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Chapter 5. Routing traffic by using Argo Rollouts for OpenShift Service Mesh

Argo Rollouts in Red Hat OpenShift GitOps support various traffic management mechanisms such as OpenShift Routes and Istio-based OpenShift Service Mesh.

The choice for selecting a traffic manager to be used with Argo Rollouts depends on the existing traffic management solution that you are using to deploy cluster workloads. For example, Red Hat OpenShift Routes provides basic traffic management functionality and does not require the use of a sidecar container. However, Red Hat OpenShift Service Mesh provides more advanced routing capabilities by using Istio but does require the configuration of a sidecar container.

You can use OpenShift Service Mesh to split traffic between two application versions.

  • Canary version: A new version of an application where you gradually route the traffic.
  • Stable version: The current version of an application. After the canary version is stable and has all the user traffic directed to it, it becomes the new stable version. The previous stable version is discarded.

The Istio-support within Argo Rollouts uses the Gateway and VirtualService resources to handle traffic routing.

  • Gateway: You can use a Gateway to manage inbound and outbound traffic for your mesh. The gateway is the entry point of OpenShift Service Mesh and handles traffic requests sent to an application.
  • VirtualService: VirtualService defines traffic routing rules and the percentage of traffic that goes to underlying services, such as the stable and canary services.

Sample deployment scenario

For example, in a sample deployment scenario, 100% of the traffic is directed towards the stable version of the application during the initial instance. The application is running as expected, and no additional attempts are made to deploy a new version.

100% of traffic in the stable version of the application

However, after deploying a new version of the application, Argo Rollouts creates a new canary deployment based on the new version of the application and routes some percentage of traffic to that new version.

When you use Service Mesh, Argo Rollouts automatically modifies the VirtualService resource to control the traffic split percentage between the stable and canary application versions. In the following diagram, 20% of traffic is sent to the canary application version after the first promotion and then 80% is sent to the stable version by the stable service.

80% of traffic in the stable version and 20% in the canary version

5.1. Configuring Argo Rollouts to route traffic by using OpenShift Service Mesh

You can use OpenShift Service Mesh to configure Argo Rollouts by creating the following items:

  • A gateway
  • Two Kubernetes services: stable and canary, which point to the pods within each version of the services
  • A VirtualService
  • A rollout custom resource (CR)

In the following example procedure, the rollout routes 20% of traffic to a canary version of the application. After a manual promotion, the rollout routes 40% of traffic. After another manual promotion, the rollout performs multiple automated promotions until all traffic is routed to the new application version.

Prerequisites

Procedure

  1. Create a Gateway object to accept the inbound traffic for your mesh.

    1. Create a YAML file with the following snippet content.

      Example gateway called rollouts-demo-gateway

      apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: rollouts-demo-gateway 1
spec:
  selector:
    istio: ingressgateway 2
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - "*"

      1
      The name of the gateway.
      2
      Specifies the name of the ingress gateway. The gateway configures exposed ports and protocols but does not include any traffic routing configuration.

    2. Apply the YAML file by running the following command. 

      $ oc apply -f gateway.yaml

  2. Create the services for the canary and stable versions of the application.

    1. In the Administrator perspective of the web console, go to Networking Services.
    2. Click Create Service.

    3. On the Create Service page, click YAML view and add the following snippet. The following example creates a stable service called rollouts-demo-stable. Stable traffic is directed to this service. 

      apiVersion: v1
kind: Service
metadata:
  name: rollouts-demo-stable
spec:
  ports: 1
  - port: 80
    targetPort: http
    protocol: TCP
    name: http
  selector: 2
    app: rollouts-demo
      1
      Specifies the name of the port used by the application for running inside the container.
      2
      Ensure that the contents of the selector field are the same in stable service and Rollout CR.
    4. Click Create to create a stable service.

