually unscheduling before deployment might be a simpler option.

The dispatcher pattern provides a scalable, deployment-friendly solution, while unscheduling works well for one-time updates.

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