Delving Deeper into Notification Services

Creating a Notification Services Instance and Application

The Notification Services instance named StockWatch and a Notification Services application named StockWatchApp are created in theMain()method of Example 18-1. The code follows—the code that creates the Notification Services instance and application is highlighted:

  static void Main(string[] args)
  {
     Server server = new Server("(local)");

                          

                 Figure 18-8.  StockWatch notification email

     // create a new instance
    NotificationServices ns = server.NotificationServices;
    nsi = new Instance(ns, "StockWatch");

    CreateDeliveryChannel(); 

    // create a new application in the StockWatch instance
    a = new Application(nsi, "StockWatchApp");
    a.BaseDirectoryPath = baseDirectoryPath;

    CreateEventClass();
    CreateSubscriptionClass();
    CreateNotificationClass();
    CreateHostedEventProvider();
    CreateGenerator();
    CreateDistributor();
    CreateVacuumSchedule();  

    a.QuantumDuration = new TimeSpan(0, 0, 15);
    a.PerformanceQueryInterval = new TimeSpan(0, 0, 5);
    a.SubscriptionQuantumLimit = 1;
    a.ChronicleQuantumLimit = 1;
    a.VacuumRetentionAge = new TimeSpan(0, 0, 1);

    nsi.Applications.Add(a);

    Console.WriteLine("Added application.");

    nsi.Create();
    nsi.RegisterLocal(serviceUserName, servicePassword);
    nsi.Enable();

    Console.WriteLine("Application enabled." + Environment.NewLine); 

    CreateSubscriber();
    CreateSubscription();

    Console.WriteLine(Environment.NewLine + "Press any key to continue.");
    Console.ReadKey();
  }  

TheNotificationServicesobject represents a Notification Services server. TheInstancesproperty of theNotificationServices class returns anInstanceCollectionobject containing a collection of Notification Services instances asInstance objects. At a minimum, you must define aDeliveryChannel object and anApplicationobject to create anInstanceobject—in this example, this is done by theCreateDeliveryChannel()andMain()methods.

TheRegisterLocal()method of theInstance class registers an instance of Notification Services on the local computer. This is the same as registering a Notification Services instance using SQL Server Management Studio by right-clicking the Notification Services instance and selecting Tasks -> Register from the context menu. You can also register a Notification Services instance by using thenscontrol registercommand. Registering an instance creates or updates registry entries for the instance, creates performance counters, and optionally creates a Windows Service to run the instance.

TheEnable()method of theInstanceclass enables all instance and application components, allowing event collection, notification generation, notification distribution, and subscription management. ANotificationServicesinstance is disabled when you create it.

The NMO classes used to manage Notification Services instances are described in Table 18-1.

Table 18-1. NMO classes for managing Notification Services instances

TheApplicationobject represents a Notification Services application. At a minimum, you must define aGeneratorobject and aDistributorobject for anApplicationobject—in this example, this is done by theCreateGenerator()andCreateDistributor()methods.

This example configures theApplicationobject by setting the following properties:

BaseDirectoryPath
   Specifies the base directory path for the ADF

QuantumDuration
   Specifies how frequently the generator tries to
   process work

PerformanceQueryInterval
   Specifies how frequently the application updates its
   performance counters

SubscriptionQuantumLimit
   Specifies how far the logical clock can fall behind the
   real-time clock before skipping subscription rule
   firings

ChronicleQuantumLimit
   Specifies how far the logical clock can fall behind the
   real-time clock before skipping event chronicle firings

VacuumRetentionAge
   Specifies the minimum age at which event and
   notification data is considered obsolete and can be
   removed

The NMO classes used to manage Notification Services applications are described in Table 18-2.

