fix(rustproxy): Use cooperative cancellation for background tasks, prune stale caches and metric entries, and switch tests to dynamic port allocation to avoid port conflicts

test/helpers/port-allocator.ts

@@ -0,0 +1,70 @@
+import * as net from 'net';
+
+/**
+ * Finds `count` free ports by binding to port 0 and reading the OS-assigned port.
+ * All servers are opened simultaneously to guarantee uniqueness.
+ * Returns an array of guaranteed-free ports.
+ */
+export async function findFreePorts(count: number): Promise<number[]> {
+  const servers: net.Server[] = [];
+  const ports: number[] = [];
+
+  // Open all servers simultaneously on port 0
+  await Promise.all(
+    Array.from({ length: count }, () =>
+      new Promise<void>((resolve, reject) => {
+        const server = net.createServer();
+        server.listen(0, '127.0.0.1', () => {
+          const addr = server.address() as net.AddressInfo;
+          ports.push(addr.port);
+          servers.push(server);
+          resolve();
+        });
+        server.on('error', reject);
+      })
+    )
+  );
+
+  // Close all servers
+  await Promise.all(
+    servers.map(
+      (server) => new Promise<void>((resolve) => server.close(() => resolve()))
+    )
+  );
+
+  return ports;
+}
+
+/**
+ * Verifies that all given ports are free (not listening).
+ * Useful as a cleanup assertion at the end of tests.
+ * Throws if any port is still in use.
+ */
+export async function assertPortsFree(ports: number[]): Promise<void> {
+  const results = await Promise.all(
+    ports.map(
+      (port) =>
+        new Promise<{ port: number; free: boolean }>((resolve) => {
+          const client = net.connect({ port, host: '127.0.0.1' });
+          client.on('connect', () => {
+            client.destroy();
+            resolve({ port, free: false });
+          });
+          client.on('error', () => {
+            resolve({ port, free: true });
+          });
+          client.setTimeout(1000, () => {
+            client.destroy();
+            resolve({ port, free: true });
+          });
+        })
+    )
+  );
+
+  const occupied = results.filter((r) => !r.free);
+  if (occupied.length > 0) {
+    throw new Error(
+      `Ports still in use after cleanup: ${occupied.map((r) => r.port).join(', ')}`
+    );
+  }
+}