libpod: fix hang on container start and attach

When a container is attached upon start, the WaitGroup counter may
never be decremented if an error is raised before start, causing
the caller to hang.
Synchronize with the start & attach goroutine using a channel, to be
able to detect failures before start.

Signed-off-by: Marco Vedovati <mvedovati@suse.com>
This commit is contained in:
Marco Vedovati
2019-06-17 15:14:54 +02:00
parent 6e9b490f5e
commit 4f56964d55
3 changed files with 18 additions and 18 deletions

View File

@ -7,7 +7,6 @@ import (
"io/ioutil"
"os"
"strconv"
"sync"
"time"
"github.com/containers/libpod/libpod/define"
@ -120,20 +119,24 @@ func (c *Container) StartAndAttach(ctx context.Context, streams *AttachStreams,
attachChan := make(chan error)
// We need to ensure that we don't return until start() fired in attach.
// Use a WaitGroup to sync this.
wg := new(sync.WaitGroup)
wg.Add(1)
// Use a channel to sync
startedChan := make(chan bool)
// Attach to the container before starting it
go func() {
if err := c.attach(streams, keys, resize, true, wg); err != nil {
if err := c.attach(streams, keys, resize, true, startedChan); err != nil {
attachChan <- err
}
close(attachChan)
}()
wg.Wait()
c.newContainerEvent(events.Attach)
select {
case err := <-attachChan:
return nil, err
case <-startedChan:
c.newContainerEvent(events.Attach)
}
return attachChan, nil
}

View File

@ -8,7 +8,6 @@ import (
"net"
"os"
"path/filepath"
"sync"
"github.com/containers/libpod/libpod/define"
"github.com/containers/libpod/pkg/kubeutils"
@ -33,22 +32,22 @@ const (
// Attach to the given container
// Does not check if state is appropriate
func (c *Container) attach(streams *AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, wg *sync.WaitGroup) error {
func (c *Container) attach(streams *AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, started chan bool) error {
if !streams.AttachOutput && !streams.AttachError && !streams.AttachInput {
return errors.Wrapf(define.ErrInvalidArg, "must provide at least one stream to attach to")
}
logrus.Debugf("Attaching to container %s", c.ID())
return c.attachContainerSocket(resize, keys, streams, startContainer, wg)
return c.attachContainerSocket(resize, keys, streams, startContainer, started)
}
// attachContainerSocket connects to the container's attach socket and deals with the IO.
// wg is only required if startContainer is true
// started is only required if startContainer is true
// TODO add a channel to allow interrupting
func (c *Container) attachContainerSocket(resize <-chan remotecommand.TerminalSize, keys string, streams *AttachStreams, startContainer bool, wg *sync.WaitGroup) error {
if startContainer && wg == nil {
return errors.Wrapf(define.ErrInternal, "wait group not passed when startContainer set")
func (c *Container) attachContainerSocket(resize <-chan remotecommand.TerminalSize, keys string, streams *AttachStreams, startContainer bool, started chan bool) error {
if startContainer && started == nil {
return errors.Wrapf(define.ErrInternal, "started chan not passed when startContainer set")
}
// Use default detach keys when keys aren't passed or specified in libpod.conf
@ -100,7 +99,7 @@ func (c *Container) attachContainerSocket(resize <-chan remotecommand.TerminalSi
if err := c.start(); err != nil {
return err
}
wg.Done()
started <- true
}
receiveStdoutError := make(chan error)

View File

@ -3,12 +3,10 @@
package libpod
import (
"sync"
"github.com/containers/libpod/libpod/define"
"k8s.io/client-go/tools/remotecommand"
)
func (c *Container) attach(streams *AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, wg *sync.WaitGroup) error {
func (c *Container) attach(streams *AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, started chan bool) error {
return define.ErrNotImplemented
}