Golang 的 Docker 文件用于调试

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我有以下适用于我的应用程序的 docker 文件。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"]

当我像下面那样采用它时，我无法将它成功部署到 kubernetes。容器因一些一般错误而崩溃，这不是我可以使用的东西。

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

这不起作用

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"]

如果有人想尝试一下，这是一个简单的程序（这是最小的可重现示例），如果您采用第一个 docker 文件，它将为您工作，但对于第二个文件，它不会。

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:])
}

解决方案

您需要使用静态链接标志编译 dlv 本身。如果没有这个，dlv 将具有到 libc 的动态链接，而 alpine 图像中不存在该链接。其他选项包括将生产映像切换为基于 debian (from debian) 或更改为基于 alpine 的 golang 映像 (from golang:1.14.7-alpine)。要编译没有动态链接的 dlv，可以使用以下 dockerfile：

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，请构建构建器映像并针对输出二进制文件运行 ldd：

$ 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)

libc 是切换到 alpine 时常见的缺失库，因为它默认使用 musl。

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