feat: provide callback for connection alive messages (shurcooL#77)

Author: sermojohn

subscription.go

@@ -107,16 +107,17 @@ type SubscriptionProtocol interface {
 // SubscriptionContext represents a shared context for protocol implementations with the websocket connection inside
 type SubscriptionContext struct {
 	context.Context
-	websocketConn    WebsocketConn
-	OnConnected      func()
-	onDisconnected   func()
-	cancel           context.CancelFunc
-	subscriptions    map[string]Subscription
-	disabledLogTypes []OperationMessageType
-	log              func(args ...interface{})
-	acknowledged     int32
-	exitStatusCodes  []int
-	mutex            sync.Mutex
+	websocketConn     WebsocketConn
+	OnConnected       func()
+	onDisconnected    func()
+	onConnectionAlive func()
+	cancel            context.CancelFunc
+	subscriptions     map[string]Subscription
+	disabledLogTypes  []OperationMessageType
+	log               func(args ...interface{})
+	acknowledged      int32
+	exitStatusCodes   []int
+	mutex             sync.Mutex
 }
 
 // Log prints condition logging with message type filters
@@ -419,6 +420,12 @@ func (sc *SubscriptionClient) OnDisconnected(fn func()) *SubscriptionClient {
 	return sc
 }
 
+// OnConnectionAlive event is triggered when the websocket receive a connection alive message (differs per protocol)
+func (sc *SubscriptionClient) OnConnectionAlive(fn func()) *SubscriptionClient {
+	sc.context.onConnectionAlive = fn
+	return sc
+}
+
 // get internal client status
 func (sc *SubscriptionClient) getClientStatus() int32 {
 	return atomic.LoadInt32(&sc.clientStatus)

subscription_graphql_ws.go

@@ -132,6 +132,9 @@ func (gws *graphqlWS) OnMessage(ctx *SubscriptionContext, subscription Subscript
 		_ = gws.Unsubscribe(ctx, message.ID)
 	case GQLPing:
 		ctx.Log(message, "server", GQLPing)
+		if ctx.onConnectionAlive != nil {
+			ctx.onConnectionAlive()
+		}
 		// send pong response message back to the server
 		msg := OperationMessage{
 			Type:    GQLPong,

subscriptions_transport_ws.go

@@ -164,6 +164,9 @@ func (stw *subscriptionsTransportWS) OnMessage(ctx *SubscriptionContext, subscri
 		_ = stw.Unsubscribe(ctx, message.ID)
 	case GQLConnectionKeepAlive:
 		ctx.Log(message, "server", GQLConnectionKeepAlive)
+		if ctx.onConnectionAlive != nil {
+			ctx.onConnectionAlive()
+		}
 	case GQLConnectionAck:
 		// Expected response to the ConnectionInit message from the client acknowledging a successful connection with the server.
 		// The client is now ready to request subscription operations.