Where is this feature documented?

I'm probably too tired or I don't know, but of course I looked at the user's guide and the admin's guide but did not found anything about this ;-) Is there another documention which I missed somehow?

OK thanks I'll check that out. I did not configure ELOG by myself, I only use it and wrote the Slack plugin ;-)

We were running ELOG for many many years in our experiments and the instance was operated on a Debian XEN server as a container. I am now trying to migrate it into our Docker Swarm cluster and I am using the https://hub.docker.com/r/de1lz/elog-docker Docker image, which works very well with our logbooks when I run it as a single container. However, when I put the container behind my load balancer (HAProxy) using the simple HTTP mode (which works very well for all the other HTTP-based services) with this simple configuration:

backend be_elog.km3net.de
    mode http
    server-template km3net-elog- 1 km3net-elog_elog:8080 check resolvers docker init-addr libc,none

I get a "too many redirects" error when I try to access one of the logbooks. The starting page works fine, but every other link leads to a pile-up of redirects.

Here is the current instance running, where you can see the behaviour: https://elog.test.km3net.de (all log entries deleted and only two logbooks activated)

My question is: what kind of redirect could go wrong here? I don't know how the internal HTTP server of ELOG works, but maybe someone faced similar issues.

My ELOG configuration is also pretty basic, and as I wrote above, everything works when I run it without the load balancer (single instance at the moment). Here is the top part of the configuration, it contains a few dozens of logbooks but they are configured the very same way. 

;User Settings
;=============
Password file = login.xml
Admin user = km3net_admin
Self register = 0
Allow password change = 0
Allow config = km3net_admin

;Group Settings:
;====
Group ELOGKM3NET = Operations IT, Operations FR

[Operations IT]
Subdir = Operations_IT
Theme = default
Default encoding = 0
Comment = KM3NeT IT Detector Operations
Attributes = Author, Type, Subject
Options Author = A, B, C
Options Type = PPM-DOM, PPM-DU, Comment, Power cut, New run
Extendable Options = Type
Required Attributes = Author, Type, Subject
Page Title = ELOG - $subject
;Sort Attributes = Author, Type
Quick filter = Date, Type, Author
Resubmit default = 2
Reverse sort = 1
Menu commands = List, New, Edit, Reply, Duplicate, Find, Config, Help, Logout
Preset on first reply Subject = Re: $Subject
Preset on reply author =

Thanks for the quick reply! Sorry, I forgot to paste the "global" part of the config, I have that URL already set:

[global]
;Main Settings
;=============
Usr = elog
Grp = elog
port = 8080
SSL = 0
URL = https://elog.test.km3net.de
Title image = <img border=0 src="KM3NeT_logo.png" alt="KM3NeT logo" height="35px">
;SMTP host = smtp.fau.de
Display mode = summary
Thumbnail size = 500>
List Menu text = clock.html
Menu text = clock.html

I also tried the default configuration (example config) and it that works behind the load balancer. So I guess it's related to the password-page, which causes this redirect loop? Our logbooks are all password protected, so when a logbook URL is clicked, it should first present the login-form, and that's where it chokes.

My problem is that I don't even reach the page where I can enter a password. If you go to https://elog.test.km3net.de and click on a logbook, you'll see that it immediately goes into a redirect loop. I already logged the routing but there is nothing else...

Attached is the log, where you can see that `Operations+IT` redirects to `Operations+IT/` and that redirects to `Operations+IT` again, which then goes to `elog.test.km3net.de` and `Operations+IT` again etc. etc.

EDIT: I  use the very same load balancer confugration for dozens of other services incl. Apache, Nginx, GitLab, Mattermost, RocketChat etc. and all work fine. As written before, also the "example" logbook works (without password protection).

I also tried `/` at the end of the URL but it has no effect.

I am pretty clueless currently...