gitlab-org--gitlab-foss/doc/administration/load_balancer.md

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Load Balancer for multi-node GitLab

In an multi-node GitLab configuration, you need a load balancer to route traffic to the application servers. The specifics on which load balancer to use or the exact configuration is beyond the scope of GitLab documentation. We hope that if you're managing HA systems like GitLab you have a load balancer of choice already. Some examples including HAProxy (open-source), F5 Big-IP LTM, and Citrix Net Scaler. This documentation outlines what ports and protocols you need to use with GitLab.

SSL

How do you want to handle SSL in your multi-node environment? There are several different options:

• Each application node terminates SSL
• The load balancer(s) terminate SSL and communication is not secure between the load balancer(s) and the application nodes
• The load balancer(s) terminate SSL and communication is secure between the load balancer(s) and the application nodes

Application nodes terminate SSL

Configure your load balancer(s) to pass connections on port 443 as 'TCP' rather than 'HTTP(S)' protocol. This passes the connection to the application nodes NGINX service untouched. NGINX has the SSL certificate and listen on port 443.

See NGINX HTTPS documentation for details on managing SSL certificates and configuring NGINX.

Load Balancer(s) terminate SSL without backend SSL

Configure your load balancer(s) to use the 'HTTP(S)' protocol rather than 'TCP'. The load balancer(s) is be responsible for managing SSL certificates and terminating SSL.

Since communication between the load balancer(s) and GitLab isn't secure, there is some additional configuration needed. See NGINX Proxied SSL documentation for details.

Load Balancer(s) terminate SSL with backend SSL

Configure your load balancer(s) to use the 'HTTP(S)' protocol rather than 'TCP'. The load balancer(s) is responsible for managing SSL certificates that end users see.

Traffic is secure between the load balancer(s) and NGINX in this scenario. There is no need to add configuration for proxied SSL since the connection is secure all the way. However, configuration must be added to GitLab to configure SSL certificates. See NGINX HTTPS documentation for details on managing SSL certificates and configuring NGINX.

Ports

Basic ports

LB Port	Backend Port	Protocol
80	80	HTTP (1)
443	443	TCP or HTTPS (1) (2)
22	22	TCP

• (1): Web terminal support requires your load balancer to correctly handle WebSocket connections. When using HTTP or HTTPS proxying, this means your load balancer must be configured to pass through the Connection and Upgrade hop-by-hop headers. See the web terminal integration guide for more details.
• (2): When using HTTPS protocol for port 443, you must add an SSL certificate to the load balancers. If you wish to terminate SSL at the GitLab application server instead, use TCP protocol.

GitLab Pages Ports

If you're using GitLab Pages with custom domain support you need some additional port configurations. GitLab Pages requires a separate virtual IP address. Configure DNS to point the pages_external_url from /etc/gitlab/gitlab.rb at the new virtual IP address. See the GitLab Pages documentation for more information.

LB Port	Backend Port	Protocol
80	Varies (1)	HTTP
443	Varies (1)	TCP (2)

• (1): The backend port for GitLab Pages depends on the gitlab_pages['external_http'] and gitlab_pages['external_https'] setting. See GitLab Pages documentation for more details.
• (2): Port 443 for GitLab Pages should always use the TCP protocol. Users can configure custom domains with custom SSL, which would not be possible if SSL was terminated at the load balancer.

Alternate SSH Port

Some organizations have policies against opening SSH port 22. In this case, it may be helpful to configure an alternate SSH hostname that allows users to use SSH on port 443. An alternate SSH hostname requires a new virtual IP address compared to the other GitLab HTTP configuration above.

Configure DNS for an alternate SSH hostname such as altssh.gitlab.example.com.

LB Port	Backend Port	Protocol
443	22	TCP

Readiness check

It is strongly recommend that multi-node deployments configure load balancers to use the readiness check to ensure a node is ready to accept traffic, before routing traffic to it. This is especially important when utilizing Puma, as there is a brief period during a restart where Puma doesn't accept requests.