Can we return the flow to on-error element when response is not success from a send-request policy?

Question

Can we return the flow to on-error element when response is not success from a send-request policy?

Anonymous

I am using a send-request policy where in upon success response would want to do certain actions but when its not 200 want to return to on-error policy to handle that error in a custom way.

What are the possible way to return the flow control to on-error element?

JananiRamesh-MSFT 29,446 Reputation points Moderator

2024-07-26T06:10:14.89+00:00
@ADM709451 (Yashaswini Mohan) Thanks for reaching out. In APIM, you can use the return-response policy to return a response to the client and stop the execution of the policy. You can use this policy to return a response to the client when the response from the backend service is successful.

To return the flow control to the on-error policy when the response from the backend service is not successful, you can use the choose policy. The choose policy allows you to define a set of conditions and execute a specific policy based on the condition that is met.

Here is an example policy that uses the choose policy to return the flow control to the on-error policy when the response from the backend service is not successful:

<policies> <inbound> <base /> <send-request mode="new" response-variable-name="backend-response" timeout="20" ignore-error="false"> <set-url>{url}</set-url> <set-method>GET</set-method> </send-request> <choose> <when condition="@(context.Response.StatusCode == 200)"> <set-header name="X-Custom-Header" exists-action="override"> <value>Custom header value</value> </set-header> <return-response response-variable-name="backend-response" /> </when> <otherwise> <return-response response-variable-name="backend-response" /> </otherwise> </choose> </inbound> <on-error> <set-header name="X-Custom-Error-Header" exists-action="override"> <value>Custom error header value</value> </set-header> </on-error> </policies>

In this example, the send-request policy is used to call the backend service and store the response in the backend-response variable. The choose policy is then used to check if the response status code is 200. If the status code is 200, the set-header policy is used to set a custom header and the return-response policy is used to return the response to the client.

If the status code is not 200, the return-response policy is still used to return the response to the client, but the flow control is returned to the on-error policy to handle the error in a custom way. This means that the on-error policy is executed and any policies defined in the on-error policy are executed to handle the error.

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

2024-07-26T06:57:58.11+00:00
Let me be more specific of my use-case:

I have a api, where in a fragment is called

The fragment has send-request with ignore-error="false"

When send-request fails/passed in both cases, control comes back to api inbound policy and continues to execute.

Expected is that it returns to api <on-error> as send-request is not successful. Is this the right understanding? If yes, could you check on the behavior mentioned in point 3? Also to add, in the provided sample code when send-request response code is not 200 we are doing return-response. The return-response send the response as is to client and does not go through on-error element.