Update leader election sample (#1281)

Co-authored-by: Ryan Baxter <[email protected]>

spring-cloud-kubernetes-examples/kubernetes-leader-election-example/README.md

@@ -83,17 +83,18 @@ items:
   - apiVersion: rbac.authorization.k8s.io/v1
     kind: Role
     metadata:
-      namespace: default
-      name: namespace-reader
+        namespace: default
+        name: namespace-reader
     rules:
-      - apiGroups: ["", "extensions", "apps"]
-        resources: ["configmaps", "pods", "services", "endpoints", "secrets"]
-        verbs: ["get", "list", "watch"]
+        - apiGroups: ["", "extensions", "apps"]
+          resources: ["configmaps", "pods", "services", "endpoints", "secrets"]
+          verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
   - apiVersion: apps/v1
     kind: Deployment
     metadata:
       name: kubernetes-leader-election-example
     spec:
+      replicas: 4
       selector:
         matchLabels:
           app: kubernetes-leader-election-example
@@ -148,17 +149,10 @@ And check the leadership information again:
 curl $SERVICE_URL
 ```
 
-Now you should receive a message like this:
-```
-I am 'kubernetes-leader-election-example-1234567890-abcde' but I am not a leader of the 'world'
-```
-
-If you wouldn't do anything for a few seconds, the same instance will become a leader again because it only yielded its leadership but stayed in the cluster.
+If another instance was able to acquire the leadership you should see a different instance is now the leadership.  You may
+have to try this a few times depending on how the service is load balanced.
 
-Now scale the application to two instances and try all the steps again:
-```
-kubectl scale --replicas=2 deployment.apps/kubernetes-leader-election-example
-```
+`DEBUG` logging is enabled so you can view the logs of the instances in order to see which instance is acquiring leadership.
 
 > Note: with multiple replicas in the cluster, `curl` command will access one of them depending on the Kubernetes load balancing configuration.
 Thus, when trying to yield the leadership, request might go to a non-leader node first. Just execute command again until it reaches the correct node.

spring-cloud-kubernetes-examples/kubernetes-leader-election-example/src/main/java/org/springframework/cloud/kubernetes/examples/LeaderController.java

@@ -47,7 +47,7 @@ public LeaderController() throws UnknownHostException {
 	 * Return a message whether this instance is a leader or not.
 	 * @return info
 	 */
-	@GetMapping
+	@GetMapping("/")
 	public String getInfo() {
 		if (this.context == null) {
 			return String.format("I am '%s' but I am not a leader of the '%s'", this.host, this.role);
@@ -63,7 +63,7 @@ public String getInfo() {
 	 * to give up the leadership.
 	 * @return info about leadership
 	 */
-	@PutMapping
+	@PutMapping("/")
 	public ResponseEntity<String> revokeLeadership() {
 		if (this.context == null) {
 			String message = String.format("Cannot revoke leadership because '%s' is not a leader", this.host);

spring-cloud-kubernetes-examples/kubernetes-leader-election-example/src/main/resources/application.properties

@@ -2,3 +2,5 @@
 spring.cloud.kubernetes.leader.role=world
 # Configmap to which leader election metadata will be saved
 spring.cloud.kubernetes.leader.config-map-name=leader
+logging.level.org.springframework.cloud.kubernetes.fabric8.leader=DEBUG
+logging.level.org.springframework.cloud.kubernetes.commons.leader=DEBUG