    5. On the Create Service page, click YAML view and add the following snippet. The following example creates a canary service called rollouts-demo-canary. Canary traffic is directed to this service. 

      apiVersion: v1
kind: Service
metadata:
  name: rollouts-demo-canary
spec:
  ports: 1
  - port: 80
    targetPort: http
    protocol: TCP
    name: http
  selector: 2
    app: rollouts-demo
      1
      Specifies the name of the port used by the application for running inside the container.
      2
      Ensure that the contents of the selector field are the same in canary service and Rollout CR.
    6. Click Create to create the canary service.

  3. Create a VirtualService to route incoming traffic to stable and canary services.

    1. Create a YAML file, and copy the following YAML into it. The following example creates a VirtualService called rollouts-demo-vsvc: 

      apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: rollouts-demo-vsvc
spec:
  gateways:
  - rollouts-demo-gateway 1
  hosts:
  - rollouts-demo-vsvc.local
  http:
  - name: primary
    route:
    - destination:
        host: rollouts-demo-stable 2
        port:
          number: 15372 3
      weight: 100
    - destination:
        host: rollouts-demo-canary 4
        port:
          number: 15372
      weight: 0
  tls: 5
  - match:
    - port: 3000
      sniHosts:
      - rollouts-demo-vsvc.local
    route:
    - destination:
        host: rollouts-demo-stable
      weight: 100
    - destination:
        host: rollouts-demo-canary
      weight: 0
      1
      The name of the gateway.
      2
      The name of the targeted stable service.
      3
      Specifies the port number used for listening to traffic.
      4
      The name of the targeted canary service.
      5
      Specifies the TLS configuration used to secure the VirtualService.

    2. Apply the YAML file by running the following command. 

      $ oc apply -f virtual-service.yaml

  4. Create the Rollout CR. In this example, Istio is used as a traffic manager.

    1. In the Administrator perspective of the web console, go to Operators Installed Operators Red Hat OpenShift GitOps Rollout.

    2. On the Create Rollout page, click YAML view and add the following snippet. The following example creates a Rollout CR called rollouts-demo: 

      apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: rollouts-demo
spec:
  replicas: 5
  strategy:
    canary:
      canaryService: rollouts-demo-canary 1
      stableService: rollouts-demo-stable 2
      trafficRouting:
        istio:
          virtualServices:
          - name: rollouts-demo-vsvc
            routes:
            - primary
      steps: 3
      - setWeight: 20
      - pause: {}
      - setWeight: 40
      - pause: {}
      - setWeight: 60
      - pause: {duration: 30}
      - setWeight: 80
      - pause: {duration: 60}
  revisionHistoryLimit: 2
  selector: 4
    matchLabels:
      app: rollouts-demo
  template:
    metadata:
      labels:
        app: rollouts-demo
        istio-injection: enabled
    spec:
      containers:
      - name: rollouts-demo
        image: argoproj/rollouts-demo:blue
        ports:
        - name: http
          containerPort: 8080
          protocol: TCP
        resources:
          requests:
            memory: 32Mi
            cpu: 5m
      1
      This value must match the name of the created canary Service.
      2
      This value must match the name of the created stable Service.
      3
      Specify the steps for the rollout. This example gradually routes 20%, 40%, 60%, and 100% of traffic to the canary version.
      4
      Ensure that the contents of the selector field are the same as in canary and stable service.
    3. Click Create.
    4. In the Rollout tab, under the Rollout section, verify that the Status field of the rollout shows Phase: Healthy.

  5. Verify that the route is directing 100% of the traffic towards the stable version of the application.

    1. Watch the progression of your rollout by running the following command: 

      $ oc argo rollouts get rollout rollouts-demo --watch -n <namespace> 1
      1
      Specify the namespace where the Rollout resource is defined.

