Add experimental_waitUntil API for long-running tasks #296
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Introduces an internal keep-alive WebSocket endpoint and the experimental_waitUntil method to allow Durable Objects to remain alive while executing long-running async functions. This mechanism uses a self-connecting WebSocket with periodic pings and requires the 'enable_ctx_exports' compatibility flag. Additional handling is added to ignore keep-alive sockets in WebSocket event methods. Based on @eastlondoner's https://github.com/eastlondoner/better-wait-until
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threepointone
changed the title
Replaces manual timeout tracking with a Promise.race approach for cleaner and more reliable timeout handling in the async function. This improves code clarity and ensures the function properly rejects if the timeout is reached.
mattzcarey
reviewed
Dec 19, 2025
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| const exports = ( | ||
| this.ctx as DurableObjectState & { exports?: Record<string, unknown> } | ||
| ).exports; | ||
| if (!exports) { | ||
| throw new Error( | ||
| "waitUntil requires the 'enable_ctx_exports' compatibility flag. " + | ||
| 'Add it to your wrangler.jsonc: { "compatibility_flags": ["enable_ctx_exports"] }' | ||
| ); | ||
| } | ||
|
|
||
| const namespace = exports[this.#ParentClass.name] as | ||
| | DurableObjectNamespace | ||
| | undefined; | ||
| if (!namespace) { | ||
| throw new Error( | ||
| `Could not find namespace for ${this.#ParentClass.name} in ctx.exports. ` + | ||
| "Make sure the class name matches your Durable Object binding." | ||
| ); | ||
| } |
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the flag is actually on by default now too
mattzcarey
approved these changes
Dec 19, 2025
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Introduces an internal keep-alive WebSocket endpoint and the experimental_waitUntil method to allow Durable Objects to remain alive while executing long-running async functions. This mechanism uses a self-connecting WebSocket with periodic pings and requires the 'enable_ctx_exports' compatibility flag. Additional handling is added to ignore keep-alive sockets in WebSocket event methods.
Based on @eastlondoner's https://github.com/eastlondoner/better-wait-until