Using GitHub Enterprise Server with a load balancer

About load balancers

A load balancer design uses a network device to direct Git and HTTP traffic to individual GitHub Enterprise Server appliances. You can use a load balancer to restrict direct traffic to the appliance for security purposes or to redirect traffic if needed without DNS record changes. We strongly recommend using a TCP-based load balancer that supports the PROXY protocol.

DNS lookups for the GitHub Enterprise Server hostname should resolve to the load balancer. We recommend that you enable subdomain isolation. If subdomain isolation is enabled, an additional wildcard record (*.HOSTNAME) should also resolve to the load balancer. For more information, see "Enabling subdomain isolation."

Handling client connection information

Because client connections to GitHub Enterprise Server come from the load balancer, the client IP address can be lost.

If your load balancer can support it, we strongly recommend implementing the PROXY protocol. When no PROXY support is available, it is also possible to load balance the HTTP and HTTPS ports using the X-Forwarded-For header.

Enabling PROXY protocol support on your GitHub Enterprise Server instance

We strongly recommend enabling PROXY protocol support for both your instance and the load balancer. Use the instructions provided by your vendor to enable the PROXY protocol on your load balancer. For more information, see the PROXY protocol documentation.

1. From an administrative account on GitHub Enterprise Server, in the upper-right corner of any page, click .

2. If you're not already on the "Site admin" page, in the upper-left corner, click Site admin.

3. In the " Site admin" sidebar, click Management Console.

4. In the "Settings" sidebar, click Privacy.

5. Under "External load balancers", select Enable support for PROXY protocol.

6. Under the "Settings" sidebar, click Save settings.

   Note: Saving settings in the Management Console restarts system services, which could result in user-visible downtime.

7. Wait for the configuration run to complete.

PROXY protocol TCP port mappings

Source port	Destination port	Service description
22	23	Git over SSH
80	81	HTTP
443	444	HTTPS
8080	8081	Management Console HTTP
8443	8444	Management Console HTTPS
9418	9419	Git

Enabling X-Forwarded-For support on your GitHub Enterprise Server instance

Use the X-Forwarded-For protocol only when the PROXY protocol is unavailable. The X-Forwarded-For header only works with HTTP and HTTPS. The IP address reported for Git connections over SSH will show the load balancer IP.

1. From an administrative account on GitHub Enterprise Server, in the upper-right corner of any page, click .

2. If you're not already on the "Site admin" page, in the upper-left corner, click Site admin.

3. In the " Site admin" sidebar, click Management Console.

4. In the "Settings" sidebar, click Privacy.

5. Under External load balancers, select Allow HTTP X-Forwarded-For header.

6. Under the "Settings" sidebar, click Save settings.

   Note: Saving settings in the Management Console restarts system services, which could result in user-visible downtime.

7. Wait for the configuration run to complete.

Protocol TCP port mappings for use without PROXY support

Source port	Destination port	Service description
22	22	Git over SSH
25	25	SMTP
80	80	HTTP
443	443	HTTPS
8080	8080	Management Console HTTP
8443	8443	Management Console HTTPS

Configuring health checks

Health checks allow a load balancer to stop sending traffic to a node that is not responding if a pre-configured check fails on that node. If the instance is offline due to maintenance or unexpected failure, the load balancer can display a status page. In a High Availability (HA) configuration, a load balancer can be used as part of a failover strategy. However, automatic failover of HA pairs is not supported. You must manually promote the replica instance before it will begin serving requests. For more information, see "Configuring high availability."

Configure the load balancer to check the following URL.

http(s)://HOSTNAME/status

The endpoint will return status code 200 (OK) if the node is healthy and available to service end-user requests. For more information, see "Monitoring a high-availability configuration."

Troubleshooting connectivity through a load balancer

If you cannot connect to services on your GitHub Enterprise Server instance through a load balancer, you can review the following information to troubleshoot the problem.

Error: "Your session has expired" for connections to the Management Console

If you enable support for the X-Forwarded-For header on your instance and load balancer, you may not be able to access your instance's Management Console. For more information about the Management Console and ports required for connections, see "Administering your instance from the Management Console" and "Network ports."

If your GitHub Enterprise Server instance indicates that your session has expired when you connect to the Management Console through a load balancer, try one of the following configurations on your load balancer.

• Disable X-Forwarded-For headers for connections to your instance on ports 8080 and 8443.
• Configure your load balancer to operate on Layer 4, and use the PROXY protocol instead of X-Forwarded-For for passthrough of client IP addresses. For more information, see "Enabling PROXY protocol support on your GitHub Enterprise Server instance."

For more information, refer to the documentation for your load balancer.

Live updates to issues and check runs not working

When your GitHub Enterprise Server instance is accessed via a load balancer or reverse proxy, expected live updates, such as new comments on issues and changes in notification badges or check run output, may not display until the page is refreshed. This is most common when the reverse proxy or load balancer is running in a layer 7 mode or does not support the required websocket protocol.

To enable live updates, you may need to reconfigure the load balancer or proxy. For more information, refer to the documentation for your load balancer.