Add JVM metric tracking and expose at /prometheus endpoint

backend/build.gradle

@@ -30,6 +30,10 @@ dependencies {
     compile("io.springfox:springfox-swagger2:" + SPRINGFOX_VERSION)
     compile("io.springfox:springfox-swagger-ui:" + SPRINGFOX_VERSION)
 
+    compile('org.springframework.boot:spring-boot-starter-actuator')
+    compile("io.micrometer:micrometer-spring-legacy:latest.release")
+    compile("io.micrometer:micrometer-registry-prometheus:1.0.4")
+
     compileOnly('org.projectlombok:lombok')
 
     runtimeOnly name: 'frontend'
@@ -49,4 +53,4 @@ afterEvaluate {
 jar {
     baseName = 'spring-react'
     version = '0.0.1'
-}
+}

backend/src/main/java/com/allstate/springreact/controller/StateController.java

@@ -1,13 +1,28 @@
 package com.allstate.springreact.controller;
 
 import com.allstate.springreact.domain.InitialState;
+import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.MeterRegistry;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RestController;
 
 @RestController
 class StateController {
+    private Counter counter;
+
+    @Autowired
+    public StateController(MeterRegistry registry) {
+       /*
+          This value is already exposed under the 'http_server_requests_seconds_count' metric,
+          but I wanted to show how to wire up a counter if desired
+        */
+        counter = Counter.builder("initial-endpoint-call-count").register(registry);
+    }
+
     @GetMapping("/state")
     public InitialState getInitialCountRequest() {
+        counter.increment();
         InitialState state = new InitialState();
         state.setText("Spring-React is wired up!");
         state.setValue(7);

backend/src/main/resources/application.yml

@@ -1,2 +1,19 @@
+spring.application.name: spring-react
+
 server:
     port: ${PORT:8080}
+
+# Enable the /prometheus endpoint to be publicly accessible
+endpoints:
+    prometheus: 
+        sensitive: false
+
+management.metrics:
+  distribution:
+    # Enable publishing of histogram metrics to allow for computing aggregable percentile approximations
+    percentiles-histogram[http.server.requests]: true
+    # Publish the median and 95th percentile values
+    percentiles[http.server.requests]: 0.5, 0.95
+  tags:
+    # Add a custom label to each metric name to differentiate from other services
+    application: ${spring.application.name}