Merge pull request #1520 from ryanjbaxter/eureka-client-zone-doc-1327

Document Eureka client zone config

docs/src/main/asciidoc/spring-cloud-netflix.adoc

@@ -305,6 +305,33 @@ production it's probably better to stick with the default because
 there are some computations internally in the server that make
 assumptions about the lease renewal period.
 
+
+=== Zones
+
+If you have deployed Eureka clients to multiple zones than you may prefer that
+those clients leverage services within the same zone before trying services
+in another zone.  To do this you need to configure your Eureka clients correctly.
+
+First, you need to make sure you have Eureka servers deployed to each zone and that
+they are peers of each other.  See the section on <<spring-cloud-eureka-server-zones-and-regions,zones and regions>> 
+for more information.
+
+Next you need to tell Eureka which zone your service is in.  You can do this using
+the `metadataMap` property.  For example if `service 1` is deployed to both `zone 1`
+and `zone 2` you would need to set the following Eureka properties in `service 1`
+
+*Service 1 in Zone 1*
+```
+eureka.instance.metadataMap.zone = zone1
+eureka.client.preferSameZoneEureka = true
+```
+
+*Service 1 in Zone 2*
+```
+eureka.instance.metadataMap.zone = zone2
+eureka.client.preferSameZoneEureka = true
+```
+
 [[spring-cloud-eureka-server]]
 == Service Discovery: Eureka Server
 
@@ -362,6 +389,7 @@ dependencyManagement {
 ----
 ====
 
+[[spring-cloud-eureka-server-zones-and-regions]]
 === High Availability, Zones and Regions
 
 The Eureka server does not have a backend store, but the service