fix: avoid "possible EventEmitter memory leak detected" warning

.changeset/hip-bikes-hunt.md

@@ -0,0 +1,8 @@
+---
+'@graphql-tools/utils': minor
+---
+
+- New helper function `getAbortPromise` to get a promise rejected when `AbortSignal` is aborted
+- New helper function `registerAbortSignalListener` to register a listener to abort a promise when `AbortSignal` is aborted
+
+Instead of using `.addEventListener('abort', () => {/* ... */})`, we register a single listener to avoid warnings on Node.js like `MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 abort listeners added. Use emitter.setMaxListeners() to increase limit`.

.changeset/selfish-worms-decide.md

@@ -0,0 +1,8 @@
+---
+'@graphql-tools/executor': patch
+---
+
+Surpress the "possible EventEmitter memory leak detected." warning occuring on Node.js when passing
+a `AbortSignal` to `execute`.
+
+Each execution will now only set up a single listener on the supplied `AbortSignal`. While the warning is harmless it can be misleading, which is the main motivation of this change.

packages/executor/src/execution/__tests__/abort-signal.test.ts

@@ -7,9 +7,18 @@ import { assertAsyncIterable } from '../../../../loaders/url/tests/test-utils';
 import { normalizedExecutor } from '../normalizedExecutor';
 
 describe('Abort Signal', () => {
+  // Always make sure that listener is registered once or never
+  let controller: AbortController;
+  let spy: jest.SpyInstance;
+  beforeEach(() => {
+    controller = new AbortController();
+    spy = jest.spyOn(controller.signal, 'addEventListener');
+  });
+  afterEach(() => {
+    expect(spy.mock.calls.length).toBeLessThanOrEqual(1);
+  });
   it('should stop the subscription', async () => {
-    expect.assertions(2);
-    const controller = new AbortController();
+    expect.assertions(3);
     let stopped = false;
     const schema = makeExecutableSchema({
       typeDefs: /* GraphQL */ `
@@ -64,7 +73,6 @@ describe('Abort Signal', () => {
     expect(results).toEqual([0, 1, 2, 3, 4]);
   });
   it('pending subscription execution is canceled', async () => {
-    const controller = new AbortController();
     const rootResolverGotInvokedD = createDeferred<void>();
     const requestGotCancelledD = createDeferred<void>();
     let aResolverGotInvoked = false;
@@ -123,8 +131,6 @@ describe('Abort Signal', () => {
     expect(aResolverGotInvoked).toEqual(false);
   });
   it('should stop the serial mutation execution', async () => {
-    const controller = new AbortController();
-
     let didInvokeFirstFn = false;
     let didInvokeSecondFn = false;
     let didInvokeThirdFn = false;
@@ -174,7 +180,6 @@ describe('Abort Signal', () => {
     expect(didInvokeThirdFn).toBe(false);
   });
   it('should stop stream execution', async () => {
-    const controller = new AbortController();
     let isAborted = false;
 
     const schema = makeExecutableSchema({
@@ -223,7 +228,6 @@ describe('Abort Signal', () => {
     expect(isAborted).toEqual(true);
   });
   it('stops pending stream execution for incremental delivery (@stream)', async () => {
-    const controller = new AbortController();
     const d = createDeferred<void>();
     let isReturnInvoked = false;
 
@@ -285,7 +289,6 @@ describe('Abort Signal', () => {
     expect(isReturnInvoked).toEqual(true);
   });
   it('stops pending stream execution for parallel sources incremental delivery (@stream)', async () => {
-    const controller = new AbortController();
     const d1 = createDeferred<void>();
     const d2 = createDeferred<void>();
 
@@ -404,7 +407,6 @@ describe('Abort Signal', () => {
         },
       },
     });
-    const controller = new AbortController();
     const result = await normalizedExecutor({
       schema,
       document: parse(/* GraphQL */ `
@@ -443,7 +445,6 @@ describe('Abort Signal', () => {
     expect(bResolverGotInvoked).toBe(false);
   });
   it('stops promise execution', async () => {
-    const controller = new AbortController();
     const d = createDeferred<void>();
 
     const schema = makeExecutableSchema({
@@ -474,7 +475,6 @@ describe('Abort Signal', () => {
     await expect(result$).rejects.toMatchInlineSnapshot(`DOMException {}`);
   });
   it('does not even try to execute if the signal is already aborted', async () => {
-    const controller = new AbortController();
     let resolverGotInvoked = false;
     const schema = makeExecutableSchema({
       typeDefs: /* GraphQL */ `

