Is it possible for and API in Azure APIM to invoke another API on the same APIM instance internally.

Question

We have an Azure APIM instance with custom DNS configured within a vNet. The APIM instance is fronted by Azure Front Door.

We currently have a need to implement a layered API architecture where an Api-X in APIM will need to invoke another API-Y within the same APIM instance. We would like to the connection between Api-X and Api-Y be internal and not have to route through front door that adds additional latency.

When we use the Api-Y Uri (with custom APIM DNS) as a backend from Api-X, we are getting an error saying

"Host (APIM) refused connection from IP (APIM private IP)".

I am curious to know if it is possible to setup internal connectivity between different APIs within the same APIM instance.

Please clarify.

Answer 1

Hi @Kumar Thanks for reaching out. Yes, it is possible for an api in Azure APIM to call other API in the same APIM instance. This can be achieved by writing a send-request policy or forward request policy
https://learn.microsoft.com/en-us/azure/api-management/api-management-advanced-policies#SendRequest
https://learn.microsoft.com/en-us/azure/api-management/api-management-advanced-policies#ForwardRequest

But it has few limitations if the APIM instance is deployed in an internal vnet. please follow this blog for more details https://techcommunity.microsoft.com/t5/azure-paas-blog/self-chained-apim-request-limitation-in-internal-virtual-network/ba-p/1940417

let me know incase of further queries, I would be happy to assist you.

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