fix(webapp): eliminate SSE abort-signal memory leak

.server-changes/fix-sse-memory-leak.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: fix
+---
+
+Fix memory leak where every aborted SSE connection pinned the full request/response graph on Node 20, caused by `AbortSignal.any()` in `sse.ts` retaining its source signals indefinitely (see nodejs/node#54614, nodejs/node#55351). Also clear the `setTimeout(abort)` timer in `entry.server.tsx` so successful HTML renders don't pin the React tree for 30s per request.

apps/webapp/app/entry.server.tsx

@@ -83,6 +83,10 @@ function handleBotRequest(
 ) {
   return new Promise((resolve, reject) => {
     let shellRendered = false;
+    // Timer handle is cleared in every terminal callback so the abort closure
+    // (which captures the full React render tree + remixContext) doesn't pin
+    // memory for 30s per successful request. See react-router PR #14200.
+    let abortTimer: NodeJS.Timeout | undefined;
     const { pipe, abort } = renderToPipeableStream(
       <OperatingSystemContextProvider platform={platform}>
         <LocaleContextProvider locales={locales}>
@@ -105,8 +109,10 @@ function handleBotRequest(
           );
 
           pipe(body);
+          clearTimeout(abortTimer);
         },
         onShellError(error: unknown) {
+          clearTimeout(abortTimer);
           reject(error);
         },
         onError(error: unknown) {
@@ -121,7 +127,7 @@ function handleBotRequest(
       }
     );
 
-    setTimeout(abort, ABORT_DELAY);
+    abortTimer = setTimeout(abort, ABORT_DELAY);
   });
 }
 
@@ -135,6 +141,10 @@ function handleBrowserRequest(
 ) {
   return new Promise((resolve, reject) => {
     let shellRendered = false;
+    // Timer handle is cleared in every terminal callback so the abort closure
+    // (which captures the full React render tree + remixContext) doesn't pin
+    // memory for 30s per successful request. See react-router PR #14200.
+    let abortTimer: NodeJS.Timeout | undefined;
     const { pipe, abort } = renderToPipeableStream(
       <OperatingSystemContextProvider platform={platform}>
         <LocaleContextProvider locales={locales}>
@@ -157,8 +167,10 @@ function handleBrowserRequest(
           );
 
           pipe(body);
+          clearTimeout(abortTimer);
         },
         onShellError(error: unknown) {
+          clearTimeout(abortTimer);
           reject(error);
         },
         onError(error: unknown) {
@@ -173,7 +185,7 @@ function handleBrowserRequest(
       }
     );
 
-    setTimeout(abort, ABORT_DELAY);
+    abortTimer = setTimeout(abort, ABORT_DELAY);
   });
 }
 

apps/webapp/app/env.server.ts

@@ -438,6 +438,7 @@ const EnvironmentSchema = z
     INTERNAL_OTEL_TRACE_SAMPLING_RATE: z.string().default("20"),
     INTERNAL_OTEL_TRACE_INSTRUMENT_PRISMA_ENABLED: z.string().default("0"),
     INTERNAL_OTEL_TRACE_DISABLED: z.string().default("0"),
+    DISABLE_HTTP_INSTRUMENTATION: BoolEnv.default(false),
 
     INTERNAL_OTEL_LOG_EXPORTER_URL: z.string().optional(),
     INTERNAL_OTEL_METRIC_EXPORTER_URL: z.string().optional(),

apps/webapp/app/presenters/v3/RunStreamPresenter.server.ts

@@ -1,7 +1,7 @@
 import { type PrismaClient, prisma } from "~/db.server";
 import { logger } from "~/services/logger.server";
 import { singleton } from "~/utils/singleton";
-import { createSSELoader, SendFunction } from "~/utils/sse";
+import { ABORT_REASON_SEND_ERROR, createSSELoader, SendFunction } from "~/utils/sse";
 import { throttle } from "~/utils/throttle";
 import { tracePubSub } from "~/v3/services/tracePubSub.server";
 
