New sample README demonstrating a Spring Cloud Stream processor
* Shows how to create a simple Spring Cloud Stream processor that converts temperatrues from Fahrenheit to Celsius * Shows how to run it both as a standalone Spring Boot microservice and then on Spring Cloud Data Flow as part of a stream. Polishing the PR
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mross1080
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custom-apps/celsius-converter-processor/README.adoc
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custom-apps/celsius-converter-processor/README.adoc
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# Custom Spring Cloud Stream Processor
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=======================================
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### Creating the project
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Today we're going to talk about how to create a custom Spring Cloud Stream application and running it on Spring Cloud Data Flow.
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We're going to go through all the steps for making a simple processor that will allow you to convert temperature from Fahrenheit to Celsius.
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We will be running the demo locally, but all the steps will work in a Cloud Foundry environment as well.
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The first step is to create a new spring cloud stream project.
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We can do that by going to http://start.spring.io/, which is the spring initializer.
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Choose the group as `demo.celsius.converter` and enter artifact name as celsius-converter-processor.
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Next, we need to choose a message transport binding as a dependency for the custom app.
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There are options for choosing ***rabbitmq*** or ***kafka*** as the message transport.
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For this demo, we choose rabbit by typing rabbit in the search bar under "Search for dependencies" and then selecting "stream rabbit".
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Hit the generate project button and then open the new project in an IDE of your choice.
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### Developing the app
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Now we're at a point where we can actually create our custom app. In our Spring Cloud Stream application, the minimum configuration is going to require two Java class files.
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* CelsiusConverterProcessorAplication.java
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* CelsiusConverterProcessorConfiguration.java
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Spring Cloud Stream applications are stand alone spring boot applications that can be run on their own.
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Spring Cloud Data Flow is the orchestration layer that ties these individual Spring Cloud Stream apps together.
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Since we named the project as celsius-converter-processor, the initializer created a class called CelsiusConverterProcessorAplication.
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We are creating a transformer that takes a Fahrenheit input and converts it to Celsius.
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We want to follow the same naming convention as the application file, so create a new file in the same directory called `CelsiusConverterProcessorConfiguration.java`.
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##### CelsiusConverterProcessorConfiguration.java
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```
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@EnableBinding(Processor.class)
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public class CelsiusConverterProcessorConfiguration {
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@Transformer(inputChannel = Processor.INPUT, outputChannel = Processor.OUTPUT)
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public int convertToCelsius(String payload) {
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int fahrenheitTemperature = Integer.parseInt(payload);
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return (farenheitTemperature-30)/2;
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}
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}
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```
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There are two important spring annotations that we introduced in the above code.
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First we annotated the class with **@EnableBinding(Processor.class)**.
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Second we created a method and annotated it with ***@Transformer(inputChannel = Processor.INPUT, outputChannel = Processor.OUTPUT)***.
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By adding these two annotations we are basically classifying this stream app as a Processor(as opposed to a source or a sink).
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This allows us to specify that the application is receiving input from upstream(Processor.input) and send the output data downstream(Processor.OUTPUT).
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The convertToCelsius method takes a `String` as input for Fahrenheit and then returns the converted Celsius as an integer.
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This method is very simple, but that is also the beauty of this programming style.
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We can add as much logic as we want to this method to enrich this processor.
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As long as we annotate it properly and return valid output, it works as a proper Spring Cloud Stream processor.
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Once we're done putting together the app, move into the origin of the project directory and build a deployable jar with Maven, possibly on the command line.
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```
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cd <PATH/TO/PROJECT>
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mvn clean install
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Make sure you have a running instance of RabbitMQ https://www.rabbitmq.com/
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java -jar target/celsius-converter-processor-0.0.1-SNAPSHOT.jar
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```
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If all goes well, we should have a running standalone Spring Boot Application.
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Once we verify that the app is started and running without any errors, we can stop it.
