SSL Error with HAproxy

Summary

Hi I'm running the GitLab-CE docker container behind a HAproxy. The issue is, that I get this error "SSL_ERROR_RX_RECORD_TOO_LONG" with firefox. When I forward the ports directly to the container it works. The other web servers (nginx and apache) work fine behind the HAproxy.

So it must a the way how the gitlab web server an the proxy are interacting with each other. I've searched for solutions on multiple Platforms, but non of them helped me.

Steps to reproduce

Setup: VMware Photon OS as docker host

docker -v Docker version 17.06.0-ce, build 02c1d87

Debian 9 as HAproxy

haproxy -v HA-Proxy version 1.8.8-1~bpo9+1 2018/04/19 Copyright 2000-2018 Willy Tarreau <willy@haproxy.org>

What is the current bug behavior?

The connection the the website fails with this error "SSL_ERROR_RX_RECORD_TOO_LONG"

What is the expected correct behavior?

The gitlab login page appears.

Results of GitLab environment info

Expand for output related to GitLab environment info 
`root@gitlab:/# gitlab-rake gitlab:env:info


System information
System:
Current User:   git
Using RVM:      no
Ruby Version:   2.3.7p456
Gem Version:    2.6.14
Bundler Version:1.13.7
Rake Version:   12.3.1
Redis Version:  3.2.11
Git Version:    2.16.3
Sidekiq Version:5.0.5
Go Version:     unknown


GitLab information
Version:        10.8.0
Revision:       55e4a0b
Directory:      /opt/gitlab/embedded/service/gitlab-rails
DB Adapter:     postgresql
URL:            https://git.dn5.ch
HTTP Clone URL: https://git.dn5.ch/some-group/some-project.git
SSH Clone URL:  git@git.dn5.ch:some-group/some-project.git
Using LDAP:     no
Using Omniauth: no


GitLab Shell
Version:        7.1.2
Repository storage paths:
  • default: /var/opt/gitlab/git-data/repositories Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks Git: /opt/gitlab/embedded/bin/git `

Results of GitLab application Check

Expand for output related to the GitLab application check 
root@gitlab:/# git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true
Unknown option: -H
usage: git [--version] [--help] [-C ] [-c name=value]
[--exec-path[=]] [--html-path] [--man-path] [--info-path]
[-p | --paginate | --no-pager] [--no-replace-objects] [--bare]
[--git-dir=] [--work-tree=] [--namespace=]
 []

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)