com.datatorrent.lib.db.cache.CacheStore.java Source code

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Here is the source code for com.datatorrent.lib.db.cache.CacheStore.java

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/**
 * 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 com.datatorrent.lib.db.cache;

import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.google.common.collect.Lists;

/**
 * A {@link CacheManager.Primary} which keeps key/value pairs in memory.<br/>
 *
 * Properties of the cache store:<br/>
 * <ul>
 * <li>Transient: It is not checkpointed.</li>
 * <li>Max Cache Size: it starts evicting entries before this limit is exceeded.</li>
 * <li>Entry expiry time: the entries epire after the specified duration.</li>
 * <li>Cache cleanup interval: the interval at which the cache is cleaned up of expired entries periodically.</li>
 * </ul>
 *
 * @since 0.9.2
 */
public class CacheStore implements CacheManager.Primary {

    @Min(0)
    protected long maxCacheSize = 2000;

    @Min(0)
    protected int entryExpiryDurationInMillis = 60000; //1 minute

    @Min(0)
    protected int cacheCleanupIntervalInMillis = 60500; //.5 seconds after entries are expired

    @NotNull
    protected ExpiryType entryExpiryStrategy = ExpiryType.EXPIRE_AFTER_ACCESS;

    private transient ScheduledExecutorService cleanupScheduler;
    private transient Cache<Object, Object> cache;
    private transient boolean open;

    @Override
    public void put(Object key, Object value) {
        cache.put(key, value);
    }

    @Override
    public Set<Object> getKeys() {
        return cache.asMap().keySet();
    }

    @Override
    public void putAll(Map<Object, Object> data) {
        cache.asMap().putAll(data);
    }

    @Override
    public void remove(Object key) {
        cache.invalidate(key);
    }

    @Override
    public Object get(Object key) {
        return cache.getIfPresent(key);
    }

    @Override
    public List<Object> getAll(List<Object> keys) {
        List<Object> values = Lists.newArrayList();
        for (Object key : keys) {
            values.add(cache.getIfPresent(key));
        }
        return values;
    }

    @Override
    public void connect() throws IOException {
        open = true;

        CacheBuilder<Object, Object> cacheBuilder = CacheBuilder.newBuilder();
        cacheBuilder.maximumSize(maxCacheSize);
        if (entryExpiryStrategy == ExpiryType.EXPIRE_AFTER_ACCESS) {
            cacheBuilder.expireAfterAccess(entryExpiryDurationInMillis, TimeUnit.MILLISECONDS);
        } else if (entryExpiryStrategy == ExpiryType.EXPIRE_AFTER_WRITE) {
            cacheBuilder.expireAfterWrite(entryExpiryDurationInMillis, TimeUnit.MILLISECONDS);
        }
        cache = cacheBuilder.build();
        this.cleanupScheduler = Executors.newScheduledThreadPool(1);
        cleanupScheduler.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                cache.cleanUp();
            }
        }, cacheCleanupIntervalInMillis, cacheCleanupIntervalInMillis, TimeUnit.MILLISECONDS);
    }

    @Override
    public boolean isConnected() {
        return open;
    }

    @Override
    public void disconnect() throws IOException {
        open = false;
        cleanupScheduler.shutdown();
    }

    /**
     * Sets the max size of cache.
     *
     * @param maxCacheSize the max size of cache in memory.
     */
    public void setMaxCacheSize(long maxCacheSize) {
        this.maxCacheSize = maxCacheSize;
    }

    /**
     * Sets the cache entry expiry strategy.
     *
     * @param expiryType the cache entry expiry strategy.
     */
    public void setEntryExpiryStrategy(ExpiryType expiryType) {
        this.entryExpiryStrategy = expiryType;
    }

    /**
     * Sets the expiry time of cache entries in millis.
     *
     * @param durationInMillis the duration after which a cache entry is expired.
     */
    public void setEntryExpiryDurationInMillis(int durationInMillis) {
        this.entryExpiryDurationInMillis = durationInMillis;
    }

    /**
     * Sets the interval at which cache is cleaned up regularly.
     *
     * @param durationInMillis the duration after which cache is cleaned up regularly.
     */
    public void setCacheCleanupInMillis(int durationInMillis) {
        this.cacheCleanupIntervalInMillis = durationInMillis;
    }

    /**
     * Strategies for time-based expiration of entries.
     */
    public enum ExpiryType {
        /**
         * Only expire the entries after the specified duration has passed since the entry was last accessed by a read
         * or a write.
         */
        EXPIRE_AFTER_ACCESS,
        /**
         * Expire the entries after the specified duration has passed since the entry was created, or the most recent
         * replacement of the value.
         */
        EXPIRE_AFTER_WRITE
    }
}