api: Notify events only if bucket notifications are set. (#2293)

While the existing code worked, it went to an entire cycle
of constructing event structure and end up not sending it.

Avoid this in the first place, but returning quickly if
notifications are not set on the bucket.

bucket-handlers.go

@@ -25,6 +25,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"path"
 	"strings"
 
 	mux "github.com/gorilla/mux"
@@ -391,14 +392,25 @@ func (api objectAPIHandlers) PostPolicyBucketHandler(w http.ResponseWriter, r *h
 
 	// Load notification config if any.
 	nConfig, err := api.loadNotificationConfig(bucket)
+	// Notifications not set, return.
+	if err == errNoSuchNotifications {
+		return
+	}
+	// For all other errors, return.
 	if err != nil {
 		errorIf(err, "Unable to load notification config for bucket: \"%s\"", bucket)
 		return
 	}
 
-	size := int64(0) // FIXME: support notify size.
-	// Notify event.
-	notifyObjectCreatedEvent(nConfig, ObjectCreatedPost, bucket, object, md5Sum, size)
+	// Fetch object info for notifications.
+	objInfo, err := api.ObjectAPI.GetObjectInfo(bucket, object)
+	if err != nil {
+		errorIf(err, "Unable to fetch object info for \"%s\"", path.Join(bucket, object))
+		return
+	}
+
+	// Notify object created event.
+	notifyObjectCreatedEvent(nConfig, ObjectCreatedPost, bucket, objInfo)
 }
 
 // HeadBucketHandler - HEAD Bucket