Flow of deployment

Keptn deploys a Kubernetes Workload by passing through a well-defined execution flow.

The execution flow goes through six main phases:

• Pre-deployments-tasks
• Pre-deployment-evaluation
• Deployment
• Post-deployment-tasks
• Post-deployment-evaluation
• Completed

Within each phase, all tasks and evaluations for each phase are executed in parallel. They are not affected by the order in which evaluations and tasks are listed in the KeptnApp resource or in the order of the pre/post-tasks and pre/post-evaluations that are listed in the Workflow manifests.

Kubernetes and Cloud Events

Kubernetes Events and CloudEvents are emitted at each phase to provide additional Observability of the execution flow.

Keptn implements a Permit Scheduler Plugin that blocks the binding of the pods to a node until all the pre-conditions are fulfilled.

A Kubernetes deployment is started by the deployment engine that is implemented (such as Flux or Argo) or can be started by the following command:

kubectl apply -f deployment.yaml

Keptn does not care how a deployment manifest is applied to the cluster. Both kubectl and Flux/Argo send the manifest to the Kubernetes API so Keptn does not differentiate the actual deployment options. This also means that one Keptn Application can include services that are deployed with different methods.

The deployment is created but the created pods are blocked and in pending state until all the required pre-deployment tasks/evaluations defined on either the KeptnApp or KeptnWorkload level pass. Only then are the pods bound to a node and deployed. If any pre-deployment evaluation or task fails, the KeptnApp issues an appropriate *Errored event and the deployment remains pending indefinitely, until further changes or external intervention If all evaluations and tasks in a phase are successful, the KeptnApp issues the appropriate *Succeeded event and initiates the next phase.

Summary of deployment flow

To view these events on your cluster, execute:

kubectl get events -n <namespace> . 

Pre-deployment phase

Pre-deployment tasks can perform any kind of action needed to prepare for the deployment, including unit tests, load tests or other similar tests.

AppPreDeployTasks
  AppPreDeployTasksStarted
  AppPreDeployTasksSucceeded OR AppPreDeployTasksErrored

Pre-deployment evaluation phase

Pre-deployment evaluation can be used to assert the status of the cluster or of services the workload depends on, to assure it is deployed only if the specified prerequisites are met.

AppPreDeployEvaluations
  AppPreDeployEvaluationsStarted
  AppPreDeployEvaluationsSucceeded OR AppPreDeployEvaluationsErrored

Deployment phase

The AppDeploy phase basically covers the entire deployment and check phase of the workloads. The KeptnApp just observes whether all pre and post-deployment tasks/evaluation are successful and that the pods are deployed successfully. When all activities are successful, the KeptnApp issues the AppDeploySucceeded event and continues to the next phase. If any of these activities fail, the KeptnApp issues the AppDeployErrored event and terminates the deployment.

AppDeploy
  AppDeployStarted
  WorkloadPreDeployTasks
    WorkloadPreDeployTasksStarted
    WorkloadPreDeployTasksSucceeded OR WorkloadPreDeployTasksErrored 
  WorkloadPreDeployEvaluations
    WorkloadPreDeployEvaluationsStarted
    WorkloadPreDeployEvaluationsSucceeded OR WorkloadPreDeployErrored
  WorkloadDeploy
    WorkloadDeployStarted
    WorkloadDeploySucceeded OR WorkloadDeployErrored
  WorkloadPostDeployTasks
    WorkloadPostDeployTasksStarted
    WorkloadPostDeployTasksSucceeded OR WorkloadPostDeployTasksErrored 
  WorkloadPostDeployEvaluations
    WorkloadPostDeployEvaluationsStarted
    WorkloadPostDeployEvaluationsSucceeded OR WorkloadPostDeployEvaluationsErrored
  AppDeploySucceeded OR AppDeployErrored

Post-deployment phase

The post-deployment phase is typically used to run tests on the freshly deployed application, such as gathering performance data.

AppPostDeployTasks
  AppPostDeployTasksStarted
  AppPostDeployTasksSucceeded OR AppPostDeployTasksErrored

Post-deployment evaluation phase

The post-deployment evaluation can be used to analyze the cluster/application status after the new workload is deployed. The result of this phase does not revert or influence the deployment but can be used by other external tools, for instance, to react to a failure.

AppPostDeployEvaluations
  AppPostDeployEvaluationsStarted
  AppPostDeployEvaluationsSucceeded OR AppPostDeployEvaluationsErrored

Completed phase

Completed

Events that are not part of the deployment flow

Additional phases/states exist, such as those that describe what happens when something fails.

Whenever something in the system happens (we create a new resource, etc.) a Kubernetes event is generated. The following events are defined as part of Keptn but they are not part of the deployment flow. These include:

CreateEvaluation
ReconcileEvaluation
ReconcileTask
CreateTask
CreateApp
CreateAppVersion
CreateWorkload
CreateWorkloadVersion
Completed
Deprecated
WorkloadDeployReconcile
WorkloadDeployReconcileErrored