Apache pulsar - function execution not effecting the output

Question

I followed the manual here: pulsar functions

I have this function declaration in Java:

package org.example.test;

import java.util.function.Function;

public class ExclamationFunction implements Function<String, String> {
   @Override
   public String apply(String input) {
       return String.format("%s!", input);
   }
}

I built the jar. Copied it to my pulsar stanalone docker and ran the following commands:

./bin/pulsar-admin functions create --classname org.example.test.ExclamationFunction --jar java-function-1.0-SNAPSHOT.jar --inputs my-topic-1 --namespace default --name JavaFunction

And then:

./bin/pulsar-admin functions trigger --tenant public --namespace default --name JavaFunction --triggerValue "test"

Now i use some client in C# to consume the queue and when i read the message i see "test" instead of "test!".

So seems the function trigger worked but the function itselft doesnt take effect.

Answer 1

You need to specify an output topic and consume the output topic: --output exclamation-topic