dotcloud/docker

package utils // import "github.com/docker/docker/distribution/utils"

import (
    "context"
    "io"
    "net"
    "os"
    "syscall"

    "github.com/containerd/log"
    "github.com/docker/docker/pkg/progress"
    "github.com/docker/docker/pkg/streamformatter"
)

// WriteDistributionProgress is a helper for writing progress from chan to JSON
// stream with an optional cancel function.
func WriteDistributionProgress(cancelFunc func(), outStream io.Writer, progressChan <-chan progress.Progress) {
    progressOutput := streamformatter.NewJSONProgressOutput(outStream, false)
    operationCancelled := false

    for prog := range progressChan {
        if err := progressOutput.WriteProgress(prog); err != nil && !operationCancelled {
            // don't log broken pipe errors as this is the normal case when a client aborts
            if isBrokenPipe(err) {
                log.G(context.TODO()).Info("Pull session cancelled")
            } else {
                log.G(context.TODO()).Errorf("error writing progress to client: %v", err)
            }
            cancelFunc()
            operationCancelled = true
            // Don't return, because we need to continue draining
            // progressChan until it's closed to avoid a deadlock.
        }
    }
}

func isBrokenPipe(e error) bool {
    if netErr, ok := e.(*net.OpError); ok {
        e = netErr.Err
        if sysErr, ok := netErr.Err.(*os.SyscallError); ok {
            e = sysErr.Err
        }
    }
    return e == syscall.EPIPE
}