Use constant tick rate for websocket keepalive

Some clients (e.g. apollographql/subscriptions-transport-ws) expect a
constant tick rate for the keepalive, not just a keepalive after x
duration of inactivity.

handler/graphql.go

@@ -26,16 +26,16 @@ type params struct {
 }
 
 type Config struct {
-	cacheSize                  int
-	upgrader                   websocket.Upgrader
-	recover                    graphql.RecoverFunc
-	errorPresenter             graphql.ErrorPresenterFunc
-	resolverHook               graphql.FieldMiddleware
-	requestHook                graphql.RequestMiddleware
-	tracer                     graphql.Tracer
-	complexityLimit            int
-	disableIntrospection       bool
-	connectionKeepAliveTimeout time.Duration
+	cacheSize                       int
+	upgrader                        websocket.Upgrader
+	recover                         graphql.RecoverFunc
+	errorPresenter                  graphql.ErrorPresenterFunc
+	resolverHook                    graphql.FieldMiddleware
+	requestHook                     graphql.RequestMiddleware
+	tracer                          graphql.Tracer
+	complexityLimit                 int
+	disableIntrospection            bool
+	connectionKeepAlivePingInterval time.Duration
 }
 
 func (c *Config) newRequestContext(es graphql.ExecutableSchema, doc *ast.QueryDocument, op *ast.OperationDefinition, query string, variables map[string]interface{}) *graphql.RequestContext {
@@ -249,7 +249,7 @@ const DefaultCacheSize = 1000
 // By default, keep-alive is disabled.
 func WebsocketKeepAliveDuration(duration time.Duration) Option {
 	return func(cfg *Config) {
-		cfg.connectionKeepAliveTimeout = duration
+		cfg.connectionKeepAlivePingInterval = duration
 	}
 }
 

handler/websocket.go

@@ -38,13 +38,13 @@ type operationMessage struct {
 }
 
 type wsConnection struct {
-	ctx            context.Context
-	conn           *websocket.Conn
-	exec           graphql.ExecutableSchema
-	active         map[string]context.CancelFunc
-	mu             sync.Mutex
-	cfg            *Config
-	keepAliveTimer *time.Timer
+	ctx             context.Context
+	conn            *websocket.Conn
+	exec            graphql.ExecutableSchema
+	active          map[string]context.CancelFunc
+	mu              sync.Mutex
+	cfg             *Config
+	keepAliveTicker *time.Ticker
 
 	initPayload InitPayload
 }
@@ -107,9 +107,6 @@ func (c *wsConnection) init() bool {
 func (c *wsConnection) write(msg *operationMessage) {
 	c.mu.Lock()
 	c.conn.WriteJSON(msg)
-	if c.cfg.connectionKeepAliveTimeout != 0 && c.keepAliveTimer != nil {
-		c.keepAliveTimer.Reset(c.cfg.connectionKeepAliveTimeout)
-	}
 	c.mu.Unlock()
 }
 
@@ -119,11 +116,10 @@ func (c *wsConnection) run() {
 	ctx, cancel := context.WithCancel(c.ctx)
 	defer cancel()
 
-	// Create a timer that will fire every interval if a write hasn't been made
-	// to keep the connection alive.
-	if c.cfg.connectionKeepAliveTimeout != 0 {
+	// Create a timer that will fire every interval to keep the connection alive.
+	if c.cfg.connectionKeepAlivePingInterval != 0 {
 		c.mu.Lock()
-		c.keepAliveTimer = time.NewTimer(c.cfg.connectionKeepAliveTimeout)
+		c.keepAliveTicker = time.NewTicker(c.cfg.connectionKeepAlivePingInterval)
 		c.mu.Unlock()
 
 		go c.keepAlive(ctx)
@@ -165,13 +161,9 @@ func (c *wsConnection) keepAlive(ctx context.Context) {
 	for {
 		select {
 		case <-ctx.Done():
-			if !c.keepAliveTimer.Stop() {
-				<-c.keepAliveTimer.C
-			}
+			c.keepAliveTicker.Stop()
 			return
-		case <-c.keepAliveTimer.C:
-			// We don't reset the timer here, because the `c.write` command
-			// will reset the timer anyways.
+		case <-c.keepAliveTicker.C:
 			c.write(&operationMessage{Type: connectionKeepAliveMsg})
 		}
 	}