如何在构建时在 Docker 镜像之间建立网络? [英] How to network between Docker images at build time?

问题描述

我有一个项目 sample 有两个服务，database 和 app，在 docker-compose.yml:

I have a project sample with two services, database and app, declared in docker-compose.yml:

version: "3.8"
services:
  database:
    image: sample/database
    build:
      context: .
      dockerfile: database.Dockerfile
      network: sample_default

    ports:
    - "8001:5432"

  app:
    image: sample/app
    build:
      context: .
      dockerfile: app.Dockerfile
      network: sample_default
      args:
        - DATABASE_URL=postgresql://postgres:password@database:5432/cluster

    depends_on:
      - database

networks:
  sample_default: {}

database.Dockerfile 负责下载和安装 Postgre，以及在该集群中启动 Postgre 集群和数据库.该数据库的表是在构建时通过 CREATE TABLE 在 RUN 命令下创建的.

database.Dockerfile takes care of downloading and installing Postgre, as well as starting a Postgre cluster and database within that cluster. The tables of this database are created through CREATE TABLE at build time under a RUN command.

app.Dockerfile 负责下载和安装编译器，以及编译源代码.

app.Dockerfile takes care of downloading and installing the compiler, as well as compiling the source code.

为了构建app.Dockerfile的镜像，必须先构建database.Dockerfile的镜像.这是因为，在编译时，源代码中的 SQL 查询字符串会根据 database.Dockerfile 中创建的数据库进行验证.

In order for app.Dockerfile's image to be built, database.Dockerfile's image must be built first. This is because, at compile time, SQL query strings within the source code are validated against the database created in database.Dockerfile.

编译器使用 DATABASE_URL 连接到 Postgre 数据库，该数据库包含用于验证查询的表.在这个 DATABASE_URL 中，指定的地址是 database:5432，因为可以在非默认桥接网络上使用服务发现.

The compiler uses DATABASE_URL to connect to the Postgre database which contains the tables to validate the queries against. Within this DATABASE_URL, the specified address is database:5432, since service discovery can be used on non-default bridge networks.

我的问题是，在运行 docker-compose up 时，app 在构建时无法连接到 database.app.Dockerfile 中的 RUN ping 数据库 失败并显示 ping: 数据库:没有与主机名关联的地址.然而，从 sample_default 网络上的两个图像启动一个容器(手动而不是通过 docker-compose)并从 运行 ping 数据库应用的容器成功.

My problem is that in running docker-compose up, app at build time cannot connect to database at build time. A RUN ping database in app.Dockerfile fails with ping: database: No address associated with hostname. Yet, starting a container from both images on the sample_default network (manually instead of through docker-compose) and running ping database from app's container is successful.

我已经在 docker-compose.yml 中的 build 下指定了 network，那么我可以在此基础上做些什么来允许在这里构建时网络?

I have already specified the network under build in docker-compose.yml, so what can I do on top of that to allow build-time networking here?

推荐答案

在构建时，没有出现网络配置.因为 Docker 容器就像 VM.您无法在启动时通过其 IP 地址连接到 VM.码头集装箱也一样.唯一不同的是容器启动过程比虚拟机快；因此，您需要等到它出现.启动容器后，它的生命周期就是运行时.

In the build-time, there is no network configuration comes up. Because Docker container is like VM. you can't connect to VM in its boot time via it's IP address. docker container also the same. The only differents is container fast booting process than the VM; therefore, you need to wait until it comes up. After booting up a container, it's life cycle is the runtime.

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