Working with Keptn tasks

A KeptnTaskDefinition resource defines tasks that the Keptn Lifecycle Toolkit runs as part of the pre- and post-deployment phases of a KeptnApp or KeptnWorkload.

A Keptn task executes as a runner in an application container, which runs as part of a Kubernetes job. A KeptnTaskDefinition includes a function that defines the action taken by that task.

To implement a Keptn task:

• Define a KeptnTaskDefinition resource that defines the runner to use for the container
• Annotate your workloads to integrate your task with Kubernetes
• Add your task to the KeptnApp resource that associates your KeptnTaskDefinition with the pre- and post-deployment tasks that should run in it

This page provides information to help you create your tasks:

• Code your task in an appropriate runner
• Understand how to use Context that contains a Kubernetes cluster, a user, a namespace, the application name, workload name, and version.
• Use parameterized functions if your task requires input parameters
• Create secret text and pass secrets to a function if necessary.

Runners and containers

Each KeptnTaskDefinition can use exactly one container with one runner. The runner you use determines the language you can use to define the task. The spec section of the KeptnTaskDefinition defines the runner to use for the container:

• The container-runtime runner provides a pure custom Kubernetes application container that you define to includes a runtime, an application and its runtime dependencies. This gives you the greatest flexibility to define tasks using the lanugage and facilities of your choice

KLT also includes two “pre-defined” runners:

• Use the deno-runtime runner to define tasks using Deno scripts, which use JavaScript/Typescript syntax with a few limitations. You can use this to specify simple actions without having to define a container.
• Use the python-runtime runner to define your task using Python 3.

For the pre-defined runners (deno-runtime and python-runtime), the actual code to be executed can be configured in one of four different ways:

• inline
• referring to an HTTP script
• referring to another KeptnTaskDefinition
• referring to a ConfigMap resource that is populated with the function to execute

See the KeptnTaskDefinition reference page for the synopsis and examples for each runner.

Context

A Kubernetes context is a set of access parameters that contains a Kubernetes cluster, a user, a namespace, the application name, workload name, and version. For more information, see Configure Access to Multiple Clusters.

You may need to include context information in the function code included in the YAML file that defines a KeptnTaskDefinition resource. For an example of how to do this, see the keptn-tasks.yaml file.

A context environment variable is available via Deno.env.get("CONTEXT"). It can be used like this:

let context = Deno.env.get("CONTEXT");
    
if (context.objectType == "Application") {
    let application_name = contextdata.appName;
    let application_version = contextdata.appVersion;
}       
        
if (context.objectType == "Workload") {
    let application_name = contextdata.appName;
    let workload_name = contextdata.workloadName;
    let workload_version = contextdata.workloadVersion;
}

Parameterized functions

KeptnTaskDefinitions can use input parameters. Simple parameters are passed as a single map of key values, while the secret parameters refer to a single Kubernetes secret.

Consider the following example:

apiVersion: lifecycle.keptn.sh/v1alpha2
kind: KeptnTaskDefinition
metadata:
  name: slack-notification-dev
spec:
  function:
    functionRef:
      name: slack-notification
    parameters:
      map:
        textMessage: "This is my configuration"
    secureParameters:
      secret: slack-token

Note the following about using parameters with functions:

• The Lifecycle Toolkit passes the values defined inside the map field as a JSON object.
• Multi-level maps are not currently supported.
• The JSON object can be read through the environment variable DATA using Deno.env.get("DATA");.
• Currently only one secret can be passed. The secret must have a key called SECURE_DATA. It can be accessed via the environment variable Deno.env.get("SECURE_DATA").

Working with secrets

A special case of parameterized functions is to pass secrets that may be required to access data that your task requires.

Create secret text

To create a secret to use in a KeptnTaskDefinition, execute this command:

kubectl create secret generic my-secret --from-literal=SECURE_DATA=foo

apiVersion: lifecycle.keptn.sh/v1alpha3
kind: KeptnTaskDefinition
metadata:
  name: dummy-task
  namespace: "default"
spec: 
  function: 
    secureParameters:
      secret: my-secret
    inline:
      code: |
        let secret_text = Deno.env.get("SECURE_DATA");
        // secret_text = "foo"        

To pass multiple variables you can create a Kubernetes secret using a JSON string:

kubectl create secret generic my-secret \
--from-literal=SECURE_DATA="{\"foo\": \"bar\", \"foo2\": \"bar2\"}"

apiVersion: lifecycle.keptn.sh/v1alpha3
kind: KeptnTaskDefinition
metadata:
  name: dummy-task
  namespace: "default"
spec:
  function:
    secureParameters:
      secret: my-secret
    inline:
      code: |
        let secret_text = Deno.env.get("SECURE_DATA");
        let secret_text_obj = JSON.parse(secret_text);
        // secret_text_obj["foo"] = "bar"
        // secret_text_obj["foo2"] = "bar2"        

Pass secrets to a function

Kubernetes secrets can be passed to the function using the secureParameters field.

Here, the secret value is the name of the Kubernetes secret, which contains a field with the key SECURE_DATA.
The value of that field is then available to the function’s runtime via an environment variable called SECURE_DATA.

For example, if you have a task function that should make use of secret data, you must first ensure that the secret containing the SECURE_DATA key exists For example:

apiVersion: v1
kind: Secret
metadata:
  name: deno-demo-secret
  namespace: default
type: Opaque
data:
  SECURE_DATA: YmFyCg== # base64 encoded string, e.g. 'bar'

Then, you can make use of that secret as follows:

apiVersion: lifecycle.keptn.sh/v1alpha3
kind: KeptnTaskDefinition
metadata:
  name: deployment-hello
  namespace: "default"
spec:
  function:
    secureParameters:
      secret: deno-demo-secret
    inline:
      code: |
        console.log("Deployment Hello Task has been executed");

        let foo = Deno.env.get('SECURE_DATA');
        console.log(foo);
        Deno.exit(0);