Nginx Blue/Green Deployment

A comprehensive guide on Kurator’s Blue/Green Deployment uses Nginx as ingress, providing an overview and quick start guide.

Prerequisites

In the subsequent sections, we’ll guide you through a hands-on demonstration.

These are some of the prerequisites needed to use Kurator Rollout:

Kubernetes Clusters

Kubernetes v1.27.3 or higher is supported.

You can use Kind to create clusters as needed. It is recommended to use Kurator’s scripts to create multi-clusters environment.

Notes: You can find the mapping between Kind node image versions and Kubernetes versions on Kind Release. Additionally, the website provides a lookup table showing compatible Kind and node image versions.

Nginx

When Nginx is specified in fleet’s rollout.trafficRoutingProvider , Kurator will install Nginx and its supporting Prometheus via helm in the fleet-managed clusters.

You can review the results a few minutes after applying fleet:

kubectl get po -n ingress-nginx --kubeconfig=/root/.kube/kurator-member1.config
NAME                                                              READY   STATUS    RESTARTS   AGE
ingress-nginx-flagger-kurator-member-7fbdfb7f7-hphc2              1/1     Running   0          5m44s
ingress-nginx-flagger-kurator-member-prometheus-56bdbf4855l4jkx   1/1     Running   0          5m44s
ingress-nginx-nginx-kurator-member-controller-6566b7886-b7g8f     1/1     Running   0          5m33s
ingress-nginx-testloader-kurator-member-loadtester-7ff7d75l2dwj   1/1     Running   0          5m51s

Kurator Rollout Plugin

Before delving into the how to Perform a Unified Rollout, ensure you have successfully installed the Rollout plugin as outlined in the Rollout plugin installation guide.

How to Perform a Unified Rollout

Configuring the Rollout Policy

You can deploy a blue-green application demo using Nginx by the following command:

kubectl apply -f examples/rollout/blue_greenNginx.yaml

Here is the configuration:

apiVersion: apps.kurator.dev/v1alpha1
kind: Application
metadata:
  name: blue-green-nginx-demo
  namespace: default
spec:
  source:
    gitRepository:
      interval: 3m0s
      ref:
        branch: master
      timeout: 1m0s
      url: https://github.com/stefanprodan/podinfo
  syncPolicies:
    - destination:
        fleet: quickstart
      kustomization:
        interval: 0s
        path: ./deploy/webapp
        prune: true
        timeout: 2m0s
      rollout:
        testLoader: true
        trafficRoutingProvider: nginx
        workload:
          apiVersion: apps/v1
          name: backend
          kind: Deployment
          namespace: webapp
        serviceName: backend
        port: 9898
        rolloutPolicy:
          trafficRouting:
            analysisTimes: 3
            timeoutSeconds: 60
            host: "app.example.com"
          trafficAnalysis:
            checkIntervalSeconds: 90
            checkFailedTimes: 2
            metrics:
              - name: nginx-request-success-rate
                intervalSeconds: 90
                thresholdRange:
                  min: 99
                customMetric:
                  provider:
                    type: prometheus
                    address: http://ingress-nginx-flagger-kurator-member-prometheus.ingress-nginx:9090
                  query: |
                    sum(
                      rate(
                        http_requests_total{
                          status!~"5.*"
                        }[{{ interval }}]
                      )
                    )
                    /
                    sum(
                      rate(
                        http_requests_total[{{ interval }}]
                      )
                    ) * 100                    
            webhooks:
              timeoutSeconds: 60
              command:
                - "hey -z 1m -q 10 -c 2 http://app.example.com/"
          rolloutTimeoutSeconds: 600
    - destination:
        fleet: quickstart
      kustomization:
        targetNamespace: default
        interval: 5m0s
        path: ./kustomize
        prune: true
        timeout: 2m0s

Notes: There is a problem with the metric provided by the current flagger, so customMetric is used.Here is the detailed API.