Creating a Delivery Channel

A file delivery channel named StockWatchFileDeliveryChannel and an email delivery channel named StockWatchEmailDeliveryChannel are created in the CreateDeliveryChannel()method of Example 18-1. The code follows:

  private static void CreateDeliveryChannel()
  {
     DeliveryChannelArgument dca;
     // add file delivery channel
     DeliveryChannel dcFile =
        new DeliveryChannel(nsi, "StockWatchFileDeliveryChannel");
     dcFile.ProtocolName = "File";
     dca = new DeliveryChannelArgument(dcFile, "FileName");
     dca.Value = baseDirectoryPath + @"\Notifications\FileNotifications.txt";
     dcFile.DeliveryChannelArguments.Add(dca);
     nsi.DeliveryChannels.Add(dcFile);
     Console.WriteLine("Added delivery channel: " + dcFile.Name);

     // add email delivery channel
     DeliveryChannel dcEmail =
        new DeliveryChannel(nsi, "StockWatchEmailDeliveryChannel");
     dcEmail.ProtocolName = "SMTP";
     nsi.DeliveryChannels.Add(dcEmail);
     Console.WriteLine("Added delivery channel: " + dcEmail.Name);
  }

You have to add at least one delivery channel to a Notification Services instance before creating it. TheProtocolNameproperty of theDeliveryChannel object must be set toSMTP,File, or the name of a custom delivery protocol.

The NMO classes used to manage delivery channels are described in Table 18-3.

Creating an Event Class

An event class named StockWatchEvents is created in the CreateEventClass() method of Example 18-1. The code follows:

  private static void CreateEventClass()  
  {
     EventClass ec = new EventClass(a, "StockWatchEvents");

     EventField ef;
     ef = new EventField(ec, "Symbol");
     ef.Type = "nvarchar(6)";
     ec.EventFields.Add(ef);
     ef = new EventField(ec, "Price");
     ef.Type = "float";
     ec.EventFields.Add(ef);

     a.EventClasses.Add(ec);

     Console.WriteLine("Added event class: " + ec.Name);
  }

An event class represents a type of event used by a Notification Services application. The event class has two fields—Symbolof typenvarchar(6)andPriceof typefloat.

Creating a Subscription Class and Subscription Event Rule

A subscription class with a single subscription event rule is created in the CreateSubscriptionClassMethod() method of Example 18-1. The code follows:

CreateSubscriptionClassMethod( ) method of Example 18-1. The code follows:A subscription class with a single subscription event rule is created in the CreateSubscriptionClassMethod( ) method of Example 18-1. The code follows:

  private static void CreateSubscriptionClass()
  {
     SubscriptionClass sc = new SubscriptionClass(a, "StockWatchSubscriptions");

     SubscriptionField sf;
     sf = new SubscriptionField(sc, "DeviceName");
     sf.Type = "nvarchar(255)";
     sc.SubscriptionFields.Add(sf);
     sf = new SubscriptionField(sc, "SubscriberLocale");
     sf.Type = "nvarchar(10)";
     sc.SubscriptionFields.Add(sf);
     sf = new SubscriptionField(sc, "Symbol");
     sf.Type = "nvarchar(6)";
     sc.SubscriptionFields.Add(sf);
     sf = new SubscriptionField(sc, "Price");
     sf.Type = "float";
     sc.SubscriptionFields.Add(sf);

     SubscriptionEventRule ser =
        new SubscriptionEventRule(sc, "StockWatchSubscriptionsEventRule");
     ser.Action = @"INSERT INTO StockWatchNotifications (" +
         "SubscriberId, DeviceName, SubscriberLocale, Symbol, Price) " +
         "SELECT s.SubscriberId, s.DeviceName, s.SubscriberLocale, " +
         "e.Symbol, e.Price " +
         "FROM StockWatchEvents e, StockWatchSubscriptions s " +
         "WHERE e.Symbol = s.Symbol";

     ser.EventClassName = "StockWatchEvents";

     sc.SubscriptionEventRules.Add(ser);

     a.SubscriptionClasses.Add(sc);

     Console.WriteLine("Added subscription class: " + sc.Name);
  }

ASubscriptionClass object defines a type of subscription within a Notification Services application. TheSubscriptionField objects added to theSubscriptionobject represent fields in the subscription class schema. ASubscriptionChronicleobject lets you store subscription information outside of tables used by the subscription class—this example does not use a subscription chronicle.

The NMO classes for managing subscription chronicles, subscription classes, and subscription fields are described in Table 18-5.

ASubscriptionEventRule object represents a rule that uses T-SQL queries to generate notifications when event batches arrive. TheActionproperty represents the T-SQL query for theSubscriptionEventRuleobject. In this example, notifications are generated when the ticker symbol of an event matches the ticker symbol specified in a subscription.

The NMO classes for managing the different types of subscription rules are described in Table 18-6.