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POIoC Task Scheduler Design with Simple Injector with code example recommendations
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  1. POIoC Task Scheduler Design with Simple Injector with code example recommendations
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    copied!<p>Hi I am using <a href="http://simpleinjector.codeplex.com/" rel="nofollow">Simple Injector</a> and I am trying to implement a scheduler service which calls command(s) at a programmable regular frequency. My design decisions are below:</p> <p>1) I have a service that runs a background thread and resolves from the container <code>ICommandHandler&lt;SyncExternalDataCommand&gt;.Handle(someParameter)</code> and calls the command handle method.</p> <p><code>RegisterCommandAsBusinessUnitCronJob</code> will be called for each BusinessUnit with the ID passed as a parameter on each call. We could also implement <code>RegistercommandAsCustomerContactCronJob</code> to loop through customer records. </p> <p><strong>Is it ok to design the scheduler in this way with a background thread?</strong></p> <p>2) I have tried to keep the coupling between the composition root container and the scheduler to a minimum.</p> <p>An approach with Action helper delegates helps to keep the code in the composition root section as opposed to within the service. <strong>By using a different design, could this coupling be reduced further or is this coupling acceptable?</strong></p> <p>Code is below (it is yet to be made thread-safe), comments on the design decisions above and improvements/redesign are very welcome.</p> <p>Thanks, Chris</p> <p><strong>Bootstrap of the container</strong></p> <pre class="lang-cs prettyprint-override"><code>void Register(Container container) { container.RegisterSingle&lt;IUnitOfWorkFactory&gt;( new UnitOfWorkFactory(container)); container.RegisterLifetimeScope&lt;IUnitOfWork, UnitOfWork&gt;(); container.RegisterSingle&lt;ILogger, Logger&gt;(); container.RegisterSingle&lt;ICronJobService, CronJobService&gt;(); container.Register&lt;ICommandHandler&lt;SyncExternalDataCommand&gt;, SyncExternalDataCommandHandler&gt;(); var cronJobService = container.GetInstance&lt;ICronJobService&gt;(); cronJobService.RegisterCommandAsBusinessUnitCronJob("* 1 * * *", (Int32 id) =&gt; { var command = new SyncExternalDataCommand() { businessUnitId = id }; using (container.BeginLifetimeScope()) { // handler must be resolved INSIDE the scope. var handler = container.GetInstance&lt;ICommandHandler&lt;SyncExternalDataCommand&gt;&gt;(); handler.Handle(command); } } ); } </code></pre> <p><strong>Scheduler service</strong></p> <pre class="lang-cs prettyprint-override"><code>// to be instantiated as a singleton by IoC container public class CronJobService : ICronJobService { // this dictionary is for tasks that will be called with // the business unit primary key (Int32). private cronJobs = new Dictionary&lt;Action&lt;Int32&gt;, string&gt;(); public void RegisterCommandAsBusinessUnitCronJob( string cronString, Action&lt;Int32&gt; commandFactory) { cronJobs.Add(commandFactory, cronString); } // this below is called when we are running a task protected static bool RunCreateAndHandleThread( object parameter) { var jobParameters = (ThreadJobParameters)parameter; if (!cancellationTokenSource.IsCancellationRequested) { // we will need to construct new graph with a // proxy command jobParameters.helper(jobParameters.businessUnitId); } return true; } protected static void SomeBackgroundLoop( RunHandlePollingLoopParameters parameters) { IUnitOfWork unitOfWork = parameters.unitOfWorkFactory.CreateUnitOfWork(); using (unitOfWork) { var businessUnits = unitOfWork.BusinessUnitRepository.Get(); // loop through cron jobs and business units foreach (var helperFactory in parameters.cronJobs.Keys) { // its time to run this job... if (isTimeToRunCronjob) { var jobParameters = new ThreadJobParameters { helper = helperFactory, businessUnitId = businessUnit.Id }; Task.Factory.StartNew&lt;bool&gt;( RunCreateAndHandleThread, jobParameters, CronJobService.cancellationTokenSource.Token, TaskCreationOptions.LongRunning, TaskScheduler.Default); } } } } } </code></pre>
 

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