René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"AsyncContextFrame may not be released when using HTTP parsers","articleBody":"### Version\n\nv25.6.1\n\n### Platform\n\n```text\nDarwin XXX 25.3.0 Darwin Kernel Version 25.3.0: Wed Jan 28 20:48:41 PST 2026; root:xnu-12377.81.4~5/RELEASE_ARM64_T6041 arm64\n```\n\n### Subsystem\n\nhttp\n\n### What steps will reproduce the bug?\n\nWhen an HTTP request is executed, data in AsyncLocalStorage isn't freed. To reproduce it:\n\n```\nimport hooks from 'node:async_hooks';\nimport http from 'node:http';\nimport net from 'node:net';\nimport crypto from 'node:crypto';\n\n// http.setMaxIdleHTTPParsers(1);\n\nconst store = new hooks.AsyncLocalStorage();\n\nfunction sendRequest() {\n  store.enterWith({body: crypto.randomBytes(512)});\n  const proxyReq = http.request({\n    agent: null,\n    createConnection: net.createConnection,\n    method: 'HEAD',\n    hostname: '127.0.0.1',\n    headers: {\n      'connection': 'close'\n    },\n    port: 9009,\n    path: '/',\n  });\n  proxyReq.end();\n}\n\nfor (let i = 0; i \u003c 10; i++) {\n  for (let j = 0; j \u003c 100; j++) {\n    sendRequest();\n  }\n}\n\nsetTimeout(() =\u003e {\n  console.log('done');\n}, 1000 * 60 * 60);\n```\n\nWhen running this with `node --inspect`, one can see that there are 1000 `AsyncContextFrame` entries in memory, as well as the buffer stored in the `AsyncLocalStorage`. This happens with `AsyncContextFrame` enabled (Node 24+)\nI stumbled upon this when making an outbound request from an HTTP server handler `(req, res) =\u003e {...}` where I was using AsyncLocalStorage to keep some request context. I noticed that the memory was freed if I made the outbound requests using `fetch()` instead of `http.request`.\n\nAlso, if `http.setMaxIdleHTTPParsers(1);` is uncommented, so that HTTP parsers aren't reused, the memory is also freed.\n\n### How often does it reproduce? Is there a required condition?\n\nAlways\n\n### What is the expected behavior? Why is that the expected behavior?\n\nWhatever is stored in an `AsyncLocalStorage` should be freed when it goes out of scope.\n\n### What do you see instead?\n\n\u003cimg width=\"2123\" height=\"1113\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/970e8e75-8e8b-4d11-85cf-6633fa6a4543\" /\u003e\n\nIt can be seen here that there are 1000 instances of `AsyncContextFrame`\n\n### Additional information\n\nI downloaded Node's source and tinkered with the parser initialization in `_http_client.js` and with the AsyncWrap logic in `node_http_parser.cc`, but couldn't fix it. I see that `freeParser()` should free everything, but it seems something is being held. I'm not familiar with the relationship between `AsyncWrap` and V8-based new `AsyncLocalStorage` implementation.\nI understand that not reusing parsers has a memory impact. I also noticed PRs like https://github.com/nodejs/node/pull/57938 and https://github.com/nodejs/node/pull/59621 that might fix this thing.\n\nThis is an issue when using libraries like Datadog's `dd-trace`, which store tracing information in `AsyncLocalStorage`","author":{"url":"https://github.com/lukiano","@type":"Person","name":"lukiano"},"datePublished":"2026-02-19T04:19:16.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/61882/node/issues/61882"}