@Override
    public void stop() {
        // this will tell the main loop to stop... looping :)
        stopped = true;
       
        // close the client, if we're in standard mode
        if (client != null) {
            client.close();
        }

        if (quickStarter != null) {
            // In quick start mode, deploy the application package if configured to do so
            if (quickStartConfig != null && quickStartConfig.isDeployPackage()) {
                quickStarter.deployer.deployApplicationPackage();
            }
        }
    }
We need to use the original event object to get the fieldName value.
For some reason, getting it from the eventData map of asyncFeed doesn't work

@param event The original event object
@param fieldName The field name to get
@return The value of the field or the field name if it doesn't exist
integration/logstash-plugins/logstash-output-vespa/src/main/java/org/logstashplugins/VespaFeed.java