用Docker弹性部署自己的服务

很久不看 docker 的东西了，之前了解的一些基本命令都忘得差不多了，适逢工作需要，再来复习巩固下。今天想完成的是：借助docker不部署下自己的服务。

环境准备

都说“巧妇难为无米之炊”，所以还是需要先准备下的。

OS：Ubuntu 16.04， 2G内存

docker：1.13.2

coding language: golang (gin web framework)

编码

将服务跑起来，是我们要完成的第一个步骤，而且是最重要的一个步骤。所以这一步需要仔细调试，为了方便，我就写的简单点。

1. app.go

package main

import (
    "os"
    "log"
        "github.com/gin-gonic/gin"
    "net/http"
    "time"
)

func GetHostName() string {
    hostname, err := os.Hostname()
    if err != nil {
        log.Fatal(err)
    }
    return hostname
}

func GetCurrentTime() string {
    timer := time.Now()
    return timer.String()
}

func startGinApp() {
    app := gin.Default()
    app.GET("/ping", func(context *gin.Context) {
        context.JSON(http.StatusOK, gin.H{
            "message": "当前为您服务的主机为：" + GetHostName(),
        })
    })
    app.GET("/", func(context *gin.Context) {
        context.JSON(http.StatusOK, gin.H{
            "message": "当前时间为：" + GetCurrentTime(),
        })
    })
    app.Run(":8080")
}

func main() {
    startGinApp()
}

2. 把服务跑起来

go run app.go

3. curl一下看看服务是否正确跑起来了

➜  gin curl http://localhost:8080
{"message":"当前时间为：2018-10-14 11:31:23.016121853 +0800 CST m=+0.254631109"}%                                                                                                 
➜  gin curl http://localhost:8080/ping
{"message":"当前为您服务的主机为：BiaodeMacBook-Pro.local"}%                                                                                                                      

➜  gin

制作Makefile

经过刚才的测试，代码可以正确跑起来了。但是要做到“一次编码，到处运行”，还是需要在构建阶段下点心思的，为了更好的维护，借助Makefile来规范构建过程，是比较合适的方法。

1. Makefile

# 这个是注释
# 开头可以声明一大堆变量名
BUILD_NAME ?= httpserver
COMPILER ?= go
BUILD ?= build


# 上方留一个空格，区分变量区和构建区
all: build test deploy clean

build:
    CGO_ENABLED=0 GOOS=linux GOARCH=amd64 $(COMPILER) $(BUILD) -o $(BUILD_NAME)

test:
    echo "test over."

deploy:
    echo "deploy over."

clean:
    echo "clean over."

.PHONY: build test deploy clean

2. 构建服务

➜  gin ls
Makefile app.go
➜  gin make all
go build -o httpserver
echo "test over."
test over.
echo "deploy over."
deploy over.
echo "clean over."
clean over.
➜  gin ls
Makefile   app.go     httpserver
➜  gin ./httpserver &
[1] 6450
➜  gin [GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.

[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
 - using env:   export GIN_MODE=release
 - using code:  gin.SetMode(gin.ReleaseMode)

[GIN-debug] GET    /ping                     --> main.startGinApp.func1 (3 handlers)
[GIN-debug] GET    /                         --> main.startGinApp.func2 (3 handlers)
[GIN-debug] Listening and serving HTTP on :8080

➜  gin curl http://localhost:8080/ping
[GIN] 2018/10/14 - 11:50:23 | 200 |     214.161µs |             ::1 | GET      /ping
{"message":"当前为您服务的主机为：BiaodeMacBook-Pro.local"}%                                                                                                                      
➜  gin

好了基本没什么问题，然后就可以通过scp命令将文件拷贝到 linux 服务器上了。

制作Dockerfile

由于golang构建出来的是二进制可执行程序，所以制作Dockerfile很简单。

1. Dockerfile

FROM ubuntu:latest

MAINTAINER guopu marksinoberg@gmail.com

WORKDIR /app

EXPOSE 8080

ADD . /app

CMD ["./httpserver"]

