For Configuration information see ZooKeeper Config
Each instance of Wookiee can automatically manages itself with ZooKeeper so that others nodes can make use of clustering. Wookiee does this through the use of Curator which then allows the platform to provide interaction with ZooKeeper through the instance of Curator that is managed.
The system is designed so that a developer simply needs to apply a trait (interface) on an actor in order to have full access to this functionality. Wookiee is responsible for managing the communication with ZooKeeper and thus a service does not need to manage its own communication. Currently, not all functionality is supported, but it does include the ability to get node data, set node data, create nodes, getting node children, receiving ZooKeeper state events, receiving node child events, and managing node leadership.
In order to take full benefit of the functionality one simply needs to apply the trait ZookeeperAdapter and then start
interacting with the system.
import com.webtrends.harness.component.zookeeper.ZookeeperAdapter
// Define the actor and have it apply the ZookeeperAdapter trait
class MyZookeeperActor extends Actor with ActorLoggingAdapter with ZookeeperAdapter {
import context.dispatcher
implicit val timeout = Timeout(2000)
val host = InetAddress.getLocalHost.getCanonicalHostName
def preStart: Unit = {
// Lets create a node and give it some data
createNode(s"/plugin-example/ephnodes/$host", true /* Is this node ephemeral? */, None /* I could give it the data here instead of making the next call */).onComplete {
case Success(path) =>
// The node was created so lets set some data
setData(path, "mydata".getBytes)
case Failure(fail) => // Handle Error
}
// We could have also combined the previous example into this call
// setData(s"/plugin-example/ephnodes/$host", "mydata".getBytes, true /* Create the node if it does not exist */, true /* Is the node ephemeral ?* /)
// Lets get some data
getData(s"/plugin-example/ephnodes/$host").onComplete {
case Success(data /* Array[Bytes] */) => // Do something with the data
case Failure(fail) => // Handle the error
}
// Lets get some information about child nodes
getChildren("s"/plugin-example/ephnodes", true /* Do we want the data as well? */).onComplete {
case Success(childrenWithData /* Seq[(String, Option[Array[Byte]])] */) => // Do something with the children and data
case Failure(fail) => Handle the error
}
}
}The ability to receive events for ZooKeeper changes are also available through the trait ZookeeperEventAdapter.
If this trait is applied to an actor then the ability to register/unregister for events becomes available.
import com.webtrends.harness.component.zookeeper.ZookeeperEventAdapter
// Define the actor and have it apply the ZookeeperEventAdapter
class MyZookeeperEventActor with Actor with ActorLoggingAdapter with ZookeeperEventAdapter {
def preStart: Unit = {
// Register for ZooKeeper State events
register(self, ZookeeperStateEventRegistration(self))
// Register for ZooKeeper Child events on the given path
register(self, ZookeeperChildEventRegistration(self, "/someparentpath"))
// Register for ZooKeeper leadership events
register(self, ZookeeperLeaderEventRegistration(self, "/someleadershippath")
}
def postStop: Unit = {
// Unregister for state events
unregister(self, ZookeeperStateEventRegistration(self))
// Unregister for child events on the given path
unregister(self, ZookeeperChildEventRegistration(self, "/someparentpath"))
// Unregister for leadership events
unregister(self, ZookeeperLeaderEventRegistration(self, "someleadershippath"))
}
def receive = {
case ZookeeperStateEvent(state) =>
// A connection state event occured (see com.netflix.curator.framework.state.ConnectionState)
case ZookeeperChildEvent(event) =>
// A child event occurred on the registered path (see com.netflix.curator.framework.recipes.cache.PathChildrenCacheEvent)
case ZookeeperLeadershipEvent(leader /* Am I the leader */) =>
// A leadership event occured on the registered path
}
}