一、compose简介
编排功能是复杂系统是否具有灵活可操作性的关键。特别在docker应用场景中，编排意味着用户可以灵活的对各种容器资源实现定义和管理。compose作为docker官方编排工具，它可以让用户通过编写一个简单的模板文件，快速的创建和管理基于docker容器的应用集群。
compose项目是docker官方的开源项目，负责实现对基于docker容器的多应用服务的快速编排。其代码目前在https://github.com/docker/compose上开源。
compose允许用户通过一个单独的docker-compose.yml模板文件来定义一组相关联的应用容器为一个服务栈。
compose几个概念
1. 任务：一个容器被称为一个任务。任务拥有独一无二的ID，在同一个服务中的多个任务序号依次递增。
2. 服务：某个相同应用镜像的容器副本集合，一个服务可以横向扩展为多个容器实例。
3. 服务栈：由多个服务组成，相互配合完成特定业务，如web应用服务、数据库服务共同构成web服务栈，一般由一个docker-compose.yml文件定义。
compose的默认管理对象是服务栈，通过子命令对栈中的多个服务进行便捷的生命周期管理。compose项目由python编写，实现上调用了docker服务提供的API来对容器进行管理。因此，只要所操作的平台支持docker API，就可以在其上利用compose来进行编排管理。
二、安装docker-compose
1. 安装compose之前，要先安装docker引擎。compose可以通过Python的pip工具进行安装。
[root@web01 ~]# curl -o /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 664 100 664 0 0 4337 0 --:--:-- --:--:-- --:--:-- 4368
[root@web01 ~]# yum install -y python-pip
[root@web01 ~]# pip install --upgrade pip
[root@web01 ~]# pip -V
pip 20.2.3 from /usr/lib/python2.7/site-packages/pip (python 2.7)
[root@web01 ~]# pip install -U docker-compose
如果执行过程中，报错1：
ERROR: Cannot uninstall 'requests'. It is a distutils installed project and thus we cannot accurately determine which files belong to it which would lead to only a partial uninstall.
解决办法：
[root@web01 ~]# pip install --ignore-installed requests
报:2：
ERROR: After October 2020 you may experience errors when installing or updating packages. This is because pip will change the way that it resolves dependency conflicts.
We recommend you use --use-feature=2020-resolver to test your packages with the new resolver before it becomes the default.
jsonschema 3.2.0 requires six>=1.11.0, but you'll have six 1.9.0 which is incompatible.
解决办法：
[root@web02 ~]# pip install six --user -U
2. 检查是否安装成功
[root@web01 ~]# docker-compose -v
/usr/lib/python2.7/site-packages/paramiko/transport.py:33: CryptographyDeprecationWarning: Python 2 is no longer supported by the Python core team. Support for it is now deprecated in cryptography, and will be removed in a future release.
from cryptography.hazmat.backends import default_backend
docker-compose version 1.26.2, build unknown
三、compose模板文件
模板文件是使用compose的核心，涉及的指令关键字比较多。默认的模板文件名称为docker-compose.yml，格式为yaml格式，目前最新的版本为v3.
[root@web01 ~]# mkdir /docker-compose
[root@web01 ~]# cd /docker-compose/
[root@web01 docker-compose]# vi docker-compose.yml
注：提前pull下mysql和wordpress两款镜像
[root@web01 docker-compose]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
wordpress latest 420b971d0f8b 9 days ago 546MB
mysql 5.7 ef08065b0a30 10 days ago 448MB
四、启动docker-compose
[root@web01 docker-compose]# docker-compose up
1. 查看相关信息
[root@web01 ~]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c7fcbdbe8f07 wordpress:latest "docker-entrypoint.s…" 39 minutes ago Up 3 minutes 0.0.0.0:32770->80/tcp docker-compose_wordpress_1
d9bc706dc5a7 mysql:5.7 "docker-entrypoint.s…" 39 minutes ago Up 6 minutes 3306/tcp, 33060/tcp docker-compose_db_1
[root@web01 ~]# docker volume ls
DRIVER VOLUME NAME
local docker-compose_db_data
local docker-compose_web_data
[root@web01 ~]# docker network ls
NETWORK ID NAME DRIVER SCOPE
406aa541b3b3 bridge bridge local
181f52e786c7 docker-compose_default bridge local
1f756a7d8624 host host local
a358bdb73e1b none null local
2. 动态扩展wordpress节点数
[root@web01 docker-compose]# docker-compose scale wordpress=3
/usr/lib/python2.7/site-packages/paramiko/transport.py:33: CryptographyDeprecationWarning: Python 2 is no longer supported by the Python core team. Support for it is now deprecated in cryptography, and will be removed in a future release.
