How to manually control the offset commit with cam

I'm using the camel kafka component and I'm unclear what is happening under the hood with committing the offsets. As can be seen below, I'm aggregating records and I think for my use case that it only makes sense to commit the offsets after the records have been saved to SFTP.

Is it possible to manually control when I can perform the commit?

private static class MyRouteBuilder extends RouteBuilder {

    @Override
    public void configure() throws Exception {

        from("kafka:{{mh.topic}}?" + getKafkaConfigString())
        .unmarshal().string()
        .aggregate(constant(true), new MyAggregationStrategy())
            .completionSize(1000)
            .completionTimeout(1000)
        .setHeader("CamelFileName").constant("transactions-" + (new Date()).getTime())
        .to("sftp://" + getSftpConfigString())

        // how to commit offset only after saving messages to SFTP?

        ;
    }

    private final class MyAggregationStrategy implements AggregationStrategy {
        @Override
        public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
            if (oldExchange == null) {
                return newExchange;
            }
            String oldBody = oldExchange.getIn().getBody(String.class); 
            String newBody = newExchange.getIn().getBody(String.class);
            String body = oldBody + newBody;
            oldExchange.getIn().setBody(body);
            return oldExchange;
        }
    }
}

private static String getSftpConfigString() {
        return "{{sftp.hostname}}/{{sftp.dir}}?"
                + "username={{sftp.username}}"
                + "&password={{sftp.password}}"
                + "&tempPrefix=.temp."
                + "&fileExist=Append"
                ;
}

private static String getKafkaConfigString() {
        return "brokers={{mh.brokers}}" 
            + "&saslMechanism={{mh.saslMechanism}}"  
            + "&securityProtocol={{mh.securityProtocol}}"
            + "&sslProtocol={{mh.sslProtocol}}"
            + "&sslEnabledProtocols={{mh.sslEnabledProtocols}}" 
            + "&sslEndpointAlgorithm={{mh.sslEndpointAlgorithm}}"
            + "&saslJaasConfig={{mh.saslJaasConfig}}" 
            + "&groupId={{mh.groupId}}"
            ;
}

回答1:

No you cannot. Kafka performs an auto commit in the background every X seconds (you can configure this).

There is no manual commit support in camel-kafka. Also this would not be possible as the aggregator is separated from the kafka consumer, and its the consumer that performs the commit.

回答2:

I think this is change in the latest version of camel (2.22.0) (the doc) you should be able to do that.

// Endpoint configuration &autoCommitEnable=false&allowManualCommit=true
public void process(Exchange exchange) {
     KafkaManualCommit manual = exchange.getIn().getHeader(KafkaConstants.MANUAL_COMMIT, KafkaManualCommit.class);
     manual.commitSync();
}