      Example output

      Name:            rollouts-demo
Namespace:       argo-rollouts
Status:          ✔ Healthy
Strategy:        Canary
  Step:          8/8
  SetWeight:     100
  ActualWeight:  100
Images:          argoproj/rollouts-demo:blue (stable)
Replicas:
  Desired:       5
  Current:       5
  Updated:       5
  Ready:         5
  Available:     5

NAME                                       KIND        STATUS     AGE    INFO
⟳ rollouts-demo                            Rollout     ✔ Healthy  4m50s
└──# revision:1
   └──⧉ rollouts-demo-687d76d795           ReplicaSet  ✔ Healthy  4m50s  stable
      ├──□ rollouts-demo-687d76d795-75k57  Pod         ✔ Running  4m49s  ready:1/1
      ├──□ rollouts-demo-687d76d795-bv5zf  Pod         ✔ Running  4m49s  ready:1/1
      ├──□ rollouts-demo-687d76d795-jsxg8  Pod         ✔ Running  4m49s  ready:1/1
      ├──□ rollouts-demo-687d76d795-rsgtv  Pod         ✔ Running  4m49s  ready:1/1
      └──□ rollouts-demo-687d76d795-xrmrj  Pod         ✔ Running  4m49s  ready:1/1

      Note

      When the first instance of the Rollout resource is created, the rollout regulates the amount of traffic to be directed towards the stable and canary application versions. In the initial instance, the creation of the Rollout resource routes all of the traffic towards the stable version of the application and skips the part where the traffic is sent to the canary version.

    2. To verify that the service mesh sends 100% of the traffic for the stable service and 0% for the canary service, run the following command: 

      $ oc describe virtualservice/rollouts-demo-vsvc -n <namespace>

    3. View the following output displayed in the terminal: 

      route
- destination:
    host: rollouts-demo-stable
  weight: 100 1
- destination:
    host: rollouts-demo-canary
  weight: 0 2
      1
      A value of 100 means that 100% of traffic is directed to the stable version.
      2
      A value of 0 means that 0% of traffic is directed to the canary version.

  6. Simulate the new canary version of the application by modifying the container image deployed in the rollout.

    1. Modify the .spec.template.spec.containers.image value from argoproj/rollouts-demo:blue to argoproj/rollouts-demo:yellow, by running the following command. 

      $ oc argo rollouts set image rollouts-demo rollouts-demo=argoproj/rollouts-demo:yellow -n <namespace>

      As a result, the container image deployed in the rollout is modified and the rollout initiates a new canary deployment.

      Note

      As per the setWeight property defined in the .spec.strategy.canary.steps field of the Rollout resource, initially 20% of traffic to the route reaches the canary version and 80% of traffic is directed towards the stable version. The rollout is paused after 20% of traffic is directed to the canary version.

    2. Watch the progression of your rollout by running the following command. 

      $ oc argo rollouts get rollout rollouts-demo --watch -n <namespace> 1
      1
      Specify the namespace where the Rollout resource is defined.

      In the following example, 80% of traffic is routed to the stable service and 20% of traffic is routed to the canary service. The deployment is then paused indefinitely until you manually promote it to the next level.

      Example output

      Name:            rollouts-demo
Namespace:       argo-rollouts
Status:          ॥ Paused
Message:         CanaryPauseStep
Strategy:        Canary
  Step:          1/8
  SetWeight:     20
  ActualWeight:  20
Images:          argoproj/rollouts-demo:blue (stable)
                 argoproj/rollouts-demo:yellow (canary)
Replicas:
  Desired:       5
  Current:       6
  Updated:       1
  Ready:         6
  Available:     6

