How to handle Callout Failures in asynchronous Apex jobs

What is the “Transaction Finalizers” feature
Overview System.Finalizer Interface
Implementation of Transaction Finalizer
Step 1
Code
Step 2
Code
Key Takeaway
Conclusion

As developers, we all have at some points, needed to check and track callout status, and sometimes it takes some extra effort to handle failure and then retry callout. And if the call out does not succeed on the second attempt, it becomes even more exhausting.

To handle callout failures, earlier we used to follow either of these two processes-

Check the status of AsyncApexJob using a SOQL query and re-enqueue the job if it fails.
Or fire BatchApexErrorEvents when a batch Apex method encounters an error or unhandled exception.

But this issue can now be resolved easily as Salesforce introduced the “Transaction Finalizers” feature in the Spring’21 release.

What is the “Transaction Finalizers” feature

Transaction Finalizers feature provides the capability to add actions to be taken when asynchronous jobs succeed or fail.

In other words, by using the System.Finalizer interface, it enables us to attach actions to asynchronous Apex jobs using the Queueable framework. Isn’t it amazing?

And the good part is that even a Queueable job that failed consecutively due to an unhandled exception can be successfully re-enqueued five times with Transaction finalizers.

Overview System.Finalizer Interface

This interface includes an execute(System.FinalizerContext cntx) method where we can define actions to take at the end of the Queuable job. Where argument FinalizerContext holds the instance of every enqueued job.

System.FinalizerContext interface contains four methods.

global Id getAsyncApexJobId {}
global String getRequestId {}
global System.ParentJobResult getResult {}
global System.Exception getException {}

Note:

getAsyncApexJobId() return ID of Queueable job for which this finalizer is defined.
System.ParentJobResult is an enum with value: SUCCESS, UNHANDLED_EXCEPTION

Implementation of Transaction Finalizer

We need to Attach the finalizer to our Queueable jobs using the System.attachFinalizer method.

This includes two steps-

Step 1

In the First step, define a class that implements the System.Finalizer interface.

Code

Step 2

Now, Attach a finalizer within a Queueable job’s execute method.

Code

Key Takeaway

A Queueable job can have only one Finalizer instance.
We can perform callout in Finalizer.
We can enqueue a single asynchronous Apex job (Queueable, Batch, or Future) in the finalizer’s implementation of the execute method.
Instead of using global finalizer use public