Github user kchilton2 commented on a diff in the pull request:
https://github.com/apache/incubator-rya/pull/251#discussion_r153274878
--- Diff:
extras/rya.pcj.fluo/pcj.fluo.app/src/main/java/org/apache/rya/indexing/pcj/fluo/app/query/FluoQueryMetadataCache.java
---
@@ -0,0 +1,247 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */package org.apache.rya.indexing.pcj.fluo.app.query;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import java.util.concurrent.Callable;
+
+import org.apache.fluo.api.client.SnapshotBase;
+import org.apache.fluo.api.data.Bytes;
+import org.apache.fluo.api.data.Column;
+import org.apache.rya.indexing.pcj.fluo.app.NodeType;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.base.Optional;
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+
+/**
+ * Wrapper for {@link FluoQueryMetadataDAO} that caches any metadata that
has been retrieved from Fluo. This class first
+ * checks the cache to see if the metadata is present before delegating to
the underlying DAO method to retrieve the
+ * data.
+ *
+ */
+public class FluoQueryMetadataCache extends FluoQueryMetadataDAO {
+
+ private static final Logger LOG =
LoggerFactory.getLogger(FluoQueryMetadataCache.class);
+ private final FluoQueryMetadataDAO dao;
+ private final Cache<String, CommonNodeMetadata>
commonNodeMetadataCache;
+ private final Cache<String, Bytes> metadataCache;
+ private int capacity;
+ private int concurrencyLevel;
+
+ /**
+ * Creates a FluoQueryMetadataCache with the specified capacity. Old,
unused results are evicted as necessary.
+ *
+ * @param capacity - max size of the cache
+ */
+ public FluoQueryMetadataCache(FluoQueryMetadataDAO dao, int capacity,
int concurrencyLevel) {
+ this.dao = dao;
--- End diff --
null check
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