LocalDBCacheStore.java

/*
 * Password Management Servlets (PWM)
 * http://www.pwm-project.org
 *
 * Copyright (c) 2006-2009 Novell, Inc.
 * Copyright (c) 2009-2017 The PWM Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package password.pwm.svc.cache;

import password.pwm.PwmApplication;
import password.pwm.error.PwmUnrecoverableException;
import password.pwm.util.java.JavaHelper;
import password.pwm.util.java.JsonUtil;
import password.pwm.util.localdb.LocalDB;
import password.pwm.util.localdb.LocalDBException;
import password.pwm.util.logging.PwmLogger;

import java.time.Instant;
import java.util.ArrayList;
import java.util.List;
import java.util.TimerTask;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.atomic.AtomicInteger;

public class LocalDBCacheStore implements CacheStore {
    private static final PwmLogger LOGGER = PwmLogger.forClass(LocalDBCacheStore.class);
    
    private static final LocalDB.DB DB = LocalDB.DB.CACHE;
    private static final int MAX_REMOVALS_PER_CYCLE = 10 * 1000;
    private static final int TICKS_BETWEEN_PURGE_CYCLES = 1000;

    private final LocalDB localDB;
    private final ExecutorService timer;
    private final AtomicInteger ticks = new AtomicInteger(0);

    private final CacheStoreInfo cacheStoreInfo = new CacheStoreInfo();

    LocalDBCacheStore(final PwmApplication pwmApplication) {
        this.localDB = pwmApplication.getLocalDB();
        try {
            localDB.truncate(DB);
        } catch (LocalDBException e) {
            LOGGER.error("error while clearing LocalDB CACHE DB during init: " + e.getMessage());
        }
        timer = JavaHelper.makeSingleThreadExecutorService(pwmApplication, LocalDBCacheStore.class);
    }

    @Override
    public void store(final CacheKey cacheKey, final Instant expirationDate, final String data)
            throws PwmUnrecoverableException
    {
        ticks.incrementAndGet();
        cacheStoreInfo.incrementStoreCount();
        try {
            localDB.put(DB,cacheKey.getHash(),JsonUtil.serialize(new CacheValueWrapper(cacheKey, expirationDate, data)));
        } catch (LocalDBException e) {
            LOGGER.error("error while writing cache: " + e.getMessage());
        }
        if (ticks.get() > TICKS_BETWEEN_PURGE_CYCLES) {
            ticks.set(0);
            timer.execute(new PurgerTask());
        }
    }

    @Override
    public String read(final CacheKey cacheKey)
            throws PwmUnrecoverableException 
    {
        cacheStoreInfo.incrementReadCount();
        final String hashKey = cacheKey.getHash();
        final String storedValue; 
        try {
            storedValue = localDB.get(DB,hashKey);
        } catch (LocalDBException e) {
            LOGGER.error("error while reading cache: " + e.getMessage());
            return null;
        }
        if (storedValue != null) {
            try {
                final CacheValueWrapper valueWrapper = JsonUtil.deserialize(storedValue, CacheValueWrapper.class);
                if (cacheKey.equals(valueWrapper.getCacheKey())) {
                    if (valueWrapper.getExpirationDate().isAfter(Instant.now())) {
                        cacheStoreInfo.getHitCount();
                        return valueWrapper.getPayload();
                    }
                }
            } catch (Exception e) {
                LOGGER.error("error reading from cache: " + e.getMessage());
            }
            try {
                localDB.remove(DB,hashKey);
            } catch (LocalDBException e) {
                LOGGER.error("error while purging record from cache: " + e.getMessage());
            }
        }
        cacheStoreInfo.incrementMissCount();
        return null;
    }

    @Override
    public CacheStoreInfo getCacheStoreInfo() {
        return cacheStoreInfo;
    }

    private boolean purgeExpiredRecords() throws LocalDBException {
        final List<String> removalKeys = new ArrayList<>();
        final LocalDB.LocalDBIterator<String> localDBIterator = localDB.iterator(DB);
        int counter = 0;
        try {
            while (localDBIterator.hasNext() && removalKeys.size() < MAX_REMOVALS_PER_CYCLE) {
                final String key = localDBIterator.next();
                counter++;
                boolean keep = false;
                try {
                    if (key != null) {
                        final String strValue = localDB.get(DB, key);
                        if (strValue != null) {
                            final CacheValueWrapper valueWrapper = JsonUtil.deserialize(strValue, CacheValueWrapper.class);
                            if (valueWrapper.getExpirationDate().isBefore(Instant.now())) {
                                keep = true;
                            }
                        }

                    }
                } catch (Exception e) {
                    LOGGER.error("error reading from cache: " + e.getMessage());
                }
                if (!keep) {
                    removalKeys.add(key);
                }
            }
        } finally {
            if (localDBIterator != null) {
                localDBIterator.close();
            }
        }
        if (!removalKeys.isEmpty()) {
            LOGGER.debug("purging " + removalKeys.size() + " expired cache records");
            localDB.removeAll(DB, removalKeys);
        } else {
            LOGGER.trace("purger examined " + counter + " records and did not discover any expired cache records");
        }
        
        return removalKeys.size() >= MAX_REMOVALS_PER_CYCLE;
    }
    
    private class PurgerTask extends TimerTask {
        @Override
        public void run() {
            try {
                purgeExpiredRecords();
            } catch (LocalDBException e) {
                LOGGER.error("error while running purger task: " + e.getMessage(),e);
            }
        }
    }

    @Override
    public int itemCount()
    {
        try {
            return localDB.size(DB);
        } catch (LocalDBException e) {
            LOGGER.error("unexpected error reading size from localDB: " + e.getMessage(), e);
        }
        return 0;
    }
}