To use Nginx, you need to provide the host it uses. Kurator will generate an ingress resource based on this field. Here is the specific configuration generated.

Given the output provided, let’s dive deeper to understand the various elements and their implications:

  • Kurator allows customizing Rollout strategies under the Spec.syncPolicies.rollout section for services deployed via kustomization. It will establish and implement Blue/Green Deployment for these services according to the configuration defined here.
  • The workload defines the target resource for the Blue/Green Deployment. The kind specifies the resource type, which can be either deployment or daemonset.
  • The serviceName and port specify the name of the service for the workload as well as the exposed port number.
  • The trafficAnalysis section defines the configuration for evaluating a new release version’s health and readiness during a rollout process.
    • The checkFailedTimes parameter specifies the maximum number of failed check results allowed throughout the Blue/Green Deployment lifecycle.
    • checkIntervalSeconds denotes the time interval between consecutive health evaluation checks.
    • The metrics identify the metrics that will be monitored to determine the deployment’s health status. You can choose between the two built-in metric types request-success-rate and request-duration or write your own metric
    • The webhooks provide an extensibility mechanism for the analysis procedures. In this configuration, webhooks communicate with the testloader to generate test traffic for the healthchecks.
  • The trafficRouting configuration specifies how traffic will be shifted to the Blue/Green Deployment during the rollout process.
    • The analysisTimes signifies the number of testing iterations that will be conducted.
  • The rolloutStatus section displays the actual processing status of rollout within the fleet.

About a minute after submitting this configuration, you can check the rollout status by running the following command:

kubectl get canary -n webapp --kubeconfig=/root/.kube/kurator-member1.config

NAME      STATUS        WEIGHT   LASTTRANSITIONTIME
backend   Initialized   0        2024-01-13T07:48:10Z

If the status shows as Initialized, it means the initialization of rollout process has completed successfully.

Notes: In the above configuration, we set the kustomization.interval to 0s. This disables Fluxcd’s periodic synchronization of configurations between the local mirror and cluster. The reason is that Flagger needs to modify the replica counts in Deployments to complete its initialization process. If you are uncertain whether the replicas for all applications in your deployments are set to zero, it is recommended to also set kustomization.interval to 0s.

Trigger Rollout

Automated Rollout

A Blue/Green Deployment can be triggered by either updating the container image referenced in the git repository configuration, or directly updating the image of the deployment resource locally in the Kubernetes cluster.

Review the results:

kubectl get canary -n webapp -w --kubeconfig=/root/.kube/kurator-member1.config

NAME      STATUS        WEIGHT   LASTTRANSITIONTIME
backend   Initialized   0        2024-01-16T08:53:40Z
backend   Progressing   0        2024-01-16T08:55:10Z
backend   Progressing   0        2024-01-16T08:56:40Z
backend   Progressing   0        2024-01-16T08:58:10Z
backend   Progressing   0        2024-01-16T08:59:40Z
backend   Progressing   0        2024-01-16T09:01:10Z
backend   Promoting     0        2024-01-16T09:02:40Z
backend   Finalising    0        2024-01-16T09:04:10Z
backend   Succeeded     0        2024-01-16T09:05:40Z
  • As shown in the diagram, after triggering a Blue/Green Deployment, the Kurator Rollout Plugin will first create pod(s) for the new version.
  • The new version will then undergo multiple test iterations. During this testing period, all incoming requests will be routed to the new version. Various testing metrics will be evaluated to determine the health and stability of the new release.
  • Upon validating the new version through testing and confirming it is ready for release, Kurator will proceed to replace the old version with the new version across the entire cluster. And redirect all incoming traffic to the primary pod.
  • It will then remove the canary pod, completing the rollout process.
kubectl get application blue-green-nginx-demo -oyaml

rolloutStatus:
      backupNameInCluster: backend
      backupStatusInCluster:
        canaryWeight: 0
        conditions:
        - lastTransitionTime: "2024-01-16T09:05:40Z"
          lastUpdateTime: "2024-01-16T09:05:40Z"
          message: Canary analysis completed successfully, promotion finished.
          reason: Succeeded
          status: "True"
          type: Promoted
        failedChecks: 1
        iterations: 0
        lastAppliedSpec: 7b779dcc48
        lastPromotedSpec: 7b779dcc48
        lastTransitionTime: "2024-01-16T09:05:40Z"
        phase: Succeeded
        trackedConfigs: {}
      clusterName: kurator-member1

