Queueable Apex
Take control of your asynchronous Apex processes by using the Queueable interface. This interface enables you to add jobs to the queue and monitor them, which is an enhanced way of running your asynchronous Apex code compared to using future methods.
For Apex processes that run for a long time, such as extensive database operations or external Web service callouts, you can run them asynchronously by implementing the Queueable interface and adding a job to the Apex job queue. In this way, your asynchronous Apex job runs in the background in its own thread and doesn’t delay the execution of your main Apex logic. A benefit of using the Queueable interface methods is that some governor limits are higher than for synchronous Apex, such as heap size limits.
Queueable Apex allows following additional benefits:
- Non-primitive types: Your Queueable class can contain member variables of non-primitive data types, such as sObjects or custom Apex types. Those objects can be accessed when the job executes.
- Monitoring: When you submit your job by invoking the System.enqueueJob method, the method returns the ID of the AsyncApexJob record. You can use this ID to identify your job and monitor its progress, either through the Salesforce user interface in the Apex Jobs page, or programmatically by querying your record from AsyncApexJob.
- Chaining jobs: You can chain one job to another job by starting a second job from a running job. Chaining jobs is useful if you need to do some sequential processing.
Example:
public class AddContact implements Queueable {
private Contact contact;
private String sta;
public AddContact(Contact con, String state) {
this.contact = con;
this.sta = state;
}
public void execute(QueueableContext context) {
List<Account> accounts = [Select ID from Account where BillingState =:sta LIMIT 200];
List<Contact> lstCon = new List<Contact>();
for (Account account : accounts) {
Contact clonedcon = contact.clone(false, false, false, false);
clonedcon.AccountID = account.ID;
lstCon.Add(clonedcon);
}
insert lstCon;
}
}
Things to Remember
Queueable Apex is a great new tool but there are a few things to watch out for:
- The execution of a queued job counts once against the shared limit for asynchronous Apex method executions.
- You can add up to 50 jobs to the queue with System.enqueueJob in a single transaction.
- When chaining jobs, you can add only one job from an executing job with System.enqueueJob, which means that only one child job can exist for each parent queueable job. Starting multiple child jobs from the same queueable job is a no-no.
- No limit is enforced on the depth of chained jobs, which means that you can chain one job to another job and repeat this process with each new child job to link it to a new child job. However, for Developer Edition and Trial orgs, the maximum stack depth for chained jobs is 5, which means that you can chain jobs four times and the maximum number of jobs in the chain is 5, including the initial parent queueable job.