Merge pull request #33030 from backstage/sennyeya/mem-leak

fix(openapi-jest-utils): memory leak in proxy clean up

.changeset/shiny-ghosts-fold.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-openapi-utils': patch
+---
+
+Fixes a memory leak during `wrapServer` where stopped servers weren't removed from the clean up list.

packages/backend-openapi-utils/src/proxy/setup.ts

@@ -58,14 +58,40 @@ export class Proxy {
     this.express.server = server;
   }
 
-  stop() {
+  async stop() {
     if (Object.keys(this.#openRequests).length > 0) {
       throw new Error('There are still open requests');
     }
-    this.server.stop();
+    if (!this.express.server) {
+      throw new Error(
+        'Proxy server was not initialized with an express server',
+      );
+    }
+    const results = await Promise.allSettled([
+      this.server.stop(),
 
-    // If this isn't expressly closed, it will cause a jest memory leak warning.
-    this.express.server?.close();
+      // If this isn't expressly closed, it will cause a jest memory leak warning.
+      new Promise((resolve, reject) => {
+        this.express.server?.close(err => {
+          if (err) {
+            reject(err);
+          } else {
+            resolve(undefined);
+          }
+        });
+      }),
+    ]);
+    if (results.some(result => result.status === 'rejected')) {
+      const errors = results
+        .filter(
+          (result): result is PromiseRejectedResult =>
+            result.status === 'rejected',
+        )
+        .map(result => result.reason);
+      throw new Error(
+        `Failed to stop proxy server: ${errors.map(e => e.message).join(', ')}`,
+      );
+    }
   }
 
   get url() {

packages/backend-openapi-utils/src/testUtils.ts

@@ -17,7 +17,7 @@ import { Express } from 'express';
 import { Server } from 'node:http';
 import { Proxy } from './proxy/setup';
 
-const proxiesToCleanup: Proxy[] = [];
+const proxiesToCleanup: Set<Proxy> = new Set();
 
 /**
  * !!! THIS CURRENTLY ONLY SUPPORTS SUPERTEST !!!
@@ -29,7 +29,7 @@ const proxiesToCleanup: Proxy[] = [];
  */
 export async function wrapServer(app: Express): Promise<Server> {
   const proxy = new Proxy();
-  proxiesToCleanup.push(proxy);
+  proxiesToCleanup.add(proxy);
   await proxy.setup();
 
   const server = app.listen(proxy.forwardTo.port);
@@ -48,10 +48,12 @@ function registerHooks() {
   }
   registered = true;
 
-  afterAll(() => {
-    for (const proxy of proxiesToCleanup) {
-      proxy.stop();
-    }
+  afterAll(async () => {
+    const stopPromises = Array.from(proxiesToCleanup).map(proxy =>
+      proxy.stop(),
+    );
+    await Promise.allSettled(stopPromises);
+    proxiesToCleanup.clear();
   });
 }