packages/executor/src/execution/execute.ts

@@ -35,6 +35,7 @@ import {
   collectFields,
   createGraphQLError,
   fakePromise,
+  getAbortPromise,
   getArgumentValues,
   getDefinedRootType,
   GraphQLResolveInfo,
@@ -52,6 +53,7 @@ import {
   Path,
   pathToArray,
   promiseReduce,
+  registerAbortSignalListener,
 } from '@graphql-tools/utils';
 import { TypedDocumentNode } from '@graphql-typed-document-node/core';
 import { DisposableSymbols } from '@whatwg-node/disposablestack';
@@ -290,9 +292,7 @@ export function execute<TData = any, TVariables = any, TContext = any>(
 function executeImpl<TData = any, TVariables = any, TContext = any>(
   exeContext: ExecutionContext<TVariables, TContext>,
 ): MaybePromise<SingularExecutionResult<TData> | IncrementalExecutionResults<TData>> {
-  if (exeContext.signal?.aborted) {
-    throw exeContext.signal.reason;
-  }
+  exeContext.signal?.throwIfAborted();
 
   // Return a Promise that will eventually resolve to the data described by
   // The "Response" section of the GraphQL specification.
@@ -322,9 +322,7 @@ function executeImpl<TData = any, TVariables = any, TContext = any>(
         return initialResult;
       },
       (error: any) => {
-        if (exeContext.signal?.aborted) {
-          throw exeContext.signal.reason;
-        }
+        exeContext.signal?.throwIfAborted();
 
         if (error.errors) {
           exeContext.errors.push(...error.errors);
@@ -558,9 +556,7 @@ function executeFieldsSerially<TData>(
     fields,
     (results, [responseName, fieldNodes]) => {
       const fieldPath = addPath(path, responseName, parentType.name);
-      if (exeContext.signal?.aborted) {
-        throw exeContext.signal.reason;
-      }
+      exeContext.signal?.throwIfAborted();
 
       return new ValueOrPromise(() =>
         executeField(exeContext, parentType, sourceValue, fieldNodes, fieldPath),
@@ -595,9 +591,7 @@ function executeFields(
 
   try {
     for (const [responseName, fieldNodes] of fields) {
-      if (exeContext.signal?.aborted) {
-        throw exeContext.signal.reason;
-      }
+      exeContext.signal?.throwIfAborted();
 
       const fieldPath = addPath(path, responseName, parentType.name);
       const result = executeField(
@@ -958,13 +952,12 @@ async function completeAsyncIteratorValue(
   iterator: AsyncIterator<unknown>,
   asyncPayloadRecord?: AsyncPayloadRecord,
 ): Promise<ReadonlyArray<unknown>> {
-  exeContext.signal?.addEventListener(
-    'abort',
-    () => {
+  if (exeContext.signal && iterator.return) {
+    registerAbortSignalListener(exeContext.signal, () => {
       iterator.return?.();
-    },
-    { once: true },
-  );
+    });
+  }
+
   const errors = asyncPayloadRecord?.errors ?? exeContext.errors;
   const stream = getStreamValues(exeContext, fieldNodes, path);
   let containsPromise = false;
@@ -1758,15 +1751,22 @@ function assertEventStream(result: unknown, signal?: AbortSignal): AsyncIterable
       'Subscription field must return Async Iterable. ' + `Received: ${inspect(result)}.`,
     );
   }
-  return {
-    [Symbol.asyncIterator]() {
-      const asyncIterator = result[Symbol.asyncIterator]();
-      signal?.addEventListener('abort', () => {
-        asyncIterator.return?.();
-      });
-      return asyncIterator;
-    },
-  };
+  if (signal) {
+    return {
+      [Symbol.asyncIterator]() {
+        const asyncIterator = result[Symbol.asyncIterator]();
+
+        if (asyncIterator.return) {
+          registerAbortSignalListener(signal, () => {
+            asyncIterator.return?.();
+          });
+        }
+
+        return asyncIterator;
+      },
+    };
+  }
+  return result;
 }
 
 function executeDeferredFragment(
@@ -2084,26 +2084,22 @@ function yieldSubsequentPayloads(
 ): AsyncGenerator<SubsequentIncrementalExecutionResult, void, void> {
   let isDone = false;
 
