Add Builder pattern for caffeine CacheMetricsCollector

Signed-off-by: Jean Hominal <[email protected]>

Author: jhominal

prometheus-metrics-instrumentation-caffeine/src/main/java/io/prometheus/metrics/instrumentation/caffeine/CacheMetricsCollector.java

@@ -27,7 +27,7 @@
  * <pre>{@code
  * // Note that `recordStats()` is required to gather non-zero statistics
  * Cache<String, String> cache = Caffeine.newBuilder().recordStats().build();
- * CacheMetricsCollector cacheMetrics = new CacheMetricsCollector();
+ * CacheMetricsCollector cacheMetrics = CacheMetricsCollector.builder().build();
  * PrometheusRegistry.defaultRegistry.register(cacheMetrics);
  * cacheMetrics.addCache("mycache", cache);
  *
@@ -271,4 +271,14 @@ public MetricSnapshots collect() {
   public List<String> getPrometheusNames() {
     return ALL_METRIC_NAMES;
   }
+
+  public static Builder builder() {
+    return new Builder();
+  }
+
+  public static class Builder {
+    public CacheMetricsCollector build() {
+      return new CacheMetricsCollector();
+    }
+  }
 }

prometheus-metrics-instrumentation-caffeine/src/test/java/io/prometheus/metrics/instrumentation/caffeine/CacheMetricsCollectorTest.java

@@ -32,7 +32,7 @@ public void cacheExposesMetricsForHitMissAndEviction() {
     final Cache<String, String> cache =
         Caffeine.newBuilder().maximumSize(2).recordStats().executor(Runnable::run).build();
 
-    final CacheMetricsCollector collector = new CacheMetricsCollector();
+    final CacheMetricsCollector collector = CacheMetricsCollector.builder().build();
     collector.addCache("users", cache);
 
     final PrometheusRegistry registry = new PrometheusRegistry();
@@ -89,7 +89,7 @@ public void weightedCacheExposesMetricsForHitMissAndEvictionWeightedSize() {
             .executor(Runnable::run)
             .build();
 
-    final CacheMetricsCollector collector = new CacheMetricsCollector();
+    final CacheMetricsCollector collector = CacheMetricsCollector.builder().build();
     collector.addCache("users", cache);
 
     final PrometheusRegistry registry = new PrometheusRegistry();
@@ -148,7 +148,7 @@ public void loadingCacheExposesMetricsForLoadsAndExceptions() throws Exception {
         .thenReturn("Third User");
 
     final LoadingCache<String, String> cache = Caffeine.newBuilder().recordStats().build(loader);
-    final CacheMetricsCollector collector = new CacheMetricsCollector();
+    final CacheMetricsCollector collector = CacheMetricsCollector.builder().build();
 
     collector.addCache("loadingusers", cache);
 
@@ -180,7 +180,7 @@ public void loadingCacheExposesMetricsForLoadsAndExceptions() throws Exception {
 
   @Test
   public void getPrometheusNamesHasSameSizeAsMetricSizeWhenScraping() {
-    final CacheMetricsCollector collector = new CacheMetricsCollector();
+    final CacheMetricsCollector collector = CacheMetricsCollector.builder().build();
 
     final PrometheusRegistry registry = new PrometheusRegistry();
     registry.register(collector);
@@ -193,7 +193,7 @@ public void getPrometheusNamesHasSameSizeAsMetricSizeWhenScraping() {
 
   @Test
   public void collectedMetricNamesAreKnownPrometheusNames() {
-    final CacheMetricsCollector collector = new CacheMetricsCollector();
+    final CacheMetricsCollector collector = CacheMetricsCollector.builder().build();
 
     final PrometheusRegistry registry = new PrometheusRegistry();
     registry.register(collector);