from cryptography.hazmat.backends import default_backend
WARNING: The scale command is deprecated. Use the up command with the --scale flag instead.
Starting docker-compose_wordpress_1 ... done
Creating docker-compose_wordpress_2 ... done
Creating docker-compose_wordpress_3 ... done
[root@web01 docker-compose]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d1d8755ab2f0 wordpress:latest "docker-entrypoint.s…" 5 seconds ago Up 4 seconds 0.0.0.0:32771->80/tcp docker-compose_wordpress_3
629fdb7cae28 wordpress:latest "docker-entrypoint.s…" 5 seconds ago Up 4 seconds 0.0.0.0:32772->80/tcp docker-compose_wordpress_2
c7fcbdbe8f07 wordpress:latest "docker-entrypoint.s…" 43 minutes ago Up 7 minutes 0.0.0.0:32770->80/tcp docker-compose_wordpress_1
d9bc706dc5a7 mysql:5.7 "docker-entrypoint.s…" 43 minutes ago Up 10 minutes 3306/tcp, 33060/tcp docker-compose_db_1
3. 配置反向代理，访问wordpress
[root@web02 ~]# yum install nginx -y
[root@web02 ~]# vim /etc/nginx/nginx.conf
[root@web02 ~]# cat /etc/nginx/nginx.conf
worker_processes 1;
events {
worker_connections 1024;
}
http {
include mime.types;
default_type application/octet-stream;
sendfile on;
keepalive_timeout 65;
upstream wordpress{
server 192.168.0.208:32770;
server 192.168.0.208:32771;
server 192.168.0.208:32772;
}
server {
listen 80;
server_name localhost;
location / {
proxy_pass http://wordpress;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}
}
[root@web02 ~]# systemctl start nginx
[root@web02 ~]# netstat -lntup
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1210/master
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 11939/nginx: master
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1342/sshd
tcp6 0 0 ::1:25 :::* LISTEN 1210/master
tcp6 0 0 :::22 :::* LISTEN 1342/sshd
udp 0 0 0.0.0.0:68 0.0.0.0:* 700/dhclient
udp 0 0 127.0.0.1:323 0.0.0.0:* 642/chronyd
udp6 0 0 ::1:323 :::* 642/chronyd
4. 访问
[root@web02 ~]# curl -v 192.168.0.184
* About to connect() to 192.168.0.184 port 80 (#0)
* Trying 192.168.0.184...
* Connected to 192.168.0.184 (192.168.0.184) port 80 (#0)
> GET / HTTP/1.1
> User-Agent: curl/7.29.0
> Host: 192.168.0.184
> Accept: */*
>
< HTTP/1.1 302 Found
< Server: nginx/1.16.1
< Date: Sun, 20 Sep 2020 10:15:59 GMT
< Content-Type: text/html; charset=UTF-8
< Content-Length: 0
< Connection: keep-alive
< X-Powered-By: PHP/7.4.10
< Expires: Wed, 11 Jan 1984 05:00:00 GMT
< Cache-Control: no-cache, must-revalidate, max-age=0
< X-Redirect-By: WordPress
< Location: http://192.168.0.184/wp-admin/install.php
<
* Connection #0 to host 192.168.0.184 left intact