-  const abortPromise = new Promise<void>((_, reject) => {
-    exeContext.signal?.addEventListener(
-      'abort',
-      () => {
-        isDone = true;
-        reject(exeContext.signal?.reason);
-      },
-      { once: true },
-    );
-  });
+  const abortPromise = exeContext.signal ? getAbortPromise(exeContext.signal) : undefined;
 
   async function next(): Promise<IteratorResult<SubsequentIncrementalExecutionResult, void>> {
     if (isDone) {
       return { value: undefined, done: true };
     }
 
-    await Promise.race([
-      abortPromise,
-      ...Array.from(exeContext.subsequentPayloads).map(p => p.promise),
-    ]);
+    const subSequentPayloadPromises = Array.from(exeContext.subsequentPayloads).map(
+      record => record.promise,
+    );
+
+    if (abortPromise) {
+      await Promise.race([abortPromise, ...subSequentPayloadPromises]);
+    } else {
+      await Promise.race(subSequentPayloadPromises);
+    }
 
     if (isDone) {
       // a different call to next has exhausted all payloads

packages/executor/src/execution/promiseForObject.ts

@@ -1,3 +1,5 @@
+import { getAbortPromise } from '@graphql-tools/utils';
+
 type ResolvedObject<TData> = {
   [TKey in keyof TData]: TData[TKey] extends Promise<infer TValue> ? TValue : TData[TKey];
 };
@@ -14,15 +16,14 @@ export async function promiseForObject<TData>(
   signal?: AbortSignal,
 ): Promise<ResolvedObject<TData>> {
   const resolvedObject = Object.create(null);
-  await new Promise<void>((resolve, reject) => {
-    signal?.addEventListener('abort', () => {
-      reject(signal.reason);
-    });
-    Promise.all(
-      Object.entries(object as any).map(async ([key, value]) => {
-        resolvedObject[key] = await value;
-      }),
-    ).then(() => resolve(), reject);
-  });
-  return resolvedObject;
+  const promises = Promise.all(
+    Object.entries(object as any).map(async ([key, value]) => {
+      resolvedObject[key] = await value;
+    }),
+  );
+  if (signal) {
+    const abortPromise = getAbortPromise(signal);
+    return Promise.race([abortPromise, promises]).then(() => resolvedObject);
+  }
+  return promises.then(() => resolvedObject);
 }

packages/utils/src/index.ts

@@ -58,3 +58,4 @@ export * from './getDirectiveExtensions.js';
 export * from './map-maybe-promise.js';
 export * from './fakePromise.js';
 export * from './createDeferred.js';
+export * from './registerAbortSignalListener.js';

packages/utils/src/registerAbortSignalListener.ts

@@ -0,0 +1,45 @@
+import { memoize1 } from './memoize.js';
+
+// AbortSignal handler cache to avoid the "possible EventEmitter memory leak detected"
+// on Node.js
+const getListenersOfAbortSignal = memoize1(function getListenersOfAbortSignal(signal: AbortSignal) {
+  const listeners = new Set<EventListener>();
+  signal.addEventListener(
+    'abort',
+    e => {
+      for (const listener of listeners) {
+        listener(e);
+      }
+    },
+    { once: true },
+  );
+  return listeners;
+});
+
+/**
+ * Register an AbortSignal handler for a signal.
+ * This helper function mainly exists to work around the
+ * "possible EventEmitter memory leak detected. 11 listeners added. Use emitter.setMaxListeners() to increase limit."
+ * warning occuring on Node.js
+ */
+export function registerAbortSignalListener(signal: AbortSignal, listener: VoidFunction) {
+  // If the signal is already aborted, call the listener immediately
+  if (signal.aborted) {
+    listener();
+    return;
+  }
+  getListenersOfAbortSignal(signal).add(listener);
+}
+
+export const getAbortPromise = memoize1(function getAbortPromise(signal: AbortSignal) {
+  return new Promise<void>((_resolve, reject) => {
+    // If the signal is already aborted, return a rejected promise
+    if (signal.aborted) {
+      reject(signal.reason);
+      return;
+    }
+    registerAbortSignalListener(signal, () => {
+      reject(signal.reason);
+    });
+  });
+});

website/theme.config.tsx

@@ -29,5 +29,6 @@ export default defineConfig({
   },
   websiteName: 'GraphQL-Tools',
   description: PRODUCTS.TOOLS.title,
+  // @ts-expect-error - Typings are not updated
   logo: PRODUCTS.TOOLS.logo({ className: 'w-9' }),
 });