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Add cache_weight_mb gauge #10640

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Add cache_weight_mb gauge #10640

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23 changes: 18 additions & 5 deletions ...e/cache/src/main/java/org/projectnessie/versioned/storage/cache/CaffeineCacheBackend.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,11 +28,14 @@
import com.github.benmanes.caffeine.cache.Cache;
import com.github.benmanes.caffeine.cache.Caffeine;
import com.github.benmanes.caffeine.cache.Expiry;
import com.github.benmanes.caffeine.cache.Policy;
import io.micrometer.core.instrument.Tag;
import io.micrometer.core.instrument.binder.cache.CaffeineStatsCounter;
import jakarta.annotation.Nonnull;
import java.lang.ref.SoftReference;
import java.time.Duration;
import java.util.List;
import java.util.OptionalLong;
import org.projectnessie.versioned.storage.common.exceptions.ObjTooLargeException;
import org.projectnessie.versioned.storage.common.persist.Obj;
import org.projectnessie.versioned.storage.common.persist.ObjId;
Expand Down Expand Up @@ -105,16 +108,26 @@ public long expireAfterRead(
.ifPresent(
meterRegistry -> {
cacheBuilder.recordStats(() -> new CaffeineStatsCounter(meterRegistry, CACHE_NAME));
meterRegistry.gauge(
"cache_capacity_mb",
singletonList(Tag.of("cache", CACHE_NAME)),
"",
x -> config.capacityMb());
List<Tag> tags = singletonList(Tag.of("cache", CACHE_NAME));
meterRegistry.gauge("cache_capacity_mb", tags, "", x -> config.capacityMb());
meterRegistry.gauge("cache_weight_mb", tags, "", x -> weightedSizeMb());
});

this.cache = cacheBuilder.build();
}

private double weightedSizeMb() {
// Note: calling Policy.Eviction::weightedSize may actually perform evictions.
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@dimas-b dimas-b Apr 3, 2025 •
edited
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I suppose evictions in this call may only happen in practice under load.

long w =
cache
.policy()
.eviction()
.map(Policy.Eviction::weightedSize)
.orElse(OptionalLong.empty())
.orElse(0L);
return (double) w / 1024L / 1024L;
}

@Override
public Persist wrap(@Nonnull Persist persist) {
ObjCacheImpl cache = new ObjCacheImpl(this, persist.config());
Expand Down