The Module Launcher provides a single entry point that bootstraps module JARs located in a Maven repository. A single Docker image can then be used to launch any of those JARs based on an environment variable. When running standalone, a system property may be used instead of an environment variable, so that multiple instances of the Module Launcher may run on a single machine. The following examples demonstrate running the modules for the ticktock stream (time-source | log-sink).

Prerequisites

1: clone and build the spring-cloud-stream project:

git clone https://github.com/spring-cloud/spring-cloud-stream.git
cd spring-cloud-stream
mvn package
cd ..

2: start redis locally via redis-server or docker-compose (there's a docker-compose.yml in spring-cloud-stream-samples). Optionally start redis-cli and use the MONITOR command to watch activity.

NOTE: redis.conf (on OSX it is found here: /usr/local/etc/redis.conf) may need to be updated to set the binding to an address other than 127.0.0.1 else the docker instances will fail to connect. For example: bind 0.0.0.0

Running Standalone

From the spring-cloud-stream/spring-cloud-stream-module-launcher directory:

java -Dmodules=org.springframework.cloud.stream.module:time-source:jar:exec:1.0.0.BUILD-SNAPSHOT -Dspring.cloud.stream.bindings.output=ticktock -jar target/spring-cloud-stream-module-launcher-1.0.0.BUILD-SNAPSHOT.jar
java -Dmodules=org.springframework.cloud.stream.module:log-sink:jar:exec:1.0.0.BUILD-SNAPSHOT -Dargs.0.server.port=8081 -Dspring.cloud.stream.bindings.input=ticktock -jar target/spring-cloud-stream-module-launcher-1.0.0.BUILD-SNAPSHOT.jar

Note that server.port needs to be specified explicitly for the log sink module as the time source module already uses the default port 8080. The module launcher is able to launch several modules, hence the args.0. prefix. The binding property is set to use the same name ticktock for both the output/input bindings of source/sink modules so that the log sink receives messages from the time source.

The time messages will be emitted every second. The console for the log module will display each:

2015-08-26 14:21:44.546  INFO 35725 --- [hannel-adapter1] o.s.cloud.stream.module.log.LogSink      : Received: 2015-08-26 14:21:44
2015-08-26 14:21:45.548  INFO 35725 --- [hannel-adapter1] o.s.cloud.stream.module.log.LogSink      : Received: 2015-08-26 14:21:45
2015-08-26 14:21:46.550  INFO 35725 --- [hannel-adapter1] o.s.cloud.stream.module.log.LogSink      : Received: 2015-08-26 14:21:46

NOTE: the two modules will be launched within a single process if both are provided (comma-delimited) via -Dmodules

Running with Docker

The easiest way to get a demo working is to use docker-compose (From the spring-cloud-stream/spring-cloud-stream-module-launcher directory):

Make sure to set DOCKER_HOST. If you are running a boot2docker VM, $(boot2docker shellinit) would set that up.

$ mvn package docker:build
$ docker-compose up
...
logsink_1    | 2015-08-11 08:25:49.909  INFO 1 --- [hannel-adapter1] o.s.cloud.stream.module.log.LogSink      : Received: 2015-08-11 08:25:49
logsink_1    | 2015-08-11 08:25:50.909  INFO 1 --- [hannel-adapter1] o.s.cloud.stream.module.log.LogSink      : Received: 2015-08-11 08:25:50
...

You can also run each module individually as a Docker process by passing environment variables for the module name as well as the host machine's IP address for the redis connection to be established within the container: To find out redis host IP:

Get the container ID of redis: `docker ps`
Get the IP address by inspecting the container: `docker inspect <containerID>`

To run the modules individually on docker:

docker run -p 8080:8080 -e MODULES=org.springframework.cloud.stream.module:time-source:jar:exec:1.0.0.BUILD-SNAPSHOT \
 -e spring.cloud.stream.bindings.output=ticktock -e SPRING_REDIS_HOST=<Redis-Host-IP> springcloud/stream-module-launcher

docker run -p 8081:8080 -e MODULES=org.springframework.cloud.stream.module:log-sink:jar:exec:1.0.0.BUILD-SNAPSHOT \
  -e spring.cloud.stream.bindings.input=ticktock -e SPRING_REDIS_HOST=<Redis-Host-IP> springcloud/stream-module-launcher

Note the binding name ticktock is specified for the source's output and sink's input. The port mapping is done so that individual modules' http endpoints can be accessed via the docker VM port.

To run pub/sub modules individually on docker, the binding name has to start with topic:.

docker run -p 8080:8080 -e MODULES=org.springframework.cloud.stream.module:time-source:jar:exec:1.0.0.BUILD-SNAPSHOT \
 -e spring.cloud.stream.bindings.output=topic:foo -e SPRING_REDIS_HOST=<Redis-Host-IP> springcloud/stream-module-launcher

docker run -p 8081:8080 -e MODULES=org.springframework.cloud.stream.module:log-sink:jar:exec:1.0.0.BUILD-SNAPSHOT \
 -e spring.cloud.stream.bindings.input=topic:foo -e SPRING_REDIS_HOST=<Redis-Host-IP> springcloud/stream-module-launcher

docker run -p 8082:8080 -e MODULES=org.springframework.cloud.stream.module:log-sink:jar:exec:1.0.0.BUILD-SNAPSHOT \
 -e spring.cloud.stream.bindings.input=topic:foo -e SPRING_REDIS_HOST=<Redis-Host-IP> springcloud/stream-module-launcher

In the above scenario, both the sink modules receive the same messages from the time source.