I use a HAProxy container as an entry point for a virtual HPC cluster. Depending on a prefix the request is forwarded to different containers.

:80/foswiki/ -> :80/foswiki/
:80/kibana/ -> :80/kibana/
:80/graphite-api/ -> :80/graphite-api/

The config I use is pretty simple:

frontend http-in
    bind *:80
    acl uri_foswiki path_beg /foswiki
    use_backend srv_foswiki if uri_foswiki
    # gitlab
    default_backend srv_gitlab

backend srv_foswiki
    balance roundrobin
    cookie SERVERID insert
    option httpclose
    option forwardfor
    server foswiki cookie

The thing is that there are webservers that serve the website directly as root, without a prefix. 'Graphite-web', e.g. or the gitlab image.

I try to cut the prefix and forward it further, but what I really want, is that the HAProxy keeps the prefix in the path and that it is transparent to the backends server. If I click on 'gitlab_server:80/dashboard/' it should come out as 'frontend_ip:80/gitlab/dashboard'.

backend srv_gitlab
    balance roundrobin
    #cookie SERVERID insert
    mode http
    reqrep ^([^\ ]*)\ /gitlab/(.*)     \1\ /\2
    balance roundrobin
    option forwardfor
    server gitlab cookie

I don't think it is a hard thing to do, but it seems to me, that my google skills are somewhat crippled. Every time I end up with rewrite rules that do not keep the prefix.

Anyone? Christian

EDIT: The internal IP addresses are not reachable by the user...

  • So is the problem that the Appserver redirects you to locations without the prefix? Jun 18, 2014 at 10:20
  • yes. I rewrite the URL 'GLOBAL_IP/gitlab/' to 'INTERNAL_IP/' (transparent to the end user agent) and afterwards the gitlab-webapp issues 'GLOBAL_IP/dashboards/', for which I would have to setup a second rewrite. I would like to have a auto-prefixing for all the links. But maybe I have to cope with the internal-webserver and his HOST_NAME. It would be cleaner if I do not have to bother with the internal webserver.
    – kniepbert
    Jun 18, 2014 at 12:06
  • Ah, so you're looking for a regex that will strip the leading gitlab/ from URIs. I'll see about an answer. Jun 18, 2014 at 13:02

1 Answer 1


To get rid of leading parts of the URI, try

reqrep ^(GET|POST)\ /gitlab/(.*) \1\ /\2

i.e., extract the HTTP method into \1 and the path following the gitlab root into \2, then catenate them to a full request.

Note that this may not cut it for many applications, because the appserver doesn't know that clients are supposed to request everything from inside a virtual gitlab/ root directory. Therefor, redirects will apparently "strip" the important root directory.

Such scenarios are solved more easily e.g. with nginx and its mod_proxy or even Apache.

  • But this would get rid of '/gitlab/' for the future, wouldn't it? I am looking for something that works like an inline-frame. If I click the link '^/dashboard/' within gitlab it should be expaned to '/gitlab/dashboard/' to be able to forward it at the haproxy-layer to the gitlab server in the backend.
    – kniepbert
    Jun 18, 2014 at 13:28
  • I see. haproxy is surprisingly bad at this, sadly (i.e., free form response header mangling). I suggest nginx in between, or even replacing haproxy. Jun 18, 2014 at 15:46

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