Merge pull request #392 from oam-dev/rollout-design

rollout trait high level design

documentation/samples/rollout-demo/README.md

@@ -82,11 +82,11 @@ Events:
    Normal  Synced  1s     flagger  Promotion completed! Scaling down rollout-demo-app.default
 ```
 
-## Verify that the prdeployment is upgraded, but the primary is not yet
+## Verify that the primary deployment is upgraded too
 ```shell script
 kubectl get deploy rollout-demo-app -o=jsonpath="{.spec.template.spec.containers[0].image}"
 luxas/autoscale-demo:v0.1.1
 
 kubectl get deploy rollout-demo-app-primary -o=jsonpath="{.spec.template.spec.containers[0].image}"
-luxas/autoscale-demo:v0.1.0
+luxas/autoscale-demo:v0.1.1
 ```

documentation/samples/rollout-demo/RolloutTraitDesign.md

@@ -0,0 +1,43 @@
+# Rollout Trait Design  
+
+## Current design
+The problem with the current flagger design is that it wants to be strictly GitOps compatible. Thus, it 
+cannot touch the image related fields in the "target" object. That's why it has to create a "primary" deployment
+and treat the "target" as the "canary" while doing the rollout. It finally "promotes" the primary 
+by copying everything from the "canary" to the "primary" after it 's done.
+
+We don't need to stick to that scheme, but we face a similar problem as our component/workload controller
+will constantly reconcile the target component too. 
+1. One way is to pin the component to a specific revision in the application configuration. The user then can modify 
+the component and that can be automatically picked up by the rollout trait. The draw-back of this approach is that
+the upgrade will end up with the workload with the latest version not the workload in the applcation configuration. 
+2. Another way is to not allow the component to specify the "replicas" by the user. In this way, a user can modify
+the container related fields which leads to a new workload of size 0 created. The rollout trait 
+can pick up the "last" revision of the component and its corresponding workload as the source. The nice part of this 
+approach is the new component will be the canary, thus keeping it under the application controller's control
+and ready to be upgraded again.
+
+We decide to take the second approach as it matches with the flow better.
+
+## Proposed design
+- Add a new "meshProvider" type "OAM", the scheduler will automatically set the meshProvider as the "routeTrait" implementation
+which is SMI for now.
+- OAM can fill the workloadRef to the `targetRef` automatically. This will point the trait to the workload 
+which has its "componentRevisionName" in its label.
+- Write an OAM flagger resource controller that works with the podSpecWorkload/containerizedWorkload/Deployment
+    - Find the last live component revision as the canary if the user didn't explicitly spell out the revisionName
+    - We need to use the workload itself as the canary, and the "source" as the primary   
+    - The Initialize function will be no-op
+    - The controller will adjust the replica size between the canary and the primary if there is HPA associated with the workload
+    - The Promote function will simply reduce the primary (source) replicas zero and bump the canary (target)  
+- It seems that we don't need an OAM specific router (even if the service/routing name is a bit mis-matched) 
+- Remove all the hard coded string literal "primary" from the scheduler.go file
+
+## What is not covered
+- This design does not cover the case that HPA is involved. This requires some changes at the OAM 
+runtime to keep the HPA trait on the old workload.
+- We need a way to translate the status of the flagger trait status back to the rollout output if we 
+don't plan to introduce a rollout CRD.
+- The rollout experience needs to be combined with the metris/route/autoscaler traits together to have
+a merely complete CD experience. The very basic case is for the canary to emit Prometheus metrics. The rollout
+trait needs to setup metrics checkers and threatholds to move to the next stages. 

documentation/samples/rollout-demo/deploy-component.yaml

@@ -23,7 +23,7 @@ spec:
             # pod-template-hash: 7564juhy8m6n785i
         spec:
           containers:
-            - image: luxas/autoscale-demo:v0.1.1
+            - image: openshift/deployment-example:v1
               name: metrics-provider
               ports:
                 - name: http

e2e/commonContext.go

@@ -73,7 +73,7 @@ var (
 
 	DeleteEnvFunc = func(context string, envName string) bool {
 		return ginkgo.Context(context, func() {
-			ginkgo.It("should print environment initiation successful message", func() {
+			ginkgo.It("should print env does not exist message", func() {
 				cli := fmt.Sprintf("vela env delete %s", envName)
 				_, err := Exec(cli)
 				gomega.Expect(err).NotTo(gomega.HaveOccurred())