pod: add exit policies

Add the notion of an "exit policy" to a pod.  This policy controls the
behaviour when the last container of pod exits.  Initially, there are
two policies:

 - "continue" : the pod continues running. This is the default policy
                when creating a pod.

 - "stop" : stop the pod when the last container exits. This is the
            default behaviour for `play kube`.

In order to implement the deferred stop of a pod, add a worker queue to
the libpod runtime.  The queue will pick up work items and in this case
helps resolve dead locks that would otherwise occur if we attempted to
stop a pod during container cleanup.

Note that the default restart policy of `play kube` is "Always".  Hence,
in order to really solve #13464, the YAML files must set a custom
restart policy; the tests use "OnFailure".

Fixes: #13464
Signed-off-by: Valentin Rothberg <vrothberg@redhat.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/libpod/runtime_worker.go b/libpod/runtime_worker.go
new file mode 100644
index 000000000..ca44a27f7
--- /dev/null
+++ b/libpod/runtime_worker.go
@@ -0,0 +1,41 @@
+package libpod
+
+import (
+	"time"
+)
+
+func (r *Runtime) startWorker() {
+	if r.workerChannel == nil {
+		r.workerChannel = make(chan func(), 1)
+		r.workerShutdown = make(chan bool)
+	}
+	go func() {
+		for {
+			// Make sure to read all workers before
+			// checking if we're about to shutdown.
+			for len(r.workerChannel) > 0 {
+				w := <-r.workerChannel
+				w()
+			}
+
+			select {
+			// We'll read from the shutdown channel only when all
+			// items above have been processed.
+			//
+			// (*Runtime).Shutdown() will block until until the
+			// item is read.
+			case <-r.workerShutdown:
+				return
+
+			default:
+				time.Sleep(100 * time.Millisecond)
+			}
+		}
+	}()
+}
+
+func (r *Runtime) queueWork(f func()) {
+	go func() {
+		r.workerChannel <- f
+	}()
+}