simplerollouttrait

README

Simple Rollout Trait

Simple-rollout trait is used to enable rollout capabilities for workloads.

More details refer to OAM Component mutable and versioning mechanism and the implementation

Support workloads

• ContainerizedWorkload
• Deployment

CR fields specification

Field	Type	Required	Description
batch	int	YES	Number of (new workload's) pods to be created each round during rollout
maxUnavailable	int	YES	Number of (old workload's) pods to be terminated each round during rollout.
replicas	int	YES	Final number of pods after rollout.

Prerequisites

Please follow common prerequisites to setup OAM runtime.

• Kubernetes v1.16+
• Helm 3
• Crossplane v0.11+ installed
• OAM controllers installed

Get started

• Clone the project into your $GOPATH

git clone https://github.com/oam-dev/catalog.git

• Load the CRD

cd catalog/traits/simplerollouttrait
make install

• Run the controller locally

go run main.go

• Apply the sample Component and ApplicationConfiguration

Two samples are prepared, based on Deployment and ContainerizedWorkload workload respectively.

cd ./config/samples/sample_containerizedworkload_workload

kubectl apply -f ./sample_component.yaml
kubectl apply -f ./sample_application_config.yaml

Verify Rollout

• Tips: Before launch rollout, you can run below commands in 3 windows to observe resouces changing during rollout.

watch -n 1 kubectl get pods

watch -n 1 kubectl get ContainerizedWorkload

watch -n 1 kubectl get deployments

• Check SimpleRollouTrait config in ApplicationConfiguration

cat sample_application_config.yaml

...
        - trait:
            apiVersion: extend.oam.dev/v1alpha2
            kind: SimpleRolloutTrait
            metadata:
              name:  example-rollout-trait
            spec:
              replica: 6
              maxUnavailable: 2
              batch: 2
...

• Update Component to rollout a new ContainerizedWorkload instance

Apply updated component then rollout starts

kubecl apply -f ./sample_component_changed.yaml

• Observe rollout progress

We can observe what happens during rollout through the changing of deployments.

watch -n 1 kubectl get deployments

## before rollout
NAME                                     READY   UP-TO-DATE   AVAILABLE   AGE
example-component-broccsh8d3b6gcr0951g   6/6     6            6           95s

## in the middle of rollout
NAME                                     READY   UP-TO-DATE   AVAILABLE   AGE
example-component-broccsh8d3b6gcr0951g   2/2     2            2           2m28s
example-component-brocg3p8d3b6gcr09520   1/3     3            1           8s

## rollout finished
NAME                                     READY   UP-TO-DATE   AVAILABLE   AGE
example-component-brocg3p8d3b6gcr09520   6/6     6            6           89s

When example-component has been updated, corresponding new workload instance, ContainerizedWorkload, is created immediately. As child resource of ContainerizedWorkload, new deployment will be launched and old deployment will be garbage collected simultaneously. Namely, there are two workload instances refering to one component at the same time.

Specifically, SimpleRolloutTrait will scale up new deployment and scale down old deployment gradually, along with the scaling span indicated by two parameters, maxUnavailable and batch. When old deployment is scaled down to zero and the new one comes into desired state, SimpleRolloutTrait will delete the old workload instance. The component instance and its child resouces enter a new state after rollout finally.