feat(core): improve reconnect handling (#15458)

#### PR Dependency Tree


* **PR #15458** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Improved realtime connection recovery with progressively longer retry
delays, capped to prevent excessive waiting.
* Connection retries now reset after successful reconnection and stop
cleanly when no longer needed.
* Reduced false error alerts by confirming repeated failures before
notifying users.
* Added cancellation handling when connection context changes or the
service is closed.

* **User Experience**
* Realtime connection alerts now identify authentication, network,
server, and timeout issues with localized messages.
* Active alerts are automatically dismissed when the connection
recovers.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/common/nbstore/src/connection/__tests__/auto-reconnection.spec.ts

@@ -117,9 +117,12 @@ test('retry when connect failed', async () => {
   class TestConnection extends AutoReconnectConnection {
     override retryDelay = 300;
     connectCount = 0;
+    retryDelayFor(retryCount: number) {
+      return this.getRetryDelay(retryCount);
+    }
     override async doConnect() {
       this.connectCount++;
-      if (this.connectCount === 3) {
+      if (this.connectCount >= 3) {
         return { hello: 'world' };
       }
       throw new Error('not connected, count: ' + this.connectCount);
@@ -127,9 +130,15 @@ test('retry when connect failed', async () => {
     override doDisconnect() {
       return Promise.resolve();
     }
+    triggerError(error: Error) {
+      this.error = error;
+    }
   }
 
   const connection = new TestConnection();
+  expect([0, 1, 2, 8].map(count => connection.retryDelayFor(count))).toEqual([
+    300, 600, 1200, 60000,
+  ]);
   connection.connect();
 
   await vitest.waitFor(() => {
@@ -149,6 +158,12 @@ test('retry when connect failed', async () => {
     expect(connection.status).toBe('connected');
     expect(connection.error).toBeUndefined();
   });
+
+  connection.triggerError(new Error('disconnected'));
+  await vitest.waitFor(() => {
+    expect(connection.connectCount).toBe(4);
+    expect(connection.status).toBe('connected');
+  });
 });
 
 test('retry when error', async () => {

packages/common/nbstore/src/connection/connection.ts

@@ -31,7 +31,9 @@ export abstract class AutoReconnectConnection<
   private _status: ConnectionStatus = 'idle';
   private _error: Error | undefined = undefined;
   retryDelay = 3000;
+  maxRetryDelay = 60000;
   connectingTimeout = 15000;
+  private retryCount = 0;
   private refCount = 0;
   private connectingAbort?: AbortController;
   private reconnectingAbort?: AbortController;
@@ -103,6 +105,7 @@ export abstract class AutoReconnectConnection<
           clearTimeout(timeout);
           if (!signal.aborted) {
             this._inner = value;
+            this.retryCount = 0;
             this.setStatus('connected');
           } else {
             try {
@@ -150,16 +153,21 @@ export abstract class AutoReconnectConnection<
 
     this.reconnectingAbort = new AbortController();
     const signal = this.reconnectingAbort.signal;
+    const retryDelay = this.getRetryDelay(this.retryCount++);
     const timeout = setTimeout(() => {
       if (!signal.aborted) {
         this.innerConnect();
       }
-    }, this.retryDelay);
+    }, retryDelay);
     signal.addEventListener('abort', () => {
       clearTimeout(timeout);
     });
   }
 
+  protected getRetryDelay(retryCount: number) {
+    return Math.min(this.retryDelay * 2 ** retryCount, this.maxRetryDelay);
+  }
+
   connect() {
     this.refCount++;
     if (this.refCount === 1) {
@@ -175,6 +183,7 @@ export abstract class AutoReconnectConnection<
     }
     if (this.refCount === 0) {
       this.innerDisconnect();
+      this.retryCount = 0;
       this.setStatus('closed');
     }
   }