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Integrate Keptn with your Applications

Keptn works on top of the default scheduler for the cluster. This allows it to:

  • Track all activities of all workloads on the cluster, no matter what tool is used for the deployment
  • Inject pre/post-deployment checks into all 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 workloads:

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 or the kubernetes annotations/labels, it creates appropriate KeptnWorkload and KeptnApp resources for the version it detects.

The basic keys that can be used for annotations or labels are: myAwesomeWorkload myAwesomeWorkloadVersion myAwesomeAppName myAwesomeContainer

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

These keys are defined as:

  • or Determines the name of the generated KeptnWorkload resource.
  • or 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").
  • or 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 that you can generate following the instructions in Auto app discovery.
  • Determines the name of the container in the workload, from which Keptn extracts the version. This applies to single- and multi-container workloads. If the given container name does not match any container in the workload no version can be determined. Note that there is no equivalent annotation/label for this label.

Keptn automatically generates appropriate KeptnApp resources that are used for observability, based on whether the or 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 or 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 keys take precedence over keys. In other words:

  • The operator first checks if the key is present in the annotations, and then in the labels.
  • If neither is the case, it looks for the 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.