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Updating the Resource status

This is Part 2 of a series illustrating how Kratix works.
👈🏾   Previous: Intentionally schedule Promise resources)
👉🏾   Next: What's next

In this tutorial, you will

Conveying information back to the application developers​

What we've focused on so far is how to define a Kratix Promise in a compelling way so that platform users choose to use the platform. A Kratix-powered platform enables users to ask for the services they need, on-demand, without having to know unnecessary business and service lifecycle requirements.

What platform users need, though, is the end-to-end experience of making a simple request, understanding what's happening with the request, then ultimately making use of the service created by the request. So how do you communicate back to platform users information about their request, and how do users use the services that the platform creates?

There are actually a number of ways you can communicate the status of a service to the platform, and the choice comes down to the Promise and Promise Workflow author.

One approach is to generate notifications for internal systems like Slack or Teams from the Promise Workflow's Pipeline container.

Another approach, which is what we'll choose today, is to follow convention and leverage the status field on Kubernetes resources. The Kratix Workflow's Pipeline has the ability to write information back to the status of the Resource.

In the context of your Promise, an example of what you might want to convey back is the configuration of the Resource (e.g. default configuration), and how to access the running Resources (e.g. a URL or connection string).

Status​

As we saw in scheduling, within the Pipeline container file system, Kratix mounts a /kratix/metadata directory to manage important configuration that is independent of the Resources definitions for your State Store.

Similar to writing destination selector rules to /kratix/metadata/destination-selectors.yaml, you will write changes to the Resource status to the /kratix/metadata/status.yaml file.

  • The status.yaml file can contain arbitrary key values, with the message key being a special key that is communicated back to the user when running kubectl get elastic-cloud.
  • All other key-value pairs are viewable by getting the full Resource definition.

Picking a status for your ECK Promise​

You want to achieve two things with the ECK Promise Resource status:

  • The Promise provides an option to pre-configure Beats with modules. Broadcast the existence of these modules as part of the message field.
  • You are providing Kibana as a user interface, and your users need a way to access the Kibana UI. Provide the initial username and password as additional status values.

Update the pipeline/run script:

pipeline/run
cat <<EOF > /kratix/metadata/status.yaml
message: "Instance ${name} provisioned with preconfigured system metrics"
initialLoginDetails:
    username: "elastic"
    passwordSecretName: "${name}-es-elastic-user"
EOF

Request a resource and check its status​

The run script is included in the Pipeline's container image, so to have these destination selector changes take effect, you need to rebuild and re-load the Docker image.

The test-pipeline script builds, loads, and runs the Docker image.

./scripts/test-pipeline

Verify that the test output directory contains the correct status:

📂 test
├── input
│   └── object.yaml
├── metadata
│   └── destination-selectors.yaml
    └── status.yaml
└── output
    ├── beats.yaml
    ├── elasticsearch.yaml
    └── kibana.yaml

Next, install the Promise:

kubectl --context $PLATFORM create --filename promise.yaml

And finally, put on the Application Developer hat and make a request for a Elastic Cloud Resource:

kubectl --context $PLATFORM apply --filename resource-request.yaml

The status of the request for the Resource will start as pending, which is the Kratix default before a Workflow runs. Once the Workflow has completed, the status will be updated.

Check the status of the Resource:

kubectl --context $PLATFORM get elastic-clouds

The above command will return something close to the following:

NAME      STATUS
example   Instance example provisioned with preconfigured system metrics

As you can see, the message field appears in the output. To see the other keys, get the full status value from Kubernetes:

kubectl --context $PLATFORM get elastic-clouds example -o yaml | yq .status
conditions:
  - lastTransitionTime: "2023-01-01T12:00:00Z"
    message: Pipeline completed
    reason: PipelineExecutedSuccessfully
    status: "True"
    type: PipelineCompleted
message: Instance example provisioned with preconfigured system metrics
initialLoginDetails:
    username: elastic
    passwordSecretName: example-es-elastic-user
🤔 Curious about the conditions fields?

The conditions field​

Conditions are a core Kubernetes concept and standard to convey information about a resources status. For example, Pods report back various conditions:

- lastProbeTime: null
  lastTransitionTime: "2023-06-20T15:02:20Z"
  status: "True"
  type: Ready
- lastProbeTime: null
  lastTransitionTime: "2023-06-20T15:02:20Z"
  status: "True"
  type: ContainersReady
- lastProbeTime: null
  lastTransitionTime: "2023-06-20T15:00:49Z"
  status: "True"
  type: PodScheduled

Conditions are also powerful for enabling you to wait for an occurrence. For example, you can wait for the health of a pod by running something like this:

kubectl --context $PLATFORM \
    wait pods \
    --namespace kratix-platform-system \
    --selector control-plane=controller-manager \
    --for condition=Ready \
    --timeout=90s

This same logic can be applied to Resources. Kratix sets the PipelineCompleted condition. For example, a user (or CI/Automation) could wait for a request to finish by running:

kubectl --context $PLATFORM wait elastic-cloud/example \
  --for=condition=PipelineCompleted --timeout=60s

Kratix supports this by default for all Resources.

Summary​

To recap what you achieved:

  1. ✅   Use metadata to set a custom Resource status

✅  This tutorial concludes an Introduction to writing a Promise.
👉🏾  You can go check what's next to learn about what else you can achieve with Kratix.