Integrate NATS with event subsystem

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

events/nats.go

@@ -0,0 +1,31 @@
+package events
+
+import (
+	"context"
+	"strings"
+
+	"github.com/docker/containerd/log"
+	nats "github.com/nats-io/go-nats"
+)
+
+type natsPoster struct {
+	nec *nats.EncodedConn
+}
+
+func GetNATSPoster(nec *nats.EncodedConn) Poster {
+	return &natsPoster{nec}
+}
+
+func (p *natsPoster) Post(ctx context.Context, e Event) {
+	subject := strings.Replace(log.GetModulePath(ctx), "/", ".", -1)
+	topic := getTopic(ctx)
+	if topic != "" {
+		subject = strings.Join([]string{subject, topic}, ".")
+	}
+
+	if subject == "" {
+		log.GetLogger(ctx).WithField("event", e).Warn("unable to post event, subject is empty")
+	}
+
+	p.nec.Publish(subject, e)
+}