public CacheStats stats() {
            var stats = this.statistics.snapshot();
            return new CacheStats(stats.hitRate(), stats.evictionCount(), children.size() + data.size());
        }
Create an empty snapshot at a given generation (as an empty snapshot is a valid partial snapshot)
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/persistence/CachingCurator.java