Integrate Keptn with your applications

Keptn works on top of the default scheduler for the cluster, so it can trace all activities of all deployment workloads on the cluster, no matter what tool is used for the deployment. This same mechanism allows Keptn to inject pre- and post-deployment checks into all deployment workloads. Keptn monitors resources that have been applied into the Kubernetes cluster and reacts if it finds a workload with special annotations/labels. Keptn uses metadata that is added to the Kubernetes workloads to identify the workloads of interest.

To integrate Keptn with your applications:

• You must first install and enable Keptn.
• Annotate or label your workloads with either Keptn or Kubernetes keys.
  • Basic annotations or labels are required for all Keptn features except Keptn metrics.
  • Pre- and post-deployment checks are required only for the Release lifecycle management feature.

Keptn uses these annotations to the Kubernetes workloads to create the KeptnWorkload and KeptnApp resources that it uses to provide observability and release lifecycle management.

Note: Annotations are not required if you are only using the metrics-operator component of Keptn to observe Keptn metrics.

Basic annotations

Keptn automatically discovers KeptnApp resources, based on the annotations or labels. This enables the Keptn observability features (based on OpenTelemetry) for existing applications, without additional Keptn configuration.

Keptn monitors your Deployment, StatefulSets, and ReplicaSets, and DaemonSets resources in the namespaces where Keptn is enabled. If Keptn finds any of these resources and the resource has either the keptn.sh or the kubernetes annotations/labels, it creates appropriate KeptnWorkload and KeptnApp resources for the version it detects.

The basic keptn.sh keys that can be used for annotations or labels are:

keptn.sh/workload: myAwesomeWorkload
keptn.sh/version: myAwesomeWorkloadVersion
keptn.sh/app: myAwesomeAppName

Alternatively, you can use Kubernetes keys for annotations or labels. These are part of the Kubernetes Recommended Labels:

app.kubernetes.io/name: myAwesomeWorkload
app.kubernetes.io/version: myAwesomeWorkloadVersion
app.kubernetes.io/part-of: myAwesomeAppName

These keys are defined as:

• keptn.sh/workload or app.kubernetes.io/name: Determines the name of the generated KeptnWorkload resource.
• keptn.sh/version or app.kubernetes.io/version: Determines the version of the KeptnWorkload that represents the Workload. If the Workload has no version annotation/labels and the pod has only one container, Keptn takes the image tag as version (unless it is “latest”).
• keptn.sh/app or app.kubernetes.io/part-of: Determines the name of the generated KeptnApp representing your Application. All Workloads that share the same value for this label are consolidated into the same KeptnApp resource.

Keptn automatically generates appropriate KeptnApp resources that are used for observability, based on whether the keptn.sh/app or app.kubernetes.io/part-of annotation/label is populated:

• If either of these annotations/labels are populated, Keptn automatically generates a KeptnApp resource that includes all workloads that have the same annotation/label, thus creating a KeptnApp resource for each defined grouping

• If only the workload and version annotations/labels are available (in other words, neither the keptn.sh/app or app.kubernetes.io/part-of annotation/label is populated), Keptn creates a KeptnApp resource for each KeptnWorkload and your observability output traces the individual Keptnworkload resources but not the combined workloads that constitute your deployed application.

See Keptn Applications and Keptn Workloads for architectural information about how KeptnApp and KeptnWorkloads are implemented.

Annotations vs. labels

The same keys can be used as annotations or labels. Both annotations and labels are can be attached to Kubernetes objects. Some key differences between the two:

• Annotations

  • Are not used to identify and select objects
  • Can contain up to 262144 chars
  • Metadata in an annotation can be small or large, structured or unstructured, and can include characters not permitted by labels

• Labels

  • Can be used to select objects and to find collections of objects that satisfy certain conditions
  • Can contain up to 63 chars
  • Are appropriate for identifying attributes of objects that are meaningful and relevant to users but do not directly imply semantics to the core system

Annotations take precedence over labels, and the keptn.sh keys take precedence over app.kubernetes.io keys. In other words:

• The operator first checks if the keptn.sh key is present in the annotations, and then in the labels.
• If neither is the case, it looks for the app.kubernetes.io equivalent, again first in the annotations, then in the labels.

In general, annotations are more appropriate than labels for integrating Keptn with your applications because they store references, names, and version information so the 63 char limitation is quite restrictive. However, labels can be used if you specifically need them and can accommodate the size restriction.

