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From keith-turner <...@git.apache.org>
Subject [GitHub] accumulo pull request #256: ACCUMULO-4463: Make block cache implementation c...
Date Tue, 09 May 2017 19:49:01 GMT
Github user keith-turner commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/256#discussion_r115579078
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/file/blockfile/cache/BlockCacheFactory.java
---
    @@ -0,0 +1,121 @@
    +/*
    + * 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.accumulo.core.file.blockfile.cache;
    +
    +import java.util.HashMap;
    +import java.util.Map;
    +
    +import org.apache.accumulo.core.conf.AccumuloConfiguration;
    +import org.apache.accumulo.core.conf.ConfigurationCopy;
    +import org.apache.accumulo.core.conf.Property;
    +import org.apache.accumulo.start.classloader.vfs.AccumuloVFSClassLoader;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +public abstract class BlockCacheFactory<B extends BlockCache,C extends BlockCacheConfiguration>
{
    +
    +  public static final String CACHE_PROPERTY_BASE = Property.GENERAL_ARBITRARY_PROP_PREFIX
+ "cache.block.";
    +
    +  private static final Logger LOG = LoggerFactory.getLogger(BlockCacheFactory.class);
    +  private static BlockCacheFactory<?,?> factory = null;
    +
    +  private final Map<CacheType,B> caches = new HashMap<>();
    +
    +  /**
    +   * Initialize the caches for each CacheType based on the configuration
    +   * 
    +   * @param conf
    +   *          accumulo configuration
    +   */
    +  public void start(AccumuloConfiguration conf) {
    +    for (CacheType type : CacheType.values()) {
    +      ConfigurationCopy props = type.getCacheProperties(conf, getCacheImplName());
    +      if (null != props) {
    +        C cc = this.createConfiguration(props, type, this);
    +        B cache = this.createCache(cc);
    +        LOG.info("Created {} cache with configuration {}", type, cc);
    +        this.caches.put(type, cache);
    +      }
    +    }
    +  }
    +
    +  /**
    +   * Stop caches and release resources
    +   */
    +  public abstract void stop();
    +
    +  /**
    +   * Get the block cache of the given type
    +   * 
    +   * @param type
    +   *          block cache type
    +   * @return BlockCache or null if not enabled
    +   */
    +  public B getBlockCache(CacheType type) {
    +    return caches.get(type);
    +  }
    +
    +  /**
    +   * Parse and validate the configuration
    +   * 
    +   * @param conf
    +   *          accumulo configuration
    +   * @param type
    +   *          cache type
    +   * @param name
    +   *          cache implementation name
    +   * @return validated block cache configuration
    +   */
    +  protected abstract C createConfiguration(AccumuloConfiguration conf, CacheType type,
BlockCacheFactory<B,C> factory);
    +
    +  /**
    +   * Create a block cache using the supplied configuration
    +   * 
    +   * @param conf
    +   *          cache configuration
    +   * @return configured block cache
    +   */
    +  protected abstract B createCache(C conf);
    +
    +  /**
    +   * Cache implementation name (e.g lru, tinylfu, etc)
    +   * 
    +   * @return name of cache implementation in lowercase
    +   */
    +  public abstract String getCacheImplName();
    +
    +  /**
    +   * Get the BlockCacheFactory specified by the property 'tserver.cache.factory.class'
    +   * 
    +   * @param conf
    +   *          accumulo configuration
    +   * @return BlockCacheFactory instance
    +   * @throws Exception
    +   */
    +  public static synchronized BlockCacheFactory<?,?> getInstance(AccumuloConfiguration
conf) throws Exception {
    +    if (null == factory) {
    +      String impl = conf.get(Property.TSERV_CACHE_FACTORY_IMPL);
    +      @SuppressWarnings("rawtypes")
    +      Class<? extends BlockCacheFactory> clazz = AccumuloVFSClassLoader.loadClass(impl,
BlockCacheFactory.class);
    +      factory = (BlockCacheFactory<?,?>) clazz.newInstance();
    --- End diff --
    
    I Think we should avoid static caching of this.  The user can can keep a ref while the
keep their caches. This could cause problems with code that attempts to recreate caches because
the config changed.


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