> ## Documentation Index
> Fetch the complete documentation index at: https://bunnynet-cb9733c2-add-new-partner-apis.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
# Middleware scripts
> Middleware scripts allow you to transform and modify HTTP requests and responses as they flow through the CDN. Manipulate requests before they reach your origin server or the cache and alter responses before they are sent back to the client.
Middleware scripts sit inside the CDN request flow. Your logic runs on requests on their way in and on responses on their way out, so you can change how traffic behaves without touching your backend, and the work happens at the edge rather than on your origin.
## Use cases
* Verify credentials and manage session tokens at the edge
* Add, modify, or remove HTTP headers on requests and responses
* Rewrite HTML, inject scripts, or otherwise change the response body before delivery
* Run A/B tests and feature flags, routing users based on headers or cookies
* Route or redirect requests based on path, geolocation, or your own logic
* Apply rate limiting, IP filtering, or bot protection
## The `servePullZone` function
The `servePullZone` function creates a middleware handler that integrates with your Pull Zone. It returns a chainable object for adding request and response middleware.
```ts theme={null}
import * as BunnySDK from "@bunny.net/edgescript-sdk";
BunnySDK.net.http
.servePullZone({ url: "https://your-origin.com" })
.onOriginRequest((ctx) => {
// Modify or intercept requests
return Promise.resolve(ctx.request);
})
.onOriginResponse((ctx) => {
// Modify responses
return Promise.resolve(ctx.response);
});
```
### Function signature
```ts theme={null}
servePullZone(options: { url: string }): PullZoneHandler
```
| Option | Type | Description |
| ------ | -------- | --------------------------------------------------------------------------------------------------------------------- |
| `url` | `string` | The origin URL to proxy requests to. Only used during local development; in production, the Pull Zone origin is used. |
The `url` option is only used during local development. When deployed to
bunny.net, requests are proxied to the origin configured in your Pull Zone
settings.
## Middleware methods
The `servePullZone` function returns a `PullZoneHandler` object with chainable middleware methods:
### `onClientRequest`
Preview
If your PullZone is configured to execute script before cache, you'll have
access to this function.
Intercepts requests before they are sent to the cache. You can modify the request
or short-circuit by returning a response directly.
```ts theme={null}
onClientRequest(
middleware: (ctx: { request: Request }) => Promise | Response | Promise | Request | void
): PullZoneHandler
```
| Property | Type | Description |
| ------------- | --------- | --------------------------- |
| `ctx.request` | `Request` | The incoming request object |
**Return value:**
* Return `Promise` to continue to the origin with the (modified) request
* Return `Promise` to short-circuit and respond immediately without
hitting the cache
### `onClientResponse`
Preview
If your PullZone is configured to execute script before cache, you'll have
access to this function.
Intercepts responses before they are returned to the user, including responses
served from the cache.
```ts theme={null}
onClientResponse(
middleware: (ctx: { request: Request; response: Response }) => Promise | Response
): PullZoneHandler
```
| Property | Type | Description |
| -------------- | ---------- | ----------------------------------- |
| `ctx.request` | `Request` | The original request object |
| `ctx.response` | `Response` | The response from the origin server |
**Return value:**
* Return `Promise` or `Response` with the (modified) response to send
to the client.
### `onOriginRequest`
Intercepts requests before they are sent to the origin server. You can modify the request or short-circuit by returning a response directly.
```ts theme={null}
onOriginRequest(
middleware: (ctx: { request: Request }) => Promise | Promise
): PullZoneHandler
```
| Property | Type | Description |
| ------------- | --------- | --------------------------- |
| `ctx.request` | `Request` | The incoming request object |
**Return value:**
* Return `Promise` to continue to the origin with the (modified) request
* Return `Promise` to short-circuit and respond immediately without hitting the origin
### `onOriginResponse`
Intercepts responses from the origin server before they are sent to the client. Modifications occur before the response is cached.
```ts theme={null}
onOriginResponse(
middleware: (ctx: { request: Request; response: Response }) => Promise
): PullZoneHandler
```
| Property | Type | Description |
| -------------- | ---------- | ----------------------------------- |
| `ctx.request` | `Request` | The original request object |
| `ctx.response` | `Response` | The response from the origin server |
**Return value:**
* Return `Promise` with the (modified) response to send to the client
## Enable before cache scripts
Preview
Before cache execution is turned on per Pull Zone. Navigate to your Pull Zone,
then go to **General** > **Origin** and enable **Run script before cache**.
Learn more about [before cache execution](/scripting/before-cache).
## Workflow
When a client makes a request to a Pull Zone, the request passes through middleware at different stages:
If your PullZone is configured to execute script before cache, you'll run the
`onClientRequest` and `onClientResponse` if those are registered.
1. **`onClientRequest`** - Called before the request is sent to the cache. Modify the request or return a response to short-circuit.
2. **`onOriginRequest`** - Called before the request is sent to the origin, so only when the cache returns a *MISS*. Modify the request or return a response to short-circuit.
3. **Origin fetch** - The request is sent to your origin server.
4. **`onOriginResponse`** - Called after the origin responds. Modify the response before it's sent to the client and cached.
5. **`onClientResponse`** - Called just before a response is sent to the client, unless you short-circuited at the `onClientRequest` layer.
```mermaid theme={null}
sequenceDiagram
participant Client
participant Cache
participant Origin
Client->>Cache: onClientRequest
Cache->>Origin: onOriginRequest
Origin-->>Cache: onOriginResponse
Cache-->>Client: onClientResponse
```
## Example
This example gates a route behind a feature flag and adds a custom header to responses:
```ts theme={null}
import * as BunnySDK from "@bunny.net/edgescript-sdk";
BunnySDK.net.http
.servePullZone({ url: "https://echo.free.beeceptor.com/" })
.onOriginRequest((ctx) => {
const optFT = ctx.request.headers.get("feature-flags");
const featureFlags = optFT
? optFT.split(",").map((v) => v.trimStart())
: [];
// Route-based matching and feature flag check
const path = new URL(ctx.request.url).pathname;
if (path === "/d") {
if (!featureFlags.includes("route-d-preview")) {
// Short-circuit: return response without hitting origin
return Promise.resolve(
new Response("You cannot use this route.", { status: 400 }),
);
}
}
// Continue to origin with the request
return Promise.resolve(ctx.request);
})
.onOriginResponse((ctx) => {
// Add custom header to response
ctx.response.headers.append("X-Via", "MyMiddleware");
return Promise.resolve(ctx.response);
});
```
### Local development
You can run middleware scripts locally using Deno:
```bash theme={null}
deno run -A script.ts
```
Test with curl:
```bash theme={null}
# Blocked - missing required feature flag
curl http://127.0.0.1:8080/d --header 'feature-flags: something-else'
# Allowed - has required feature flag
curl http://127.0.0.1:8080/d --header 'feature-flags: route-d-preview, something-else'
```