[Exist-open] HTTP Header Vary: User-Agent

[Mathias G. <go...@su...>]

Hi existdb community,

since i recently worked towards a cache in front of existdb, i wonder 
why there is the value "User-Agent" added to a Vary header i cannot 
control from Xquery. Using the response module to insert a Vary header 
(my hope was, i can just override with), gives me a duplicate header 
what is worse, because it might confuses clients. I investigated on the 
issue and identified the gzip compression lib added to the jetty config. 
And that is confusing me, because i dont see any relation by the gzip 
compression to a User-Agent Vary…

Maybe i am on a good track and we can agree on a change here? One could 
also argue, that XQuery-MVC-users should be able to control the final 
response. For the REST- and RESTXQ-Interface, i also dont see any reason…

Also i noticed that you configured existdb.org different, so the header 
is not present. There are some ways fixing this issue, so let us discuss 
about the default setting.

best,
Mathias


setup:

    *docker run -p 8080:8080 existdb/existdb:6.4.1*

    *curl localhost:8080/exist/rest/db -l -v -o /dev/null*
    * Host localhost:8080 was resolved.
    * IPv6: ::1
    * IPv4: 127.0.0.1
       % Total    % Received % Xferd  Average Speed   Time    Time  
      Time  Current
                                      Dload  Upload   Total  Spent   
    Left  Speed
       0     0    0     0    0     0      0      0 --:--:-- --:--:--
    --:--:--     0*   Trying [::1]:8080...
    * Connected to localhost (::1) port 8080
    * using HTTP/1.x
     > GET /exist/rest/db HTTP/1.1
     > Host: localhost:8080
     > User-Agent: curl/8.15.0
     > Accept: */*
     >
    * Request completely sent off
    < HTTP/1.1 200 OK
    < Date: Mon, 30 Mar 2026 07:29:02 GMT
    < Content-Type: application/xml; charset=UTF-8
    < Last-Modified: Mon, 30 Mar 2026 07:28:04 GMT
    < Created: Mon, 30 Mar 2026 07:28:04 GMT
    *< Vary: Accept-Encoding, User-Agent*
    < Transfer-Encoding: chunked
    < Server: Jetty(9.4.58.v20250814)
    <
    { [485 bytes data]
    100   480    0   480    0     0   102k      0 --:--:-- --:--:--
    --:--:--  117k
    * Connection #0 to host localhost left intact

    *curl localhost:8080/exist/apps/fundocs/ -l -v -o /dev/null*
    * Host localhost:8080 was resolved.
    * IPv6: ::1
    * IPv4: 127.0.0.1
       % Total    % Received % Xferd  Average Speed   Time    Time  
      Time  Current
                                      Dload  Upload   Total  Spent   
    Left  Speed
       0     0    0     0    0     0      0      0 --:--:-- --:--:--
    --:--:--     0*   Trying [::1]:8080...
    * Connected to localhost (::1) port 8080
    * using HTTP/1.x
     > GET /exist/apps/fundocs/ HTTP/1.1
     > Host: localhost:8080
     > User-Agent: curl/8.15.0
     > Accept: */*
     >
    * Request completely sent off
    < HTTP/1.1 200 OK
    < Date: Mon, 30 Mar 2026 07:28:23 GMT
    < Last-Modified: Mon, 30 Mar 2026 07:28:11 GMT
    < Created: Mon, 30 Mar 2026 07:28:11 GMT
    < X-XQuery-Cached: false
    < Content-Type: text/html;charset=utf-8
    *< Vary: Accept-Encoding, User-Agent*
    < Transfer-Encoding: chunked
    < Server: Jetty(9.4.58.v20250814)
    <
    { [11443 bytes data]
    100 11437    0 11437    0     0  33554      0 --:--:-- --:--:--
    --:--:-- 33638
    * Connection #0 to host localhost left intact