How to identify error if it is raised by backend

[edu4krishanu]

Hi All,

In my target fault rules, i have a javascript where I want to identify error source type. For example, I can receive 503/502 which can be caused in below scenarios,

1. APIGEE tried to connect to backend and got the errors.

2. Backend sent 503/502 to apigee in response.

Now I want to differentiate the above scenarios, Is there any apigee reference variable I can use for this purpose.

Thanks,

Krish