One way to launch a task using the task-launcher is to use the triggertask source. The triggertask source will emit a message with a TaskLaunchRequest object containing the required launch information. The triggertask can be added to the available sources by executing the app register command as follows (for the Rabbit Binder):

app register --type source --name triggertask --uri maven://org.springframework.cloud.stream.app:triggertask-source-rabbit:1.2.0.RELEASE

An example of this would be to launch the timestamp task once every 60 seconds, the stream to implement this would look like:

stream create foo --definition "triggertask --triggertask.uri=maven://org.springframework.cloud.task.app:timestamp-task:jar:1.2.0.RELEASE --trigger.fixed-delay=60 --triggertask.environment-properties=spring.datasource.url=jdbc:h2:tcp://localhost:19092/mem:dataflow,spring.datasource.username=sa | task-launcher-local --maven.remote-repositories.repo1.url=http://repo.spring.io/libs-release" --deploy

If you execute runtime apps you can find the log file for the task launcher sink. Tailing that file you can find the log file for the launched tasks. The setting of triggertask.environment-properties is so that all the task executions can be collected in the same H2 database used in the local version of the Data Flow Server. You can then see the list of task executions using the shell command task execution list

dataflow:>task execution list
╔════════════════════╤══╤════════════════════════════╤════════════════════════════╤═════════╗
║     Task Name      │ID│         Start Time         │          End Time          │Exit Code║
╠════════════════════╪══╪════════════════════════════╪════════════════════════════╪═════════╣
║timestamp-task_26176│4 │Tue May 02 12:13:49 EDT 2017│Tue May 02 12:13:49 EDT 2017│0        ║
║timestamp-task_32996│3 │Tue May 02 12:12:49 EDT 2017│Tue May 02 12:12:49 EDT 2017│0        ║
║timestamp-task_58971│2 │Tue May 02 12:11:50 EDT 2017│Tue May 02 12:11:50 EDT 2017│0        ║
║timestamp-task_13467│1 │Tue May 02 12:10:50 EDT 2017│Tue May 02 12:10:50 EDT 2017│0        ║
╚════════════════════╧══╧════════════════════════════╧════════════════════════════╧═════════╝

Another option to start a task using the task-launcher would be to create a stream using the Tasklaunchrequest-transform processor to translate a message payload to a TaskLaunchRequest.

The tasklaunchrequest-transform can be added to the available processors by executing the app register command as follows (for the Rabbit Binder):

app register --type processor --name tasklaunchrequest-transform --uri maven://org.springframework.cloud.stream.app:tasklaunchrequest-transform-processor-rabbit:1.2.0.RELEASE

For example:

stream create task-stream --definition "http --port=9000 | tasklaunchrequest-transform --uri=maven://org.springframework.cloud.task.app:timestamp-task:jar:1.2.0.RELEASE | task-launcher-local --maven.remote-repositories.repo1.url=http://repo.spring.io/libs-release"

A composed task can be launched using one of the task-launcher sinks as discussed here. Since we will be using the ComposedTaskRunner directly we will need to setup the task definitions it will use prior to the creation of the composed task launching stream. So let’s say that we wanted to create the following composed task definition AAA && BBB. The first step would be to create the task definitions. For example:

task create AAA --definition "timestamp"
task create BBB --definition "timestamp"

Now that the task definitions we need for composed task definition are ready, we need to create a stream that will launch ComposedTaskRunner. So in this case we will create a stream that has a trigger that will emit a message once every 30 seconds, a transformer that will create a TaskLaunchRequest for each message received, and a task-launcher-local sink that will launch a the ComposedTaskRunner on our local machine. The stream should look something like this:

stream create ctr-stream --definition "time --fixed-delay=30 | tasklaunchrequest-transform --uri=maven://org.springframework.cloud.task.app:composedtaskrunner-task:<current release> --command-line-arguments='--graph=AAA&&BBB --increment-instance-enabled=true --spring.datasource.url=...' | task-launcher-local"

In the example above we see that the tasklaunchrequest-transform is establishing 2 primary components:

For now let’s focus on the configuration that is required to launch the ComposedTaskRunner:

	Note
	Releases of ComposedTaskRunner can be found here