The Redirect Traffic Policy action enables you redirect incoming requests to new URLs by modifying the original URLs with regular expressions. Redirection is performed using the Location header.

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Configuration Reference

The Traffic Policy configuration reference for this action.

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Supported Phases

on_http_request

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Type

redirect

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Configuration Fields

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from
string
Supports CEL
A regular expression pattern used to match a part of the URL.
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to
string
Required
Supports CEL
A regular expression pattern used to replace the matched part of the URL.
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status_code
integer
A 3xx status code used for redirecting. Default is 302.
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headers
object
Supports CEL
Map of key-value headers to be added to the response. Maximum 10 headers can be specified.

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Behavior

If the specified from regular expression matches the request URL, the URL will be modified according to the to field. If no from field is specified, the entire URL will be treated as a match. When a match is found and the request URL is modified by the to field, the action will return a temporary 302 redirect by default, unless specified otherwise through the status_code field. If the request URL is not changed, the action will take no further action.

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Note about CEL Interpolation

All CEL interpolation will occur before regular expressions are evaluated.

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Examples

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Redirect using Paths

The following Traffic Policy configuration demonstrates how to use the redirect action to redirect incoming requests from /products to /store/products.

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Example Traffic Policy Document

on_http_request:
  - actions:
      - type: redirect
        config:
          from: /products
          to: /store/products
This configuration will redirect any request from /products to /store/products with the default 302 Found status code.

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Example Request

$ curl -i https://example.ngrok.app/products

HTTP/1.1 302 Found
location: https://example.ngrok.app/store/products
In this example, a request to /products will be redirected to /store/products with a 302 Found status code, and the Location header will indicate the new URL.

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Redirect using Regular Expressions

The following Traffic Policy configuration demonstrates how to use the redirect action to redirects requests from an old API endpoint to a new one.

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Example Traffic Policy Document

on_http_request:
  - expressions:
      - req.url.path.startsWith('/api/')
    actions:
      - type: redirect
        config:
          from: /api/v1/users?id=([0-9]+)
          to: /api/v2/users/$1/
          status_code: 301
          headers:
            x-redirected: 'true'
In this configuration we match requests from /api/v1/users?id=([0-9]+) and redirect them to /api/v2/users/$1/ with a 301 status code. Additionally, a custom header x-redirected: true is added to the response.

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Example Request

$ curl -i https://example.ngrok.app/api/v1/users?id=123

HTTP/1.1 301 Moved Permanently
location: https://example.ngrok.app/api/v2/users/123/
x-redirected: true
The request will be redirected to the new URL /api/v2/users/123/, with a 301 Moved Permanently status and a custom header.

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Redirect with CEL Interpolation

The following Traffic Policy configuration demonstrates how to use the redirect action to redirect users while using CEL Interpolation.

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Example Traffic Policy Document

on_http_request:
  - expressions:
      - req.url.path in ['/api/v2/geo', '/api/v2/geo/']
    actions:
      - type: redirect
        config:
          to: /api/v2/geo?city=${conn.geo.city}
This configuration will redirect any request from /api/v2/geo or /api/v2/geo/ to /api/v2/geo?city=${conn.geo.city} using CEL Interpolation to insert the city from the connection’s geolocation data.

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Example Request

$ curl -i https://example.ngrok.app/api/v2/geo

HTTP/1.1 302 Found
location: https://example.ngrok.app/api/v2/geo?city=San%20Francisco
In this example, a request to https://example.ngrok.app/api/v2/geo will be redirected to https://example.ngrok.app/api/v2/geo?city=San Francisco, with the 302 Found status code and the Location header indicating the new URL that includes the city from the connection’s geolocation data.

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Action Result Variables

The following variables are made available for use in subsequent expressions and CEL interpolations after the action has run. Variable values will only apply to the last action execution, results are not concatenated.
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actions.ngrok.redirect.matches
array of strings
A list of elements that were matched during redirection. These represent the request components (e.g., path or query parameters) that triggered the action and resulted in the redirect.
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actions.ngrok.redirect.url
string
The URL to which the traffic was redirected. This is the destination URL returned as part of the redirect response after the action was executed.
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actions.ngrok.redirect.error.code
string
A machine-readable code describing an error that occurred during the action’s execution.
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actions.ngrok.redirect.error.message
string
A human-readable message providing details about an error that occurred during the action’s execution.