Fix unnecessary admin server shutdown due to brief disconnections

Without this, when the device goes to sleep, in many cases the server
stops, and the client disconnects, then attempts and fails to reconnect,
before the machine restarts, resulting in full disconnection and a
self-shutdown of the whole session. This causes problems in HTTP Toolkit
on Windows, where it can be triggered easily in normal usage.

We now retry multiple times, with a brief delay after the first retry.

src/client/admin-client.ts

@@ -12,7 +12,7 @@ import { print } from 'graphql';
 import { DEFAULT_ADMIN_SERVER_PORT } from "../types";
 
 import { MaybePromise, RequireProps } from '../util/type-utils';
-import { isNode } from '../util/util';
+import { delay, isNode } from '../util/util';
 import { isErrorLike } from '../util/error';
 import { getDeferred } from '../util/promise';
 
@@ -219,7 +219,7 @@ export class AdminClient<Plugins extends { [key: string]: AdminPlugin<any, any>
     private attachStreamWebsocket(adminSessionBaseUrl: string, targetStream: Duplex): Duplex {
         const adminSessionBaseWSUrl = adminSessionBaseUrl.replace(/^http/, 'ws');
         const wsStream = connectWebSocketStream(`${adminSessionBaseWSUrl}/stream`, {
-            headers: this.adminClientOptions?.requestOptions?.headers // Only used in Node.js (via WS)
+            headers: this.adminClientOptions.requestOptions?.headers // Only used in Node.js (via WS)
         });
 
         let streamConnected = false;
@@ -246,26 +246,7 @@ export class AdminClient<Plugins extends { [key: string]: AdminPlugin<any, any>
                 targetStream.emit('server-shutdown');
             } else if (streamConnected && (await this.running) === true) {
                 console.warn('Admin client stream unexpectedly disconnected', closeEvent);
-
-                this.emit('stream-reconnecting');
-
-                // Unclean shutdown means something has gone wrong somewhere. Try to reconnect.
-                const newStream = this.attachStreamWebsocket(adminSessionBaseUrl, targetStream);
-
-                new Promise((resolve, reject) => {
-                    newStream.once('connect', resolve);
-                    newStream.once('error', reject);
-                }).then(() => {
-                    // On a successful connect, business resumes as normal.
-                    console.warn('Admin client stream reconnected');
-                    this.emit('stream-reconnected');
-                }).catch((err) => {
-                    // On a failed reconnect, we just shut down completely.
-                    console.warn('Admin client stream reconnection failed, shutting down:', err.message);
-                    if (this.debug) console.warn(err);
-                    this.emit('stream-reconnect-failed', err);
-                    targetStream.emit('server-shutdown');
-                });
+                this.tryToReconnectStream(adminSessionBaseUrl, targetStream);
             }
             // If never connected successfully, we do nothing.
         });
@@ -280,6 +261,40 @@ export class AdminClient<Plugins extends { [key: string]: AdminPlugin<any, any>
         return wsStream;
     }
 
+    /**
+     * Attempt to recreate a stream after disconnection, up to a limited number of retries. This is
+     * different to normal connection setup, as it assumes the target stream is otherwise already
+     * set up and active.
+     */
+    private async tryToReconnectStream(adminSessionBaseUrl: string, targetStream: Duplex, retries = 3) {
+        this.emit('stream-reconnecting');
+
+        // Unclean shutdown means something has gone wrong somewhere. Try to reconnect.
+        const newStream = this.attachStreamWebsocket(adminSessionBaseUrl, targetStream);
+
+        new Promise((resolve, reject) => {
+            newStream.once('connect', resolve);
+            newStream.once('error', reject);
+        }).then(() => {
+            // On a successful connect, business resumes as normal.
+            console.warn('Admin client stream reconnected');
+            this.emit('stream-reconnected');
+        }).catch(async (err) => {
+            if (retries > 0) {
+                // We delay re-retrying briefly - this helps to handle cases like the computer going
+                // to sleep (where the server & client pause in parallel, but race to do so).
+                await delay(50);
+                return this.tryToReconnectStream(adminSessionBaseUrl, targetStream, retries - 1);
+            }
+
+            // Otherwise, once retries have failed, we give up entirely:
+            console.warn('Admin client stream reconnection failed, shutting down:', err.message);
+            if (this.debug) console.warn(err);
+            this.emit('stream-reconnect-failed', err);
+            targetStream.emit('server-shutdown');
+        });
+    }
+
     private openStreamToMockServer(adminSessionBaseUrl: string): Promise<Duplex> {
         // To allow reconnects, we need to not end the client stream when an individual web socket ends.
         // To make that work, we return a separate stream, which isn't directly connected to the websocket