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kubevela/docs/en/application.md
Jianbo Sun ce20f55382 add an overview for end user guide (#1469)
* add an overview for end user guide

end user guide

* add explore section

* finish scale section

* add expose section

* remove trait already contains as built-in feature

* try fix flaky test
2021-04-14 21:38:04 +08:00

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---
title: Deploy Application
---
This documentation will walk through a full application deployment workflow on KubeVela platform.
## Introduction
KubeVela is a fully self-service platform. All capabilities an application deployment needs are maintained as building block modules in this platform. Specifically:
- Components - deployable/provisionable entities that composed your application deployment
- e.g. a Kubernetes workload, a MySQL database, or a AWS OSS bucket
- Traits - attachable operational features per your needs
- e.g. autoscaling rules, rollout strategies, ingress rules, sidecars, security policies etc
## Step 1: Check Capabilities in the Platform
As user of this platform, you could check available components you can deploy, and available traits you can attach.
```console
$ kubectl get componentdefinitions -n vela-system
NAME WORKLOAD-KIND DESCRIPTION AGE
task Job Describes jobs that run code or a script to completion. 5h52m
webservice Deployment Describes long-running, scalable, containerized services that have a stable network endpoint to receive external network traffic from customers. 5h52m
worker Deployment Describes long-running, scalable, containerized services that running at backend. They do NOT have network endpoint to receive external network traffic. 5h52m
```
```console
$ kubectl get traitdefinitions -n vela-system
NAME APPLIES-TO DESCRIPTION AGE
ingress ["webservice","worker"] Configures K8s ingress and service to enable web traffic for your service. Please use route trait in cap center for advanced usage. 6h8m
cpuscaler ["webservice","worker"] Configure k8s HPA with CPU metrics for Deployment 6h8m
```
To show the specification for given capability, you could use `vela` CLI. For example, `vela show webservice` will return full schema of *Web Service* component and `vela show webservice --web` will open its capability reference documentation in your browser.
## Step 2: Design and Deploy Application
In KubeVela, `Application` is the main API to define your application deployment based on available capabilities. Every `Application` could contain multiple components, each of them can be attached with a number of traits per needs.
Now let's define an application composed by *Web Service* and *Worker* components.
```yaml
# sample.yaml
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
name: website
spec:
components:
- name: frontend
type: webservice
properties:
image: nginx
traits:
- type: cpuscaler
properties:
min: 1
max: 10
cpuPercent: 60
- type: sidecar
properties:
name: "sidecar-test"
image: "fluentd"
- name: backend
type: worker
properties:
image: busybox
cmd:
- sleep
- '1000'
```
In this sample, we also attached `sidecar` and `cpuscaler` traits to the `frontend` component.
So after deployed, the `frontend` component instance (a Kubernetes Deployment workload) will be automatically injected
with a `fluentd` sidecar and automatically scale from 1-10 replicas based on CPU usage.
### Deploy the Application
Apply application YAML to Kubernetes:
```shell
$ kubectl apply -f https://raw.githubusercontent.com/oam-dev/kubevela/master/docs/examples/enduser/sample.yaml
application.core.oam.dev/website created
```
You'll get the application becomes `running`.
```shell
$ kubectl get application website -o yaml
apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
name: website
....
status:
components:
- apiVersion: core.oam.dev/v1alpha2
kind: Component
name: backend
- apiVersion: core.oam.dev/v1alpha2
kind: Component
name: frontend
....
status: running
```
### Verify the Deployment
You could see a Deployment named `frontend` is running, with port exposed, and with a container `fluentd` injected.
```shell
$ kubectl get deploy frontend
NAME READY UP-TO-DATE AVAILABLE AGE
frontend 1/1 1 1 97s
```
```shell
$ kubectl get deploy frontend -o yaml
...
spec:
containers:
- image: nginx
imagePullPolicy: Always
name: frontend
ports:
- containerPort: 80
protocol: TCP
- image: fluentd
imagePullPolicy: Always
name: sidecar-test
...
```
Another Deployment is also running named `backend`.
```shell
$ kubectl get deploy backend
NAME READY UP-TO-DATE AVAILABLE AGE
backend 1/1 1 1 111s
```
An HPA was also created by the `cpuscaler` trait.
```shell
$ kubectl get HorizontalPodAutoscaler frontend
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
frontend Deployment/frontend <unknown>/50% 1 10 1 101m
```