eu.databata.engine.util.PropagatorLock.java Source code

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Here is the source code for eu.databata.engine.util.PropagatorLock.java

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/**
 *   Copyright 2014 Nortal AS
 *
 *   Licensed 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 eu.databata.engine.util;

import eu.databata.engine.dao.PropagationDAO;

import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Logger;
import org.springframework.dao.EmptyResultDataAccessException;
import org.springframework.jdbc.BadSqlGrammarException;

/**
 * Contains logic for locking and unlocking propagator execution.
 * 
 * @author Maksim Boiko  {@literal<mailto:max.boiko@gmail.com>}
 *
 */
public class PropagatorLock {
    private static final Logger log = Logger.getLogger(PropagatorLock.class);
    private PropagationDAO propagationDAO;

    public PropagatorLock(PropagationDAO propagationDAO) {
        this.propagationDAO = propagationDAO;
    }

    public boolean lock() {
        log.info("Checking lock state...");
        String token = null;
        try {
            token = propagationDAO.getLockToken();
        } catch (BadSqlGrammarException e) {
            log.info("No lock table found. Creating.");
            propagationDAO.createLockTable();
        } catch (EmptyResultDataAccessException e) {
            log.info("Inserting empty record for lock table.");
            propagationDAO.insertLockRecord();
        }
        int rowsChanged = 0;
        String myToken = null;
        //    do {
        //      if (token != null) {
        //        log.info("Database is locked by another propagator. Waiting.");
        //        waitPropagation();
        //      }
        myToken = generateToken();
        rowsChanged = propagationDAO.updateLock(myToken);
        token = propagationDAO.getLockToken();
        boolean lockAquired = myToken.equals(token) && rowsChanged == 1;
        if (!lockAquired) {
            log.info("Still locked.");
        }

        return lockAquired;
        //    return true;
    }

    public void unlock() {
        propagationDAO.deleteLock();
    }

    //  private void waitPropagation() {
    //    String token = null;
    //    do {
    //      try {
    //        Thread.sleep(5000);
    //      } catch (InterruptedException e) {
    //        e.printStackTrace();
    //      }
    //      log.info("Checking lock state...");
    //      token = propagationDAO.getLockToken();
    //      if (token != null) {
    //        log.info("Still locked.");
    //      }
    //    } while (token != null);
    //    log.info("Database is unlocked!");
    //  }

    private String generateToken() {
        return StringUtils.abbreviate("" + Math.random(), 200);
    }
}