com.moss.bdbwrap.bdbsession.WorkAtom.java Source code

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Here is the source code for com.moss.bdbwrap.bdbsession.WorkAtom.java

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/**
 * Copyright (C) 2013, Moss Computing Inc.
 *
 * This file is part of bdbwrap.
 *
 * bdbwrap 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, or (at your option)
 * any later version.
 *
 * bdbwrap 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 bdbwrap; see the file COPYING.  If not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 *
 * Linking this library statically or dynamically with other modules is
 * making a combined work based on this library.  Thus, the terms and
 * conditions of the GNU General Public License cover the whole
 * combination.
 *
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent
 * modules, and to copy and distribute the resulting executable under
 * terms of your choice, provided that you also meet, for each linked
 * independent module, the terms and conditions of the license of that
 * module.  An independent module is a module which is not derived from
 * or based on this library.  If you modify this library, you may extend
 * this exception to your version of the library, but you are not
 * obligated to do so.  If you do not wish to do so, delete this
 * exception statement from your version.
 */
package com.moss.bdbwrap.bdbsession;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.moss.bdbwrap.DbWrap.RetriesFailureException;
import com.moss.bdbwrap.EnvironmentWrap;
import com.sleepycat.je.LockConflictException;
import com.sleepycat.je.Transaction;

public abstract class WorkAtom {

    private final Log log = LogFactory.getLog(this.getClass());

    private final EnvironmentWrap e;

    public WorkAtom(EnvironmentWrap e) {
        super();
        this.e = e;
    }

    public final void run() {
        Transaction tx = e.begin();
        try {
            doWork(tx);
            tx.commit();
        } catch (Throwable t) {
            tx.abort();
            throw new RuntimeException(
                    getClass().getSimpleName() + " aborted due to uncaught " + t.getClass().getSimpleName(), t);
        }
    }

    public final void runRetry() throws RetriesFailureException {
        runRetry(3);
    }

    public void runRetry(int attempts) throws RetriesFailureException {

        if (attempts < 0) {
            throw new RuntimeException("Number of attempts must be greater than zero.");
        }

        int remainingRetries = attempts;
        LockConflictException lockConflict = null;

        while (remainingRetries > 0) {

            Transaction tx = null;
            try {
                tx = e.begin();

                doWork(tx);

                tx.commit();
                tx = null;

                lockConflict = null;
            } catch (LockConflictException ex) {
                if (tx != null) {
                    try {
                        tx.abort();
                    } catch (Throwable e) {
                        log.error("Failed to abort tx", e);
                    }
                }
                lockConflict = ex;
            } catch (Throwable ex) {
                if (tx != null) {
                    try {
                        tx.abort();
                    } catch (Throwable e) {
                        log.error("Failed to abort tx", e);
                    }
                }
                throw new RuntimeException(ex);
            }

            if (lockConflict == null) {
                return;
            }

            remainingRetries--;
            log.warn(getClass().getSimpleName() + " aborted due to lock conflict "
                    + lockConflict.getClass().getSimpleName() + ", will retry (attempt "
                    + (attempts - remainingRetries + 1) + ")", lockConflict);
        }

        throw new RuntimeException(
                getClass().getSimpleName() + " aborted due to lock conflict "
                        + lockConflict.getClass().getSimpleName() + ", failed after " + attempts + " attempts.",
                lockConflict);
    }

    public WorkAtom add(final WorkAtom other) {
        final WorkAtom thisAtom = this;

        if (other.e != e) {
            throw new RuntimeException("Cannot merge work atoms because they correspond to different environments");
        }

        return new WorkAtom(e) {
            @Override
            protected void doWork(Transaction tx) throws Exception {
                other.doWork(tx);
                thisAtom.doWork(tx);
            }
        };
    }

    protected abstract void doWork(Transaction tx) throws Exception;
}