GitLab is taking too much time to respond

Hi.
Firstly, sorry for my bad english.

I’m trying to install GitLab on CentOs through RPM package, but i always get this error when i try to access the url:

502 - GitLab is taking too much time to respond

This error occurs instantly when i access the GitLab url (not after 30/60 seconds).
I have tried in two CentOs installations (6.6 and 7.1) and gave the same problem.

What are the possible causes of this problem?
Thank You!

Maybe you install tomcat server use the port 8080.
Change the unicorn port from 8080 to 8081, then
sudo gitlab-ctl reconfigure

##########################
# GitLab git http server #
##########################
# see https://gitlab.com/gitlab-org/gitlab-git-http-server/blob/master/README.md

# gitlab_git_http_server['enable'] = true
# gitlab_git_http_server['ha'] = false
# gitlab_git_http_server['repo_root'] = "/var/opt/gitlab/git-data/repositories"
# gitlab_git_http_server['listen_network'] = "unix"
# gitlab_git_http_server['listen_umask'] = 000
# gitlab_git_http_server['listen_addr'] = "/var/opt/gitlab/gitlab-git-http-server/socket"
 gitlab_git_http_server['auth_backend'] = "http://localhost:8081"
# gitlab_git_http_server['pprof_listen_addr'] = "''" # put an empty string on the command line
# gitlab_git_http_server['dir'] = "/var/opt/gitlab/gitlab-git-http-server"
# gitlab_git_http_server['log_dir'] = "/var/log/gitlab/gitlab-git-http-server"

##################
# GitLab Unicorn #
##################
## Tweak unicorn settings.

# unicorn['worker_timeout'] = 60
# unicorn['worker_processes'] = 2

## Advanced settings
# unicorn['listen'] = '127.0.0.1'
unicorn['port'] = 8081
# unicorn['socket'] = '/var/opt/gitlab/gitlab-rails/sockets/gitlab.socket'
# unicorn['pidfile'] = '/opt/gitlab/var/unicorn/unicorn.pid'
# unicorn['tcp_nopush'] = true
# unicorn['backlog_socket'] = 1024
# Make sure somaxconn is equal or higher then backlog_socket
# unicorn['somaxconn'] = 1024
# We do not recommend changing this setting
# unicorn['log_directory'] = "/var/log/gitlab/unicorn"