使用Draft简化容器应用的开发流程

Draft是微软Deis团队开源(见Azure/draft)的容器应用开发辅助工具,它可以帮助开发人员简化容器应用程序的开发流程。

Draft主要由三个命令组成

  • draft init:初始化docker registry账号,并在Kubernetes集群中部署draftd(负责镜像构建、将镜像推送到docker registry以及部署应用等)
  • draft create:draft根据packs检测应用的开发语言,并自动生成Dockerfile和Kubernetes Helm Charts
  • draft up:根据Dockfile构建镜像,并使用Helm将应用部署到Kubernetes集群(支持本地或远端集群)。同时,还会在本地启动一个draft client,监控代码变化,并将更新过的代码推送给draftd。

Draft安装

由于Draft需要构建镜像并部署应用到Kubernetes集群,因而在安装Draft之前需要

  • 部署一个Kubernetes集群,部署方法可以参考kubernetes部署方法(注意minikube的支持还有问题,暂时不要使用)
  • 安装并初始化helm(需要v2.4.x版本,并且不要忘记运行helm init),具体步骤可以参考helm使用方法
  • 注册docker registry账号,比如Docker HubQuay.io
  • 配置Ingress Controller并在DNS中设置通配符域*的A记录(如*.http://draft.example.com)到Ingress IP地址。最简单的Ingress Controller创建方式是使用helm:
# 部署nginx ingress controller
$ helm install stable/nginx-ingress --namespace=kube-system --name=nginx-ingress
# 等待ingress controller配置完成,并记下外网IP
$ kubectl --namespace kube-system get services -w nginx-ingress-nginx-ingress-controller

初始化好Kubernetes集群和Helm后,可以在这里下载draft二进制文件,并配置draft

# 注意修改用户名、密码和邮件
$ token=$(echo '{"username":"feisky","password":"secret","email":"feisky@email.com"}' | base64)
# 注意修改registry.org和basedomain
$ draft init --set registry.url=docker.io,registry.org=feisky,registry.authtoken=${token},basedomain=app.feisky.xyz

Draft入门

draft源码中提供了很多应用的示例,我们来看一下怎么用draft来简化python应用的开发流程。

$ git clone [Azure/draft](https://github.com/Azure/draft.git)
$ cd draft/examples/python
$ ls
app.py           requirements.txt

$ cat requirements.txt
flask
$ cat app.py
from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return "Hello, World!\n"

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8080)

Draft create生成Dockerfile和chart

$ draft create
--> Python app detected
--> Ready to sail
$ ls
Dockerfile       app.py           chart            draft.toml       requirements.txt
$ cat Dockerfile
FROM python:onbuild
EXPOSE 8080
ENTRYPOINT ["python"]
CMD ["app.py"]
$ cat draft.toml
[environments]
  [environments.development]
    name = "virulent-sheep"
    namespace = "default"
    watch = true
    watch_delay = 2

Draft Up构建镜像并部署应用

$ draft up
--> Building Dockerfile
Step 1 : FROM python:onbuild
onbuild: Pulling from library/python
10a267c67f42: Pulling fs layer
....
Digest: sha256:5178d22192c2b8b4e1140a3bae9021ee0e808d754b4310014745c11f03fcc61b
Status: Downloaded newer image for python:onbuild
# Executing 3 build triggers...
Step 1 : COPY requirements.txt /usr/src/app/
Step 1 : RUN pip install --no-cache-dir -r requirements.txt
....
Successfully built f742caba47ed
--> Pushing docker.io/feisky/virulent-sheep:de7e97d0d889b4cdb81ae4b972097d759c59e06e
....
de7e97d0d889b4cdb81ae4b972097d759c59e06e: digest: sha256:7ee10c1a56ced4f854e7934c9d4a1722d331d7e9bf8130c1a01d6adf7aed6238 size: 2840
--> Deploying to Kubernetes
    Release "virulent-sheep" does not exist. Installing it now.
--> Status: DEPLOYED
--> Notes:

  [http://virulent-sheep.app.feisky.xyzto](http://virulent-sheep.app.feisky.xyzto) access your application

Watching local files for changes...

打开一个新的shell,就可以通过子域名来访问应用了

$ curl virulent-sheep.app.feisky.xyz
Hello, World!

 

本文转自Kubernetes Handbook,欢迎关注。

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