Docker容器服务编排利器详解_云虚拟主机

一、使用docker compose必要性及定义

用容器运行一个服务,需要使用docker run命令。但如果我要运行多个服务呢?

假设我要运行一个web服务,还要运行一个db服务,那么是用一个容器运行,还是用多个容器运行呢?

一个容器运行多个服务会造成镜像的复杂度提高,docker倾向于一个容器运行一个应用。

那么复杂的架构就会需要很多的容器,并且需要它们之间有关联(容器之间的依赖和连接)就更复杂了。

这个复杂的问题需要解决,这就涉及到了**容器编排**的问题了。

compose
编排
- 是对多个容器进行启动和管理的方法
- 例如：lnmt，先启动mysql,再启动tomcat，最后启动nginx
服务架构的演进
单体服务架构
分布式服务架构
微服务架构
超微服务架构
容器编排工具
docker machine
在虚拟机中部署docker容器引擎的工具
docker compose
是一个用于定义和运行多容器docker的应用程序工具
docker swarm
是docker host主机批量管理及资源调度管理工具
mesos+marathon
mesos 对计算机计算资源进行管理和调度
marathon 服务发现及负载均衡的功能
kubernetes
google开源的容器编排工具

二、docker compose应用参考资料

网址 https://docs.docker.com/compose/

yaml格式

https://yaml.org/

三、docker compose应用最佳实践步骤

3.1 概念

工程（project）
服务 (service)
容器 (container)

3.2 步骤

1.定义应用的dockerfile文件，为了anywhere进行构建。

2.使用docker-compose.yaml定义一套服务，这套服务可以一起在一个隔离环境中运行。

3.使用docker-compose up就可以启动整套服务。

四、docker compose安装

# wget https://github.com/docker/compose/releases/download/v2.2.3/docker-compose-linux-x86_64

# mv docker-compose-linux-x86_64 /usr/bin/docker-compose

# chmod +x /usr/bin/docker-compose

# docker-compose version
docker compose version v2.2.3

五、docker compose应用案例

运行python语言开发的网站

5.1 网站文件准备

# mkdir flaskproject
[root@localhost ~]# cd flaskproject/
[root@localhost flaskproject]#

[root@localhost flaskproject]# vim app.py
[root@localhost flaskproject]# cat app.py
import time

import redis
from flask import flask

app = flask(__name__)
cache = redis.redis(host='redis', port=6379)

def get_hit_count():
    retries = 5
    while true:
        try:
            return cache.incr('hits')
        except redis.exceptions.connectionerror as exc:
            if retries == 0:
                raise exc
            retries -= 1
            time.sleep(0.5)

@app.route('/')
def hello():
    count = get_hit_count()
    return 'hello world! i have been seen {} times.\n'.format(count)

[root@localhost flaskproject]# vim requirements.txt
[root@localhost flaskproject]# cat requirements.txt
flask
redis

5.2 dockerfile文件准备

[root@localhost flaskproject]# vim dockerfile
[root@localhost flaskproject]# cat dockerfile
from python:3.7-alpine
workdir /code
env flask_app app.py
env flask_run_host 0.0.0.0
run apk add --no-cache gcc musl-dev linux-headers
copy requirements.txt requirements.txt
run pip install -r requirements.txt
copy . .
cmd ["flask", "run"]

5.3 compose文件准备

[root@localhost flaskproject]# vim docker-compose.yaml
[root@localhost flaskproject]# cat docker-compose.yaml
version: '3'
services:
  web:
    build: .
    ports:
      - "5000:5000"
  redis:
    image: "redis:alpine"

5.4 使用docker-compose up启动容器

[root@localhost flaskproject]# ls
app.py  docker-compose.yaml  dockerfile  requirements.txt

