Load balancing

The proxy gives each new request to the next instance of the service, in turn.

The first request goes to instance 1.

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A service can have more than one instance. Then the proxy shares the requests between them. This is load balancing.

The rule is round-robin: each instance gets a request in its turn.

The rules

A route points only at instances that accept TCP connections.
A GET or HEAD request with no body cannot reach an instance: the proxy tries it one more time on a different instance.
The proxy does not try other requests again.
During a deploy, the proxy moves to the new instances in one step, after they pass their health check. See Deploys.

Terminal

ferry scale shop 3

How the proxy routes a request

The proxy reads the Host header of each request, finds the service and sends the request to one instance.

Error pages of the proxy

If the proxy cannot send a request to your app, it answers with its own page and an x-ferry-error header.