Files
supabase/apps/docs/content/guides/functions/background-tasks.mdx
T
Vaibhav 549c1fb6ca fix(docs): align edge function docs (#47148)
## TL;DR 
aligns the remaining Phase 2 Edge Functions docs snippets with
`@supabase/server`

## Whats Fixed? 
updated outdated imports and version references, and refreshed JSON
examples to use Response.json()
where it makes sense. left non-JSON responses as is where the
integration or format actually needs them
## Ref: 
- towards COM-269 


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Documentation**
* Updated numerous Edge Function guides and examples to use modern
`npm:`/`jsr:` import specifiers instead of legacy Deno URL imports.
* Standardized success and error responses to return JSON consistently
(using `Response.json()` and equivalent helpers) and added/clarified
appropriate HTTP status codes.
* Improved example error payload shapes in several guides for clearer,
structured failures.
* **Chores**
* Refreshed version ranges in documentation and examples across SDKs and
client libraries.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
2026-06-22 16:06:12 -05:00

101 lines
3.2 KiB
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---
id: 'function-background-tasks'
title: 'Background Tasks'
description: 'How to run background tasks in an Edge Function outside of the request handler'
subtitle: 'Run background tasks in an Edge Function outside of the request handler.'
---
Edge Function instances can process background tasks outside of the request handler. Background tasks are useful for asynchronous operations like uploading a file to Storage, updating a database, or sending events to a logging service. You can respond to the request immediately and leave the task running in the background.
This allows you to:
- Respond quickly to users while processing continues
- Handle async operations without blocking the response
---
## Overview
You can use `EdgeRuntime.waitUntil(promise)` to explicitly mark background tasks. The Function instance continues to run until the promise provided to `waitUntil` completes.
```ts
import { withSupabase } from 'npm:@supabase/server@^1'
// Mark the asyncLongRunningTask's returned promise as a background task.
// ⚠️ We are NOT using `await` because we don't want it to block!
EdgeRuntime.waitUntil(asyncLongRunningTask())
export default {
fetch: withSupabase({ auth: 'user' }, async (req, ctx) => {
return Response.json({ ok: true })
}),
}
```
You can call `EdgeRuntime.waitUntil` in the request handler too. This will not block the request.
```ts
import { withSupabase } from 'npm:@supabase/server@^1'
export default {
fetch: withSupabase({ auth: 'user' }, async (req, ctx) => {
// Won't block the request, runs in background.
EdgeRuntime.waitUntil(asyncLongRunningTask())
return Response.json({ ok: true })
}),
}
```
You can listen to the `beforeunload` event handler to be notified when the Function is about to be shut down.
```tsx
import { withSupabase } from 'npm:@supabase/server@^1'
EdgeRuntime.waitUntil(asyncLongRunningTask())
// Use beforeunload event handler to be notified when function is about to shutdown
addEventListener('beforeunload', (ev) => {
console.log('Function will be shutdown due to', ev.detail?.reason)
// Save state or log the current progress
})
export default {
fetch: withSupabase({ auth: 'user' }, async (req, ctx) => {
return Response.json({ ok: true })
}),
}
```
## Handling errors
We recommend using `try`/`catch` blocks within your background task function to handle errors.
You can also add an event listener to [`unhandledrejection`](https://developer.mozilla.org/en-US/docs/Web/API/Window/unhandledrejection_event) to handle any promises without a rejection handler.
```tsx
addEventListener('unhandledrejection', (ev) => {
console.log('unhandledrejection', ev.reason)
ev.preventDefault()
})
```
<Admonition type="note">
The maximum duration is capped based on the wall-clock, CPU, and memory limits. The function will shut down when it reaches one of these [limits](/docs/guides/functions/limits).
</Admonition>
---
## Testing background tasks locally
When testing Edge Functions locally with Supabase CLI, the instances are terminated automatically after a request is completed. This will prevent background tasks from running to completion.
To prevent that, you can update the `supabase/config.toml` with the following settings:
```toml
[edge_runtime]
policy = "per_worker"
```