Vary header mechanism

[basaran]

Environment info:

Version: 2.6.0
Linux 6.7.7-1-MANJARO x86_64

Describe what are you trying to do:
I have a request header which limits the number of records returned from an API. I need to have Krakend pay attention to the Vary header.

To be on the safe side, I added Vary to the allowed headers.

      "allow_headers": [
        "Origin",
        "Authorization",
        "Content-Type",
        "Cache-Control",
        "prefer",
        "Vary"
      ],

I sent my request with the following headers:

Content-Type: application/x-www-form-urlencoded
User-Agent: insomnium/0.2.3-a
Cache-Control: max-age=604800
prefer: maxpagesize=10
Vary: prefer

When I change the value of the maxpagesize, I still hit the same cache. To be on the safe side, I also tried:

Content-Type: application/x-www-form-urlencoded
User-Agent: insomnium/0.2.3-a
Cache-Control: max-age=604800
prefer: maxpagesize=10
Vary: *

According to MDN, the asterisk implies cache should not be returned.

[thedae]

Hi @basaran , I've been doing some tests and I'm not able to reproduce your case, check this config out in case you've something missing in your setup:

{
  "$schema": "https://krakend.io/schema/krakend.json",
  "version": 3,
  "echo_endpoint": true,
  "endpoints": [
    {
      "endpoint": "/",
      "input_headers": ["prefer"],
      "backend": [
        {
          "host": ["http://localhost:9000"],
          "url_pattern": "/vary-header",
          "extra_config": {
            "qos/http-cache": {}
          }
        }
      ]
    }
  ]
}

The backend is rather simple, just a mock server returning Cache-control and Vary headers:

 curl -i http://localhost:9000/vary-header
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Vary: prefer
Cache-Control: public, max-age=600
Content-Length: 34
Date: Wed, 12 Feb 2025 12:37:06 GMT
Connection: keep-alive
Keep-Alive: timeout=5
...

With the setup above, Krakend cache layer is working as expected: the cache cardinality depends on the prefer header value

Let me know if this helps and feel free to reopen if needed