Moved restore code out of create and made to be called after create.

Docker expects containers to be created before they are restored.
However, gVisor restoring requires specificactions regarding the kernel
and the file system. These actions were originally in booting the sandbox.

Now setting up the file system is deferred until a call to a call to
runsc start. In the restore case, the kernel is destroyed and a new kernel
is created in the same process, as we need the same process for Docker.

These changes required careful execution of concurrent processes which
required the use of a channel.

Full docker integration still needs the ability to restore into the same
container.

PiperOrigin-RevId: 205161441
Change-Id: Ie1d2304ead7e06855319d5dc310678f701bd099f

1 files changed, 19 insertions, 3 deletions

diff --git a/runsc/container/container.go b/runsc/container/container.go
index c4e5bf9f6..574075b00 100644
--- a/runsc/container/container.go
+++ b/runsc/container/container.go
@@ -190,7 +190,7 @@ func List(rootDir string) ([]string, error) {
 
 // Create creates the container in a new Sandbox process, unless the metadata
 // indicates that an existing Sandbox should be used.
-func Create(id string, spec *specs.Spec, conf *boot.Config, bundleDir, consoleSocket, pidFile string, restoreFile string) (*Container, error) {
+func Create(id string, spec *specs.Spec, conf *boot.Config, bundleDir, consoleSocket, pidFile string) (*Container, error) {
 	log.Debugf("Create container %q in root dir: %s", id, conf.RootDir)
 	if err := validateID(id); err != nil {
 		return nil, err
@@ -221,7 +221,7 @@ func Create(id string, spec *specs.Spec, conf *boot.Config, bundleDir, consoleSo
 		log.Debugf("Creating new sandbox for container %q", id)
 		// Start a new sandbox for this container. Any errors after this point
 		// must destroy the container.
-		s, err := sandbox.Create(id, spec, conf, bundleDir, consoleSocket, restoreFile)
+		s, err := sandbox.Create(id, spec, conf, bundleDir, consoleSocket)
 		if err != nil {
 			c.Destroy()
 			return nil, err
@@ -309,10 +309,26 @@ func (c *Container) Start(conf *boot.Config) error {
 	return c.save()
 }
 
+// Restore takes a container and replaces its kernel and file system
+// to restore a container from its state file.
+func (c *Container) Restore(spec *specs.Spec, conf *boot.Config, restoreFile string) error {
+	log.Debugf("Restore container %q", c.ID)
+
+	if c.Status != Created {
+		return fmt.Errorf("cannot restore container in state %s", c.Status)
+	}
+
+	if err := c.Sandbox.Restore(c.ID, spec, conf, restoreFile); err != nil {
+		return err
+	}
+	c.Status = Running
+	return c.save()
+}
+
 // Run is a helper that calls Create + Start + Wait.
 func Run(id string, spec *specs.Spec, conf *boot.Config, bundleDir, consoleSocket, pidFile string) (syscall.WaitStatus, error) {
 	log.Debugf("Run container %q in root dir: %s", id, conf.RootDir)
-	c, err := Create(id, spec, conf, bundleDir, consoleSocket, pidFile, "")
+	c, err := Create(id, spec, conf, bundleDir, consoleSocket, pidFile)
 	if err != nil {
 		return 0, fmt.Errorf("error creating container: %v", err)
 	}