APIM rewrite-uri Policy Functionality

Question

Hello,

Wondering what the rewrite-uri policy in apim actually does? The documentation says it "converts a request URL from its public form to the form expected by the web service". However, I thought that's what apim was already doing as it sends it to a backend api?

Thanks,

Karl

Answer 1

@Karl Gardner Thanks for reaching out. The rewrite-uri policy in APIM is more specific than the general routing that APIM performs.

When you set up an API in APIM, you define a public endpoint that clients use to access your API. APIM then routes these requests to the appropriate backend service based on the configuration you provide.

The rewrite-uri policy allows you to modify the request URL before it is sent to the backend service. This can be useful in several scenarios, such as path adjustments, versioning.

For example, if your public API endpoint is https://api.example.com/v1/products but your backend service expects https://backend.example.com/api/products, you can use the rewrite-uri policy to adjust the URL accordingly.

Here’s a simple example of how you might configure this policy:

<inbound>
    <base />
    <rewrite-uri template="/api/products" />
</inbound>

This policy ensures that when a request comes to https://api.example.com/v1/products, it is rewritten to https://backend.example.com/api/products before being sent to the backend.

hope this helps! do let me know incase of further queries, I would be happy to assist you.

Answer 2

Hi Karl Gardner,

APIM provides a layer of abstraction between the public API and the backend API. While APIM routes requests to the backend, it doesn’t inherently know how to modify the path unless you tell it. So, the rewrite-URI policy gives you fine-grained control to adjust the request path for compatibility with the backend, without changing how it looks to the client.

You may read more about Rewrite API here

https://learn.microsoft.com/en-us/azure/api-management/rewrite-uri-policy