2. 构建自己的镜像

root@Server218 /h/d/g/d/httpserver# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
ginserver           latest              6277a0180f4f        19 hours ago        101 MB
flaskindocker       latest              170c6c0a41db        22 hours ago        131 MB
python              2.7-slim            14dad3ead5f4        4 days ago          120 MB
docker/compose      1.23.0-rc2          dc59a0b5e981        5 days ago          45.6 MB
ubuntu              latest              cd6d8154f1e1        5 weeks ago         84.1 MB
root@Server218 /h/d/g/d/httpserver# docker build -t httpserver .
Sending build context to Docker daemon 17.07 MB
Step 1/6 : FROM ubuntu:latest
 ---> cd6d8154f1e1
Step 2/6 : MAINTAINER guopu marksinoberg@gmail.com
 ---> Running in 7106748df3ad
 ---> 0ae808029537
Removing intermediate container 7106748df3ad
Step 3/6 : WORKDIR /app
 ---> 7278bf9659e7
Removing intermediate container f7fdc76b19a8
Step 4/6 : EXPOSE 8080
 ---> Running in bedfabcb4b16
 ---> edf4c123f72f
Removing intermediate container bedfabcb4b16
Step 5/6 : ADD . /app
 ---> 36390e554a2f
Removing intermediate container b14cce9da53e
Step 6/6 : CMD ./httpserver
 ---> Running in 6682c8364717
 ---> b490fef8a9ca
Removing intermediate container 6682c8364717
Successfully built b490fef8a9ca
root@Server218 /h/d/g/d/httpserver# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
httpserver          latest              b490fef8a9ca        4 seconds ago       101 MB
ginserver           latest              6277a0180f4f        19 hours ago        101 MB
flaskindocker       latest              170c6c0a41db        22 hours ago        131 MB
python              2.7-slim            14dad3ead5f4        4 days ago          120 MB
docker/compose      1.23.0-rc2          dc59a0b5e981        5 days ago          45.6 MB
ubuntu              latest              cd6d8154f1e1        5 weeks ago         84.1 MB
root@Server218 /h/d/g/d/httpserver#

3. 让服务在docker中跑起来

root@Server218 /h/d/g/d/httpserver# docker run -d  -p 8000:8080 httpserver
ebb1926206cdaf16eae9f4e13d5a7e70dd695da91463b438f77e45c6f65d3323
root@Server218 /h/d/g/d/httpserver# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                    NAMES
ebb1926206cd        httpserver          "./httpserver"      4 seconds ago       Up 3 seconds        0.0.0.0:8000->8080/tcp   nostalgic_wright
root@Server218 /h/d/g/d/httpserver# curl http://localhost:8000/ping
{"message":"当前为您服务的主机为：ebb1926206cd"}~                                                                                                                                 
root@Server218 /h/d/g/d/httpserver# curl http://localhost:8000/
{"message":"当前时间为：2018-10-14 04:14:29.116207751 +0000 UTC"}~                                                                                                                root@Server218 /h/d/g/d/httpserver#

至此，看起来服务已经成功在服务器环境下的docker中运行了。

弹性服务

一个容器跑一个服务，有些服务访问峰差很大的场景，就需要做下弹性适配，于是需要用一下docker swarm服务。这个在linux环境下需要进行安装。具体可以参考官网链接： https://github.com/docker/compose/releases

其运行以来一个YAML配置文件，具体细节不多说，上手吧。

1. docker-compose.yml

version: "3"
services:
    web:
        image: httpserver:latest
        deploy:
            replicas: 5
            resources:
                limits:
                    cpus: "0.1"
                    memory: 50M
            restart_policy:
                condition: on-faliure
        ports:
            - "8000:8080"
        networks:
            - webnet
networks:
    webnet:

