问题

我正在寻找有关从使用Docker客户端库的基于Golang的客户端发送的dockerd（buildkit/moby）镜像构建请求中提取图像构建日志的帮助。

我可以成功请求图像构建，并接收到JSON消息的日志流，然后将其解码为Jsonmessage实例。但是，构建器的实际日志行似乎是在每个JSON消息的aux字段中进行了Base64编码。

我可以轻松解码Base64，但它们似乎包含奇怪的终端控制字符和可能是错误编码的数据，这让我想知道它们是否实际上是某种我应该解包的结构的Base64编码。

让我困惑的是，当显示docker buildx build的构建进度时，我找不到docker-ce或moby代码中似乎对aux有效载荷进行Base64解码的任何内容。

据我所知，buildx代码对aux有效载荷没有进行任何特殊处理：https://github.com/docker/docker-ce/blob/523cf7e71252013fbb6a590be67a54b4a88c1dae/components/cli/cli/command/image/build_buildkit.go#L325

例如，简化的构建代码如下：

        image := Image{Name:      "test"}
        contextreader, err := archive.TarWithOptions(buildConf.Build.Context, &archive.TarOptions{})
        if err != nil {
                return err
        }
        imageBuildResponse, err := b.client.ImageBuild(
                ctx,
                contextreader,
                types.ImageBuildOptions{
                      Version:     types.BuilderBuildKit,
                      Context:     contextreader,
                      Dockerfile:  dockerfile,
                })
        if err != nil {
                return err
        }
        defer imageBuildResponse.Body.Close()


        buf := bytes.NewBuffer(nil)

        imageID := ""
        writeAux := func(msg jsonmessage.JSONMessage) {
                if msg.ID == "moby.image.id" {
                        var result types.BuildResult
                        if err := json.Unmarshal(*msg.Aux, &result); err != nil {
                            panic("don't do this in your real code")
                        }
                        imageID = result.ID
                        return
                }
                return err
        }

        err := jsonmessage.DisplayJSONMessagesStream(imageBuildResponse.Body, buf, os.Stderr.Fd(), false /* not terminal */, writeAux)
        if err != nil {
                if jerr, ok := err.(*jsonmessage.JSONError); ok {
                        // If no error code is set, default to 1
                        if jerr.Code == 0 {
                                jerr.Code = 1
                        }
                        return fmt.Errorf("error while building image: %s", jerr.Message)
                }
        }

将会像这样将JSON有效载荷写入stderr：

{"id":"moby.buildkit.trace","aux":"Cn0KR3NoYTI1NjozZThhMzMxYmRkZGFjNWZkYmNjOGVhMDFmYWFhYmM3MjA0MDkwMmYwNjdmYzRhOGY0NDJmMmIzYWVlN2RkNGIyGiRbaW50ZXJuYWxdIGxvYWQgcmVtb3RlIGJ1aWxkIGNvbnRleHQqDAiYw8KaBhCykpCqAg=="}
{"id":"moby.buildkit.trace","aux":"CokBCkdzaGEyNTY6M2U4YTMzMWJkZGRhYzVmZGJjYzhlYTAxZmFhYWJjNzIwNDA5MDJmMDY3ZmM0YThmNDQyZjJiM2FlZTdkZDRiMhokW2ludGVybmFsXSBsb2FkIHJlbW90ZSBidWlsZCBjb250ZXh0KgwImMPCmgYQspKQqgIyCgiZw8KaBhD08F0="}

这里的Base64字符串解码后不是有效的UTF-8，并且它们也不符合ISO-8859-1。例如，使用UTF-8控制台编码：

$ base64 -d <<< 'Cn0KR3NoYTI1NjozZThhMzMxYmRkZGFjNWZkYmNjOGVhMDFmYWFhYmM3MjA0MDkwMmYwNjdmYzRhOGY0NDJmMmIzYWVlN2RkNGIyGiRbaW50ZXJuYWxdIGxvYWQgcmVtb3RlIGJ1aWxkIGNvbnRleHQqDAiYw8KaBhCykpCqAg=='

}
Gsha256:3e8a331bdddac5fdbcc8ea01faaabc72040902f067fc4a8f442f2b3aee7dd4b2�$[internal] load remote build context*
                                                                                                              ������

看起来它可能是一个结构体，但是我无论如何都找不到解码和处理它的方法。

        image := Image{Name:      "test"}
contextreader, err := archive.TarWithOptions(buildConf.Build.Context, &archive.TarOptions{})
if err != nil {
return err
}
imageBuildResponse, err := b.client.ImageBuild(
ctx,
contextreader,
types.ImageBuildOptions{
Version:     types.BuilderBuildKit,
Context:     contextreader,
Dockerfile:  dockerfile,
})
if err != nil {
return err
}
defer imageBuildResponse.Body.Close()
buf := bytes.NewBuffer(nil)
imageID := ""
writeAux := func(msg jsonmessage.JSONMessage) {
if msg.ID == "moby.image.id" {
var result types.BuildResult
if err := json.Unmarshal(*msg.Aux, &result); err != nil {
panic("don't do this in your real code")
}
imageID = result.ID
return
}
return err
}
err := jsonmessage.DisplayJSONMessagesStream(imageBuildResponse.Body, buf, os.Stderr.Fd(), false /* not terminal */, writeAux)
if err != nil {
if jerr, ok := err.(*jsonmessage.JSONError); ok {
// If no error code is set, default to 1
if jerr.Code == 0 {
jerr.Code = 1
}
return fmt.Errorf("error while building image: %s", jerr.Message)
}
}

{"id":"moby.buildkit.trace","aux":"Cn0KR3NoYTI1NjozZThhMzMxYmRkZGFjNWZkYmNjOGVhMDFmYWFhYmM3MjA0MDkwMmYwNjdmYzRhOGY0NDJmMmIzYWVlN2RkNGIyGiRbaW50ZXJuYWxdIGxvYWQgcmVtb3RlIGJ1aWxkIGNvbnRleHQqDAiYw8KaBhCykpCqAg=="}
{"id":"moby.buildkit.trace","aux":"CokBCkdzaGEyNTY6M2U4YTMzMWJkZGRhYzVmZGJjYzhlYTAxZmFhYWJjNzIwNDA5MDJmMDY3ZmM0YThmNDQyZjJiM2FlZTdkZDRiMhokW2ludGVybmFsXSBsb2FkIHJlbW90ZSBidWlsZCBjb250ZXh0KgwImMPCmgYQspKQqgIyCgiZw8KaBhD08F0="}

$ base64 -d <<<'Cn0KR3NoYTI1NjozZThhMzMxYmRkZGFjNWZkYmNjOGVhMDFmYWFhYmM3MjA0MDkwMmYwNjdmYzRhOGY0NDJmMmIzYWVlN2RkNGIyGiRbaW50ZXJuYWxdIGxvYWQgcmVtb3RlIGJ1aWxkIGNvbnRleHQqDAiYw8KaBhCykpCqAg=='
}
Gsha256:3e8a331bdddac5fdbcc8ea01faaabc72040902f067fc4a8f442f2b3aee7dd4b2�$[internal] load remote build context*
������

答案1

得分: 1

当我写SO问题时，我当然找到了答案...

在build_buildkit.go中的writeAux函数调用了一个tracer实例的write方法，这才是真正的工作。我一定是瞎了。

这些消息是来自github.com/moby/buildkit/api/services/control包中的StatusResponse的序列化实例。它们被解码为base64字节序列并进行检查。如果你只想要日志并跳过其他内容，只需查找具有非空Logs成员数组的实例，例如在上述的writeAux函数中的以下代码：

                } else if msg.ID == "moby.buildkit.trace" {
                        // Process the message like
                        // https://github.com/docker/docker-ce/blob/523cf7e71252013fbb6a590be67a54b4a88c1dae/components/cli/cli/command/image/build_buildkit.go#L386
                        // the 'tracer.write' method in build_buildkit.go
                        var resp controlapi.StatusResponse
                        var dt []byte
                        // ignoring all messages that are not understood
                        if err := json.Unmarshal(*msg.Aux, &dt); err != nil {
                                return
                        }
                        if err := (&resp).Unmarshal(dt); err != nil {
                                return
                        }
                        for _, v := range resp.Vertexes {
                                fmt.Printf("layer: %+v", v)
                        }
                        for _, v := range resp.Statuses {
                                fmt.Printf("status: %+v", v)
                        }
                        for _, v := range resp.Logs {
                                fmt.Printf("log: msg.Msg)
                        }
                  }

json.Unmarshal和controlapi.StatusResponse.Unmarshal会为您进行base64解码和拆包。

                } else if msg.ID == "moby.buildkit.trace" {
// Process the message like
// https://github.com/docker/docker-ce/blob/523cf7e71252013fbb6a590be67a54b4a88c1dae/components/cli/cli/command/image/build_buildkit.go#L386
// the 'tracer.write' method in build_buildkit.go
var resp controlapi.StatusResponse
var dt []byte
// ignoring all messages that are not understood
if err := json.Unmarshal(*msg.Aux, &dt); err != nil {
return
}
if err := (&resp).Unmarshal(dt); err != nil {
return
}
for _, v := range resp.Vertexes {
fmt.Printf("layer: %+v", v)
}
for _, v := range resp.Statuses {
fmt.Printf("status: %+v", v)
}
for _, v := range resp.Logs {
fmt.Printf("log: msg.Msg)
}
}