Add caffeine_cache_weighted_size gauge metric to caffeine-instrumenta…

…tion Signed-off-by: Jean Hominal <[email protected]>
prometheus · Jan 7, 2025 · 2f962b3 · 2f962b3
1 parent a917c02
commit 2f962b3
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diff --git a/...e/src/main/java/io/prometheus/metrics/instrumentation/caffeine/CacheMetricsCollector.java b/...e/src/main/java/io/prometheus/metrics/instrumentation/caffeine/CacheMetricsCollector.java
@@ -3,6 +3,7 @@
 import com.github.benmanes.caffeine.cache.AsyncCache;
 import com.github.benmanes.caffeine.cache.Cache;
 import com.github.benmanes.caffeine.cache.LoadingCache;
+import com.github.benmanes.caffeine.cache.Policy;
 import com.github.benmanes.caffeine.cache.stats.CacheStats;
 import io.prometheus.metrics.model.registry.MultiCollector;
 import io.prometheus.metrics.model.snapshots.CounterSnapshot;
@@ -14,6 +15,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 
@@ -63,6 +65,7 @@ public class CacheMetricsCollector implements MultiCollector {
   private static final String METRIC_NAME_CACHE_LOAD_FAILURE = "caffeine_cache_load_failure";
   private static final String METRIC_NAME_CACHE_LOADS = "caffeine_cache_loads";
   private static final String METRIC_NAME_CACHE_ESTIMATED_SIZE = "caffeine_cache_estimated_size";
+  private static final String METRIC_NAME_CACHE_WEIGHTED_SIZE = "caffeine_cache_weighted_size";
   private static final String METRIC_NAME_CACHE_LOAD_DURATION_SECONDS =
       "caffeine_cache_load_duration_seconds";
 
@@ -77,6 +80,7 @@ public class CacheMetricsCollector implements MultiCollector {
               METRIC_NAME_CACHE_LOAD_FAILURE,
               METRIC_NAME_CACHE_LOADS,
               METRIC_NAME_CACHE_ESTIMATED_SIZE,
+              METRIC_NAME_CACHE_WEIGHTED_SIZE,
               METRIC_NAME_CACHE_LOAD_DURATION_SECONDS));
 
   protected final ConcurrentMap<String, Cache<?, ?>> children = new ConcurrentHashMap<>();
@@ -162,6 +166,11 @@ public MetricSnapshots collect() {
     final GaugeSnapshot.Builder cacheSize =
         GaugeSnapshot.builder().name(METRIC_NAME_CACHE_ESTIMATED_SIZE).help("Estimated cache size");
 
+    final GaugeSnapshot.Builder cacheWeightedSize =
+        GaugeSnapshot.builder()
+            .name(METRIC_NAME_CACHE_WEIGHTED_SIZE)
+            .help("Approximate accumulated weight of cache entries");
+
     final SummarySnapshot.Builder cacheLoadSummary =
         SummarySnapshot.builder()
             .name(METRIC_NAME_CACHE_LOAD_DURATION_SECONDS)
@@ -183,6 +192,15 @@ public MetricSnapshots collect() {
         // EvictionWeight metric is unavailable, newer version of Caffeine is needed.
       }
 
+      final Optional<? extends Policy.Eviction<?, ?>> eviction = c.getValue().policy().eviction();
+      if (eviction.isPresent() && eviction.get().weightedSize().isPresent()) {
+        cacheWeightedSize.dataPoint(
+            GaugeSnapshot.GaugeDataPointSnapshot.builder()
+                .labels(labels)
+                .value(eviction.get().weightedSize().getAsLong())
+                .build());
+      }
+
       cacheHitTotal.dataPoint(
           CounterSnapshot.CounterDataPointSnapshot.builder()
               .labels(labels)
@@ -244,6 +262,7 @@ public MetricSnapshots collect() {
         .metricSnapshot(cacheLoadFailure.build())
         .metricSnapshot(cacheLoadTotal.build())
         .metricSnapshot(cacheSize.build())
+        .metricSnapshot(cacheWeightedSize.build())
         .metricSnapshot(cacheLoadSummary.build())
         .build();
   }

diff --git a/...c/test/java/io/prometheus/metrics/instrumentation/caffeine/CacheMetricsCollectorTest.java b/...c/test/java/io/prometheus/metrics/instrumentation/caffeine/CacheMetricsCollectorTest.java
@@ -78,6 +78,66 @@ public void cacheExposesMetricsForHitMissAndEviction() {
     assertThat(convertToOpenMetricsFormat(registry)).isEqualTo(expected);
   }
 
