libraries/scheduler/src/main/java/org/apache/zest/library/scheduler/internal/TaskRunner.java

/*
 * 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.
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 */

package org.apache.zest.library.scheduler.internal;

import java.lang.reflect.UndeclaredThrowableException;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.zest.api.injection.scope.Structure;
import org.apache.zest.api.injection.scope.Uses;
import org.apache.zest.api.structure.Module;
import org.apache.zest.api.unitofwork.UnitOfWork;
import org.apache.zest.api.usecase.UsecaseBuilder;
import org.apache.zest.library.scheduler.Task;
import org.apache.zest.library.scheduler.Schedule;

public class TaskRunner
    implements Runnable
{
    private static ReentrantLock lock = new ReentrantLock();

    @Structure
    private Module module;

    @Uses
    private ScheduleTime schedule;

    @Override
    public void run()
    {
        // TODO: (niclas) I am NOT happy with this implementation, requiring 3 UnitOfWorks to be created. 15-20 milliseconds on my MacBook. If there is a better way to detect overrun, two of those might not be needed.
        UnitOfWork uow = module.newUnitOfWork( UsecaseBuilder.newUsecase( "Task Runner initialize" ) );
        try
        {
            lock.lock();
            Schedule schedule = uow.get( Schedule.class, this.schedule.scheduleIdentity() );
            if( !schedule.running().get() )  // check for overrun.
            {
                try
                {
                    schedule.taskStarting();
                    schedule.running().set( true );
                    uow.complete();                     // This completion is needed to detect overrun

                    uow = module.newUnitOfWork( UsecaseBuilder.newUsecase( "Task Runner" ) );
                    schedule = uow.get( schedule );     // re-attach the entity to the new UnitOfWork
                    Task task = schedule.task().get();
                    lock.unlock();
                    task.run();
                    lock.lock();
                    uow.complete();
                    uow = module.newUnitOfWork( UsecaseBuilder.newUsecase( "Task Runner conclude" ) );
                    schedule = uow.get( schedule );     // re-attach the entity to the new UnitOfWork
                    schedule.running().set( false );
                    schedule.taskCompletedSuccessfully();
                    schedule.executionCounter().set( schedule.executionCounter().get() + 1 );
                }
                catch( RuntimeException ex )
                {
                    schedule.running().set( false );
                    processException( schedule, ex );
                }
            }
            else
            {
                schedule.overrun().set( schedule.overrun().get() + 1 );
            }
            uow.complete();
        }
        catch( Exception e )
        {
            e.printStackTrace();
            throw new UndeclaredThrowableException( e );
        }
        finally
        {
            uow.discard();
            try
            {
                lock.unlock();
            }
            catch( IllegalMonitorStateException e )
            {
                // ignore, as it may happen on certain exceptions.
            }
        }
    }

    private void processException( Schedule schedule, RuntimeException ex )
    {
        Throwable exception = ex;
        while( exception instanceof UndeclaredThrowableException )
        {
            exception = ( (UndeclaredThrowableException) ex ).getUndeclaredThrowable();
        }
        schedule.taskCompletedWithException( exception );
        schedule.exceptionCounter().set( schedule.exceptionCounter().get() + 1 );
    }
}