Cache updates (#50)

Outstanding changes from projectnessie/nessie#10629 (other parts are already there)

Author: snazy

nosql/persistence/cache/src/main/java/org/apache/polaris/persistence/cache/CaffeineCacheBackend.java

@@ -76,8 +76,8 @@ class CaffeineCacheBackend implements CacheBackend {
   private static final Logger LOGGER = LoggerFactory.getLogger(CaffeineCacheBackend.class);
 
   public static final String METER_CACHE_CAPACITY = "cache.capacity";
+  public static final String METER_CACHE_ADMIT_CAPACITY = "cache.capacity.admitted";
   public static final String METER_CACHE_WEIGHT = "cache.weight-reported";
-  public static final String METER_CACHE_REJECTIONS = "cache.rejections";
   public static final String METER_CACHE_REJECTED_WEIGHT = "cache.rejected-weight";
 
   public static final String CACHE_NAME = "polaris-objects";
@@ -170,13 +170,13 @@ public long expireAfterRead(
                       .tag("cache", CACHE_NAME)
                       .baseUnit(BaseUnits.BYTES)
                       .register(reg);
-                  Gauge.builder(METER_CACHE_WEIGHT, "", x -> (double) currentWeightReported())
-                      .description("Current reported weight of the objects cache in bytes.")
+                  Gauge.builder(METER_CACHE_ADMIT_CAPACITY, "", x -> admitWeight)
+                      .description("Admitted capacity of the objects cache in bytes.")
                       .tag("cache", CACHE_NAME)
                       .baseUnit(BaseUnits.BYTES)
                       .register(reg);
-                  Gauge.builder(METER_CACHE_REJECTIONS, "", x -> rejections.get())
-                      .description("Number of cache-puts that have been rejected.")
+                  Gauge.builder(METER_CACHE_WEIGHT, "", x -> (double) currentWeightReported())
+                      .description("Current reported weight of the objects cache in bytes.")
                       .tag("cache", CACHE_NAME)
                       .baseUnit(BaseUnits.BYTES)
                       .register(reg);

nosql/persistence/cache/src/test/java/org/apache/polaris/persistence/cache/TestCacheOvershoot.java

@@ -19,8 +19,9 @@
 package org.apache.polaris.persistence.cache;
 
 import static java.util.concurrent.CompletableFuture.delayedExecutor;
+import static org.apache.polaris.persistence.cache.CaffeineCacheBackend.METER_CACHE_ADMIT_CAPACITY;
+import static org.apache.polaris.persistence.cache.CaffeineCacheBackend.METER_CACHE_CAPACITY;
 import static org.apache.polaris.persistence.cache.CaffeineCacheBackend.METER_CACHE_REJECTED_WEIGHT;
-import static org.apache.polaris.persistence.cache.CaffeineCacheBackend.METER_CACHE_REJECTIONS;
 import static org.apache.polaris.persistence.cache.CaffeineCacheBackend.METER_CACHE_WEIGHT;
 
 import com.google.common.base.Strings;
@@ -76,9 +77,10 @@ private void testCacheOvershoot(Executor evictionExecutor) throws Exception {
         meterRegistry.getMeters().stream()
             .collect(Collectors.toMap(m -> m.getId().getName(), Function.identity(), (a, b) -> a));
     soft.assertThat(metersByName)
-        .containsKeys(METER_CACHE_WEIGHT, METER_CACHE_REJECTIONS, METER_CACHE_REJECTED_WEIGHT);
+        .containsKeys(METER_CACHE_WEIGHT, METER_CACHE_ADMIT_CAPACITY, METER_CACHE_REJECTED_WEIGHT);
     var meterWeightReported = (Gauge) metersByName.get(METER_CACHE_WEIGHT);
-    var meterRejections = (Gauge) metersByName.get(METER_CACHE_REJECTIONS);
+    var meterAdmittedCapacity = (Gauge) metersByName.get(METER_CACHE_ADMIT_CAPACITY);
+    var meterCapacity = (Gauge) metersByName.get(METER_CACHE_CAPACITY);
     var meterRejectedWeight = (DistributionSummary) metersByName.get(METER_CACHE_REJECTED_WEIGHT);
 
     var maxWeight = cache.capacityBytes();
@@ -97,7 +99,9 @@ private void testCacheOvershoot(Executor evictionExecutor) throws Exception {
     soft.assertThat(cache.currentWeightReported()).isLessThanOrEqualTo(maxWeight);
     soft.assertThat(cache.rejections()).isEqualTo(0L);
     soft.assertThat(meterWeightReported.value()).isGreaterThan(0d);
-    soft.assertThat(meterRejections.value()).isEqualTo((double) cache.rejections());
+    soft.assertThat(meterAdmittedCapacity.value()).isEqualTo((double) admitWeight);
+    soft.assertThat(meterCapacity.value())
+        .isEqualTo((double) config.sizing().orElseThrow().fixedSize().orElseThrow().asLong());
 
     var seenOvershoot = false;
     var stop = new AtomicBoolean();
@@ -126,7 +130,6 @@ private void testCacheOvershoot(Executor evictionExecutor) throws Exception {
 
     soft.assertThat(cache.currentWeightReported()).isLessThanOrEqualTo(admitWeight);
     soft.assertThat(cache.rejections()).isEqualTo(0L);
-    soft.assertThat(meterRejections.value()).isEqualTo(0d);
     soft.assertThat(meterRejectedWeight.totalAmount()).isEqualTo(0d);
     soft.assertThat(seenOvershoot).isFalse();
   }