Push signal-delivery and wait into the sandbox.

This is another step towards multi-container support.

Previously, we delivered signals directly to the sandbox process (which then
forwarded the signal to PID 1 inside the sandbox). Similarly, we waited on a
container by waiting on the sandbox process itself. This approach will not work
when there are multiple containers inside the sandbox, and we need to
signal/wait on individual containers.

This CL adds two new messages, ContainerSignal and ContainerWait. These
messages include the id of the container to signal/wait. The controller inside
the sandbox receives these messages and signals/waits on the appropriate
process inside the sandbox.

The container id is plumbed into the sandbox, but it currently is not used. We
still end up signaling/waiting on PID 1 in all cases.  Once we actually have
multiple containers inside the sandbox, we will need to keep some sort of map
of container id -> pid (or possibly pid namespace), and signal/kill the
appropriate process for the container.

PiperOrigin-RevId: 197028366
Change-Id: I07b4d5dc91ecd2affc1447e6b4bdd6b0b7360895

1 files changed, 7 insertions, 3 deletions

diff --git a/runsc/container/container.go b/runsc/container/container.go
index 97115cd6b..ae86e40c9 100644
--- a/runsc/container/container.go
+++ b/runsc/container/container.go
@@ -120,9 +120,13 @@ func Load(rootDir, id string) (*Container, error) {
 	//
 	// This is inherently racey.
 	if c.Status == Running || c.Status == Created {
-		// Send signal 0 to check if container still exists.
-		if err := c.Signal(0); err != nil {
-			// Container no longer exists.
+		// Check if the sandbox process is still running.
+		if c.Sandbox.IsRunning() {
+			// TODO: Send a message into the sandbox to
+			// see if this particular container is still running.
+		} else {
+			// Sandbox no longer exists, so this container
+			// definitly does not exist.
 			c.Status = Stopped
 			c.Sandbox = nil
 		}