2. 初始化swarm

root@Server218 /h/d/g/d/httpserver# docker swarm init
Swarm initialized: current node (atiuy6c8k1qcig5w3br1bwf0n) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join \
    --token SWMTKN-1-5e0sj0glbwl5w5rqytyqokeg91n7piwdyw9ik598x0poiz5s20-do445zhrdr5io93lplov42c2y \
    172.31.237.68:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

root@Server218 /h/d/g/d/httpserver#

3. 发布服务到swarm中

root@Server218 /h/d/g/d/httpserver# docker stack deploy -c docker-compose.yml httpserver
Creating service httpserver_web
root@Server218 /h/d/g/d/httpserver#
root@Server218 /h/d/g/d/httpserver#
root@Server218 /h/d/g/d/httpserver#
root@Server218 /h/d/g/d/httpserver# docker stack ps httpserver
ID            NAME              IMAGE              NODE       DESIRED STATE  CURRENT STATE           ERROR  PORTS
kvpvwptlj44c  httpserver_web.1  httpserver:latest  Server218  Running        Running 14 seconds ago
6549g79dz5iz  httpserver_web.2  httpserver:latest  Server218  Running        Running 14 seconds ago
xkz42mnetmws  httpserver_web.3  httpserver:latest  Server218  Running        Running 14 seconds ago
rpziwzmpogn2  httpserver_web.4  httpserver:latest  Server218  Running        Running 14 seconds ago
y2kfe8bp09ld  httpserver_web.5  httpserver:latest  Server218  Running        Running 6 seconds ago

root@Server218 /h/d/g/d/httpserver# curl http://localhost:8000/ping
{"message":"当前为您服务的主机为：a5419e3d3f9c"}~                                                                                                                                 
root@Server218 /h/d/g/d/httpserver# curl http://localhost:8000/ping
{"message":"当前为您服务的主机为：f636819bd9c4"}~                                                                                                                                 
root@Server218 /h/d/g/d/httpserver# curl http://localhost:8000/ping
{"message":"当前为您服务的主机为：97a6e3c9a064"}~                                                                                                                                 
root@Server218 /h/d/g/d/httpserver# curl http://localhost:8000/ping
{"message":"当前为您服务的主机为：7f1b28e14970"}~                                                                                                                                 
root@Server218 /h/d/g/d/httpserver# curl http://localhost:8000/ping
{"message":"当前为您服务的主机为：0ce251661188"}~                                                                                                                                 
root@Server218 /h/d/g/d/httpserver# curl http://localhost:8000/ping
{"message":"当前为您服务的主机为：a5419e3d3f9c"}~                                                                                                                                 
root@Server218 /h/d/g/d/httpserver#

4. 实例弹性变化

   具体的操作只需要修改 docker-compose.yml 中的replicas的数量即可。然后重新使用：

docker stack deploy -c docker-compose.yml httpserver

发布就可以了，可以看出swarm管理下的实例会进行自动的负载均衡。

5. 关停服务

root@Server218 /h/d/g/d/httpserver# docker stack ls
NAME        SERVICES
httpserver  1
root@Server218 /h/d/g/d/httpserver# docker stack rm httpserver
Removing service httpserver_web
Removing network httpserver_webnet
root@Server218 /h/d/g/d/httpserver# docker stack ls
NAME  SERVICES
root@Server218 /h/d/g/d/httpserver#

6. 关掉swarm

root@Server218 /h/d/g/d/httpserver# docker swarm leave --force
Node left the swarm.
root@Server218 /h/d/g/d/httpserver#

总结

最后，回头看看这个目录。

root@Server218 /h/d/g/d/httpserver# ls -al
total 16688
drwxr-xr-x 2 root root     4096 Oct 14 12:20 ./
drwxr-xr-x 5 root root     4096 Oct 14 12:00 ../
-rw-r--r-- 1 root root      121 Oct 14 12:11 Dockerfile
-rw-r--r-- 1 root root      362 Oct 14 12:01 Makefile
-rw-r--r-- 1 root root      682 Oct 14 12:01 app.go
-rw-r--r-- 1 root root      385 Oct 14 12:27 docker-compose.yml
-rwxr-xr-x 1 root root 17063672 Oct 14 12:03 httpserver*
root@Server218 /h/d/g/d/httpserver#

基本上，在docker中弹性部署自己的服务就结束了，基本上也能满足需要。