Koa 服务

创建 koa-service 项目文件夹

mkdir koa-service
cd koa-service

yarn init -y

yarn add koa

创建 index.js 文件并写入以下代码来创建一个简单的 Node 服务

const Koa = require('koa')

const app = new Koa()

app.use((ctx) => {
  ctx.body = 'koa service'
})

app.listen(3000, () => {
  console.log('koa server listen at: http://localhost:3000')
})

DockerFile

在根目录下创建 Dockerfile 文件，并写入以下代码

FROM node:16-alpine

EXPOSE 3000

WORKDIR /app

COPY ./package.json .

RUN yarn config set registry https://registry.npm.taobao.org
RUN yarn

COPY . .

CMD [ "node", "index.js" ]

• FROM node:lts-alpine - 从 docker hub 获取最新的 node 镜像
• WORKDIR /app - 设置在镜像中的工作目录, 这将被用在之后的命令，如： COPY , RUN 和 CMD
• COPY package.json /app - 复制package.json 文件到镜像中的 /app 文件夹中.
• RUN yarn install — 在镜像内执行 yarn install命令，安装应用所需的依赖.
• COPY . /app — 复制应用中所有的文件到镜像中/app 文件夹中.
• EXPOSE 3000 — 为由这个镜像创建的容器暴露 3000 端口，因为我们的应用监听 3000 端口，容器默认忽略对所有端口的监听。

创建 Docker 镜像

开启命令行界面，定位到 koa-service 文件夹，执行以下命令

# Build a image docker build -t <image-name> <relative-path-to-your-dockerfile>

docker build -t koa-service .

This command creates a hello-world image on our host.

• -t is used to give a name to our image which is koa-service here.
• . is the relative path to docker file, since we are in folder koa-service we used dot to represent path to docker file.

You will see an output on your command line something like this:

Sending build context to Docker daemon  4.096kB
Step 1/7 : FROM node:8
    ---> 4f01e5319662
Step 2/7 : WORKDIR /app
    ---> Using cache
    ---> 5c173b2c7b76
Step 3/7 : COPY package.json /app
    ---> Using cache
    ---> ceb27a57f18e
Step 4/7 : RUN npm install
    ---> Using cache
    ---> c1baaf16812a
Step 5/7 : COPY . /app
    ---> 4a770927e8e8
Step 6/7 : EXPOSE 8081
    ---> Running in 2b3f11daff5e
Removing intermediate container 2b3f11daff5e
    ---> 81a7ce14340a
Step 7/7 : CMD node index.js
    ---> Running in 3791dd7f5149
Removing intermediate container 3791dd7f5149
    ---> c80301fa07b2
Successfully built c80301fa07b2
Successfully tagged hello-world:latest

As you can see it ran the steps in our docker file and output a docker image. When you try it first time it will take a few minutes, but from next time it will start to use the cache and build much faster and output will be like the one shown above. Now, try following command in your terminal to see if your image is there or not :

# Get a list of images on your host
docker images

it should have a list of images in your host. something like this

REPOSITORY    TAG      IMAGE ID      CREATED         SIZE
hello-world   latest   c80301fa07b2  22 minutes ago  896MB

创建 Docker 容器

With our images created we can spin up a container from this image.

# Default command for this is docker container run <image-name>
docker container run -p 3000：3000  koa-service

This command is used to create and run a docker container.

• -p 3000：3000 — this is publish flag, it maps host port 4000 to container port 8081 which we opened through expose command in dockerfile. Now all the requests to host port 4000 will be listened by container port 8081.

• koa-service — this is the name we gave our image earlier when we ran docker-build command.

You will receive some output like this :

app listening on port 8081!

If you want to enter your container and mount a bash terminal to it you can run

# Enter the container
docker exec -it <container id> /bin/bash

In order to check if container is running or not, open another terminal and type

docker ps

You should see your running container like this

    CONTAINER ID    IMAGE        COMMAND                  CREATED
`<container id>`  hello-world  "/bin/sh -c 'node in…"   11 seconds ago

STATUS              PORTS                    NAMES
Up 11 seconds       0.0.0.0:4000->8081/tcp   some-random-name

It means our container with id <container id> created from hello-world image, is up and running and listening to port 8081. Now our small Node.js app is completely containerised. You can run http://localhost:3000/ on your browser