questions about composed processor and sink - spring-cloud-dataflow

Question

I'm using Spring Could Data Flow 1.7.2.RELEASE and am trying to follow this blog post
to create a "a combination of processor + sink into a single application: “a new sink”."
When I structured my code as the blog's example I had problems and I figured it was because the blog's example used java.util.Function which is akin to a Processor.
I guessed I should use java.util.Consumer because I am trying to change my existing Sink into a Processor-Sink hybrid
My class looks like this:
#EnableBinding(Sink.class)
public class SampleCombinedSink extends Something {
String modifiedPayload;
Logger log;
Consumer<String> consumer = i -> { modifiedPayload="STUFF ADDED BY CONSUMER i=["+i+"]"; };
public void accept(String s){
log.info("SampleCombinedSink.accept() s="+s);
}
#StreamListener(Sink.INPUT)
public void doSink(String payload) {
consumer.accept(payload);
log.info("SampleCombinedSink.doSink() Payload received.");
log.info("SampleCombinedSink.doSink() payload="+ payload);
log.info("SampleCombinedSink.doSink() modifiedPayload="+ modifiedPayload);
}
}
My output looks like this:
SampleCombinedSink.doSink() Payload received.
SampleCombinedSink.doSink() payload=Friday 11 January 2019 19:03:53.330+0000
SampleCombinedSink.doSink() modifiedPayload=STUFF ADDED BY CONSUMER i=[Friday 11 January 2019 19:03:53.330+0000]
SampleCombinedSink.doSink() Payload received.
SampleCombinedSink.doSink() payload=Friday 11 January 2019 19:03:54.332+0000
SampleCombinedSink.doSink() modifiedPayload=STUFF ADDED BY CONSUMER i=[Friday 11 January 2019 19:03:54.332+0000]
SampleCombinedSink.doSink() Payload received.
SampleCombinedSink.doSink() payload=Friday 11 January 2019 19:03:55.333+0000
SampleCombinedSink.doSink() modifiedPayload=STUFF ADDED BY CONSUMER i=[Friday 11 January 2019 19:03:55.333+0000]
SampleCombinedSink.doSink() Payload received.
SampleCombinedSink.doSink() payload=Friday 11 January 2019 19:03:56.313+0000
SampleCombinedSink.doSink() modifiedPayload=STUFF ADDED BY CONSUMER i=[Friday 11 January 2019 19:03:56.313+0000]
My Source emits a timestamp every second.
I'm confused by my Consumer.
Consumer<String> consumer = i -> { modifiedPayload="STUFF ADDED BY CONSUMER i=["+i+"]"; };
I thought I'd be able to do something like:
Consumer<String> consumer = i -> { i="STUFF ADDED BY CONSUMER i=["+i+"]"; };
and then payload in
#StreamListener(Sink.INPUT)
public void doSink(String payload) {
would contain "STUFF ADDED BY CONSUMER i=[timestamp]"
It didn't.
I want to change the input to doSink and change it by adding "STUFF ADDED BY CONSUMER" so that when the input reaches doSink(String payload) payload will contain "STUFF ADDED BY CONSUMER i=[timestamp]"
How do I achieve that?

Answer 1

In this case, you don't have to change anything with your Sink application instead, just use the same function plumbing at the Sink application side.
For instance, to make:
a combination of processor + sink into a single application: “a new sink”."
all you need is to have your function beans as part of the Sink application or even having the function beans in a separate artifact but in the classpath of Sink application. Once you have this, you can define the spring.cloud.stream.function.definition for the Sink application.
You can see a sample for this here. The app log-composed has the function beans defined.
To run the sample:
dataflow:>app register --name http-transformer --type source --uri file:///Users/igopinathan/dev/git/ilayaperumalg/sandbox/function-composition/http-transformer/target/http-transformer-2.1.0.BUILD-SNAPSHOT.jar
Successfully registered application 'source:http-transformer'
dataflow:>app register --name log-composed --type sink --uri file:///Users/igopinathan/.m2/repository/org/springframework/cloud/stream/app/log-composed/2.1.0.BUILD-SNAPSHOT/log-composed-2.1.0.BUILD-SNAPSHOT.jar
Successfully registered application 'sink:log-composed'
dataflow:>stream create helloComposed --definition "http-transformer --server.port=9001 | log-composed"
Created new stream 'helloComposed'
dataflow:>stream deploy helloComposed --properties "app.log-composed.spring.cloud.stream.function.definition=upper|concat,deployer.*.local.inheritLogging=true"
Deployment request has been sent for stream 'helloComposed'
dataflow:>http post --data "friend" --target "http://localhost:9001"
In the stream deploy command, you can see the app being used to specify the function composition is log-composed.