Redeploy/Restart an Application

A KeptnApp can fail because of an unsuccessful pre-deployment evaluation or pre-deployment task. For example, this happens if the target value of a KeptnEvaluationDefinition resource is misconfigured or a pre-deployment evaluation checks the wrong URL.

After you fix the configuration that caused the pre-deployment evaluation or task to fail, you can increment the spec.revision value and apply the updated KeptnApp manifest to create a new revision of the KeptnApp without modifying the version.

Afterwards, all related KeptnWorkloadVersions automatically refer to the newly created revision of the KeptnAppVersion to determine whether they are allowed to enter their respective deployment phases.

To illustrate this, consider the following example:

apiVersion: v1
kind: Namespace
metadata:
  name: restartable-apps
  annotations:
    keptn.sh/lifecycle-toolkit: "enabled"
---
apiVersion: lifecycle.keptn.sh/v1
kind: KeptnAppContext
metadata:
  name: podtato-head
  namespace: restartable-apps
spec:
  preDeploymentTasks:
    - pre-deployment-check
---
apiVersion: lifecycle.keptn.sh/v1
kind: KeptnTaskDefinition
metadata:
  name: pre-deployment-check
  namespace: restartable-apps
spec:
  deno:
    inline:
      code: |
        console.error("I failed")
        process.exit(1)
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: podtato-head-entry
  namespace: restartable-apps
  labels:
    app: podtato-head
spec:
  selector:
    matchLabels:
      component: podtato-head-entry
  template:
    metadata:
      labels:
        component: podtato-head-entry
        keptn.sh/workload: podtato-head-entry
        keptn.sh/app: podtato-head
        keptn.sh/version: "0.1.2"
    spec:
      terminationGracePeriodSeconds: 5
      containers:
        - name: server
          image: ghcr.io/podtato-head/entry:0.2.7
          imagePullPolicy: Always
          ports:
            - containerPort: 9000
          env:
            - name: PODTATO_PORT
              value: "9000"

Applying these resources causes a KeptnApp to be created. The KeptnApp contains all workloads that are part of the application, and a version number that is derived from the workloads:

apiVersion: lifecycle.keptn.sh/v1
kind: KeptnApp
metadata:
  name: podtato-head
  namespace: restartable-apps
  annotations:
    app.kubernetes.io/managed-by: "keptn"
spec:
  version: "0.1.2"
  revision: 1
  workloads:
    - name: podtato-head-entry
      version: "0.1.2"

Then, based on the KeptnApp and KeptnAppContext, a KeptnAppVersion is created automatically and the execution of the pre-deployment checks defined in the KeptnAppContext starts. In this example, the pre-deployment checks contain a task which clearly fails. Therefore, the KeptnAppVersion is not able to proceed with the deployment.

You can inspect the status of the created KeptnAppVersion:

$ kubectl get keptnappversions.lifecycle.keptn.sh -n restartable-apps
NAME                   APPNAME        VERSION   PHASE
podtato-head-0.1.2-ab1223js   podtato-head   0.1.1     AppPreDeployTasks

Notice that the KeptnAppVersion stays in the AppPreDeployTasks phase for a while, due to the pre-check trying to run until the failure threshold is reached. Eventually, the KeptnAppVersion's PredeploymentPhase is in a Failed state, with the remaining phases being Deprecated.

$ kubectl get keptnappversions.lifecycle.keptn.sh -n restartable-apps -owide
NAME                          APPNAME        VERSION   PHASE               PREDEPLOYMENTSTATUS   PREDEPLOYMENTEVALUATIONSTATUS   WORKLOADOVERALLSTATUS   POSTDEPLOYMENTSTATUS   POSTDEPLOYMENTEVALUATIONSTATUS
podtato-head-0.1.2-ab1223js   podtato-head   0.1.2     AppPreDeployTasks   Failed                Deprecated                      Deprecated              Deprecated             Deprecated

To fix the deployment of this application, we first need to fix the task that has failed earlier. To do so, edit the pre-deployment-check KeptnTaskDefinition:

kubectl -n restartable-apps edit keptntaskdefinitions.lifecycle.keptn.sh pre-deployment-check

Modify the manifest to look like this:

apiVersion: lifecycle.keptn.sh/v1
kind: KeptnTaskDefinition
metadata:
  name: pre-deployment-check
  namespace: restartable-apps
spec:
  deno:
    inline:
      code: |
        console.error("Success")

To restart the deployment of our KeptnApplication, edit the manifest:

kubectl -n restartable-apps edit keptnapps.lifecycle.keptn.sh podtato-head

Increment the value of the spec.revision field by one:

apiVersion: lifecycle.keptn.sh/v1
kind: KeptnApp
metadata:
  name: podtato-head
  namespace: restartable-apps
spec:
  version: "0.1.2"
  revision: 2 # Increased this value from 1 to 2
  workloads:
    - name: podtato-head-entry
      version: "0.1.2"

After those changes have been made, you will notice a new revision of the podtato-head KeptnAppVersion:

$ kubectl get keptnappversions.lifecycle.keptn.sh -n restartable-apps       
NAME                          APPNAME        VERSION   PHASE
podtato-head-0.1.2-ab1223js   podtato-head   0.1.2     AppPreDeployTasks
podtato-head-0.1.2-xbhj9073   podtato-head   0.1.2     AppDeploy

See that the newly created revision podtato-head-0.1.2-xbhj9073 has made it beyond the pre-deployment check phase and has reached its AppDeployPhase.

You can also verify the execution of the pre-deployment-check by retrieving the list of KeptnTasks in the restartable-apps namespace:

$ kubectl get keptntasks.lifecycle.keptn.sh -n restartable-apps
NAME                             APPNAME        APPVERSION   WORKLOADNAME   WORKLOADVERSION   JOB NAME                              STATUS
pre-pre-deployment-check-49827   podtato-head   0.1.2                                         klc-pre-pre-deployment-check--77601   Failed
pre-pre-deployment-check-65056   podtato-head   0.1.2                                         klc-pre-pre-deployment-check--57313   Succeeded

Notice that the previous failed instances are still available for both KeptnAppVersions and KeptnTasks. This may be useful historical data to keep track of what went wrong during earlier deployment attempts.

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