Ignore "owners" and other subtrees from the Kafka High Level Consumer ZK space

References #2

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

@@ -20,6 +20,14 @@ class StandardTreeWatcher extends AbstractTreeWatcher {
         if (data == null) {
             return null
         }
+
+        /* There are non-offset related subtrees in /consumers that we don't
+         * care about, let's just skip over them
+         */
+        if (!isOffsetSubtree(data.path)) {
+            return null
+        }
+
         /*
 ChildData{path='/consumers/offtopic-spock-test/offsets/topic/7', stat=8595174473,8595174478,1416808804928,1416808805262,1,0,0,0,1,0,8595174473, data=[48]}
         */
@@ -33,9 +41,22 @@ ChildData{path='/consumers/offtopic-spock-test/offsets/topic/7', stat=8595174473
 
         offset.groupName = pathParts[2]
         offset.topic = pathParts[4]
-        offset.partition = new Integer(pathParts[5])
-        offset.offset = new Integer(new String(data.data))
+
+        try {
+            offset.partition = new Integer(pathParts[5])
+            offset.offset = new Integer(new String(data.data))
+        }
+        catch (NumberFormatException ex) {
+            logger.error("Failed to parse an Integer: ${data}")
+            return null
+        }
 
         return offset
     }
+
+
+    Boolean isOffsetSubtree(String path) {
+        return (path =~ /\/consumers\/(.*)\/offsets\/(.*)/)
+    }
+
 }

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

@@ -37,4 +37,20 @@ class StandardTreeWatcherSpec extends Specification {
         offset.partition == 3
         offset.offset == 0
     }
+
+    def "isOffsetSubtree should return true for a valid subtree path"() {
+        given:
+        String path = '/consumers/offtopic-spock-test/offsets/topic/7'
+
+        expect:
+        watcher.isOffsetSubtree(path) == true
+    }
+
+    def "isOffsetSubtree should return false for a non-offset subtree path"() {
+        given:
+        String path = '/consumers/offtopic-1025413624/owners/spock-hostname/0'
+
+        expect:
+        watcher.isOffsetSubtree(path) == false
+    }
 }