ZOOKEEPER-4934: Add metrics for TTL node creation (#2287)

* ZOOKEEPER-4934: Add metrics for TTL node creation

* Trigger CI

Author: ivandika3

zookeeper-server/src/main/java/org/apache/zookeeper/server/DataTree.java

@@ -486,6 +486,7 @@ public void createNode(final String path, byte[] data, List<ACL> acl, long ephem
                 containers.add(path);
             } else if (ephemeralType == EphemeralType.TTL) {
                 ttls.add(path);
+                ServerMetrics.getMetrics().TTL_NODE_CREATED_COUNT.add(1);
             } else if (ephemeralOwner != 0) {
                 HashSet<String> list = ephemerals.computeIfAbsent(ephemeralOwner, k -> new HashSet<>());
                 synchronized (list) {

zookeeper-server/src/main/java/org/apache/zookeeper/server/ServerMetrics.java

@@ -271,6 +271,7 @@ private ServerMetrics(MetricsProvider metricsProvider) {
         QUOTA_EXCEEDED_ERROR_PER_NAMESPACE = metricsContext.getCounterSet(QuotaMetricsUtils.QUOTA_EXCEEDED_ERROR_PER_NAMESPACE);
 
         TTL_NODE_DELETED_COUNT = metricsContext.getCounter("ttl_node_deleted_count");
+        TTL_NODE_CREATED_COUNT = metricsContext.getCounter("ttl_node_created_count");
     }
 
     /**
@@ -550,9 +551,10 @@ private ServerMetrics(MetricsProvider metricsProvider) {
     public final CounterSet QUOTA_EXCEEDED_ERROR_PER_NAMESPACE;
 
     /**
-     * Count of deleted TTL nodes
+     * Count of created and deleted TTL nodes
      */
     public final Counter TTL_NODE_DELETED_COUNT;
+    public final Counter TTL_NODE_CREATED_COUNT;
 
     private final MetricsProvider metricsProvider;
 

zookeeper-server/src/test/java/org/apache/zookeeper/server/CreateTTLTest.java

@@ -95,8 +95,9 @@ public void testCreate() throws KeeperException, InterruptedException {
         containerManager.checkContainers();
         assertNull(zk.exists("/foo", false), "Ttl node should have been deleted");
 
-        // validate deleted TTL nodes count
+        // validate created and deleted TTL nodes count
         Map<String, Object> metrics = MetricsUtils.currentServerMetrics();
+        assertTrue((long) metrics.get("ttl_node_created_count") >= 1);
         assertTrue((long) metrics.get("ttl_node_deleted_count") >= 1);
     }