Improve APIv2 support for Attach

A few major fixes here:
- Support for attaching to Configured containers, to match Docker
  behavior.
- Support for stream parameter has been improved (we now properly
  handle cases where it is not set).
- Initial support for logs parameter has been added.
- Setting attach streams when the container has a terminal is now
  supported.
- Errors are properly reported once the hijack has begun.

Signed-off-by: Matthew Heon <mheon@redhat.com>

libpod/container_api.go

@@ -6,10 +6,13 @@ import (
 	"io/ioutil"
 	"net"
 	"os"
+	"strings"
+	"sync"
 	"time"
 
 	"github.com/containers/libpod/libpod/define"
 	"github.com/containers/libpod/libpod/events"
+	"github.com/containers/libpod/libpod/logs"
 	"github.com/opentracing/opentracing-go"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -244,15 +247,28 @@ func (c *Container) Attach(streams *define.AttachStreams, keys string, resize <-
 // forwarded to the client.
 // This function returns when the attach finishes. It does not hold the lock for
 // the duration of its runtime, only using it at the beginning to verify state.
-func (c *Container) HTTPAttach(httpCon net.Conn, httpBuf *bufio.ReadWriter, streams *HTTPAttachStreams, detachKeys *string, cancel <-chan bool) error {
+// The streamLogs parameter indicates that all the container's logs until present
+// will be streamed at the beginning of the attach.
+// The streamAttach parameter indicates that the attach itself will be streamed
+// over the socket; if this is not set, but streamLogs is, only the logs will be
+// sent.
+// At least one of streamAttach and streamLogs must be set.
+func (c *Container) HTTPAttach(httpCon net.Conn, httpBuf *bufio.ReadWriter, streams *HTTPAttachStreams, detachKeys *string, cancel <-chan bool, streamAttach, streamLogs bool) (deferredErr error) {
+	isTerminal := false
+	if c.config.Spec.Process != nil {
+		isTerminal = c.config.Spec.Process.Terminal
+	}
+	// Ensure our contract of writing errors to and closing the HTTP conn is
+	// honored.
+	defer func() {
+		hijackWriteErrorAndClose(deferredErr, c.ID(), isTerminal, httpCon, httpBuf)
+	}()
+
 	if !c.batched {
 		c.lock.Lock()
 		if err := c.syncContainer(); err != nil {
 			c.lock.Unlock()
 
-			// Write any errors to the HTTP buffer before we close.
-			hijackWriteErrorAndClose(err, c.ID(), httpCon, httpBuf)
-
 			return err
 		}
 		// We are NOT holding the lock for the duration of the function.
@@ -260,16 +276,80 @@ func (c *Container) HTTPAttach(httpCon net.Conn, httpBuf *bufio.ReadWriter, stre
 	}
 
 	if !c.ensureState(define.ContainerStateCreated, define.ContainerStateRunning) {
-		toReturn := errors.Wrapf(define.ErrCtrStateInvalid, "can only attach to created or running containers")
+		return errors.Wrapf(define.ErrCtrStateInvalid, "can only attach to created or running containers")
+	}
 
-		// Write any errors to the HTTP buffer before we close.
-		hijackWriteErrorAndClose(toReturn, c.ID(), httpCon, httpBuf)
-
-		return toReturn
+	if !streamAttach && !streamLogs {
+		return errors.Wrapf(define.ErrInvalidArg, "must specify at least one of stream or logs")
 	}
 
 	logrus.Infof("Performing HTTP Hijack attach to container %s", c.ID())
 
+	if streamLogs {
+		// Get all logs for the container
+		logChan := make(chan *logs.LogLine)
+		logOpts := new(logs.LogOptions)
+		logOpts.Tail = -1
+		logOpts.WaitGroup = new(sync.WaitGroup)
+		errChan := make(chan error)
+		go func() {
+			var err error
+			// In non-terminal mode we need to prepend with the
+			// stream header.
+			logrus.Debugf("Writing logs for container %s to HTTP attach", c.ID())
+			for logLine := range logChan {
+				if !isTerminal {
+					device := logLine.Device
+					var header []byte
+					headerLen := uint32(len(logLine.Msg))
+
+					switch strings.ToLower(device) {
+					case "stdin":
+						header = makeHTTPAttachHeader(0, headerLen)
+					case "stdout":
+						header = makeHTTPAttachHeader(1, headerLen)
+					case "stderr":
+						header = makeHTTPAttachHeader(2, headerLen)
+					default:
+						logrus.Errorf("Unknown device for log line: %s", device)
+						header = makeHTTPAttachHeader(1, headerLen)
+					}
+					_, err = httpBuf.Write(header)
+					if err != nil {
+						break
+					}
+				}
+				_, err = httpBuf.Write([]byte(logLine.Msg))
+				if err != nil {
+					break
+				}
+				_, err = httpBuf.Write([]byte("\n"))
+				if err != nil {
+					break
+				}
+				err = httpBuf.Flush()
+				if err != nil {
+					break
+				}
+			}
+			errChan <- err
+		}()
+		go func() {
+			logOpts.WaitGroup.Wait()
+			close(logChan)
+		}()
+		if err := c.ReadLog(logOpts, logChan); err != nil {
+			return err
+		}
+		logrus.Debugf("Done reading logs for container %s", c.ID())
+		if err := <-errChan; err != nil {
+			return err
+		}
+	}
+	if !streamAttach {
+		return nil
+	}
+
 	c.newContainerEvent(events.Attach)
 	return c.ociRuntime.HTTPAttach(c, httpCon, httpBuf, streams, detachKeys, cancel)
 }