@@ -66,8 +66,10 @@ export class RunStreamPresenter {
                   });
                 }
               }
-              // Abort the stream on send error
-              context.controller.abort("Send error");
+              // Abort the stream on send error. Uses a stackless string sentinel
+              // from sse.ts — a no-arg abort() would create a DOMException with a
+              // stack trace, which is unnecessary retention on the signal.reason.
+              context.controller.abort(ABORT_REASON_SEND_ERROR);
             }
           },
           1000

apps/webapp/app/utils/sse.ts

@@ -38,14 +38,27 @@ type SSEOptions = {
 // This is used to track the open connections, for debugging
 const connections: Set<string> = new Set();
 
+// Stackless sentinel reasons passed to AbortController#abort. Calling .abort()
+// with no argument produces a DOMException that captures a ~500-byte stack
+// trace; a string reason is stored verbatim with no stack. The choice of
+// reason type does not cause the retention we saw in prod (that was the
+// AbortSignal.any composite — see comment near the timeoutTimer below for the
+// Node issue refs), but naming the sentinels keeps call sites readable and
+// lets future signal.reason consumers branch on the cause.
+export const ABORT_REASON_REQUEST = "request_aborted";
+export const ABORT_REASON_TIMEOUT = "timeout";
+export const ABORT_REASON_SEND_ERROR = "send_error";
+export const ABORT_REASON_INIT_STOP = "init_requested_stop";
+export const ABORT_REASON_ITERATOR_STOP = "iterator_requested_stop";
+export const ABORT_REASON_ITERATOR_ERROR = "iterator_error";
+
 export function createSSELoader(options: SSEOptions) {
   const { timeout, interval = 500, debug = false, handler } = options;
 
   return async function loader({ request, params }: LoaderFunctionArgs) {
     const id = request.headers.get("x-request-id") || Math.random().toString(36).slice(2, 8);
 
     const internalController = new AbortController();
-    const timeoutSignal = AbortSignal.timeout(timeout);
 
     const log = (message: string) => {
       if (debug)
@@ -60,16 +73,20 @@ export function createSSELoader(options: SSEOptions) {
           if (!internalController.signal.aborted) {
             originalSend(event);
           }
-          // If controller is aborted, silently ignore the send attempt
         } catch (error) {
           if (error instanceof Error) {
             if (error.message?.includes("Controller is already closed")) {
-              // Silently handle controller closed errors
               return;
             }
             log(`Error sending event: ${error.message}`);
           }
-          throw error; // Re-throw other errors
+          // Abort before rethrowing so timer + request-abort listener are cleaned
+          // up immediately. Otherwise a send-failure in initStream leaves them
+          // alive until `timeout` fires.
+          if (!internalController.signal.aborted) {
+            internalController.abort(ABORT_REASON_SEND_ERROR);
+          }
+          throw error;
         }
       };
     };
@@ -92,51 +109,57 @@ export function createSSELoader(options: SSEOptions) {
 
     const requestAbortSignal = getRequestAbortSignal();
 
-    const combinedSignal = AbortSignal.any([
-      requestAbortSignal,
-      timeoutSignal,
-      internalController.signal,
-    ]);
-
     log("Start");
 
-    requestAbortSignal.addEventListener(
-      "abort",
-      () => {
-        log(`request signal aborted`);
-        internalController.abort("Request aborted");
-      },
-      { once: true, signal: internalController.signal }
-    );
+    // Single-signal abort chain: everything rolls up into internalController.
+    // Timeout is a plain setTimeout cleared on abort rather than an
+    // AbortSignal.timeout() combined via AbortSignal.any() — AbortSignal.any
+    // keeps its source signals in an internal Set<WeakRef> managed by a
+    // FinalizationRegistry, and under sustained request traffic those entries
+    // accumulate faster than they get cleaned up, pinning every source signal
+    // (and its listeners, and anything those listeners close over) until the
+    // parent signal is GC'd or aborts. Reproduced locally in isolation; shape
+    // matches the ChainSafe Lodestar production case described in
+    // nodejs/node#54614. See also nodejs/node#55351 (mechanism confirmed by
+    // @jasnell, narrow fix in 22.12.0 via #55354) and nodejs/node#57584
+    // (circular-dep variant, still open).
+    const timeoutTimer = setTimeout(() => {
+      if (!internalController.signal.aborted) internalController.abort(ABORT_REASON_TIMEOUT);
+    }, timeout);
+
+    const onRequestAbort = () => {
+      log("request signal aborted");
+      if (!internalController.signal.aborted) internalController.abort(ABORT_REASON_REQUEST);
+    };
 
