Improved stability, better timeout system

Author: MackinnonBuck

src/Components/Web.JS/src/Boot.Server.Common.ts

@@ -23,6 +23,7 @@ import { CircuitDotNetCallDispatcher } from './Platform/Circuits/CircuitDotNetCa
 
 let renderingFailed = false;
 let started = false;
+let circuitActive = false;
 let startCircuitPromise: Promise<boolean> | undefined;
 let connection: HubConnection;
 let circuit: CircuitDescriptor;
@@ -113,6 +114,7 @@ export function startCircuit(components: RootComponentManager<ServerComponentDes
     throw new Error('Cannot start the circuit until Blazor Server has started.');
   }
 
+  circuitActive = true;
   startCircuitPromise ??= (async () => {
     const appState = discoverPersistedState(document);
     renderQueue = new RenderQueue(logger);
@@ -132,29 +134,21 @@ export function startCircuit(components: RootComponentManager<ServerComponentDes
   return startCircuitPromise;
 }
 
-export function hasStartedServer(): boolean {
-  return started;
-}
-
-export function isCircuitActive(): boolean {
-  return startCircuitPromise !== undefined;
-}
-
-export function attachCircuitAfterRenderCallback(callback: typeof afterRenderCallback) {
-  if (afterRenderCallback) {
-    throw new Error('A Blazor Server after render batch callback was already attached.');
+export async function disposeCircuit() {
+  if (!circuitActive) {
+    return;
   }
 
-  afterRenderCallback = callback;
-}
+  circuitActive = false;
 
-export function disposeCircuit() {
-  if (startCircuitPromise === undefined) {
+  await startCircuitPromise;
+
+  if (circuitActive) {
+    // A call to 'startCircuit' was made while we were waiting to dispose the circuit.
+    // Therefore, we should abort the disposal.
     return;
   }
 
-  startCircuitPromise = undefined;
-
   // We dispose the .NET dispatcher to prevent it from being used in the future.
   // This avoids cases where, for example, .NET object references from a
   // disconnected circuit start pointing to .NET objects for a new circuit.
@@ -163,6 +157,25 @@ export function disposeCircuit() {
   connection.stop();
 
   detachWebRendererInterop(WebRendererId.Server);
+
+  // Setting this to undefined allows a new circuit to be started in the future.
+  startCircuitPromise = undefined;
+}
+
+export function hasStartedServer(): boolean {
+  return started;
+}
+
+export function isCircuitActive(): boolean {
+  return circuitActive;
+}
+
+export function attachCircuitAfterRenderCallback(callback: typeof afterRenderCallback) {
+  if (afterRenderCallback) {
+    throw new Error('A Blazor Server after render batch callback was already attached.');
+  }
+
+  afterRenderCallback = callback;
 }
 
 async function initializeConnection(logger: Logger, circuit: CircuitDescriptor): Promise<HubConnection> {

src/Components/Web.JS/src/Boot.Web.ts

@@ -21,7 +21,7 @@ import { attachComponentDescriptorHandler, registerAllComponentDescriptors } fro
 import { hasProgrammaticEnhancedNavigationHandler, performProgrammaticEnhancedNavigation } from './Services/NavigationUtils';
 
 let started = false;
-const rootComponentManager = new WebRootComponentManager();
+let rootComponentManager: WebRootComponentManager;
 
 function boot(options?: Partial<WebStartOptions>) : Promise<void> {
   if (started) {
@@ -43,6 +43,8 @@ function boot(options?: Partial<WebStartOptions>) : Promise<void> {
   setCircuitOptions(options?.circuit);
   setWebAssemblyOptions(options?.webAssembly);
 
+  rootComponentManager = new WebRootComponentManager(options?.ssr?.circuitInactivityTimeoutMs ?? 2000);
+
   attachComponentDescriptorHandler(rootComponentManager);
   attachStreamingRenderingListener(options?.ssr, rootComponentManager);
 

src/Components/Web.JS/src/Platform/SsrStartOptions.ts

@@ -7,4 +7,10 @@ export interface SsrStartOptions {
    * (for example, during enhanced navigation or streaming rendering).
    */
   disableDomPreservation?: boolean;
+
+  /**
+   * Configures how long to wait after all Blazor Server components have been removed from the document
+   * before closing the circuit.
+   */
+  circuitInactivityTimeoutMs?: number;
 }

src/Components/Web.JS/src/Rendering/DomMerging/DomSync.ts

@@ -11,7 +11,7 @@ import { UpdateCost, ItemList, Operation, computeEditScript } from './EditScript
 let descriptorHandler: DescriptorHandler | null = null;
 
 export interface DescriptorHandler {
-  registerComponentDescriptor(descriptor: ComponentDescriptor): void;
+  registerComponent(descriptor: ComponentDescriptor): void;
 }
 
 export function attachComponentDescriptorHandler(handler: DescriptorHandler) {
@@ -22,7 +22,7 @@ export function registerAllComponentDescriptors(root: Node) {
   const descriptors = upgradeComponentCommentsToLogicalRootComments(root);
 
   for (const descriptor of descriptors) {
-    descriptorHandler?.registerComponentDescriptor(descriptor);
+    descriptorHandler?.registerComponent(descriptor);
   }
 }
 
@@ -244,7 +244,7 @@ function treatAsInsertion(nodeToInsert: Node, nextNode: Node | null, parentNode:
   while (iterator.nextNode()) {
     const logicalRootDescriptor = getLogicalRootDescriptor(iterator.referenceNode as unknown as LogicalElement);
     if (logicalRootDescriptor) {
-      descriptorHandler?.registerComponentDescriptor(logicalRootDescriptor);
+      descriptorHandler?.registerComponent(logicalRootDescriptor);
     }
   }
 }