NAME                                       KIND        STATUS     AGE    INFO
⟳ rollouts-demo                            Rollout     ॥ Paused   6m51s
├──# revision:2
│  └──⧉ rollouts-demo-6cf78c66c5           ReplicaSet  ✔ Healthy  99s    canary
│     └──□ rollouts-demo-6cf78c66c5-zrgd4  Pod         ✔ Running  98s    ready:1/1
└──# revision:1
   └──⧉ rollouts-demo-687d76d795           ReplicaSet  ✔ Healthy  9m51s  stable
      ├──□ rollouts-demo-687d76d795-75k57  Pod         ✔ Running  9m50s  ready:1/1
      ├──□ rollouts-demo-687d76d795-jsxg8  Pod         ✔ Running  9m50s  ready:1/1
      ├──□ rollouts-demo-687d76d795-rsgtv  Pod         ✔ Running  9m50s  ready:1/1
      └──□ rollouts-demo-687d76d795-xrmrj  Pod         ✔ Running  9m50s  ready:1/1

      Example with 80% directed to the stable version and 20% of traffic directed to the canary version.

      route
- destination:
    host: rollouts-demo-stable
  weight: 80 1
- destination:
    host: rollouts-demo-canary
  weight: 20 2

      1
      A value of 80 means that 80% of traffic is directed to the stable version.
      2
      A value of 20 means that 20% of traffic is directed to the canary version.

  7. Manually promote the deployment to the next promotion step. 

    $ oc argo rollouts promote rollouts-demo -n <namespace> 1
    1
    Specify the namespace where the Rollout resource is defined.

    1. Watch the progression of your rollout by running the following command: 

      $ oc argo rollouts get rollout rollouts-demo --watch -n <namespace> 1
      1
      Specify the namespace where the Rollout resource is defined.

      In the following example, 60% of traffic is routed to the stable service and 40% of traffic is routed to the canary service. The deployment is then paused indefinitely until you manually promote it to the next level.

      Example output

      Name:            rollouts-demo
Namespace:       argo-rollouts
Status:          ॥ Paused
Message:         CanaryPauseStep
Strategy:        Canary
  Step:          3/8
  SetWeight:     40
  ActualWeight:  40
Images:          argoproj/rollouts-demo:blue (stable)
                 argoproj/rollouts-demo:yellow (canary)
Replicas:
  Desired:       5
  Current:       7
  Updated:       2
  Ready:         7
  Available:     7

NAME                                       KIND        STATUS     AGE    INFO
⟳ rollouts-demo                            Rollout     ॥ Paused   9m21s
├──# revision:2
│  └──⧉ rollouts-demo-6cf78c66c5           ReplicaSet  ✔ Healthy  99s    canary
│     └──□ rollouts-demo-6cf78c66c5-zrgd4  Pod         ✔ Running  98s    ready:1/1
└──# revision:1
   └──⧉ rollouts-demo-687d76d795           ReplicaSet  ✔ Healthy  9m51s  stable
      ├──□ rollouts-demo-687d76d795-75k57  Pod         ✔ Running  9m50s  ready:1/1
      ├──□ rollouts-demo-687d76d795-jsxg8  Pod         ✔ Running  9m50s  ready:1/1
      ├──□ rollouts-demo-687d76d795-rsgtv  Pod         ✔ Running  9m50s  ready:1/1
      └──□ rollouts-demo-687d76d795-xrmrj  Pod         ✔ Running  9m50s  ready:1/1

      Example of 60% traffic directed to the stable version and 40% directed to the canary version.

      route
- destination:
    host: rollouts-demo-stable
  weight: 60 1
- destination:
    host: rollouts-demo-canary
  weight: 40 2

      1
      A value of 60 means that 60% of traffic is directed to the stable version.
      2
      A value of 40 means that 40% of traffic is directed to the canary version.

  8. Increase the traffic weight in the canary version to 100% and discard the traffic in the previous stable version of the application by running the following command: 

    $ oc argo rollouts promote rollouts-demo -n <namespace> 1
    1
    Specify the namespace where the Rollout resource is defined.

    1. Watch the progression of your rollout by running the following command: 

      $ oc argo rollouts get rollout rollouts-demo --watch -n <namespace> 1
      1
      Specify the namespace where the Rollout resource is defined.

After successful completion, weight on the stable service is 100% and 0% on the canary service.

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