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From hanm <...@git.apache.org>
Subject [GitHub] zookeeper pull request #684: ZOOKEEPER-3180: Add response cache to improve t...
Date Thu, 01 Nov 2018 04:38:59 GMT
Github user hanm commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/684#discussion_r229936526
  
    --- Diff: zookeeper-server/src/main/java/org/apache/zookeeper/server/ResponseCache.java
---
    @@ -0,0 +1,84 @@
    +/**
    + * 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.zookeeper.server;
    +
    +import java.util.Collections;
    +import java.util.LinkedHashMap;
    +import java.util.Map;
    +
    +import org.apache.jute.Record;
    +import org.apache.zookeeper.data.Stat;
    +
    +@SuppressWarnings("serial")
    +public class ResponseCache {
    +    private static final int DEFAULT_RESPONSE_CACHE_SIZE = 400;
    +
    +    private static class Entry {
    +        public Stat stat;
    +        public byte[] data;
    +    }
    +
    +    private Map<String, Entry> cache = Collections.synchronizedMap(
    +        new LRUCache<String, Entry>(getResponseCacheSize()));
    +
    +    public ResponseCache() {
    +    }
    +
    +    public void put(String path, byte[] data, Stat stat) {
    +        Entry entry = new Entry();
    +        entry.data = data;
    +        entry.stat = stat;
    +        cache.put(path, entry);
    +    }
    +
    +    public byte[] get(String key, Stat stat) {
    +        Entry entry = cache.get(key);
    +        if (entry == null) {
    +            return null;
    +        }
    +        if (!stat.equals(entry.stat)) {
    +            // The node has been modified, invalidate cache.
    +            cache.remove(key);
    +            return null;
    +        } else {
    +            return entry.data;
    +        }
    +    }
    +
    +    private static int getResponseCacheSize() {
    +        String value = System.getProperty("zookeeper.maxResponseCacheSize");
    --- End diff --
    
    would be good to put this in document, but this can be done in a different jira if you
like.


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