APIM Response Headers Different Between Azure Portal, Developer Portal and Postman

Question

I am learning Azure API Management and am seeing different response headers between Azure Portal, Developer Portal and Postman.

I'm doing an HTTP Get on this endpoint: https://secondattempt.azure-api.net/speakers

With https://conferenceapi.azurewebsites.net/ as the web service URL.

I have compared them here:

Azure Portal:

1. Cache-Control
2. Pragma
3. Transfer-Encoding
4. Content-Type
5. Expires
6. Set-Cookie (not present)
7. Date
8. Op-Apim-Trace-Location
9. Vary

Developer Portal:

1. Cache-Control
2. Pragma
3. Transfer-Encoding
4. Content-Type
5. Expires
6. Set-Cookie
7. Date
8. Ocp-Apim-Trace-Location
9. Vary (not present)

Postman:

1. Cache-Control
2. Pragma
3. Transfer-Encoding
4. Content-Type
5. Expires
6. Set-Cookie
7. Date
8. Ocp-Apim-Trace-Location (not present)
9. Vary (not present)

And here are what they actually look like in the UI:

Azure Portal:

Developer Portal:

Postman:

Why are some headers present in some environments but not others?

Also, why are the headers appearing in different orders?

Answer 1

1. For Postman (Ocp-Apim-Trace-Location not present)

   The OCP-Apim-Trace feature enables you to specify whether or not APIM should generate a trace file on blob storage.

   While doing a GET request from Postman, OCP-Apim-Trace is not enabled.

   Setting the header to 'true' within Postman, for example, will give you back an HTTP Header in the response called OCP-Apim-Trace-Location.

   This will contain the URL to your trace file, which you can open in any browser.

2. For Postman and Developer portal (Vary not resent)

   A request is not cached. Each request for a URL is supposed to be treated as a unique and uncacheable request.

3. For Azure Portal ( Set-Cookie not present)

   See Trace and then forward request we do see "name": "Set-Cookie", "value": "ARRAffinity