Pre- and post-deployment checks

To implement the Keptn Release Lifecycle feature that handles pre- and post-deployment evaluations and tasks, do the following:

• Define the KeptnMetric and KeptnEvaluationDefinition resources for each evaluation you want. A KeptnEvaluationDefinition compares the value of a KeptnMetric to the threshold that is specified.
• You will also need to define the necessary KeptnMetricsProvider and resource for each instance of each data source used for the KeptnEvaluationDefinition resources you define.
• Define a KeptnTaskDefinition resource for each task you want to execute. KeptnTaskDefinition resources contain re-usable “functions” that can execute before and after the deployment. For example, before the deployment starts, you might run a check for open problems in your infrastructure and invoke a pipeline to run performance tests. The deployment is kept in a pending state until the infrastructure is capable of accepting deployments again. See Working with Keptn tasks for more information.
• Annotate your Workloads Deployments, StatefulSets, and DaemonSets to include each evaluation and task you want run for specific workloads.
• Manually edit all KeptnApp resources to specify evaluations and tasks to be run for the KeptnApp itself.

Annotations to KeptnApp

The annotations to workloads do not define the tasks and evaluations to be run for KeptnApp resources themselves. To define pre- and post-deployment evaluations and tasks for a KeptnApp, you must manually edit the YAML file to add them.

Specify one of the following annotations/labels for each evaluation or task you want to execute:

keptn.sh/pre-deployment-evaluations: <`EvaluationDefinition`-name>
keptn.sh/pre-deployment-tasks: <`TaskDefinition`-name>
keptn.sh/post-deployment-evaluations: <`EvaluationDefinition`-name>
keptn.sh/post-deployment-tasks: <`TaskDefinition`-name>

The value of these annotations corresponds to the name of Keptn resources called KeptnTaskDefinition resources These resources contain re-usable “functions” that can execute before and after the deployment. For example, before the deployment starts, you might run a check for open problems in your infrastructure and invoke a pipeline to run performance tests. The deployment is kept in a pending state until the infrastructure is capable of accepting deployments again.

If everything is fine, the deployment continues and afterward, a Slack notification is sent with the result of the deployment

Use Keptn automatic app discovery

The automatically generated KeptnApp file aggregates the workloads to include in the application, based on annotations made to the workloads themselves. This enables you to run Keptn observability features on your cluster.

Afterward, you can monitor the status of the deployment using a command like the following:

kubectl get keptnworkloadinstance -n podtato-kubectl -w

The generated KeptnApp file includes metadata that names this KeptnApp and identifies the Namespace where it resides.

metadata:
  name: simpleapp
  namespace: simplenode-dev

It also includes a spec.workloads list that defines the workloads to be included.

Pre-/post-deployment tasks and evaluations for the KeptnApp can also be added to this resource manually but this is not required for observability.

As an example, consider the following application, consisting of multiple deployments, which is going to be deployed into a Keptn-enabled namespace. Note that:

1. Keptn is enabled for the namespace where your application runs.
2. The Deployment workloads are annotated appropriately. This example does not use other workloads.

apiVersion: v1
kind: Namespace
metadata:
  name: podtato-kubectl
  annotations:
    keptn.sh/lifecycle-toolkit: "enabled"

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: podtato-head-frontend
  namespace: podtato-kubectl
spec:
  template:
    metadata:
      labels:
        app.kubernetes.io/name: podtato-head-frontend
        app.kubernetes.io/part-of: podtato-head
        app.kubernetes.io/version: 0.1.0
    spec:
      containers:
        - name: podtato-head-frontend
          image: podtato-head-frontend
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: podtato-head-hat
  namespace: podtato-kubectl
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app.kubernetes.io/name: podtato-head-hat
        app.kubernetes.io/part-of: podtato-head
        app.kubernetes.io/version: 0.1.1
    spec:
      containers:
        - name: podtato-head-hat
          image: podtato-head-hat

Applying these resources results in the creation of the following KeptnApp resource:

apiVersion: lifecycle.keptn.sh/v1alpha2
kind: KeptnApp
metadata:
  name: podtato-head
  namespace: podtato-kubectl
  annotations:
    app.kubernetes.io/managed-by: "klt"
spec:
  version: "<version string based on a hash of all containing workloads>"
  workloads:
  - name: podtato-head-frontend
    version: 0.1.0
  - name: podtato-head-hat
    version: 1.1.1

With the KeptnApp resource created, you get observability of your application’s deployments by using the OpenTelemetry tracing features that are provided by Keptn:

Example of pre- and post-deployment actions

A comprehensive example of pre- and post-deployment evaluations and tasks can be found in our examples folder, where we use Podtato-Head to run some simple pre-deployment checks.

To run the example, use the following commands:

cd ./examples/podtatohead-deployment/
kubectl apply -f .

Afterward, you can monitor the status of the deployment using

kubectl get keptnworkloadinstance -n podtato-kubectl -w

The deployment for a Workload stays in a Pending state until the respective pre-deployment check is successfully completed. Afterwards, the deployment starts and when the workload is deployed, the post-deployment checks start.