Skip to main content

Quartz.NET and MEF

I have been implementing a scheduler service for several different jobs on several difference schedules, which led me into using Quartz.NET. This is a really nice framework, but since we're using MEF I ran into some issues.

Quartz.NET basically consists of the scheduler engine which runs jobs implementing the IJob interface. The interface simply consists of an Execute method. I export each job with the IJob interface using MEF.

public class MyJob : IJob
    public void Execute(JobExecutionContext context)

In my scheduler implementation the jobs are imported into an IEnumerable<IJob>.

public IEnumerable<IJob> Jobs { get; set; }

The initialization of the scheduled tasks is pretty straight forward. A standard scheduler factory is initialized which in turn gives us a scheduler instance. Each job that was imported by MEF is then added to the scheduler, here with a simple 10 minute trigger just to make things easier.

var factory = new StdSchedulerFactory();
var scheduler = factory.GetScheduler();
foreach (var job in Jobs)
    var jobDetail = new JobDetail("Job name", job.GetType());
    var trigger = TriggerUtils.MakeMinutelyTrigger("Trigger name", 10, SimpleTrigger.RepeatIndefinitely);
    scheduler.ScheduleJob(jobDetail, trigger);

That is about everything we need to get the jobs going. The issue with MEF however is that each time a job is triggered to run the scheduler creates a new instance of the job. To prevent this behaviour we must create a custom implementation of the scheduler. The IJobFactory interface contains a NewJob method that is run each time a job is about to be run. We would like to return the same instance every time.

public class MefJobFactory : IJobFactory
    public IJob NewJob(TriggerFiredBundle bundle)
            var jobs = Bootstrapper.Instance.Container.GetExports<IJob>();
            return jobs.First(job => job.GetType() == bundle.JobDetail.JobType).Value;
        catch (Exception exception)
            throw new SchedulerException("Problem instantiating class " + bundle.JobDetail.JobType, exception);

There is one last thing to do to actually implement this custom job factory. Nothing in the code above needs to be changed. All we have to do is to add a few lines to the app.config to instruct Quartz.NET to use our custom implementation instead of the default.

        <section name="quartz" type="System.Configuration.NameValueSectionHandler, System, Version=1.0.5000.0,Culture=neutral, PublicKeyToken=b77a5c561934e089" />
        <add key="quartz.scheduler.jobFactory.type" value="MyScheduler.MefJobFactory, MyScheduler" />

And thats it! Instead of creating a new instance of the job on each run, my custom implementation is used to get the MEF exported job.


Post a Comment

Popular posts from this blog

Binding Enum with DescriptionAttribute in WPF

Binding an enumeration to a ComboBox can be done in several ways. In most cases you don't want to display the value itself, but a more user friendly description. One common approach is to use the DescriptionAttribute on the Enum values to supply a description for each value.  This is all possible in a very MVVM friendly way. First step is to add the  DescriptionAttribute  to the values of the enumeration. public enum MyValues { [Description("First value")] First, [Description("Second value")] Second } To retrieve the description from the enum we use a simple extension method. This method returns the value of the DescriptionAttribute if it exists, otherwise the string representation of the enum value is returned. public static string GetDescription(this Enum value) { var fieldInfo = value.GetType().GetField(value.ToString()); var attribute = fieldInfo.GetCustomAttributes(typeof(DescriptionAttribute), false).FirstOrDefault() as

User.Identity returns old login name after name change

When a person gets married or makes a name change for some other reason this usually means that the login name for the Active Directory-account changes as well. This is rarely a problem, but it turned out to cause some issues on our web server, where the  User.Identity  property was still returning the old login name. The user logged on with the new login name, but was identified by the web application as the old login name. The reason this occurs is because the  User.Identity  property relies on the  LsaLookupSids  method to convert the user SID to a login name. The method first calls the local  LSA-cache , which is not synchronized with the Active Directory. For this purpose a simple reboot of the web server to clear the  LSA-cache  propably would have sufficed. But since we didn't want to take the application offline rebooting was not an option. Instead, it is possible to set the registry value  LsaLookupCacheMaxSize in HKLM\SYSTEM\CurrentControlSet\Control\Lsa. If this val

Programming AD with C#.NET – part 4

Our transition to the  System.DirectoryServices.Protocols  has in the whole gone very smooth, but there have been some issues with one environment that contains subdomains. Most things are working fine, but writing to a subdomain does not work in the same way as it did before. What is generally bad with the  System.DirectoryServices.Protocols is the documentation, which is practically non-existent. But most things can  be figured out anyway since most classes just are wrappers for the wldap32.dll, which in turn is way better documented. I would like to have as little bindings to a specific server as possible but still be able to access the domain. In the  LdapConnection  it is possible to set the identifier to null and use the executing computer as a starting point to find a domain controller. But sometimes I must know that I am using a Global Catalog, and with more and more RODC in the environment I sometimes must know that I am working against a writeable domain controller.