Each service can register one or more URL prefixes for which it servestraffic. A URL prefix is ahost/path combination without a scheme since SSLhas already been terminated and all traffic is expected to be HTTP. Toregister a URL prefix add a tagurlprefix-host/path to the servicedefinition.

By default, traffic is distributed evenly across all service instances whichregister a URL prefix but you can set the amount of traffic a set of instanceswill receive ("Canary testing"). See [Traffic Shaping](#Traffic Shaping)below.

A background process watches for service definition and health status changesin consul. When a change is detected a new routing table is constructed usingthe commands described in [Config Commands](#Config Commands).

Consul allows to discover services by two different names:

• mysvc.service.consul
• mysvc.service.dc1.consul

Assuming thatdc1 is the datacenter of the local agent during servicediscovery the first name may return instances from a different datacenterwhereas the second name will only return instances fromdc1.

If you have multiple environments with separate consul servers and distinguishthem via datacenter then you can use${DC} in theurlprefix- tag to simplifythe registration.

This way you can always register your service with the same set of tagsurlprefix-mysvc.service.consul,urlprefix-mysvc.service.${DC}.consul withoutknowing the consul configuration.