Docker-compose参数不传递给Dockerfile

Question

version: '3'

services:

  scd-service:
    build:
      context: ./cmd/some-service/
      dockerfile: Dockerfile
      args:
        broker: redis:6379
        queue: somequeue
    depends_on:
      - redis
    networks:
      - backend

  redis:
    image: "redis:alpine"
    restart: unless-stopped
    networks:
      - backend

然而，这将失败。broker和queue参数从不传递给给定的DockerFile。

DockerFile示例：

FROM golang:1.11

// stuff...

ARG broker
ARG queue

CMD ["go", "run", "/go/src/github.com/org/project/cmd/some-service/some-service.go", "--broker $broker", "--queue $queue"]

正如在构建阶段中显而易见的那样,它们从未被解析过：

Step 7/7 : CMD ["go", "run", "/go/src/github.com/org/project/cmd/some-service/some-service.go", "--broker $broker", "--queue $queue"]

ARG broker
ARG queue

RUN echo ${broker}

产出：

Step 7/8 : RUN echo ${broker}
 ---> Running in c84828847d9a
redis:6379

如何不将其解析到cmd上？

Answer 1

这里有两个问题。arg仅在生成时（创建映像时）使用，cmd在运行容器时定义一个步骤。arg作为run步骤的环境变量实现，因此由shell来扩展环境变量。并且json语法不运行shell。因此，要使用cmd执行此操作，需要进行两个更改。

首先，您需要将arg保存为env值，该值保存到映像元数据中，并在创建容器时用于设置环境。

其次，您需要从用于运行cmd的exec/json语法切换到运行将扩展这些变量的shell。Docker通过字符串语法为您实现了这一点。

FROM golang:1.11

// stuff...

ARG broker
ENV broker=${broker}
ARG queue
ENV queue=${queue}

CMD go run /go/src/github.com/org/project/cmd/some-service/some-service.go --broker "$broker" --queue "$queue"

另外，您还应该注意，exec语法中的每个参数都需要是一个单独的数组条目，例如：

CMD ["go", "run", "/go/src/github.com/org/project/cmd/some-service/some-service.go", "--broker $broker", "--queue $queue"]

类似于运行：

go run /go/src/github.com/org/project/cmd/some-service/some-service.go "--broker $broker" "--queue $queue"

当你真的想跑的时候：

CMD ["go", "run", "/go/src/github.com/org/project/cmd/some-service/some-service.go", "--broker", "your_broker", "--queue", "your_queue"]

go run /go/src/github.com/org/project/cmd/some-service/some-service.go --broker "your_broker" --queue "your_queue"