[root@localhost flaskproject]# docker-compose up

输出：
[+] running 7/7
 ⠿ redis pulled                                                                         15.8s
   ⠿ 59bf1c3509f3 pull complete                                                          2.9s
   ⠿ 719adce26c52 pull complete                                                          3.0s
   ⠿ b8f35e378c31 pull complete                                                          5.8s
   ⠿ d034517f789c pull complete                                                          6.5s
   ⠿ 3772d4d76753 pull complete                                                          6.6s
   ⠿ 211a7f52febb pull complete                                                          6.8s
sending build context to docker daemon     714b
step 1/9 : from python:3.7-alpine
3.7-alpine: pulling from library/python
59bf1c3509f3: already exists
07a400e93df3: already exists
bdabb07397e1: already exists
cd0af01c7b70: already exists
d0f18e022200: already exists
digest: sha256:5a776e3b5336827faf7a1c3a191b73b5b2eef4cdcfe8b94f59b79cb749a2b5d8
status: downloaded newer image for python:3.7-alpine
 ---> e72b511ad78e
step 2/9 : workdir /code
 ---> running in 2b9d07bef719
removing intermediate container 2b9d07bef719
 ---> 7d39e96fadf1
step 3/9 : env flask_app app.py
 ---> running in 9bcb28bd632a
removing intermediate container 9bcb28bd632a
 ---> 79f656a616d5
step 4/9 : env flask_run_host 0.0.0.0
 ---> running in 8470c2dbd6c2
removing intermediate container 8470c2dbd6c2
 ---> e212ba688fcd
step 5/9 : run apk add --no-cache gcc musl-dev linux-headers
 ---> running in 6e9ca0766bc8
fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/main/x86_64/apkindex.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/community/x86_64/apkindex.tar.gz
(1/13) installing libgcc (10.3.1_git20211027-r0)
(2/13) installing libstdc++ (10.3.1_git20211027-r0)
(3/13) installing binutils (2.37-r3)
(4/13) installing libgomp (10.3.1_git20211027-r0)
(5/13) installing libatomic (10.3.1_git20211027-r0)
(6/13) installing libgphobos (10.3.1_git20211027-r0)
(7/13) installing gmp (6.2.1-r1)
(8/13) installing isl22 (0.22-r0)
(9/13) installing mpfr4 (4.1.0-r0)
(10/13) installing mpc1 (1.2.1-r0)
(11/13) installing gcc (10.3.1_git20211027-r0)
(12/13) installing linux-headers (5.10.41-r0)
(13/13) installing musl-dev (1.2.2-r7)
executing busybox-1.34.1-r3.trigger
ok: 143 mib in 49 packages
removing intermediate container 6e9ca0766bc8
 ---> 273d4f04dfbc
step 6/9 : copy requirements.txt requirements.txt
 ---> daf51c54e8ba
step 7/9 : run pip install -r requirements.txt
 ---> running in 2aa2d30c5311
collecting flask
  downloading flask-2.0.3-py3-none-any.whl (95 kb)
collecting redis
  downloading redis-4.1.3-py3-none-any.whl (173 kb)
collecting jinja2>=3.0
  downloading jinja2-3.0.3-py3-none-any.whl (133 kb)
collecting itsdangerous>=2.0
  downloading itsdangerous-2.0.1-py3-none-any.whl (18 kb)
collecting click>=7.1.2
  downloading click-8.0.3-py3-none-any.whl (97 kb)
collecting werkzeug>=2.0
  downloading werkzeug-2.0.3-py3-none-any.whl (289 kb)
collecting deprecated>=1.2.3
  downloading deprecated-1.2.13-py2.py3-none-any.whl (9.6 kb)
collecting packaging>=20.4
  downloading packaging-21.3-py3-none-any.whl (40 kb)
collecting importlib-metadata>=1.0
  downloading importlib_metadata-4.11.1-py3-none-any.whl (17 kb)
collecting wrapt<2,>=1.10
  downloading wrapt-1.13.3-cp37-cp37m-musllinux_1_1_x86_64.whl (78 kb)
collecting typing-extensions>=3.6.4
  downloading typing_extensions-4.1.1-py3-none-any.whl (26 kb)
collecting zipp>=0.5
  downloading zipp-3.7.0-py3-none-any.whl (5.3 kb)
collecting markupsafe>=2.0
  downloading markupsafe-2.0.1-cp37-cp37m-musllinux_1_1_x86_64.whl (30 kb)
collecting pyparsing!=3.0.5,>=2.0.2
  downloading pyparsing-3.0.7-py3-none-any.whl (98 kb)
installing collected packages: zipp, typing-extensions, wrapt, pyparsing, markupsafe, importlib-metadata, werkzeug, packaging, jinja2, itsdangerous, deprecated, click, redis, flask
successfully installed jinja2-3.0.3 markupsafe-2.0.1 werkzeug-2.0.3 click-8.0.3 deprecated-1.2.13 flask-2.0.3 importlib-metadata-4.11.1 itsdangerous-2.0.1 packaging-21.3 pyparsing-3.0.7 redis-4.1.3 typing-extensions-4.1.1 wrapt-1.13.3 zipp-3.7.0
warning: running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. it is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
warning: you are using pip version 21.2.4; however, version 22.0.3 is available.
you should consider upgrading via the '/usr/local/bin/python -m pip install --upgrade pip' command.
removing intermediate container 2aa2d30c5311
 ---> dd8f52b132f8
step 8/9 : copy . .
 ---> b36938a26cf5
step 9/9 : cmd ["flask", "run"]
 ---> running in 260cbfa02959
removing intermediate container 260cbfa02959
 ---> fa04dfec6ff2
successfully built fa04dfec6ff2
successfully tagged flaskproject_web:latest

