fix(cloudflare): Don't hold Durable Object invocations open with the segment-end flush timer

packages/cloudflare/src/client.ts

@@ -6,6 +6,7 @@ import {
   applySdkMetadata,
   debug,
   spanIsSampled,
+  spanStreamingIntegration,
 } from '@sentry/core';
 import type { ServerRuntimeClientOptions } from '@sentry/core/server';
 import { ServerRuntimeClient } from '@sentry/core/server';
@@ -15,6 +16,10 @@ import type { makeFlushLock } from './flush';
 import type { CloudflareTransportOptions } from './transport';
 import { getInvocationState, getInvocationWaitUntil } from './utils/invocationContext';
 
+declare const __SENTRY_TRACING__: boolean;
+
+const SPAN_STREAMING_INTEGRATION_NAME = 'SpanStreaming';
+
 /**
  * The Sentry Cloudflare SDK Client.
  *
@@ -59,6 +64,17 @@ export class CloudflareClient extends ServerRuntimeClient {
       _flushInterval: 0,
     };
 
+    // workerd can't unref timers, so the default 500ms segment-end flush timer holds every
+    // Durable Object invocation open (and billed) until it fires, sampled or not. The boundary
+    // flush and the eager drain already deliver streamed spans here.
+    if (
+      (typeof __SENTRY_TRACING__ === 'undefined' || __SENTRY_TRACING__) &&
+      clientOptions.traceLifecycle !== 'static' &&
+      !clientOptions.integrations.some(i => i.name === SPAN_STREAMING_INTEGRATION_NAME)
+    ) {
+      clientOptions.integrations.push(spanStreamingIntegration({ flushOnSegmentEnd: false }));
+    }
+
     super(clientOptions);
     this._flushLock = flushLock;
     this.isCachedClient = options.cacheClient === true;

packages/cloudflare/test/sdk.test.ts

@@ -1,6 +1,6 @@
 import * as SentryCore from '@sentry/core';
 import type { Envelope, Integration } from '@sentry/core';
-import { getClient } from '@sentry/core';
+import { getClient, startSpan } from '@sentry/core';
 import { afterEach, beforeEach, describe, expect, test, vi } from 'vitest';
 import type { CloudflareOptions } from '../src/client';
 import { CloudflareClient } from '../src/client';
@@ -69,6 +69,32 @@ describe('init', () => {
     );
   });
 
+  test('does not leave a timer pending when a segment span ends', () => {
+    vi.useFakeTimers();
+    try {
+      init({ dsn: 'https://public@dsn.ingest.sentry.io/1337', tracesSampleRate: 0 });
+
+      startSpan({ name: 'alarm' }, () => undefined);
+
+      // A pending timer keeps a Durable Object invocation open until it fires.
+      expect(vi.getTimerCount()).toBe(0);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
+  test("doesn't add spanStreamingIntegration when tracing is excluded from the bundle", () => {
+    vi.stubGlobal('__SENTRY_TRACING__', false);
+    try {
+      const client = init({ dsn: 'https://public@dsn.ingest.sentry.io/1337' });
+      const integrations = client?.getOptions().integrations.filter(i => i.name === 'SpanStreaming');
+
+      expect(integrations).toEqual([]);
+    } finally {
+      vi.unstubAllGlobals();
+    }
+  });
+
   type MarkedIntegration = Integration & { _custom?: boolean };
 
   test("doesn't add spanStreamingIntegration if user added it manually", () => {