Enterprise business apps often require that some code
is executed on regular basis as scheduled task (e.g. notifications, state
polling,..). There are some common ways how to achieve that:
- writing Windows Service application with a timer
- writing external .exe application run by Windows
Task Scheduler
- plumbing some timer specific code
- ...
- ...
- using Quartz.net
Quartz.net 2.0 is open
source job scheduling framework that can be used from smallest apps to large
scale enterprise systems. Quartz.net is a pure .NET library written in C#. It
is ported from popular open source Java scheduling framework Quartz.
Below is a simple recipe how to add support for
scheduled jobs under ASP.NET (MVC) app. I use this approach for polling
MSMQ queue on specific intervals to receive new data packets. It is worth noting
that the Quartz.net framework is very powerful and we use only basic features.
1. Quartz.net configuration can be done either
programmatically or using external XML config file. The main components
of Quartz that need to be configured are:
- ThreadPool: provides a
set of threads to use when executing jobs;
- JobStore: is
responsible for keeping track of all work data that is given to the scheduler
(jobs, triggers, calendars). There are two job store implementations (custom
stores can be added by implementing IJobStore interface): RAMJobStore, AdoJobStore.
- Scheduler: scheduler
itself by a given name and handled instances of a JobStore and ThreadPool.
We add the following lines in web.config (app.config)
file (reference to Quartz.dll is required):
…
<configSections>
<section name="quartz" type="System.Configuration.NameValueSectionHandler" />
</configSections>
<quartz>
<!-- configure Thread Pool -->
<add key="quartz.threadPool.type" value="Quartz.Simpl.SimpleThreadPool, Quartz" />
<add key="quartz.threadPool.threadCount" value="10" />
<add key="quartz.threadPool.threadPriority" value="Normal" />
<!-- configure Job Store -->
<add key="quartz.jobStore.misfireThreshold" value="60000" />
<add key="quartz.jobStore.type" value="Quartz.Simpl.RAMJobStore, Quartz" />
<!-- configure scheduler -->
<add key="quartz.scheduler.instanceName" value="MSMQScheduler" />
<!-- configure jobs and triggers
definition -->
<add key="quartz.plugin.xml.type" value="Quartz.Plugin.Xml.XMLSchedulingDataProcessorPlugin, Quartz" />
<add key="quartz.plugin.xml.fileNames" value="~/quartzjobs.config" />
<add key="quartz.plugin.xml.scanInterval" value="10" />
</quartz>
…
2. Definition of jobs & triggers can be also done
programmatically or using external XML config file (quartzjobs.config). About
jobs and triggers:
- Job: we make
.NET class executable by the scheduler simply by making it implement the IJob interface that has only one method Execute(...). It is
executed by the scheduler.
Here is our implementation of the MessageQueueJob:
namespace EE.SmsFramework.Dispatcher.Scheduler {
public class MessageQueueJob: IJob {
public void Execute(IJobExecutionContext context) {
try {
Logger.Info("QUARTZ: Scheduled Job started");
// packet dispatcher
PacketDispatcher dispatcher = new PacketDispatcher();
dispatcher.ProcessMessages();
Logger.Info("QUARTZ: Scheduled Job ended");
} catch (Exception ex) {
Logger.Error(" --> PacketDispatcher Execute Error:", ex);
}
}
}
}
- Trigger: it is used
to fire the execution of jobs.Most commonly used types are SimpleTrigger (single execution of a job at a given time) and CronTrigger (calendar-like schedules with CRON
expressions).
Here is our definition of a single job (MSMQJob) and a single trigger (MSMQJobTrigger) inside
quartzjobs.config:
<?xml version="1.0"?>
<job-scheduling-data xmlns="http://quartznet.sourceforge.net/JobSchedulingData"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.0">
<processing-directives>
<overwrite-existing-data>true</overwrite-existing-data>
</processing-directives>
<schedule>
<job>
<name>MSMQJob</name>
<group>MSMQJobs</group>
<description>Dispatches messages from MSMQ and sends them to SMS Postar.</description>
<job-type>EE.SmsFramework.Dispatcher.Scheduler.MessageQueueJob, SmsFramework.Dispatcher</job-type>
<durable>true</durable>
<recover>false</recover>
</job>
<trigger>
<cron>
<name>MSMQJobTrigger</name>
<group>MSMQJobs</group>
<description>Triggers MSMQ dispatcher job</description>
<job-name>MSMQJob</job-name>
<job-group>MSMQJobs</job-group>
<!-- every 15 minutes -->
<cron-expression>0 0/15 * * * ?</cron-expression>
</cron>
</trigger>
</schedule>
</job-scheduling-data>
3. Instantiation of a Quartz.net Scheduler instance is
maintained by StdSchedulerFactory which implements ISchedulerFactory. It uses a set of properties (NameValueCollection) to create and initialize a Quartz Scheduler. The
properties are generally stored in and loaded from a file, but can also be
created by your program and handed directly to the factory. Simply calling GetScheduler() on the factory will produce the scheduler, initialize
it (and its ThreadPool and JobStore), and return a handle to its public interface.
We instantiate Scheduler instance inside the HttpApplication OnStart event
(Global.asax). Web application instance is required to be always alive (IIS
application pool must not be stopped). This is simply done by executing void
web request inside OnEnd event.
public class MvcApplication : HttpApplication {
private IScheduler scheduler = null;
protected void Application_Start(object sender, EventArgs e) {
...
// quartz scheduler
ISchedulerFactory factory = new StdSchedulerFactory();
this.scheduler = factory.GetScheduler();
this.scheduler.Start();
...
}
protected void Application_End(object sender, EventArgs e) {
...
this.PingServer();
}
/// <summary>
/// Pings the server - startup the IIS application pool.
/// </summary>
private void PingServer() {
try {
WebClient client = new WebClient();
client.DownloadString(string.Format("http://{0}{1}", Environment.MachineName, VirtualPathUtility.ToAbsolute("~/")));
} catch (WebException webex) {
// possible 'Unauthorized' - do nothing
} catch (Exception ex) {
Logger.Error(" PingServer error:", ex);
}
}
...
}
The job MSMQJob is
triggered in its own thread every 15 minutes:
...
13:45:00.0133
[Thread:Worker-2] EE.SmsFramework.Common.Logger[INFO]: QUARTZ: Scheduled Job
started
13:45:01.0133
[Thread:Worker-2] EE.SmsFramework.Common.Logger[INFO]: QUARTZ: Scheduled Job
ended
14:00:00.0133
[Thread:Worker-1] EE.SmsFramework.Common.Logger[INFO]: QUARTZ: Scheduled Job
started
14:00:01.0133
[Thread:Worker-1] EE.SmsFramework.Common.Logger[INFO]: QUARTZ: Scheduled Job
ended
14:15:00.0133
[Thread:Worker-4] EE.SmsFramework.Common.Logger[INFO]: QUARTZ: Scheduled Job
started
14:15:01.0133
[Thread:Worker-4] EE.SmsFramework.Common.Logger[INFO]: QUARTZ: Scheduled Job
ended
...