-    combinedSignal.addEventListener(
+    internalController.signal.addEventListener(
       "abort",
       () => {
-        log(`combinedSignal aborted: ${combinedSignal.reason}`);
+        clearTimeout(timeoutTimer);
+        requestAbortSignal.removeEventListener("abort", onRequestAbort);
       },
-      { once: true, signal: internalController.signal }
+      { once: true }
     );
 
-    timeoutSignal.addEventListener(
-      "abort",
-      () => {
-        if (internalController.signal.aborted) return;
-        log(`timeoutSignal aborted: ${timeoutSignal.reason}`);
-        internalController.abort("Timeout");
-      },
-      { once: true, signal: internalController.signal }
-    );
+    // The request could have been aborted during `await handler(context)` above.
+    // AbortSignal listeners added after the signal is already aborted never fire,
+    // so invoke cleanup synchronously in that case instead of waiting for `timeout`.
+    if (requestAbortSignal.aborted) {
+      onRequestAbort();
+    } else {
+      requestAbortSignal.addEventListener("abort", onRequestAbort, { once: true });
+    }
 
     if (handlers.beforeStream) {
       const shouldContinue = await handlers.beforeStream();
       if (shouldContinue === false) {
         log("beforeStream returned false, so we'll exit before creating the stream");
-        internalController.abort("Init requested stop");
+        internalController.abort(ABORT_REASON_INIT_STOP);
         return;
       }
     }
 
-    return eventStream(combinedSignal, function setup(send) {
+    return eventStream(internalController.signal, function setup(send) {
       connections.add(id);
       const safeSend = createSafeSend(send);
 
@@ -147,14 +170,14 @@ export function createSSELoader(options: SSEOptions) {
             const shouldContinue = await handlers.initStream({ send: safeSend });
             if (shouldContinue === false) {
               log("initStream returned false, so we'll stop the stream");
-              internalController.abort("Init requested stop");
+              internalController.abort(ABORT_REASON_INIT_STOP);
               return;
             }
           }
 
           log("Starting interval");
           for await (const _ of setInterval(interval, null, {
-            signal: combinedSignal,
+            signal: internalController.signal,
           })) {
             log("PING");
 
@@ -165,13 +188,16 @@ export function createSSELoader(options: SSEOptions) {
                 const shouldContinue = await handlers.iterator({ date, send: safeSend });
                 if (shouldContinue === false) {
                   log("iterator return false, so we'll stop the stream");
-                  internalController.abort("Iterator requested stop");
+                  internalController.abort(ABORT_REASON_ITERATOR_STOP);
                   break;
                 }
               } catch (error) {
                 log("iterator threw an error, aborting stream");
                 // Immediately abort to trigger cleanup
-                internalController.abort(error instanceof Error ? error.message : "Iterator error");
+                if (error instanceof Error && error.name !== "AbortError") {
+                  log(`iterator error: ${error.message}`);
+                }
+                internalController.abort(ABORT_REASON_ITERATOR_ERROR);
                 // No need to re-throw as we're handling it by aborting
                 return; // Exit the run function immediately
               }

apps/webapp/app/v3/tracer.server.ts

@@ -302,13 +302,15 @@ function setupTelemetry() {
   provider.register();
 
   let instrumentations: Instrumentation[] = [
-    new HttpInstrumentation(),
-    new ExpressInstrumentation(),
     new AwsSdkInstrumentation({
       suppressInternalInstrumentation: true,
     }),
   ];
 
+  if (!env.DISABLE_HTTP_INSTRUMENTATION) {
+    instrumentations.unshift(new HttpInstrumentation(), new ExpressInstrumentation());
+  }
+
   if (env.INTERNAL_OTEL_TRACE_INSTRUMENT_PRISMA_ENABLED === "1") {
     instrumentations.push(new PrismaInstrumentation());
   }