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From GitBox <...@apache.org>
Subject [GitHub] [hadoop] arp7 commented on a change in pull request #798: HDDS-1499. OzoneManager Cache.
Date Wed, 15 May 2019 17:18:51 GMT
arp7 commented on a change in pull request #798: HDDS-1499. OzoneManager Cache.
URL: https://github.com/apache/hadoop/pull/798#discussion_r284363840
 
 

 ##########
 File path: hadoop-hdds/common/src/main/java/org/apache/hadoop/utils/db/cache/TableCache.java
 ##########
 @@ -0,0 +1,73 @@
+/*
+ * 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.hadoop.utils.db.cache;
+
+import org.apache.hadoop.classification.InterfaceAudience.Private;
+import org.apache.hadoop.classification.InterfaceStability.Evolving;
+
+/**
+ * Cache used for RocksDB tables.
+ * @param <CACHEKEY>
+ * @param <CACHEVALUE>
+ */
+
+@Private
+@Evolving
+public interface TableCache<CACHEKEY extends CacheKey,
+    CACHEVALUE extends CacheValue> {
+
+  /**
+   * Return the value for the key if it is present, otherwise return null.
+   * @param cacheKey
+   * @return CACHEVALUE
+   */
+  CACHEVALUE get(CACHEKEY cacheKey);
+
+  /**
+   * Add an entry to the cache, if the key already exists it overrides.
+   * @param cacheKey
+   * @param value
+   */
+  void put(CACHEKEY cacheKey, CACHEVALUE value);
+
+  /**
+   * Removes all the entries from the cache which are having epoch value less
+   * than or equal to specified epoch value.
+   * @param epoch
+   */
+  void cleanup(long epoch);
+
+  /**
+   * Return the size of the cache.
+   * @return size
+   */
+  int size();
+
+  /**
+   * Defines type of cache need to be used by OM RocksDB tables.
+   */
+  enum CACHETYPE {
 
 Review comment:
   Okay let's skip the full cache then for now. We can add it later as an optimization. All
caches will be partial, and if an entry is not found in the cache we always go to RocksDB.
It should simplify the patch a bit. What do you think?

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