core-how-to-mark-message-as-successfully-processed.md

Core - How to mark messages as successfully processed

There are currently a few ways that can be used to mark that a message has been successfully processed and therefore it can be resolved (deleted from the SQS Queue).

Returning without exception

The easiest method is to just make your method not throw an exception when it is executed. In this scenario the MessageProcessor sees that the processing was successful, by not throwing an exception, and it will resolve the message.

Example

public class MyClass {

    private final SomeService someService;

    public MyClass(final SomeService someService) {
        this.someService = someService;
    }

    public void myMethod(@Payload final String payload) {
        someService.importantProcessing(payload);
    }
}

Including an Acknowledge Object in the method signature

When the method includes an Acknowledge parameter, it is now the message listener's responsibility to manually resolve the message by calling acknowledge.acknowledgeSuccessful(). If this is never done then the message will not be deleted and will potentially be replaced into the queue depending on the re-drive policy.

Note: that this returns a CompletableFuture and will only guarantee to be completed if that future resolves successfully.

Example

public class MyClass {

    private final SomeService someService;

    public MyClass(final SomeService someService) {
        this.someService = someService;
    }

    public void myMethod(@Payload final String payload, final Acknowledge acknowledge) {
        someService.importantProcessing(payload);

        acknowledge.acknowledgeSuccessful(); // If there is an exception thrown from now on the message will still be a success

        someService.unimportantProcessing(payload);
    }
}

The method returns a CompletableFuture

When the method does not include an Acknowledge parameter, and it returns a CompletableFuture, then the message will be successfully resolved when that future resolves.

Warning: If this CompletableFuture is never completed, the MessageProcessor will wait forever and ultimately you will have no more messages processing as all threads are waiting for the future to complete.

Example

public class MyClass {

    private final SomeService someService;

    public MyClass(final SomeService someService) {
        this.someService = someService;
    }

    public CompletableFuture<?> myMethod(@Payload final String payload) {
        return someService.importantProcessingAsync(payload);
    }
}