[docker]九、compose

1、compose

是docker官方推出的一个用python编写的容器编排工具。可以理解为启动容器的脚本，在脚本里指明启动容器的顺序，启动多少容器

那么有以下问题

• 对容器进行什么编排 *** 作呢？

启动容器，可以指定端口、卷、链接、使用哪个镜像等

docker run -dp 8080:80 -v /web:/usr/local/bginx/html --name sc-nginx-1 nginx:1.12.1

• 对多少容器进行编排 *** 作呢？

>=1

• 对多少台宿主机上的容器进行编排 *** 作呢？

一台

还有两个比较厉害的软件swarm和k8s

1.1、compose的好处

1. 可以快速批量启动容器，效率高
2. 不容易出错，可靠性高

1.2、安装compose

[root@centos7-docker nginx1]# uname -s
Linux
[root@centos7-docker nginx1]# uname -m
x86_64
[root@centos7-docker nginx1]# uname -r
3.10.0-1160.el7.x86_64

[root@centos7-docker nginx1]# curl -L "https://github.com/docker/compose/releases/download/1.29.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

# 若是上边那个命令安装不了可以使用
[root@centos7-docker nginx1]# curl -L "https://get.daocloud.io/docker/compose/releases/download/1.29.2/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
[root@centos7-docker nginx1]# chmod +x  /usr/local/bin/docker-compose
# 授予可执行权限

[结果查看]

[root@centos7-docker nginx1]# docker-compose -v
docker-compose version 1.29.2, build 5becea4c

1.3、使用compose

官方参考资料：Get started with Docker Compose | Docker Documentation

Step 1: Setup

1、Create a directory for the project:

[root@centos7-docker nginx1]# mkdir /composetest
[root@centos7-docker nginx1]# cd /composetest

2、Create a file called app.py in your project directory and paste this in:

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)

In this example, redis is the hostname of the redis container on the application’s network. We use the default port for Redis, 6379.（在这个例子中，redis是应用程序网络中redis容器的主机名。我们使用Redis的默认端口6379。）

3、Create another file called requirements.txt in your project directory and paste this in:

flask
redis

Step 2: Create a Dockerfile

In your project directory, create a file named Dockerfile and paste the following:

# syntax=docker/dockerfile:1
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
EXPOSE 5000
COPY . .
CMD ["flask", "run"]

This tells Docker to:

• Build an image starting with the Python 3.7 image.
• Set the working directory to /code.
• Set environment variables used by the flask command.
• Install gcc and other dependencies
• Copy requirements.txt and install the Python dependencies.
• Add metadata to the image to describe that the container is listening on port 5000
• Copy the current directory . in the project to the workdir . in the image.
• Set the default command for the container to flask run.

For more information on how to write Dockerfiles, see the Docker user guide and the Dockerfile reference.