Add unstable envvar to disable server keepalives (#43483)

lib/inventory/controller.go

@@ -188,6 +188,7 @@ type Controller struct {
 	serviceCounter             *serviceCounter
 	auth                       Auth
 	authID                     string
+	serverKeepAliveEnabled     bool
 	serverKeepAlive            time.Duration
 	serverTTL                  time.Duration
 	instanceTTL                time.Duration
@@ -202,6 +203,18 @@ type Controller struct {
 	cancel                     context.CancelFunc
 }
 
+// serverKeepAliveDisabledEnv checks if the periodic server keepalive has been
+// explicitly disabled via environment variable.
+func serverKeepAliveDisabledEnv() bool {
+	return os.Getenv("TELEPORT_UNSTABLE_DISABLE_SERVER_KEEPALIVE") == "yes"
+}
+
+// instanceHeartbeatsDisabledEnv checks if instance heartbeats have been explicitly disabled
+// via environment variable.
+func instanceHeartbeatsDisabledEnv() bool {
+	return os.Getenv("TELEPORT_UNSTABLE_DISABLE_INSTANCE_HB") == "yes"
+}
+
 // NewController sets up a new controller instance.
 func NewController(auth Auth, usageReporter usagereporter.UsageReporter, opts ...ControllerOption) *Controller {
 	var options controllerOptions
@@ -220,6 +233,7 @@ func NewController(auth Auth, usageReporter usagereporter.UsageReporter, opts ..
 	return &Controller{
 		store:                      NewStore(),
 		serviceCounter:             &serviceCounter{},
+		serverKeepAliveEnabled:     !serverKeepAliveDisabledEnv(),
 		serverKeepAlive:            options.serverKeepAlive,
 		serverTTL:                  apidefaults.ServerAnnounceTTL,
 		instanceTTL:                apidefaults.InstanceHeartbeatTTL,
@@ -325,9 +339,10 @@ func (c *Controller) handleControlStream(handle *upstreamHandle) {
 		c.testEvent(handlerClose)
 	}()
 
-	// keepAliveInit tracks wether or not we've initialized the server keepalive sub-interval. we do this lazily
-	// upon receipt of the first heartbeat since not all servers send heartbeats.
-	var keepAliveInit bool
+	// keepAliveNeedInit tracks wether or not we should initialize the server
+	// keepalive sub-interval upon receiving a heartbeat. We do this lazily upon
+	// receipt of the first heartbeat since not all servers send heartbeats.
+	keepAliveNeedInit := c.serverKeepAliveEnabled
 
 	for {
 		select {
@@ -344,15 +359,15 @@ func (c *Controller) handleControlStream(handle *upstreamHandle) {
 					handle.CloseWithError(err)
 					return
 				}
-				if !keepAliveInit {
+				if keepAliveNeedInit {
 					// this is the first heartbeat, so we need to initialize the keepalive sub-interval
 					handle.ticker.Push(interval.SubInterval[intervalKey]{
 						Key:           serverKeepAliveKey,
 						Duration:      c.serverKeepAlive,
 						FirstDuration: halfJitter(c.serverKeepAlive),
 						Jitter:        seventhJitter,
 					})
-					keepAliveInit = true
+					keepAliveNeedInit = false
 				}
 			case proto.UpstreamInventoryPong:
 				c.handlePong(handle, m)
@@ -391,12 +406,6 @@ func (c *Controller) handleControlStream(handle *upstreamHandle) {
 	}
 }
 
-// instanceHeartbeatsDisabledEnv checks if instance heartbeats have been explicitly disabled
-// via environment variable.
-func instanceHeartbeatsDisabledEnv() bool {
-	return os.Getenv("TELEPORT_UNSTABLE_DISABLE_INSTANCE_HB") == "yes"
-}
-
 func (c *Controller) heartbeatInstanceState(handle *upstreamHandle, now time.Time) error {
 	if !c.instanceHBEnabled {
 		return nil

lib/inventory/controller_test.go

@@ -545,6 +545,18 @@ func TestInstanceHeartbeatDisabledEnv(t *testing.T) {
 	require.False(t, controller.instanceHBEnabled)
 }
 
+func TestServerKeepaliveDisabledEnv(t *testing.T) {
+	t.Setenv("TELEPORT_UNSTABLE_DISABLE_SERVER_KEEPALIVE", "yes")
+
+	controller := NewController(
+		&fakeAuth{},
+		usagereporter.DiscardUsageReporter{},
+	)
+	defer controller.Close()
+
+	require.False(t, controller.serverKeepAliveEnabled)
+}
+
 // TestInstanceHeartbeat verifies basic expected behaviors for instance heartbeat.
 func TestInstanceHeartbeat(t *testing.T) {
 	const serverID = "test-instance"