Quartz integration in JEE

public class SimpleQuartzJeeThreadPool implements ThreadPool {
    private static final Logger LOG = LoggerFactory.getLogger(SimpleQuartzJeeThreadPool.class);

    private final ManagedExecutorService executorService;
    private final List<WeakReference<Future<?>>> tasks = Collections.synchronizedList(new ArrayList<>());
    /** the max pool size, could also be the max size of the custom executor services created */
    private final int poolSize;
    private boolean shutdown = false;

    public SimpleQuartzJeeThreadPool(ManagedExecutorService executorService, int poolSize) {
        this.executorService = executorService;
        this.poolSize = poolSize;
        Objects.requireNonNull(this.executorService, "ManagedExecutorService cannot be null.");
    }
 
    @Override
    public boolean runInThread(Runnable runnable) {
        if (shutdown) return false;
        try {
            tasks.add(new WeakReference<>(executorService.submit(runnable)));
            return true;
        } catch (RejectedExecutionException e) {
            LOG.info("runInThread was rejected, the pool capacitiy is exceeded! {}", e.getMessage());
            return false;
        }
    }

    @Override
    public int blockForAvailableThreads() {
        if (shutdown) return -1;
        try {
            // check if we have a thread available again and block for quartz // and purge
            this.executorService.submit(this::purge).get();

            return poolSize - tasks.size();
        } catch (Exception e) {
            LOG.warn("blockForAvailableThreads failed to pruge queue!", e);
            return poolSize - tasks.size();
        }
    }
  
    /**
     * Removes all monitored jobs and returns the removed count.
     * @return the removed jobn count
     */
    public int purge() {
        int removed = 0;
        if (!tasks.isEmpty()) {   
            List<WeakReference<Future<?>>> doneJobs = tasks.stream().filter(e -> e.isEnqueued() || e.get() == null || e.get().isDone())
                    .collect(Collectors.toList());

            removed = doneJobs.size();
            this.tasks.removeAll(doneJobs);
            doneJobs.clear();
        }
        return removed;
    }

    @Override
    public void initialize() {
    }
    @Override
    public void shutdown(boolean waitForJobsToComplete) {
        this.shutdown = true;
    }
    @Override
    public int getPoolSize() {
        return poolSize;
    }
    @Override
    public void setInstanceId(String schedInstId) {
    }
    @Override
    public void setInstanceName(String schedName) {
    }
}

@Startup
@Singleton
public class TimerConfiguration {
    // this data source should be non transactional in the container
    private static final String QUARTZ_DS = "jdbc/quartz-datasource";
    @Resource(lookup = QUARTZ_DS)
    private DataSource quartzDataSource;
    // the default application datasource
    private static final String APP_DS = "jdbc/app-datasource";
    @Resource(lookup = APP_DS)
    private DataSource appDataSource;
    
    @Inject InjectionJobFactory jobFactory;
	// executor service for our jobs to quartz
    @Resource(name = "concurrent/quartz-executor")
    private ManagedExecutorService executorService;

    private Scheduler scheduler;
    
    @PostConstruct
    public void start() {
        try {
            // Get scheduler and start it
            final DirectSchedulerFactory schedulerFactory = DirectSchedulerFactory.getInstance();
			// provide the datasources            
            DBConnectionManager.getInstance()
                    .addConnectionProvider(APP_DS, new SimpleConnectionProvider(appDataSource));
            DBConnectionManager.getInstance()
                    .addConnectionProvider(QUARTZ_DS, new SimpleConnectionProvider(quartzDataSource));
            
            JobStoreCMT jobStore = new JobStoreCMT();
            jobStore.setInstanceName("quartz-job-example-store");
            jobStore.setDataSource(APP_DS);
            jobStore.setNonManagedTXDataSource(QUARTZ_DS);
            // use the JEE executor service
            jobStore.setThreadExecutor(new ThreadExecutor() {
                @Override
                public void execute(Thread thread) {
                    executorService.execute(thread);
                }
                @Override
                public void initialize() {
                }
            });
            jobStore.setIsClustered(true);
            jobStore.setDriverDelegateClass("org.quartz.impl.jdbcjobstore.PostgreSQLDelegate");
            // note: the id matters as it defines if the times is seens as an own node ...
            schedulerFactory.createScheduler("JEE-QUARTZ", "JEE-QUARTZ-ID", new SimpleQuartzJeeThreadPool(executorService, 20), jobStore);
            
            scheduler = schedulerFactory.getScheduler("JEE-QUARTZ");

            // Use the CDI managed job factory
            scheduler.setJobFactory(jobFactory);

            // Start scheduler
            scheduler.start();

        } catch (Exception e) {
            throw new RuntimeException("Failed to configure and start quartz.", e);
        }
    }

@ApplicationScoped
public class InjectionJobFactory implements JobFactory {    
    @Inject @Any
    private Instance<Job> jobs;
    
    @Override
    public Job newJob(TriggerFiredBundle bundle, Scheduler scheduler) throws SchedulerException {
        final Class<? extends Job> clazz = bundle.getJobDetail().getJobClass();
        final Instance<? extends Job> bean = jobs.select(clazz);
        if (bean.isUnsatisfied()) throw new SchedulerException("No job bean of type " + clazz + " found.");
        return bean.get();
    }
}

// Create a QuarzJob to run
JobDetail jeeJob = JobBuilder.newJob(CdiTimer.class)
        .withIdentity(CdiTimer.class.getSimpleName())
        .build();

// Create a Trigger to trigger the job every five minutes 
Trigger trigger = TriggerBuilder.newTrigger()
                 // run every 10 seconds
                 .withSchedule(CronScheduleBuilder.cronSchedule("0/10 * * * * ?"))
                 .forJob(jeeJob)			
                 .build();

// Register Job and Trigger with the scheduler
scheduler.scheduleJob(jeeJob, trigger);

import org.quartz.Job;
import javax.enterprise.context.ApplicationScoped;
// our simple CDI timer bean
@ApplicationScoped // timer don't have a scope or web request ...
public class CdiTimer implements Job {

    @Override
    public void execute(JobExecutionContext context) {
        // the CDI timer code
    }   
}

import javax.ejb.LocalBean;
import javax.ejb.Stateless;
import org.quartz.Job;
// tells JEE to not mess around because we use an interface, this is not a remote EJB!
@LocalBean 
@Stateless
public class EjbTimer implements Job {

    @Override
    public void execute(JobExecutionContext context) {
        // the EJB timer code
    }
}

// important is the usage of the WeldInstance instead of Instance
@Inject @Any
WeldInstance Job jobs;

// which would allow us to add the destroy code after the timer was used
// problem of course is to find the correct point in Quartz to postion this part
if (Dependent.class.equals(handler.getBean().getScope()) {
    // Destroy only dependent CDI beans
    handler.destroy();
}

try (Connection c = dataSource.getConnection()) {
    Liquibase l = new Liquibase(
            "/liquibase.quartz.init.xml", 
            new ClassLoaderResourceAccessor(getClass().getClassLoader()),
            DatabaseFactory.getInstance().findCorrectDatabaseImplementation(new JdbcConnection(c)));
    l.update("QUARTZ-SCHEMA");
} catch (Exception e) {
    throw new RuntimeException("Failed to init quartz schema.", e);
}