Golang调试的Docker文件

Question

我有以下的 Docker 文件，可以工作于我的应用程序。我能够访问简单的 Web 应用服务器。

FROM golang:1.14.7 AS builder
RUN go get github.com/go-delve/delve/cmd/dlv
RUN mkdir /app

ADD . /app
WORKDIR /app
RUN CGO_ENABLED=0 GOOS=linux go build -gcflags="all=-N -l" -o main ./...

FROM alpine:3.12.0 AS production
COPY --from=builder /app .
EXPOSE 8000 40000
ENV PORT=8000
CMD ["./main"]

当我像下面这样采用它时，我无法成功将其部署到Kubernetes。容器崩溃并出现一些一般性错误，而不是我可以使用的东西。

standard_init_linux.go:190: exec user process caused "no such file or directory"

这个不能工作

FROM golang:1.14.7 AS builder
RUN go get github.com/go-delve/delve/cmd/dlv
RUN mkdir /app

ADD . /app
WORKDIR /app
RUN CGO_ENABLED=0 GOOS=linux go build -gcflags="all=-N -l" -o main ./...

FROM alpine:3.12.0 AS production
COPY --from=builder /app .
COPY --from=builder /go/bin/dlv /
EXPOSE 8000 40000
ENV PORT=8000
CMD ["/dlv", "--listen=:40000", "--headless=true", "--api-version=2", "--accept-multiclient", "exec", "./main"]

如果有人想要尝试，这是一个简单的程序（最小可重现示例），如果你使用第一个Docker文件，它将适用于你，而对于第二个Docker文件则不行。

package main

import (
    "fmt"
    "net/http"
    "os"
)

func main() {
    fmt.Println("app is starting!")

    var port string
    if port = os.Getenv("PORT"); len(port) == 0 {
        port = "8080"
    }
    http.HandleFunc("/", handler)
    http.ListenAndServe(":"+port, nil)

}

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hi there,  %s!", r.URL.Path[1:])
}

- PJEM

---

尝试在基于alpine的构建器镜像上构建，例如golang:1.14.6-alpine3.12。 - Henry

@Henry - 我试了一下，也不起作用，还有其他的想法吗？ - PJEM

@shmsr - 错误是：`standard_init_linux.go:190: exec用户进程引起“没有这个文件或目录”。 - PJEM

@mh-cbon - 谢谢，我现在会尝试它，但不确定它是如何工作的，因为第一个 Docker 文件可以工作，并且我没有更改任何go build命令arch等。 - PJEM

也许可以运行 RUN GOARCH=amd64 go get github.com/go-delve/delve/cmd/dlv？ - user4466350

Answer 1

您需要使用静态链接标志编译dlv自身。否则，dlv将会动态链接到libc库，而这个库在alpine镜像中不存在。其他选项包括将您的生产镜像切换为debian基础镜像（FROM debian），或者更改golang镜像以基于alpine（FROM golang:1.14.7-alpine）。以下Dockerfile可用于编译没有动态链接的dlv：

FROM golang:1.14.7 AS builder
RUN CGO_ENABLED=0 go get -ldflags '-s -w -extldflags -static' github.com/go-delve/delve/cmd/dlv
RUN mkdir /app

ADD . /app
WORKDIR /app
RUN CGO_ENABLED=0 GOOS=linux go build -gcflags="all=-N -l" -o main ./...

FROM alpine:3.12.0 AS production
COPY --from=builder /app .
COPY --from=builder /go/bin/dlv /
EXPOSE 8000 40000
ENV PORT=8000
CMD ["/dlv", "--listen=:40000", "--headless=true", "--api-version=2", "--accept-multiclient", "exec", "./main"]    

要查看动态链接，请构建您的生成器映像并运行 ldd 对输出二进制文件进行分析：

$ docker build --target builder -t test-63403272 .
[+] Building 4.6s (11/11) FINISHED                                                                                                                                                                                 
 => [internal] load build definition from Dockerfile                                                                                                                                                          0.0s
 => => transferring dockerfile: 570B                                                                                                                                                                          0.0s
 => [internal] load .dockerignore                                                                                                                                                                             0.0s
 => => transferring context: 2B                                                                                                                                                                               0.0s
 => [internal] load metadata for docker.io/library/golang:1.14.7                                                                                                                                              0.2s
 => [builder 1/6] FROM docker.io/library/golang:1.14.7@sha256:1364cfbbcd1a5f38bdf8c814f02ebbd2170c93933415480480104834341f283e                                                                                0.0s
 => [internal] load build context                                                                                                                                                                             0.0s
 => => transferring context: 591B                                                                                                                                                                             0.0s
 => CACHED [builder 2/6] RUN go get github.com/go-delve/delve/cmd/dlv                                                                                                                                         0.0s
 => CACHED [builder 3/6] RUN mkdir /app                                                                                                                                                                       0.0s
 => [builder 4/6] ADD . /app                                                                                                                                                                                  0.1s
 => [builder 5/6] WORKDIR /app                                                                                                                                                                                0.0s
 => [builder 6/6] RUN CGO_ENABLED=0 GOOS=linux go build -gcflags="all=-N -l" -o main ./...                                                                                                                    4.0s
 => exporting to image                                                                                                                                                                                        0.2s
 => => exporting layers                                                                                                                                                                                       0.2s
 => => writing image sha256:d2ca7bbc0bb6659d0623e1b8a3e1e87819d02d0c7f0a0762cffa02601799c35e                                                                                                                  0.0s
 => => naming to docker.io/library/test-63403272                                                                                                                                                              0.0s

$ docker run -it --rm test-63403272 ldd /go/bin/dlv
        linux-vdso.so.1 (0x00007ffda66ee000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007faa4824d000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007faa4808c000)
        /lib64/ld-linux-x86-64.so.2 (0x00007faa48274000)

在切换到Alpine操作系统时，由于默认使用musl库，因此常见的缺失库是Libc。

- BMitch