ISSUE-155 Enable prometheus monitoring for zookeeper pods

Since 3.6.0 ZooKeeper supports native Prometheus monitoring
https://github.com/apache/zookeeper/blob/master/zookeeper-docs/src/main/resources/markdown/zookeeperMonitor.md#prometheus

This patch
- enables `PrometheusMetricsProvider` in zoo.cfg
- expose a new `metrics` port to ZK pods, ZK services
- disambiguate the headless and client service labels by adding a new label,
 so it can be used in Prometheus `ServiceMonitors`

pkg/apis/zookeeper/v1beta1/zookeepercluster_types.go

@@ -95,6 +95,10 @@ func (s *ZookeeperClusterSpec) withDefaults(z *ZookeeperCluster) (changed bool)
 				Name:          "leader-election",
 				ContainerPort: 3888,
 			},
+			{
+				Name:          "metrics",
+				ContainerPort: 7000,
+			},
 		}
 		changed = true
 	}
@@ -182,6 +186,8 @@ func (z *ZookeeperCluster) ZookeeperPorts() Ports {
 			ports.Quorum = p.ContainerPort
 		} else if p.Name == "leader-election" {
 			ports.Leader = p.ContainerPort
+		} else if p.Name == "metrics" {
+			ports.Metrics = p.ContainerPort
 		}
 	}
 	return ports
@@ -194,9 +200,10 @@ func (z *ZookeeperCluster) GetClientServiceName() string {
 
 // Ports groups the ports for a zookeeper cluster node for easy access
 type Ports struct {
-	Client int32
-	Quorum int32
-	Leader int32
+	Client  int32
+	Quorum  int32
+	Leader  int32
+	Metrics int32
 }
 
 // ContainerImage defines the fields needed for a Docker repository image. The

pkg/apis/zookeeper/v1beta1/zookeepercluster_types_test.go

@@ -216,6 +216,10 @@ var _ = Describe("ZookeeperCluster Types", func() {
 		It("should have a leader port", func() {
 			Ω(p.Leader).To(BeEquivalentTo(3888))
 		})
+
+		It("should have a metrics port", func() {
+			Ω(p.Metrics).To(BeEquivalentTo(7000))
+		})
 	})
 
 })

pkg/zk/generators.go

@@ -184,6 +184,7 @@ func MakeHeadlessService(z *v1beta1.ZookeeperCluster) *v1.Service {
 	svcPorts := []v1.ServicePort{
 		{Name: "quorum", Port: ports.Quorum},
 		{Name: "leader-election", Port: ports.Leader},
+		{Name: "metrics", Port: ports.Metrics},
 	}
 	return makeService(headlessSvcName(z), svcPorts, false, z)
 }
@@ -194,6 +195,9 @@ func makeZkConfigString(s v1beta1.ZookeeperClusterSpec) string {
 		"standaloneEnabled=false\n" +
 		"reconfigEnabled=true\n" +
 		"skipACL=yes\n" +
+		"metricsProvider.className=org.apache.zookeeper.metrics.prometheus.PrometheusMetricsProvider\n" +
+		"metricsProvider.httpPort=7000\n" +
+		"metricsProvider.exportJvmInfo=true\n" +
 		"initLimit=" + strconv.Itoa(s.Conf.InitLimit) + "\n" +
 		"syncLimit=" + strconv.Itoa(s.Conf.SyncLimit) + "\n" +
 		"tickTime=" + strconv.Itoa(s.Conf.TickTime) + "\n" +
@@ -259,7 +263,7 @@ func makeService(name string, ports []v1.ServicePort, clusterIP bool, z *v1beta1
 					Kind:    "ZookeeperCluster",
 				}),
 			},
-			Labels:      map[string]string{"app": z.GetName()},
+			Labels:      map[string]string{"app": z.GetName(), "headless": strconv.FormatBool(!clusterIP)},
 			Annotations: annotationMap,
 		},
 		Spec: v1.ServiceSpec{