After installing GitLab Omnibus package on Debian 7, we need to properly configure it to work with an external Nginx web server. The key configuration in /etc/gitlab/gitlab.rb should include:

external_url 'http://git.mydomain.fr'
web_server['external_users'] = ['www-data']
nginx['enable'] = false
ci_nginx['enable'] = false

The error logs show a critical issue with worker connections:

2015/02/28 14:29:16 [alert] 4137#0: *14738 768 worker_connections are not enough...

This indicates the default Nginx configuration isn't sufficient for handling GitLab traffic. We need to create a custom Nginx configuration that properly proxies requests to the GitLab workhorse service.

Create /etc/nginx/sites-available/gitlab with these essential directives:

upstream gitlab-workhorse {
  server unix:/var/opt/gitlab/gitlab-workhorse/socket fail_timeout=0;
}

server {
  listen *:80;
  server_name git.mydomain.fr;
  server_tokens off;
  
  location / {
    proxy_pass http://gitlab-workhorse;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    
    # Important for large repositories
    client_max_body_size 0;
    proxy_request_buffering off;
  }
  
  # Error handling
  error_page 502 /502.html;
  location = /502.html {
    root /opt/gitlab/embedded/service/gitlab-rails/public;
  }
}

In /etc/nginx/nginx.conf, add these performance-related settings:

worker_processes auto;
worker_rlimit_nofile 100000;
events {
  worker_connections 4096;
  multi_accept on;
  use epoll;
}

http {
  # Buffer optimizations
  client_body_buffer_size 1m;
  client_header_buffer_size 1m;
  large_client_header_buffers 4 8m;
  
  # Timeouts
  client_body_timeout 60;
  client_header_timeout 60;
  keepalive_timeout 75;
  send_timeout 60;
}

After making these changes:

1. Test Nginx configuration: sudo nginx -t
2. Reload Nginx: sudo systemctl reload nginx
3. Restart GitLab: sudo gitlab-ctl restart
4. Verify socket permissions: sudo chmod 770 /var/opt/gitlab/gitlab-workhorse/socket

If you still encounter 502 errors, check these components:

• Workhorse service status: sudo gitlab-ctl status gitlab-workhorse
• Socket file existence and permissions
• Nginx error logs: tail -f /var/log/nginx/error.log

For high-traffic installations, consider increasing these values in gitlab.rb:

unicorn['worker_processes'] = 4
postgresql['max_worker_processes'] = 8
sidekiq['concurrency'] = 25

When setting up GitLab Omnibus with an external NGINX web server, the most common issue you'll encounter is the 502 Bad Gateway error. Let's examine the critical components:

# /etc/gitlab/gitlab.rb critical settings
external_url 'http://git.mydomain.fr'
web_server['external_users'] = ['www-data']
nginx['enable'] = false
ci_nginx['enable'] = false

You'll need to create a custom NGINX configuration. Here's a working template:

# /etc/nginx/sites-available/gitlab.conf
upstream gitlab-workhorse {
  server unix:/var/opt/gitlab/gitlab-workhorse/socket fail_timeout=0;
}

server {
  listen 80;
  server_name git.mydomain.fr;
  server_tokens off;
  
  location / {
    proxy_pass http://gitlab-workhorse;
    proxy_set_header Host $http_host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
  }

  error_log /var/log/nginx/gitlab_error.log;
  access_log /var/log/nginx/gitlab_access.log;
}

The error log shows "worker_connections are not enough". Add these to your nginx.conf:

events {
  worker_connections 10240;
}

http {
  # Add these to prevent connection flooding
  limit_req_zone $binary_remote_addr zone=gitlab:10m rate=10r/s;
  limit_req zone=gitlab burst=20 nodelay;
}

Ensure proper permissions for the workhorse socket:

sudo chown git:www-data /var/opt/gitlab/gitlab-workhorse/socket
sudo chmod 775 /var/opt/gitlab/gitlab-workhorse/socket

1. Test NGINX configuration: sudo nginx -t
2. Reload NGINX: sudo systemctl reload nginx
3. Check workhorse status: sudo gitlab-ctl status gitlab-workhorse
4. Verify socket exists: ls -la /var/opt/gitlab/gitlab-workhorse/