通过多阶段构建在Docker容器中复制时出现文件未找到的问题

huangapple
go评论115阅读模式
英文:

File not found when copied in docker container via multistage build

问题

在通过Docker多阶段构建将文件复制到容器中时，我遇到了一个问题，无法从位于项目根目录的Golang中打开一个简单的文件。然而，我可以在容器中看到该文件。

这是我的Dockerfile：

  1. # Start from a base Go image
  2. FROM golang:1.19 as builder
  4. # Set the working directory inside the container
  5. WORKDIR /app
  7. # Copy the Go module files
  8. COPY go.mod go.sum ./
  10. # Download the dependencies
  11. RUN go mod download
  13. # Copy the rest of the application code
  14. COPY . .
  16. # Copy the promotions.csv into the container
  17. RUN chmod +r /app/promotions.csv
  18. COPY promotions.csv /app/promotions.csv
  20. # Run with disabled cross-compilation
  21. RUN CGO_ENABLED=0 GOOS=linux go build -o app .
  23. # Final stage
  24. FROM alpine:3.18
  26. RUN apk --no-cache add ca-certificates
  28. WORKDIR /root/
  30. COPY --from=builder --chown=${USERNAME}:${USERNAME} /app/app .
  32. EXPOSE 1321
  34. CMD ["./app"]

promotions.csv 文件确实存在于容器文件系统中。

然而，main.go 中的 records, err := readCSVFile("promotions.csv") 代码返回一个错误：

open promotions.csv: no such file or directory

更奇怪的是，当我不使用多阶段构建时，一切都正常工作：

  1. # Start from a base Go image
  2. FROM golang:1.19 as builder
  4. # Set the working directory inside the container
  5. WORKDIR /app
  7. # Copy the Go module files
  8. COPY go.mod go.sum ./
  10. # Download the dependencies
  11. RUN go mod download
  13. #COPY promotions.csv ./
  15. # Copy the rest of the application code
  16. COPY . .
  18. # Copy the promotions folder into the container
  20. # Run with disabled cross-compilation
  21. RUN go build -o main
  23. EXPOSE 1321
  25. CMD ["./main"]

这是 docker-compose.yml 文件：

  1. version: '3'
  3. services:
  4.   postgres:
  5.     image: postgres:15.3-alpine
  6.     restart: always
  7.     ports:
  8.       - 5432:5432
  9.     environment:
  10.       POSTGRES_USER: postgres
  11.       POSTGRES_PASSWORD: password
  12.       POSTGRES_DB: vrstore
  14.   app:
  15.     build:
  16.       context: .
  17.       dockerfile: Dockerfile
  18.     restart: always
  19.     ports:
  20.       - 1321:1321
  21.     depends_on:
  22.       - postgres
  23.     volumes:
  24.       - .:/app
  25.     environment:
  26.       DATABASE_HOST: postgres
  27.       DATABASE_PORT: 5432
  28.       DATABASE_NAME: vrstore
  29.       DATABASE_USER: postgres
  30.       DATABASE_PASSWORD: password

可能导致第一种情况下出现错误的原因是什么？也许我漏掉了一些明显的东西？谢谢。

英文:

Having a trouble to open a simple file from Golang located in project root when copied in container via Docker multistage build. However I can see the file in container.

Here is my Dockerfile:

  1. # Start from a base Go image
  2. FROM golang:1.19 as builder
  4. # Set the working directory inside the container
  5. WORKDIR /app
  7. # Copy the Go module files
  8. COPY go.mod go.sum ./
  10. # Download the dependencies
  11. RUN go mod download
  13. # Copy the rest of the application code
  14. COPY . .
  16. # Copy the promotions.csv into the container
  17. RUN chmod +r /app/promotions.csv
  18. COPY promotions.csv /app/promotions.csv
  20. # Run with disabled cross-compilation
  21. RUN CGO_ENABLED=0 GOOS=linux go build -o app .
  23. # Final stage
  24. FROM alpine:3.18
  26. RUN apk --no-cache add ca-certificates
  28. WORKDIR /root/
  30. COPY --from=builder --chown=${USERNAME}:${USERNAME} /app/app .
  32. EXPOSE 1321
  34. CMD ["./app"]

promotions.csv file exists though in container file system:
通过多阶段构建在Docker容器中复制时出现文件未找到的问题

However records, err := readCSVFile("promotions.csv") code from main.go returns an error:

> open promotions.csv: no such file or directory

More strangely everything is working fine when I don't use mutistage build:

  1. # Start from a base Go image
  2. FROM golang:1.19 as builder
  4. # Set the working directory inside the container
  5. WORKDIR /app
  7. # Copy the Go module files
  8. COPY go.mod go.sum ./
  10. # Download the dependencies
  11. RUN go mod download
  13. #COPY promotions.csv ./
  15. # Copy the rest of the application code
  16. COPY . .
  18. # Copy the promotions folder into the container
  20. # Run with disabled cross-compilation
  21. RUN go build -o main
  23. EXPOSE 1321
  25. CMD ["./main"]

Here is the docker-compose.yml:

  1. version: '3'
  3. services:
  4.   postgres:
  5.     image: postgres:15.3-alpine
  6.     restart: always
  7.     ports:
  8.       - 5432:5432
  9.     environment:
  10.       POSTGRES_USER: postgres
  11.       POSTGRES_PASSWORD: password
  12.       POSTGRES_DB: vrstore
  14.   app:
  15.     build:
  16.       context: .
  17.       dockerfile: Dockerfile
  18.     restart: always
  19.     ports:
  20.       - 1321:1321
  21.     depends_on:
  22.       - postgres
  23.     volumes:
  24.       - .:/app
  25.     environment:
  26.       DATABASE_HOST: postgres
  27.       DATABASE_PORT: 5432
  28.       DATABASE_NAME: vrstore
  29.       DATABASE_USER: postgres
  30.       DATABASE_PASSWORD: password

What could possibly be the reason of the error in the first case? Maybe I'm missing something obvious?
Thanks.

答案1

得分: 2

文件在镜像中不存在，因为你没有将它复制到那里。

在容器中，你将文件作为卷挂载到/app目录下：

  1.     volumes:
  2.       - .:/app

然而，你正在/root目录下运行二进制文件：

  1. WORKDIR /root/
  2. COPY --from=builder --chown=${USERNAME}:${USERNAME} /app/app .
  3. CMD ["./app"]

所以二进制文件正在寻找/root/promotions.csv，但找不到它。你需要切换到/app目录或者使用完整路径打开文件。

英文:

The file does not exist in the image since you don't copy it there.

In the container, you are mounting the files as a volume into /app:

  1.     volumes:
  2.       - .:/app

However you are running the binary from /root:

  1. WORKDIR /root/
  2. COPY --from=builder --chown=${USERNAME}:${USERNAME} /app/app .
  3. CMD ["./app"]

So the binary is looking for /root/promotions.csv and cannot find it. You would need to change directory to /app or open the file with the fully qualified path.

huangapple
  • 本文由 发表于 2023年5月20日 22:28:28
  • 转载请务必保留本文链接：https://go.coder-hub.com/76295727.html
  • docker
  • docker-compose
  • docker-multi-stage-build
  • go
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