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)
+}

events/poster.go

@@ -3,8 +3,8 @@ package events
 import (
 	"context"
 
-	"github.com/Sirupsen/logrus"
 	"github.com/docker/containerd/log"
+	"github.com/sirupsen/logrus"
 )
 
 var (
@@ -13,13 +13,17 @@ var (
 
 // Poster posts the event.
 type Poster interface {
-	Post(event Event)
+	Post(ctx context.Context, event Event)
 }
 
 type posterKey struct{}
 
+func WithPoster(ctx context.Context, poster Poster) context.Context {
+	return context.WithValue(ctx, posterKey{}, poster)
+}
+
 func GetPoster(ctx context.Context) Poster {
-	poster := ctx.Value(ctx)
+	poster := ctx.Value(posterKey{})
 	if poster == nil {
 		logger := log.G(ctx)
 		tx, _ := getTx(ctx)
@@ -27,7 +31,7 @@ func GetPoster(ctx context.Context) Poster {
 
 		// likely means we don't have a configured event system. Just return
 		// the default poster, which merely logs events.
-		return posterFunc(func(event Event) {
+		return posterFunc(func(ctx context.Context, event Event) {
 			fields := logrus.Fields{"event": event}
 
 			if topic != "" {
@@ -48,8 +52,8 @@ func GetPoster(ctx context.Context) Poster {
 	return poster.(Poster)
 }
 
-type posterFunc func(event Event)
+type posterFunc func(ctx context.Context, event Event)
 
-func (fn posterFunc) Post(event Event) {
-	fn(event)
+func (fn posterFunc) Post(ctx context.Context, event Event) {
+	fn(ctx, event)
 }

events/transaction.go

@@ -18,6 +18,7 @@ func nexttxID() int64 {
 }
 
 type transaction struct {
+	ctx        context.Context
 	id         int64
 	parent     *transaction // if nil, no parent transaction
 	finish     sync.Once
@@ -25,17 +26,18 @@ type transaction struct {
 }
 
 // begin creates a sub-transaction.
-func (tx *transaction) begin(poster Poster) *transaction {
+func (tx *transaction) begin(ctx context.Context, poster Poster) *transaction {
 	id := nexttxID()
 
 	child := &transaction{
+		ctx:    ctx,
 		id:     id,
 		parent: tx,
 		start:  time.Now(),
 	}
 
 	// post the transaction started event
-	poster.Post(child.makeTransactionEvent("begin")) // tranactions are really just events
+	poster.Post(ctx, child.makeTransactionEvent("begin")) // tranactions are really just events
 
 	return child
 }
@@ -44,7 +46,7 @@ func (tx *transaction) begin(poster Poster) *transaction {
 func (tx *transaction) commit(poster Poster) {
 	tx.finish.Do(func() {
 		tx.end = time.Now()
-		poster.Post(tx.makeTransactionEvent("commit"))
+		poster.Post(tx.ctx, tx.makeTransactionEvent("commit"))
 	})
 }
 
@@ -53,7 +55,7 @@ func (tx *transaction) rollback(poster Poster, cause error) {
 		tx.end = time.Now()
 		event := tx.makeTransactionEvent("rollback")
 		event = fmt.Sprintf("%s error=%q", event, cause.Error())
-		poster.Post(event)
+		poster.Post(tx.ctx, event)
 	})
 }
 
@@ -84,7 +86,7 @@ func getTx(ctx context.Context) (*transaction, bool) {
 func WithTx(pctx context.Context) (ctx context.Context, commit func(), rollback func(err error)) {
 	poster := G(pctx)
 	parent, _ := getTx(pctx)
-	tx := parent.begin(poster)
+	tx := parent.begin(pctx, poster)
 
 	return context.WithValue(pctx, txKey{}, tx), func() {
 			tx.commit(poster)