subscription: add ModifySubscription functionality

README.md

@@ -241,7 +241,7 @@ Here is the current set of supported services. For low-level access use the clie
 |                             | SetMonitoringMode             | Yes    | Yes    |              |
 |                             | SetTriggering                 |        |        |              |
 | Subscription Service Set    | CreateSubscription            | Yes    | Yes    |              |
-|                             | ModifySubscription            |        |        |              |
+|                             | ModifySubscription            | Yes    |        |              |
 |                             | SetPublishingMode             |        |        |              |
 |                             | Publish                       | Yes    | Yes    |              |
 |                             | Republish                     |        |        |              |

client_sub.go

@@ -72,7 +72,7 @@ func (c *Client) Subscribe(ctx context.Context, params *SubscriptionParameters,
 	}
 
 	c.subs[sub.SubscriptionID] = sub
-	c.updatePublishTimeout_NeedsSubMuxRLock()
+	c.updatePublishTimeout_NeedsSubMuxLock()
 	return sub, nil
 }
 
@@ -89,7 +89,7 @@ func (c *Client) SubscriptionIDs() []uint32 {
 }
 
 // recreateSubscriptions creates new subscriptions
-// with the same parameters to replace the previous ones
+// with the same parameters to replace the previous one
 func (c *Client) recreateSubscription(ctx context.Context, id uint32) error {
 	c.subMux.Lock()
 	defer c.subMux.Unlock()
@@ -98,7 +98,10 @@ func (c *Client) recreateSubscription(ctx context.Context, id uint32) error {
 	if !ok {
 		return ua.StatusBadSubscriptionIDInvalid
 	}
-	return sub.recreate_NeedsSubMuxLock(ctx)
+
+	sub.recreate_delete(ctx)
+	c.forgetSubscription_NeedsSubMuxLock(ctx, id)
+	return sub.recreate_create(ctx)
 }
 
 // transferSubscriptions ask the server to transfer the given subscriptions
@@ -230,7 +233,7 @@ func (c *Client) forgetSubscription(ctx context.Context, id uint32) {
 
 func (c *Client) forgetSubscription_NeedsSubMuxLock(ctx context.Context, id uint32) {
 	delete(c.subs, id)
-	c.updatePublishTimeout_NeedsSubMuxRLock()
+	c.updatePublishTimeout_NeedsSubMuxLock()
 	stats.Subscription().Add("Count", -1)
 
 	if len(c.subs) == 0 {
@@ -240,7 +243,7 @@ func (c *Client) forgetSubscription_NeedsSubMuxLock(ctx context.Context, id uint
 	}
 }
 
-func (c *Client) updatePublishTimeout_NeedsSubMuxRLock() {
+func (c *Client) updatePublishTimeout_NeedsSubMuxLock() {
 	maxTimeout := uasc.MaxTimeout
 	for _, s := range c.subs {
 		if d := s.publishTimeout(); d < maxTimeout {
@@ -470,7 +473,7 @@ func (c *Client) publish(ctx context.Context) error {
 		}
 
 		// handle the publish response for a specific subscription
-		c.handleNotification_NeedsSubMuxLock(ctx, sub, res)
+		c.handleNotification_NeedsSubMuxLock(sub, res)
 		c.subMux.Unlock()
 
 		c.notifySubscription(ctx, sub, res.NotificationMessage)
@@ -513,7 +516,7 @@ func (c *Client) handleAcks_NeedsSubMuxLock(res []ua.StatusCode) {
 	dlog.Printf("notAcked=%v", notAcked)
 }
 
-func (c *Client) handleNotification_NeedsSubMuxLock(ctx context.Context, sub *Subscription, res *ua.PublishResponse) {
+func (c *Client) handleNotification_NeedsSubMuxLock(sub *Subscription, res *ua.PublishResponse) {
 	dlog := debug.NewPrefixLogger("publish: sub %d: ", res.SubscriptionID)
 
 	// keep-alive message

examples/subscribe/subscribe.go

@@ -97,6 +97,14 @@ func main() {
 		log.Fatal(err)
 	}
 
+	// Uncomment the following to try modifying the subscription
+	//
+	// var params opcua.SubscriptionParameters
+	// params.Interval = time.Millisecond * 2000
+	// if _, err := sub.ModifySubscription(ctx, params); err != nil {
+	// 	log.Fatal(err)
+	// }
+
 	// read from subscription's notification channel until ctx is cancelled
 	for {
 		select {

subscription.go

@@ -22,15 +22,14 @@ const (
 	DefaultSubscriptionPriority                   = 0
 )
 
