在码头组合中，链接和缩放方式如何协同工作？ [英] How do links and scaling work together in docker compose?

问题描述

这是我对docker撰写的理解：

Here's my understanding of docker compose:

• 您可以缩放服务，一次将其运行在多个容器中。 li>
  
• 如果将服务A链接到服务B，服务A可以访问运行服务B的容器。

我的理解是否正确，如果是，如果有多个容器运行服务，链接在哪里连接？

Is my understanding correct, and if so, where does a link connect if there are multiple containers running the service?

推荐答案

首先，我将澄清，默认情况下，使用或不将容器与其他链接链接，所有容器都可以访问在同一主机中运行的其他容器（使用容器IP）。您可以使用docker守护程序中的 icc = true 标志来更改此行为。

First of all I would clarify that, by default, with or without linking a container with other, all container has visibility to other containers running in the same host (using the container IP). You can change this behavior using the icc=true flag in docker daemon.

关于与docker的链接-compose，这些都是在创建具有链接的容器时生成的。我们来看一个例子。使用此docker-compose.yml

In respect of the links with docker-compose, these are generated when the container with the links are created. Let's see it with an example. Using this docker-compose.yml

web:
  build: .
  command: python app.py
  ports:
   - "5000:5000"
  volumes:
   - .:/code
  links:
   - redis
redis:
  image: redis

运行 docker-compos up -d web_1 容器与容器链接，<？c $ c> redis_1 ：

After running docker-compose up -d the web_1 container is linked with the container with redis_1:

        (...)
        "Links": [
        "/compose_redis_1:/compose_web_1/compose_redis_1",
        "/compose_redis_1:/compose_web_1/redis",
        "/compose_redis_1:/compose_web_1/redis_1"
    ], (...)

现在我们要使用来缩放 redis docker-compose scale redis = 2 。运行它（并创建一个新的容器 redis_2 ）后， web_1 中的链接保持不变。

Now we want to scale the redis service using docker-compose scale redis=2. After running it (and create a new container redis_2), the links in web_1 keeps unchanged.

        (...)
        "Links": [
        "/compose_redis_1:/compose_web_1/compose_redis_1",
        "/compose_redis_1:/compose_web_1/redis",
        "/compose_redis_1:/compose_web_1/redis_1"
    ], (...)

需要停止，删除并运行 web_1 才能看到创建的链接： p>

It is needed to stop, remove and run web_1 to see these links created:

docker-compose stop web
docker-compose rm web
docker-compose run -d web
docker inspect compose_web_run_2
(...)        "Links": [
        "/compose_redis_1:/compose_web_run_2/compose_redis_1",
        "/compose_redis_2:/compose_web_run_2/compose_redis_2",
        "/compose_redis_1:/compose_web_run_2/redis",
        "/compose_redis_1:/compose_web_run_2/redis_1",
        "/compose_redis_2:/compose_web_run_2/redis_2"
    ],(...)

而 / etc / hosts web_1 container：

And the /etc/hosts of web_1 container:

172.17.0.24 7be2dabea910
127.0.0.1   localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.17.0.21 compose_redis_1 8a1297a5b3e4
172.17.0.23 compose_redis_2 069dd46836aa
172.17.0.21 redis 8a1297a5b3e4 compose_redis_1
172.17.0.21 redis_1 8a1297a5b3e4 compose_redis_1
172.17.0.23 redis_2 069dd46836aa compose_redis_2

所以要生成新的链接，您需要停止，删除和再次运行容器。

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