use 'docker scan' to run snyk tests against images to find vulnerabilities and learn how to fix them
[+] running 3/3
 ⠿ network flaskproject_default    created                                               0.1s
 ⠿ container flaskproject-redis-1  created                                               0.1s
 ⠿ container flaskproject-web-1    created                                               0.1s
attaching to flaskproject-redis-1, flaskproject-web-1
flaskproject-redis-1  | 1:c 15 feb 2022 14:14:21.696 # oo0ooo0ooo0oo redis is starting oo0ooo0ooo0oo
flaskproject-redis-1  | 1:c 15 feb 2022 14:14:21.696 # redis version=6.2.6, bits=64, commit=00000000, modified=0, pid=1, just started
flaskproject-redis-1  | 1:c 15 feb 2022 14:14:21.696 # warning: no config file specified, using the default config. in order to specify a config file use redis-server /path/to/redis.conf
flaskproject-redis-1  | 1:m 15 feb 2022 14:14:21.697 * monotonic clock: posix clock_gettime
flaskproject-redis-1  | 1:m 15 feb 2022 14:14:21.698 * running mode=standalone, port=6379.
flaskproject-redis-1  | 1:m 15 feb 2022 14:14:21.698 # warning: the tcp backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
flaskproject-redis-1  | 1:m 15 feb 2022 14:14:21.698 # server initialized
flaskproject-redis-1  | 1:m 15 feb 2022 14:14:21.698 # warning overcommit_memory is set to 0! background save may fail under low memory condition. to fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
flaskproject-redis-1  | 1:m 15 feb 2022 14:14:21.698 * ready to accept connections
flaskproject-web-1    |  * serving flask app 'app.py' (lazy loading)
flaskproject-web-1    |  * environment: production
flaskproject-web-1    |    warning: this is a development server. do not use it in a production deployment.
flaskproject-web-1    |    use a production wsgi server instead.
flaskproject-web-1    |  * debug mode: off
flaskproject-web-1    |  * running on all addresses.
flaskproject-web-1    |    warning: this is a development server. do not use it in a production deployment.
flaskproject-web-1    |  * running on http://172.18.0.2:5000/ (press ctrl+c to quit)