Issue ReactiveX#354: Use tags instead of gauge values to indicate circuit breaker state (ReactiveX#416)

Author: leonard84

resilience4j-micrometer/src/main/java/io/github/resilience4j/micrometer/CircuitBreakerMetrics.java

@@ -80,10 +80,15 @@ public static CircuitBreakerMetrics ofIterable(String prefix, Iterable<CircuitBr
 
     @Override
     public void bindTo(MeterRegistry registry) {
+        final CircuitBreaker.State[] states = CircuitBreaker.State.values();
         for (CircuitBreaker circuitBreaker : circuitBreakers) {
             final String name = circuitBreaker.getName();
-            Gauge.builder(getName(prefix, name, STATE), circuitBreaker, (cb) -> cb.getState().getOrder())
-                    .register(registry);
+            for (CircuitBreaker.State state : states) {
+                Gauge.builder(getName(prefix, name, STATE), circuitBreaker, (cb) -> cb.getState() == state ? 1 : 0)
+                        .tag("state", state.name().toLowerCase())
+                        .register(registry);
+            }
+
             Gauge.builder(getName(prefix, name, BUFFERED_MAX), circuitBreaker, (cb) -> cb.getMetrics().getMaxNumberOfBufferedCalls())
                     .register(registry);
             Gauge.builder(getName(prefix, name, BUFFERED), circuitBreaker, (cb) -> cb.getMetrics().getNumberOfBufferedCalls())

resilience4j-prometheus/src/main/java/io/github/resilience4j/prometheus/collectors/CircuitBreakerMetricsCollector.java

@@ -91,8 +91,8 @@ private CircuitBreakerMetricsCollector(MetricNames names, Supplier<? extends Ite
     public List<MetricFamilySamples> collect() {
         GaugeMetricFamily stateFamily = new GaugeMetricFamily(
             names.getStateMetricName(),
-            "The state of the circuit breaker: 0 - CLOSED, 1 - OPEN, 2 - HALF_OPEN",
-            LabelNames.NAME
+            "The state of the circuit breaker:",
+            LabelNames.NAME_AND_STATE
         );
         GaugeMetricFamily callsFamily = new GaugeMetricFamily(
             names.getCallsMetricName(),
@@ -109,17 +109,22 @@ public List<MetricFamilySamples> collect() {
             "The maximum number of buffered calls",
             LabelNames.NAME
         );
-
-        GaugeMetricFamily failureRateFamily = new GaugeMetricFamily(
+      
+      GaugeMetricFamily failureRateFamily = new GaugeMetricFamily(
                 names.getFailureRateMetricName(),
                 "The failure rate",
                 LabelNames.NAME
         );
 
+        final CircuitBreaker.State[] states = CircuitBreaker.State.values();
+      
         for (CircuitBreaker circuitBreaker : supplier.get()) {
             List<String> nameLabel = singletonList(circuitBreaker.getName());
 
-            stateFamily.addMetric(nameLabel, circuitBreaker.getState().getOrder());
+            for (CircuitBreaker.State state : states) {
+                stateFamily.addMetric(asList(circuitBreaker.getName(), state.name().toLowerCase()),
+                        circuitBreaker.getState() == state ? 1 : 0);
+            }
 
             Metrics metrics = circuitBreaker.getMetrics();
             callsFamily.addMetric(asList(circuitBreaker.getName(), "successful"), metrics.getNumberOfSuccessfulCalls());

resilience4j-prometheus/src/main/java/io/github/resilience4j/prometheus/collectors/LabelNames.java

@@ -26,4 +26,5 @@ private LabelNames() {}
 
     public static final List<String> NAME = Collections.singletonList("name");
     public static final List<String> NAME_AND_KIND = Arrays.asList("name", "kind");
+    public static final List<String> NAME_AND_STATE = Arrays.asList("name", "state");
 }

resilience4j-prometheus/src/test/java/io/github/resilience4j/prometheus/collectors/CircuitBreakerMetricsCollectorTest.java

@@ -15,12 +15,6 @@
  */
 package io.github.resilience4j.prometheus.collectors;
 
-import io.github.resilience4j.circuitbreaker.CircuitBreaker;
-import io.prometheus.client.CollectorRegistry;
-import org.junit.Before;
-import org.junit.Test;
-
-
 import static io.github.resilience4j.prometheus.collectors.CircuitBreakerMetricsCollector.MetricNames.DEFAULT_CIRCUIT_BREAKER_BUFFERED_CALLS;
 import static io.github.resilience4j.prometheus.collectors.CircuitBreakerMetricsCollector.MetricNames.DEFAULT_CIRCUIT_BREAKER_CALLS_METRIC_NAME;
 import static io.github.resilience4j.prometheus.collectors.CircuitBreakerMetricsCollector.MetricNames.DEFAULT_CIRCUIT_BREAKER_FAILURE_RATE;
@@ -29,6 +23,12 @@
 import static java.util.Collections.singletonList;
 import static org.assertj.core.api.Assertions.assertThat;
 
+import org.junit.Before;
+import org.junit.Test;
+
+import io.github.resilience4j.circuitbreaker.CircuitBreaker;
+import io.prometheus.client.CollectorRegistry;
+
 public class CircuitBreakerMetricsCollectorTest {
 
     CollectorRegistry registry;
@@ -50,8 +50,8 @@ public void setup() {
     public void stateReportsCorrespondingValue() {
         double state = registry.getSampleValue(
             DEFAULT_CIRCUIT_BREAKER_STATE_METRIC_NAME,
-            new String[]{"name"},
-            new String[]{circuitBreaker.getName()}
+            new String[]{"name", "state"},
+            new String[]{circuitBreaker.getName(), circuitBreaker.getState().name().toLowerCase()}
         );
 
         assertThat(state).isEqualTo(circuitBreaker.getState().getOrder());
@@ -155,8 +155,8 @@ public void customMetricNamesOverrideDefaultOnes() {
         )).isNotNull();
         assertThat(registry.getSampleValue(
             "custom_state",
-            new String[]{"name"},
-            new String[]{"backendA"}
+            new String[]{"name", "state"},
+            new String[]{"backendA", "closed"}
         )).isNotNull();
         assertThat(registry.getSampleValue(
             "custom_max_buffered_calls",