A Blue/Green Deployment is triggered by changes in any of the following objects:

  • Deployment PodSpec (container image, command, ports, env, resources, etc)
  • ConfigMaps mounted as volumes or mapped to environment variables
  • Secrets mounted as volumes or mapped to environment variables

Notes: If you apply new changes to the deployment during the analysis, Kurator Rollout will restart the analysis.

Automated Rollback

If the new version fails testing during the blue/green deployment, Kurator will automatically roll back to the previous version to ensure continuous service operations.

During the analysis you can generate HTTP 500 errors and high latency to test Kurator’s rollback.

Exec into the testlaoder pod to generate HTTP 500 errors and Generate latency.

kubectl -n webapp exec -it backend-testloader-5f7bcd85bb-6bgdd sh

watch curl http://backend-canary.webapp:9898/status/500

watch curl http://backend-canary.webapp:9898/delay/1

Review the results:

kubectl get canary -n webapp -w --kubeconfig=/root/.kube/kurator-member1.config

NAME      STATUS        WEIGHT   LASTTRANSITIONTIME
backend   Initialized   0        2024-01-13T08:06:10Z
backend   Progressing   0        2024-01-13T08:10:40Z
backend   Progressing   0        2024-01-13T08:12:10Z
backend   Progressing   0        2024-01-13T08:13:40Z
backend   Progressing   0        2024-01-13T08:15:10Z
backend   Failed        0        2024-01-13T08:16:40Z
backend   Failed        0        2024-01-13T08:18:10Z
  • As shown in the diagram, after triggering a Blue/Green Deployment, the Kurator Rollout Plugin will first create pod(s) for the new version.
  • During the testing period, all traffic will be incrementally routed to the Green version. A variety of testing metrics will be collected from this live environment validation.
  • If the number of errors or failures encountered during testing exceeds the checkFailedTimes, all traffic will automatically be rerouted back to the original stable version.
  • It will then remove the canary pod, completing the rollback process.
kubectl get application blue-green-nginx-demo -oyaml

rolloutStatus:
      backupNameInCluster: backend
      backupStatusInCluster:
        canaryWeight: 0
        conditions:
        - lastTransitionTime: "2024-01-13T08:16:40Z"
          lastUpdateTime: "2024-01-13T08:16:40Z"
          message: Canary analysis failed, Deployment scaled to zero.
          reason: Failed
          status: "False"
          type: Promoted
        failedChecks: 0
        iterations: 0
        lastAppliedSpec: 79d699c99
        lastPromotedSpec: 7b779dcc48
        lastTransitionTime: "2024-01-13T08:40:40Z"
        phase: Failed
        trackedConfigs: {}
      clusterName: kurator-member1

Cleanup

1.Cleanup the Rollout Policy

If you only need to remove the Rollout Policy, simply edit the current application and remove the corresponding description:

kubectl edit application blue-green-nginx-demo

To check the results of the deletion, you can observe that the rollout-related pods have been removed:

kubectl get po -A --kubeconfig=/root/.kube/kurator-member1.config
kubectl get po -A --kubeconfig=/root/.kube/kurator-member2.config

If you want to configure a Blue/Green Deployment for it again, you can simply edit the application and add the necessary configurations.

2.Cleanup the Application

When the application is delete, all associated resources will also be removed:

kubectl delete application blue-green-nginx-demo