在docker exec响应开始时解释并删除无用的字节

Question

Im running the docker api function:

func (cli *Client) ContainerExecAttach(ctx context.Context, execID string, config types.ExecConfig) (types.HijackedResponse, error)

When I read the response using the built in bufio reader:

line, _, err := resp.Reader.ReadLine()

I get no error but if I try to convert the bytes to a string the app crashes - the app in question is a windows service, and i think because of this I'm struggling to get an error out of it.

I have now managed to view the output using (logs to event viewer):

logger.Infof("res: %q", line)

the output from this is:

res: "\x01\x00\x00\x00\x00\x00\x00X{\"updating\":false,\"scanning\":false,\"progress\":0,\"discovering\":false,\"registered\":false}"

Now, I was expecting the json but the funky prefix is most unwelcome, any idea what these bytes are are and why they are there? I'm hoping this will inform my next question; what is the cleanest way to remove them or not receive them in the first place?

I'm currently left trimming the bytes by a fixed length but I think I need to do something more sophisticated. I'm thinking left trim these bytes: \x01 \x00 but not sure if I should expect any others

Answer 1

The HTTP response you are getting back is the Docker stream format as documented here.

You should consider using the github.com/docker/docker/pkg/stdcopy.StdCopy function to demultiplex the stream into stdout / stderr.