+  @Test
+  public void cacheExposesMetricsForHitMissAndEvictionForWeightedCache() {
+    // Run cleanup in same thread, to remove async behavior with evictions
+    final Cache<String, String> cache =
+        Caffeine.newBuilder()
+            .weigher((String k, String v) -> k.length() + v.length())
+            .maximumWeight(35)
+            .recordStats()
+            .executor(Runnable::run)
+            .build();
+
+    final CacheMetricsCollector collector = new CacheMetricsCollector();
+    collector.addCache("users", cache);
+
+    final PrometheusRegistry registry = new PrometheusRegistry();
+    registry.register(collector);
+
+    cache.getIfPresent("user1");
+    cache.getIfPresent("user1");
+    cache.put("user1", "First User");
+    cache.getIfPresent("user1");
+
+    // Add to cache to trigger eviction.
+    cache.put("user2", "Second User");
+    cache.put("user3", "Third User");
+    cache.put("user4", "Fourth User");
+
+    assertCounterMetric(registry, "caffeine_cache_hit", "users", 1.0);
+    assertCounterMetric(registry, "caffeine_cache_miss", "users", 2.0);
+    assertCounterMetric(registry, "caffeine_cache_requests", "users", 3.0);
+    assertCounterMetric(registry, "caffeine_cache_eviction", "users", 2.0);
+    assertCounterMetric(registry, "caffeine_cache_eviction_weight", "users", 31.0);
+
+    final String expected =
+        "# TYPE caffeine_cache_estimated_size gauge\n"
+            + "# HELP caffeine_cache_estimated_size Estimated cache size\n"
+            + "caffeine_cache_estimated_size{cache=\"users\"} 2.0\n"
+            + "# TYPE caffeine_cache_eviction counter\n"
+            + "# HELP caffeine_cache_eviction Cache eviction totals, doesn't include manually removed entries\n"
+            + "caffeine_cache_eviction_total{cache=\"users\"} 2.0\n"
+            + "# TYPE caffeine_cache_eviction_weight counter\n"
+            + "# HELP caffeine_cache_eviction_weight Weight of evicted cache entries, doesn't include manually removed entries\n"
+            + "caffeine_cache_eviction_weight_total{cache=\"users\"} 31.0\n"
+            + "# TYPE caffeine_cache_hit counter\n"
+            + "# HELP caffeine_cache_hit Cache hit totals\n"
+            + "caffeine_cache_hit_total{cache=\"users\"} 1.0\n"
+            + "# TYPE caffeine_cache_miss counter\n"
+            + "# HELP caffeine_cache_miss Cache miss totals\n"
+            + "caffeine_cache_miss_total{cache=\"users\"} 2.0\n"
+            + "# TYPE caffeine_cache_requests counter\n"
+            + "# HELP caffeine_cache_requests Cache request totals, hits + misses\n"
+            + "caffeine_cache_requests_total{cache=\"users\"} 3.0\n"
+            + "# TYPE caffeine_cache_weighted_size gauge\n"
+            + "# HELP caffeine_cache_weighted_size Approximate accumulated weight of cache entries\n"
+            + "caffeine_cache_weighted_size{cache=\"users\"} 31.0\n"
+            + "# EOF\n";
+
+    assertThat(convertToOpenMetricsFormat(registry)).isEqualTo(expected);
+  }
+
   @SuppressWarnings("unchecked")
   @Test
   public void loadingCacheExposesMetricsForLoadsAndExceptions() throws Exception {