Load balancing

When the same app runs on several machines, Teitunnel can put Cloudflare's load balancer in front of it: visitors go to whichever machines are healthy, and traffic moves away from one that goes down.

What you need

• Cloudflare Load Balancing, a paid add-on. Turn it on in the Cloudflare dashboard under Traffic ▸ Load Balancing.
• The token permissions Account · Load Balancing: Monitors and Pools · Edit and Zone · Load Balancers · Edit. If they're missing, Teitunnel shows how to add them.
• The same route on each machine: run Teitunnel (or teitunnel-cli on a server) on every machine, and add the route with the same hostname on each.

Turn it on

Select the route in Routes and choose Load Balance…, or from the terminal:

teitunnel-cli route balance app.example.com

The plan shows what's created before anything is:

• a health check that requests https://app.example.com/ through each tunnel and expects a 2xx answer (after redirects);
• a pool with one endpoint per machine: each tunnel's <id>.cfargotunnel.com, with your hostname as the Host header, as Cloudflare recommends for tunnels;
• a load balancer named after the hostname. It takes precedence over the DNS record, so the record stays as a fallback.

With only one machine serving the route so far, the plan warns you: add the route on another machine and balance again to include it.

See how each machine is doing

The route's details list Machines: every endpoint of the pool, with the result of Cloudflare's health checks from each region that checks it ("Healthy in all 3 regions", "Healthy in 2 of 3 regions", or failing with Cloudflare's reason, such as a timeout). The machine you're on is marked. Checks run about once a minute; the list refreshes while it's open.

Machines joining and leaving

A machine that adds the route later joins the pool by itself, instead of taking the DNS record over. Removing the route on a machine takes it out of the pool; when the last one goes, the load balancer, pool and health check go too.

Turn it off

Stop Load Balancing… (or teitunnel-cli route unbalance app.example.com) deletes the load balancer, pool and health check. The hostname's DNS record serves it again.

Teitunnel marks what it creates (teitunnel:lb=<hostname> in the description) and only changes those. If a load balancer made elsewhere already answers for the hostname, the plan stops and asks you to manage it in the dashboard. Every step can be undone, and a failure part-way puts back what was there.