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Kaj Kowalski
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74 lines
2.0 KiB
Markdown
74 lines
2.0 KiB
Markdown
---
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title: Use after() for Non-Blocking Operations
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impact: MEDIUM
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impactDescription: faster response times
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tags: server, async, logging, analytics, side-effects
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---
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## Use after() for Non-Blocking Operations
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Use Next.js's `after()` to schedule work that should execute after a response is sent. This prevents logging, analytics, and other side effects from blocking the response.
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**Incorrect (blocks response):**
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```tsx
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import { logUserAction } from "@/app/utils";
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export async function POST(request: Request) {
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// Perform mutation
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await updateDatabase(request);
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// Logging blocks the response
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const userAgent = request.headers.get("user-agent") || "unknown";
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await logUserAction({ userAgent });
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return new Response(JSON.stringify({ status: "success" }), {
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status: 200,
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headers: { "Content-Type": "application/json" },
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});
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}
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```
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**Correct (non-blocking):**
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```tsx
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import { after } from "next/server";
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import { headers, cookies } from "next/headers";
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import { logUserAction } from "@/app/utils";
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export async function POST(request: Request) {
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// Perform mutation
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await updateDatabase(request);
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// Log after response is sent
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after(async () => {
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const userAgent = (await headers()).get("user-agent") || "unknown";
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const sessionCookie = (await cookies()).get("session-id")?.value || "anonymous";
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logUserAction({ sessionCookie, userAgent });
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});
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return new Response(JSON.stringify({ status: "success" }), {
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status: 200,
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headers: { "Content-Type": "application/json" },
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});
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}
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```
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The response is sent immediately while logging happens in the background.
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**Common use cases:**
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- Analytics tracking
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- Audit logging
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- Sending notifications
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- Cache invalidation
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- Cleanup tasks
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**Important notes:**
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- `after()` runs even if the response fails or redirects
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- Works in Server Actions, Route Handlers, and Server Components
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Reference: [https://nextjs.org/docs/app/api-reference/functions/after](https://nextjs.org/docs/app/api-reference/functions/after)
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