org.cyclop.service.queryprotocoling.intern.AsyncFileStore.java Source code

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Here is the source code for org.cyclop.service.queryprotocoling.intern.AsyncFileStore.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 org.cyclop.service.queryprotocoling.intern;

import java.util.HashMap;
import java.util.Map;
import java.util.Optional;

import javax.annotation.PreDestroy;
import javax.inject.Inject;
import javax.inject.Named;

import org.cyclop.model.QueryHistory;
import org.cyclop.model.UserIdentifier;
import org.cyclop.service.common.FileStorage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.Scheduled;

/** @author Maciej Miklas */
@Named
class AsyncFileStore<H> {

    private final static int FLUSH_MILIS = 30000;

    @Inject
    private FileStorage fileStorage;

    private final static Logger LOG = LoggerFactory.getLogger(AsyncFileStore.class);

    private final Map<UserIdentifier, H> diskQueue = new HashMap<>();

    public void store(UserIdentifier identifier, H history) {
        synchronized (diskQueue) {
            diskQueue.put(identifier, history);
        }
    }

    public Optional<H> getFromWriteQueue(UserIdentifier identifier) {
        LOG.debug("Reading history from queue for: {}", identifier);
        synchronized (diskQueue) {
            final H hist = diskQueue.get(identifier);
            LOG.trace("Found history: {}", hist);
            return Optional.ofNullable(hist);
        }
    }

    /**
     * method must be synchronized to avoid parallel write access on files for
     * single user-id. Second synchronization block on map ensures short lock
     * time on map, so that {@link #store(UserIdentifier, QueryHistory)} method
     * block time is reduced
     */
    @Scheduled(initialDelay = FLUSH_MILIS, fixedDelay = FLUSH_MILIS)
    @PreDestroy
    public synchronized void flush() {
        LOG.debug("Flushing history");
        while (true) {
            UserIdentifier identifier;
            H history;

            // synchronize #historyMap only for short time to not block
            // store(...) function by file operation
            synchronized (diskQueue) {
                LOG.debug("Got into mutex");
                if (diskQueue.isEmpty()) {
                    LOG.debug("Flush done - no more entries found");
                    return;
                }
                identifier = diskQueue.keySet().iterator().next();
                history = diskQueue.remove(identifier);
            }
            fileStorage.store(identifier, history);
        }
    }

}