Run Tasks

You can execute short-lived workflows by running them as Tasks in Kf. Tasks are run under Apps, meaning that each Task must have an associated App. Each Task execution uses the build artifacts from the parent App. Because Tasks are short-lived, the App is not deployed as a long-running application, and no routes should be created for the App or the Task.

Push an App for running Tasks

1. Clone the test-app repo repo:

   git clone https://github.com/cloudfoundry-samples/test-app test-app
   
   cd test-app
   

2. Push the App.

   Push the App with the kf push APP_NAME --task command. The --task flag indicates that the App is meant to be used for running Tasks, and thus no routes are created on the App, and it is not deployed as a long-running application:

   kf push test-app --task
   

3. Confirm that no App instances or routes were created by listing the App:

   kf apps
   

   Notice that the App is not started and has no URLs:

   Listing Apps in Space: test-space
   Name                     Instances  Memory  Disk  CPU   URLs
   test-app                 stopped    1Gi     1Gi   100m  <nil>
   

Run a Task on the App

When you run a Task on the App, you can optionally specify a start command by using the --command flag. If no start command is specified, it uses the start command specified on the App. If the App doesn’t have a start command specified, it looks up the CMD configuration of the container image. A start command must exist in order to run the Task successfully.

kf run-task test-app --command "printenv"

You see something similar to this, confirming that the Task was submitted:

Task test-app-gd8dv is submitted successfully for execution.

The Task name is automatically generated, prefixed with the App name, and suffixed with an arbitrary string. The Task name is a unique identifier for Tasks within the same cluster.

Specify Task resource limits

Resource limits (such as CPU cores/Memory limit/Disk quota) can be specified in the App (during kf push) or during the kf run-task command. The limits specified in the kf run-task command take prededence over the limits specified on the App.

To specify resource limits in an App, you can use the --cpu-cores, --memory-limit, and --disk-quota flags in the kf push command:

kf push test-app --command "printenv" --cpu-cores=0.5 --memory-limit=2G --disk-quota=5G --task

To override these limits in the App, you can use the --cpu-cores, --memory-limit, and --disk-quota flags in the kf run-task command:

kf run-task test-app --command "printenv" --cpu-cores=0.5 --memory-limit=2G --disk-quota=5G

Specify a custom display name for a Task

You can optionally use the --name flag to specify a custom display name for a Task for easier identification/grouping:

$ kf run-task test-app --command "printenv" --name foo
Task test-app-6swct is submitted successfully for execution.

$ kf tasks test-app
Listing Tasks in Space: test space
Name              ID  DisplayName        Age    Duration  Succeeded  Reason
test-app-6swct    3   foo                1m     21s       True       <nil>

Manage Tasks

View all Tasks of an App with the kf tasks APP_NAME command:

$ kf tasks test-app
Listing Tasks in Space: test space
Name              ID  DisplayName        Age    Duration  Succeeded  Reason
test-app-gd8dv    1   test-app-gd8dv     1m     21s       True       <nil>

Cancel a Task

Cancel an active Task by using the kf terminate-task command:

• Cancel a Task by Task name:

  $ kf terminate-task test-app-6w6mz
  Task "test-app-6w6mz" is successfully submitted for termination
  

• Or cancel a Task by APP_NAME + Task ID:

  $ kf terminate-task test-app 2
  Task "test-app-6w6mz" is successfully submitted for termination
  

Cancelled Tasks have PipelineRunCancelled status.

$ kf tasks test-app
Listing Tasks in Space: test space
Name              ID  DisplayName        Age    Duration  Succeeded  Reason
test-app-gd8dv    1   test-app-gd8dv     1m     21s       True       <nil>
test-app-6w6mz    2   test-app-6w6mz     38s    11s       False      PipelineRunCancelled

View Task logs

View logs of a Task by using the kf logs APP_NAME --task command:

$ kf logs test-app --task