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## Deploying Locally on Spring Cloud Data Flow
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#### Prerequisites
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In order to get started, make sure that you have the following components:
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* Local build of https://github.com/spring-cloud/spring-cloud-dataflow [Spring Cloud Data Flow]
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* Running instance of RabbitMQ https://www.rabbitmq.com/
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Launch the locally built `server`
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```
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$ cd <PATH/TO/SPRING-CLOUD-DATAFLOW>
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$ java -jar spring-cloud-dataflow-server-local/target/spring-cloud-dataflow-server-local-<VERSION>.jar
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```
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Connect to Spring Cloud Data Flow's `shell`
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```
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$ cd <PATH/TO/SPRING-CLOUD-DATAFLOW>
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$ java -jar spring-cloud-dataflow-shell/target/spring-cloud-dataflow-shell-<VERSION>.jar
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____ ____ _ __
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/ ___| _ __ _ __(_)_ __ __ _ / ___| | ___ _ _ __| |
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\___ \| '_ \| '__| | '_ \ / _` | | | | |/ _ \| | | |/ _` |
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___) | |_) | | | | | | | (_| | | |___| | (_) | |_| | (_| |
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|____/| .__/|_| |_|_| |_|\__, | \____|_|\___/ \__,_|\__,_|
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____ |_| _ __|___/ __________
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| _ \ __ _| |_ __ _ | ___| | _____ __ \ \ \ \ \ \
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| | | |/ _` | __/ _` | | |_ | |/ _ \ \ /\ / / \ \ \ \ \ \
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| |_| | (_| | || (_| | | _| | | (_) \ V V / / / / / / /
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|____/ \__,_|\__\__,_| |_| |_|\___/ \_/\_/ /_/_/_/_/_/
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<VERSION>
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Welcome to the Spring Cloud Data Flow shell. For assistance hit TAB or type "help".
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dataflow:>version
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<VERSION>
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```
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[Register](https://github.com/spring-cloud/spring-cloud-dataflow/blob/master/spring-cloud-dataflow-docs/src/main/asciidoc/streams.adoc#register-a-stream-app) RabbitMQ binder variant of out-of-the-box applications
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```
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dataflow:>app import --uri http://bit.ly/Bacon-RELEASE-stream-applications-rabbit-maven
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```
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```
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app register --type processor --name convertToCelsius --uri <File URL of the jar file on the local filesystem where you built the project above> --force
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```
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Create the stream.
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We want to create a stream that uses the out of the box apps `http` and `log` and then connect them with our custom celsius converter app.
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```
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dataflow:>stream create --name convertToCelsiusStream --definition "http --port=9090 | convertToCelsius | log" --deploy
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Created and deployed new stream 'convertToCelsiusStream'
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```
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Verify the stream is successfully deployed
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```
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dataflow:>stream list
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```
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Verify that the apps have successfully deployed
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```
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dataflow:>runtime apps
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```
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Since we are running locally, note the file location of the logs.
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```
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2016-09-27 10:03:11.988 INFO 95234 --- [nio-9393-exec-9] o.s.c.d.spi.local.LocalAppDeployer : deploying app convertToCelsiusStream.log instance 0
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Logs will be in /var/folders/2q/krqwcbhj2d58csmthyq_n1nw0000gp/T/spring-cloud-dataflow-3236898888473815319/convertToCelsiusStream-1474984991968/convertToCelsiusStream.log
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2016-09-27 10:03:12.397 INFO 95234 --- [nio-9393-exec-9] o.s.c.d.spi.local.LocalAppDeployer : deploying app convertToCelsiusStream.convertToCelsius instance 0
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Logs will be in /var/folders/2q/krqwcbhj2d58csmthyq_n1nw0000gp/T/spring-cloud-dataflow-3236898888473815319/convertToCelsiusStream-1474984992392/convertToCelsiusStream.convertToCelsius
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2016-09-27 10:03:14.445 INFO 95234 --- [nio-9393-exec-9] o.s.c.d.spi.local.LocalAppDeployer : deploying app convertToCelsiusStream.http instance 0
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Logs will be in /var/folders/2q/krqwcbhj2d58csmthyq_n1nw0000gp/T/spring-cloud-dataflow-3236898888473815319/convertToCelsiusStream-1474984994440/convertToCelsiusStream.http
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```
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Post sample data pointing to the `http` endpoint: `http://localhost:9090` [`9090` is the `server.port` we specified for the `http` source in this case]
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```
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dataflow:>http post --target http://localhost:9090 --data 76
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> POST (text/plain;Charset=UTF-8) http://localhost:9090 76
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> 202 ACCEPTED
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```
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Open the log file for the convertToCelsiusStream.log app to see the output of our stream
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```
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tail -f /var/folders/2q/krqwcbhj2d58csmthyq_n1nw0000gp/T/spring-cloud-dataflow-7563139704229890655/convertToCelsiusStream-1474990317406/convertToCelsiusStream.log/stdout_0.log
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```
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You should see the temperature you posted converted to Celsius!
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```
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2016-09-27 10:05:34.933 INFO 95616 --- [CelsiusStream-1] log.sink : 23
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```
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In conclusion, we created a simple Spring Cloud Stream processor that converts the incoming Fahrenheit temperature data to Celsius.
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We ran it first as a standalone Spring Boot microservice application and then took the same app to Spring Cloud Data Flow to orchestrate it to be part of a stream that contains other apps.
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