Refactor the handling of TreeCache into the AbstractTreeWatcher itself

This should lay the groundwork for refactoring much of the BrokerTreeWatcher up
into the AbstractTreeWatcher

src/main/groovy/com/github/lookout/verspaetung/Main.groovy

@@ -55,10 +55,9 @@ class Main {
 
         client.start()
 
-        TreeCache cache = new TreeCache(client, '/consumers')
         KafkaPoller poller = setupKafkaPoller(consumers, statsd, cli.hasOption('n'))
         BrokerTreeWatcher brokerWatcher = new BrokerTreeWatcher(client)
-        StandardTreeWatcher consumerWatcher = new StandardTreeWatcher(consumers)
+        StandardTreeWatcher consumerWatcher = new StandardTreeWatcher(client, consumers)
 
 
         consumerWatcher.onInitComplete << {
@@ -69,10 +68,8 @@ class Main {
             poller.refresh(brokers)
         }
 
-        cache.listenable.addListener(consumerWatcher)
-
         brokerWatcher.start()
-        cache.start()
+        consumerWatcher.start()
 
         logger.info("Started wait loop...")
 

src/main/groovy/com/github/lookout/verspaetung/zk/AbstractTreeWatcher.groovy

@@ -7,6 +7,7 @@ import groovy.transform.TypeChecked
 
 import org.apache.curator.framework.CuratorFramework
 import org.apache.curator.framework.recipes.cache.ChildData
+import org.apache.curator.framework.recipes.cache.TreeCache
 import org.apache.curator.framework.recipes.cache.TreeCacheListener
 import org.apache.curator.framework.recipes.cache.TreeCacheEvent
 import org.slf4j.Logger
@@ -23,11 +24,17 @@ abstract class AbstractTreeWatcher implements TreeCacheListener {
     protected AbstractMap<TopicPartition, List<ConsumerOffset>> consumersMap
     protected List<Closure> onInitComplete
     protected Logger logger
+    protected CuratorFramework client
+    protected TreeCache cache
 
-    AbstractTreeWatcher(AbstractMap consumers) {
+    AbstractTreeWatcher(CuratorFramework client, AbstractMap consumers) {
+        this.client = client
         this.consumersMap = consumers
         this.onInitComplete = []
         this.logger = LoggerFactory.getLogger(this.class)
+
+        this.cache = new TreeCache(client, zookeeperPath())
+        this.cache.listenable.addListener(this)
     }
 
     /**
@@ -35,6 +42,19 @@ abstract class AbstractTreeWatcher implements TreeCacheListener {
      */
     abstract ConsumerOffset processChildData(ChildData data)
 
+    /**
+     * Return the String of the path in Zookeeper this class should watch. This
+     * method must be safe to call from the initializer of the class
+     */
+    abstract String zookeeperPath()
+
+    /**
+     * Start our internal cache
+     */
+    void start() {
+        this.cache?.start()
+    }
+
     /**
      * Primary TreeCache event processing callback
      */

src/main/groovy/com/github/lookout/verspaetung/zk/StandardTreeWatcher.groovy

@@ -11,6 +11,11 @@ import org.apache.curator.framework.recipes.cache.ChildData
 @TypeChecked
 @InheritConstructors
 class StandardTreeWatcher extends AbstractTreeWatcher {
+    private static final String ZK_PATH = '/consumers'
+
+    String zookeeperPath() {
+        return ZK_PATH
+    }
 
     /**
      * Extract the necessary information from a standard (i.e. high-level Kafka

src/test/groovy/com/github/lookout/verspaetung/zk/AbstractTreeWatcherSpec.groovy

@@ -11,9 +11,11 @@ class AbstractTreeWatcherSpec extends Specification {
 
     class MockWatcher extends AbstractTreeWatcher {
         MockWatcher() {
-            super([:])
+            super(null, [:])
         }
         ConsumerOffset processChildData(ChildData d) { }
+
+        String zookeeperPath() { return '/zk/spock' }
     }
 
     def setup() {

src/test/groovy/com/github/lookout/verspaetung/zk/StandardTreeWatcherSpec.groovy

@@ -2,13 +2,16 @@ package com.github.lookout.verspaetung.zk
 
 import spock.lang.*
 
+import org.apache.curator.framework.CuratorFramework
 import org.apache.curator.framework.recipes.cache.ChildData
 
 class StandardTreeWatcherSpec extends Specification {
     private StandardTreeWatcher watcher
+    private CuratorFramework mockCurator
 
     def setup() {
-        this.watcher = new StandardTreeWatcher([:])
+        this.mockCurator = Mock(CuratorFramework)
+        this.watcher = new StandardTreeWatcher(this.mockCurator, [:])
     }
 
     def "processChildData should return null if null is given"() {