Clustering
Available as of Camel 2.20
| Warning | Experimental feature | 
In Camel 2.20 we have introduced the following cluster related SPI:
- 
Cluster Service A regular Camel service that manages cluster resources such as views (see below) 
- 
Cluster View Represent a view of the cluster with its own set of isolated resources. As today views provide supports for: - 
Leader Election 
- 
Topology events like members joining/leaving the clutser) 
 
- 
- 
Cluster Member Represent a member of the clutser. 
Cluster SPI Set-Up
A Cluster Service is just like any other camel service so set it up you only need to register your implementations to the camel context:
MyClusterServiceImpl service = new MyClusterServiceImpl();
context.addService(service);The configuration of the Cluster Service depends on the implementation you have choosed. Out of the box camel provides the following implementations:
| Type | Module | Class | 
|---|---|---|
| atomix | camel-atomix | org.apache.camel.component.atomix.ha.AtomixClusterService | 
| consul | camel-consul | org.apache.camel.component.consul.ha.ConsulClusterService | 
| file | camel-core | org.apache.camel.component.file.ha.FileLockClusterService | 
| kubernetes | camel-kubernetes | org.apache.camel.component.kubernetes.ha.KubernetesClusterService | 
| zookeeper | camel-zookeeper | org.apache.camel.component.zookeeper.ha.ZooKeeperClusterService | 
On Spring/Bluepring all the Cluster Service instances are automatically added to the camel context.
Configuration examples:
- 
Spring Boot camel.component.file.cluster.service.enabled = true camel.component.file.cluster.service.id = ${random.uuid} camel.component.file.cluster.service.root = ${java.io.tmpdir}
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Spring XML <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd"> <bean id="zx" class="org.apache.camel.component.zookeeper.ha.ZooKeeperClusterService"> <property name="id" value="node-1"/> <property name="basePath" value="/camel/ha"/> <property name="nodes" value="localhost:2181"/> </bean> <camelContext xmlns="http://camel.apache.org/schema/spring" autoStartup="false"> ... </camelContext> </beans>
Cluster SPI Usage
The Cluster SPI is leveraged by the folowing new implementations:
- 
ClusteredRoutePolicy This is an implementation of a RoutePolicy that starts the routes it is associated to when the Cluster View it uses takes the leadership context.addRoutes(new RouteBuilder { @Override public void configure() throws Exception { // Create the route policy RoutePolicy policy = ClusteredRoutePolicy.forNamespace("my-ns"); // bind the policy to one or more routes from("timer:clustered?delay=1s&period=1s") .routePolicy(policy) .log("Route ${routeId} is running ..."); } });To apply the same policy to all the rooutes a dedicated RoutePolicyFactory can be used: // add the clustered route policy factory to context context.addRoutePolicyFactory(ClusteredRoutePolicyFactory.forNamespace("my-ns")); context.addRoutes(new RouteBuilder { @Override public void configure() throws Exception { // bind the policy to one or more routes from("timer:clustered?delay=1s&period=1s") .log("Route ${routeId} is running ..."); } });
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ClusteredRouteController This is an implementation of the RouteController SPI that lets the camel context start then starts/stops the routes when the leadership is taken/lost. This is well integrated with spring-boot apps so assuming you have tour routes set-up like: @Bean public RouteBuilder routeBuilder() { return new RouteBuilder() { @Override public void configure() throws Exception { from("timer:heartbeat?period=10s") .routeId("heartbeat") .log("HeartBeat route (timer) ..."); from("timer:clustered?period=5s") .routeId("clustered") .log("Clustered route (timer) ..."); } }; }You can then leverage spring-boot configuration to make them clustered: # enable the route controller camel.clustered.controller.enabled = true # define the default namespace for routes camel.clustered.controller.namespace = my-ns # exlude the route with id 'heartbeat' from the clustered ones camel.clustered.controller.routes[heartbeat].clustered = false
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Master Component The master component is similar to a ClusteredRoutePolicy but it works on consumer level so it ensure the only a single endpoint in a cluster is consuming resources at any point in time. Set it up is very easy and all you need is to prefix singleton endpoints according to the master component syntax: master:namespace:delegateUriA concrete example: @Bean public RouteBuilder routeBuilder() { return new RouteBuilder() { @Override public void configure() throws Exception { from("timer:heartbeat?period=10s") .routeId("heartbeat") .log("HeartBeat route (timer) ..."); from("master:my-ns:timer:clustered?period=5s") .routeId("clustered") .log("Clustered route (timer) ..."); } }; }