-const terminatedSubscriptionID uint32 = 0xC0CAC01B
-
 type Subscription struct {
 	SubscriptionID            uint32
 	RevisedPublishingInterval time.Duration
 	RevisedLifetimeCount      uint32
 	RevisedMaxKeepAliveCount  uint32
 	Notifs                    chan<- *PublishNotificationData
 	params                    *SubscriptionParameters
+	paramsMu                  sync.Mutex
 	items                     map[uint32]*monitoredItem
 	itemsMu                   sync.Mutex
 	lastSeq                   uint32
@@ -111,6 +110,40 @@ func (s *Subscription) delete(ctx context.Context) error {
 	}
 }
 
+func (s *Subscription) ModifySubscription(ctx context.Context, params SubscriptionParameters) (*ua.ModifySubscriptionResponse, error) {
+	stats.Subscription().Add("ModifySubscription", 1)
+
+	params.setDefaults()
+	req := &ua.ModifySubscriptionRequest{
+		SubscriptionID:              s.SubscriptionID,
+		RequestedPublishingInterval: float64(params.Interval.Milliseconds()),
+		RequestedLifetimeCount:      params.LifetimeCount,
+		RequestedMaxKeepAliveCount:  params.MaxKeepAliveCount,
+		MaxNotificationsPerPublish:  params.MaxNotificationsPerPublish,
+		Priority:                    params.Priority,
+	}
+
+	var res *ua.ModifySubscriptionResponse
+	err := s.c.Send(ctx, req, func(v ua.Response) error {
+		return safeAssign(v, &res)
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	// update subscription parameters
+	s.paramsMu.Lock()
+	s.params = &params
+	s.paramsMu.Unlock()
+	// update revised subscription parameters
+	s.RevisedPublishingInterval = time.Duration(res.RevisedPublishingInterval) * time.Millisecond
+	s.RevisedLifetimeCount = res.RevisedLifetimeCount
+	s.RevisedMaxKeepAliveCount = res.RevisedMaxKeepAliveCount
+
+	return res, nil
+}
+
 func (s *Subscription) Monitor(ctx context.Context, ts ua.TimestampsToReturn, items ...*ua.MonitoredItemCreateRequest) (*ua.CreateMonitoredItemsResponse, error) {
 	stats.Subscription().Add("Monitor", 1)
 	stats.Subscription().Add("MonitoredItems", int64(len(items)))
@@ -358,29 +391,31 @@ func (p *SubscriptionParameters) setDefaults() {
 	}
 }
 
-// recreate_NeedsSubMuxLock creates a new subscription based on the previous subscription
-// parameters and monitored items.
-func (s *Subscription) recreate_NeedsSubMuxLock(ctx context.Context) error {
-	dlog := debug.NewPrefixLogger("sub %d: recreate: ", s.SubscriptionID)
-
-	if s.SubscriptionID == terminatedSubscriptionID {
-		dlog.Printf("subscription is not in a valid state")
-		return nil
+// recreate_delete is called by the client when it is trying to
+// recreate an existing subscription. This function deletes the
+// existing subscription from the server.
+func (s *Subscription) recreate_delete(ctx context.Context) error {
+	dlog := debug.NewPrefixLogger("sub %d: recreate_delete: ", s.SubscriptionID)
+	req := &ua.DeleteSubscriptionsRequest{
+		SubscriptionIDs: []uint32{s.SubscriptionID},
 	}
+	var res *ua.DeleteSubscriptionsResponse
+	_ = s.c.Send(ctx, req, func(v ua.Response) error {
+		return safeAssign(v, &res)
+	})
+	dlog.Print("subscription deleted")
+	return nil
+}
+
+// recreate_create is called by the client when it is trying to
+// recreate an existing subscription. This function creates a
+// new subscription with the same parameters as the previous one.
+func (s *Subscription) recreate_create(ctx context.Context) error {
+	dlog := debug.NewPrefixLogger("sub %d: recreate_create: ", s.SubscriptionID)
 
+	s.paramsMu.Lock()
 	params := s.params
-	{
-		req := &ua.DeleteSubscriptionsRequest{
-			SubscriptionIDs: []uint32{s.SubscriptionID},
-		}
-		var res *ua.DeleteSubscriptionsResponse
-		_ = s.c.Send(ctx, req, func(v ua.Response) error {
-			return safeAssign(v, &res)
-		})
-		dlog.Print("subscription deleted")
-	}
-	s.c.forgetSubscription_NeedsSubMuxLock(ctx, s.SubscriptionID)
-	dlog.Printf("subscription forgotton")
+	s.paramsMu.Unlock()
 
 	req := &ua.CreateSubscriptionRequest{
 		RequestedPublishingInterval: float64(params.Interval / time.Millisecond),