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The URL Rewrite Traffic Policy action allows you to modify the incoming request URL using regular expressions before it reaches the upstream server, while keeping the URL seen by the client unchanged. This action is particularly useful for routing users without exposing internal system details.

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Configuration reference

This is the Traffic Policy configuration reference for this action.

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Supported phases

on_http_request

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Type

url-rewrite

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Configuration fields

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Behavior

This action replaces all occurrences of the from regular expression in the request URL with the to replacement value.

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Matching

Matching is performed against the entire URL, including the scheme, userinfo, host, and port, not just the path. To match requests that begin with /products, use CEL Interpolation and write ^${req.url.authority}/products, or use an expression like req.url.path.startsWith('/products') in the phase rule’s expressions field.

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Note about CEL interpolation

All CEL Interpolation will occur before regular expressions are evaluated.

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Non-terminating action

This is a Non-terminating action. It does not return a response, and will allow Traffic Policy processing to continue to the next Action in the chain. All Cloud Endpoint Traffic Policies must end with a terminating action. This requirement does not apply to Agent Endpoints.

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Examples

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Rewrite using paths

The following Traffic Policy configuration demonstrates how to use the url-rewrite action to transparently rewrite the request URL from /products to /products.php.

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Example Traffic Policy document

on_http_request:
  - expressions:
      - req.url.path == '/products'
    actions:
      - type: url-rewrite
        config:
          from: /products
          to: /products.php
This configuration will rewrite any request to /products to /products.php without changing the URL seen by the client. This is useful for hiding away the underlying implementation details of your service.

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Example request

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

HTTP/2 200 OK
Example server logs
GET /product.php               200 OK

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Conclusion

In this example, a request to /products is internally routed to /products.php, and the response is served from products.php while the client remains unaware of the URL rewrite.

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Rewrite using regular expressions

The following Traffic Policy configuration demonstrates how to use the url-rewrite action to transparently rewrite the request URL from /products/* to /products.php.

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Example Traffic Policy document

on_http_request:
  - expressions:
      - req.url.path.startsWith('/products')
    actions:
      - type: url-rewrite
        config:
          from: /products/?([.*]+)?
          to: /products.php?query=$1
This configuration will rewrite any request to /products/* to /products.php?query=$1 without changing the URL seen by the client. This is useful for hiding away the underlying implementation details of your service.

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Example request

$ curl -i https://example.ngrok.app/products/123

HTTP/2 200 OK
Example server logs
GET /product.php?query=123          200 OK

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Conclusion

In this example, a request to /products is internally routed to /products.php?query=123, and the response is served from products.php while the client remains unaware of the URL rewrite.

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Rewrite using CEL interpolation

The following Traffic Policy configuration demonstrates how to use the url-rewrite action to transparently rewrite the request URL from /products/* to /products.php using a global policy rule (no expression) by leveraging CEL Interpolation.

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Example Traffic Policy document

on_http_request:
  - actions:
      - type: url-rewrite
        config:
          from: ${req.url.authority}/products/?([.*]+)?
          to: /products.php?query=$1
This configuration will rewrite any request urls that start with /products/* to /products.php?query=$1 without changing the URL seen by the client. It does this by leveraging CEL Interpolation to replace the from value with the request URL authority. This is useful for hiding away the underlying implementation details of your service.

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Example request

$ curl -i https://example.ngrok.app/products/123

HTTP/2 200 OK
Example server logs
GET /product.php?query=123          200 OK

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Conclusion

In this example, a request to /products is internally routed to /products.php?query=123, and the response is served from products.php while the client remains unaware of the URL rewrite.

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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.