try catch finally and inserting records

Question

We have an error log object where we store the errors and I have a simple try catch like below... My issue is that the insert in the finally does not appear to be happening. Any advice? or is that a limitation in the try-catch error handling?

list<Error_Log__c> error_logs = new list<Error_Log__c> ()
try {
   if(status__c == '100') {
      \\do something
   } else {
       throw new AuraHandledException('System Error');
   }  
} Catch (Exception e) {
   Error_Log__c rec = new Error_Log__c(Name="Error Message: ");
   error_logs.add(rec);
   throw new AuraHandledException('System Error');
} finally {
  insert error_logs;
} 

Answer 1

Since all DML is rolled back on an unhandled exception, my typical solution is to instead throw the error back to the client, then have the client log the exception in a separate call. We have "unlimited" calls in LWC, so there's no need to be ultra-conservative. You just need a separate method:

@AuraEnabled(cacheable=false) public static logError(Error_Log__c log) {
  insert log;
}

You, nor your users, will notice the few extra milliseconds it takes to make a separate call, in most cases.

In your code, the finally code is executed, but the results are rolled back anyways after the finally completes, because it's still in the same transaction where the exception was thrown.

Answer 2

If you allow an exception to propagate unhandled out of your code, which you do at the end of your catch block, you will cause the Salesforce platform to treat the session as failed and therefore all DML will be rolled back. That means even the error log insert will be undone.

The first option is to change how you notify your component about the error. Alternatively you ensure the error logs are handled in a separate session.

One option for the latter is to package your error details into a "publish immediately" platform event that you publish on the event bus in your finally. Being publish immediately, this event operates outside the current session and will not be rolled back because of the session failing.

You can then implement a trigger-based platform event subscriber that converts the platform event into an error log record and performs a DML insert. This DML runs in a separate session and thus can still succeed despite the original session failure.

Answer 3

So you are trying to throw an exception in the catch block. This won't work since the new throw is not in the try block directly, which means it will be thrown up to the next try-catch in the hierarchy.