# Kube Startup CPU Boost is a controller that increases CPU resource requests and limits during Kubernetes workload startup time


# Kube Startup CPU Boost

Kube Startup CPU Boost is a controller that increases CPU resource requests and limits during Kubernetes workload startup time. Once the workload is up and running, the resources are set back to their original values.

## Description

The primary use cases for Kube Startup CPU Boosts are workloads that require extra CPU resources during startup phase - typically JVM based applications.

The Kube Startup CPU Boost leverages [In-place Resource Resize for Kubernetes Pods](https://kubernetes.io/blog/2023/05/12/in-place-pod-resize-alpha/) feature introduced in Kubernetes 1.27. It allows to revert workload's CPU resource requests and limits back to their original values without the need to recreate the Pods.

The increase of resources is achieved by Mutating Admission Webhook. By default, the webhook also removes CPU resource limits if present. The original resource values are set by operator after given period of time or when the POD condition is met.

## Installation

**Requires Kubernetes 1.27 on newer with** `InPlacePodVerticalScaling` feature gate enabled.

To install the latest release of Kube Startup CPU Boost in your cluster, run the following command:

```basic
kubectl apply -f https://github.com/google/kube-startup-cpu-boost/releases/download/v0.10.0/manifests.yaml
```

The Kube Startup CPU Boost components run in `kube-startup-cpu-boost-system` namespace.

### Install with Kustomize

You can use [Kustomize](https://github.com/kubernetes-sigs/kustomize) to install the Kube Startup CPU Boost with your own kustomization file.

```basic
cat <<EOF > kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- https://github.com/google/kube-startup-cpu-boost?ref=v0.10.0
EOF
kubectl kustomize | kubectl apply -f -
```

### Installation on Kind cluster

You can use [KIND](https://github.com/kubernetes-sigs/kind) to get a local cluster for testing.

```basic
cat <<EOF > kind-poc-cluster.yaml
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
name: poc
nodes:
- role: control-plane
- role: worker
- role: worker
featureGates:
  InPlacePodVerticalScaling: true 
EOF
kind create cluster --config kind-poc-cluster.yaml
```

### Installation on GKE cluster

You can use [GKE Alpha cluster](https://cloud.google.com/kubernetes-engine/docs/concepts/alpha-clusters) to run against the remote cluster.

```basic
gcloud container clusters create poc \
    --enable-kubernetes-alpha \
    --no-enable-autorepair \
    --no-enable-autoupgrade \
    --region europe-central2
```

## Usage

1. Create `StartupCPUBoost` object in your workload's namespace
    
    ```basic
    apiVersion: autoscaling.x-k8s.io/v1alpha1
    kind: StartupCPUBoost
    metadata:
      name: boost-001
      namespace: demo
    selector:
      matchExpressions:
      - key: app.kubernetes.io/name
        operator: In
        values: ["spring-demo-app"]
    spec:
      resourcePolicy:
        containerPolicies:
        - containerName: spring-demo-app
          percentageIncrease:
            value: 50
      durationPolicy:
        podCondition:
          type: Ready
          status: "True"
    ```
    
    The above example will boost CPU requests and limits of a container `spring-demo-app` in a PODs with `app.kubernetes.io/name=spring-demo-app` label in `demo` namespace. The resources will be increased by 50% until the [POD Condition](https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#pod-conditions) `Ready` becomes `True`.
    
2. Schedule your workloads and observe the results
    

## Features

### \[Boost target\] POD label selector

Define the PODs that will be subject for resource boost with a label selector.

```basic
spec:
  selector:
    matchExpressions:
    - key: app.kubernetes.io/name
       operator: In
       values: ["spring-rest-jpa"]
```

### \[Boost resources\] percentage increase

Define the percentage increase for a target container(s). The CPU requests and limits of selected container(s) will be increase by the given percentage value.

```basic
spec:
  containerPolicies:
   - containerName: spring-rest-jpa
     percentageIncrease:
       value: 50
```

### \[Boost resources\] fixed target

Define the fixed resources for a target container(s). The CPU requests and limits of selected container(s) will be set to the given values. Note that specified requests and limits have to be higher than the ones in the container.

```basic
spec:
  containerPolicies:
   - containerName: spring-rest-jpa
     fixedResources:
       requests: "1"
       limits: "2"
```

### \[Boost duration\] fixed time

Define the fixed amount of time, the resource boost effect will last for it since the POD creation.

```basic
spec:
 durationPolicy:
  fixedDuration:
    unit: Seconds
    value: 60
```

### \[Boost duration\] POD condition

Define the POD condition, the resource boost effect will last until the condition is met.

```basic
spec:
 durationPolicy:
   podCondition:
     type: Ready
     status: "True" 
```

## Configuration

Kube Startup CPU Boost operator can be configured with environmental variables.

| Variable | Type | Default | Description |
| --- | --- | --- | --- |
| `POD_NAMESPACE` | `string` | `kube-startup-cpu-boost-system` | Kube Startup CPU Boost operator namespace |
| `MGR_CHECK_INTERVAL` | `int` | `5` | Duration in seconds between boost manager checks for time based boost duration policy |
| `LEADER_ELECTION` | `bool` | `false` | Enables leader election for controller manager |
| `METRICS_PROBE_BIND_ADDR` | `string` | `:8080` | Address the metrics endpoint binds to |
| `HEALTH_PROBE_BIND_ADDR` | `string` | `:8081` | Address the health probe endpoint binds to |
| `SECURE_METRICS` | `bool` | `false` | Determines if the metrics endpoint is served securely |
| `ZAP_LOG_LEVEL` | `int` | `0` | Log level for ZAP logger |
| `ZAP_DEVELOPMENT` | `bool` | `false` | Enables development mode for ZAP logger |
| `HTTP2` | `bool` | `false` | Determines if the HTTP/2 protocol is used for webhook and metrics servers |
| `REMOVE_LIMITS` | `bool` | `true` | Enables operator to remove container CPU limits during the boost time |