[[ServiceRegistry-ServiceRegistry]]
== Service Registry

*Available as of Camel 2.22*

[WARNING]
====
*Experimental feature*
====

Service registration is a key part of service discovery which Camel leverages through the _Service Call EIP_ and as of v 2.22.0 Camel provides an experimental support to ease the process to expose routes in a cloud environment and consume them with minimal configuration.

=== Service Registry Set-Up

A _Service Registry_ is just like any other camel service so set it up you only need to register your implementations to the camel context:

[source,java]
----
ServiceRegistry service = new MyServiceRegistry();

context.addService(service);
----

The configuration of the _Service Registry_ depends on the implementation you have chosen.
Out of the box camel provides the following implementations:

[cols="1,1,2", options="header"]
|====
|Type         |Module             | Class
|consul       |camel-consul       | org.apache.camel.component.consul.cloud.ConsulServiceRegistry
|zookeeper    |camel-zookeeper    | org.apache.camel.component.zookeeper.cloud.ZooKeeperServiceRegistry
|spring-cloud |camel-spring-cloud | org.apache.camel.component.spring.cloud.CamelSpringCloudServiceRegistry
|====

On Spring/Blueprint all the _Service Registry_ instances are automatically added to the camel context.

=== Serice Registry Usage

The _Service Registry SPI_ is leveraged by the following new implementations:

- *ServiceRegistryRoutePolicy*
+
This is an implementation of a RoutePolicy that register/deregister routes to a given _Service Registry_ according to route's life-cycle
+
[source,java]
----
fiRoutePolicy policy = new ServiceRegistrationRoutePolicy()

// bind the policy to one or more routes
from("undertow:http://0.0.0.0:8080")
    .routePolicy(policy)
    .log("Route ${routeId} has been invoked");
----
+
To apply the same policy to all the routes a dedicated _RoutePolicyFactory_ can be used:
+
[source,java]
----
// add the service registry route policy factory to context
context.addRoutePolicyFactory(new ServiceRegistrationRoutePolicyFactory()));
----
+
To configure how the service is exposed you can add route specific properties like:
+
[source,java]
----
// bind the policy to one or more routes
from("undertow:http://0.0.0.0:8080")
    .routePolicy(policy)
    .routeProperty(ServiceDefinition.SERVICE_META_NAME, "my-service")
    .routeProperty(ServiceDefinition.SERVICE_META_ID, "my-id")
    .routeProperty(ServiceDefinition.SERVICE_META_PORT, "8080")
    .log("Route ${routeId} has been invoked");
----
+
Service name and service id can also be provided by _routeId_ and _routeGroup_
+
[source,java]
----
// bind the policy to one or more routes
from("undertow:http://0.0.0.0:8080")
    .routePolicy(policy)
    .routeGroup("my-service")
    .routeId("my-id")
    .routeProperty(ServiceDefinition.SERVICE_META_PORT, "8080")
    .log("Route ${routeId} has been invoked");
----
+
[TIP]
====
Some component such has camel-undertow and those based on camel-http-common implement _DiscoverableService_ and they can automatically provide the metadata needed for service registration.
====
+
[TIP]
====
Any property prefixed with _service._ is automatically added to the service's metadata.
====

- *Service Component*
+
The service component is similar to a _ServiceRegistrationRoutePolicyFactory_ but let to "tags" routes that need to be registered to the _Service Registry_ by prefixing the related endpoints according to the service component syntax:
+
[source]
----
service:serviceName:delegateUri[?options]
----
+
Example:
+
[source,java]
----
from("service:my-service:undertow:http://0.0.0.0:8080")
    .log("Route ${routeId} has been invoked");
----

To configure how the service is exposed you can add service specific endpoint options such as:

[source,java]
----
from("service:my-service:undertow:http://0.0.0.0:8080?service.id=my-service-id")
    .log("Route ${routeId} has been invoked");
----

[TIP]
====
Any option prefixed with _service._ is automatically added to the service's metadata.
====

== Spring Cloud

The _Service Registry_ binding for _Spring Cloud_ let you register your route with minimal code changes a a _Service Registry_ is automatically added to the Camel Context as soon as the camel-spring-cloud dependency is added to the classpath.

[WARNING]
====
As the spring-cloud backend has some limitations you need to include also some additional dependencies according to the selected backend. At the moment, the following implementations are provided:

[options="header"]
|====
|Spring Cloud           |Camel
|spring-cloud-consul    |camel-spring-cloud-consul
|spring-cloud-zookeeper |camel-spring-cloud-zookeeper
|====
====

Assuming the consul backend has been chosen the following code will configure and activate the _Service Registry_:

[source,properties]
----
# Spring cloud
spring.cloud.consul.enabled = true
spring.cloud.consul.discovery.enabled = true

# Camel Cloud
camel.cloud.service-registry.service-host = localhost
----

To register a route, the easy way is then to use the _service_ component as described above.
