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New Message on MumbaiUserGroup
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From: Swapnil_B1
Message 1 in Discussion
Web Event Providers
Web event providers provide the interface between Microsoft ASP.NET's health
monitoring subsystem and data sources for the events ("Web events") fired by
that subsystem. ASP.NET 2.0 ships with the following Web event providers:
· EventLogWebEventProvider, which logs Web events in the Windows event
log.
· SqlWebEventProvider, which log Web events in Microsoft SQL Server
and Microsoft SQL Server Express databases.
· SimpleMailWebEventProvider and TemplatedMailWebEventProvider, which
respond to Web events by sending e-mail.
· TraceWebEventProvider, which forwards Web events to diagnostics
trace.
· WmiWebEventProvider, which forwards Web events to the Microsoft
Windows Management Instrumentation (WMI) subsystem.
The Microsoft .NET Framework's System.Web.Management namespace includes a class
named WebEventProvider that defines the basic characteristics of a Web event
provider. It also contains a WebEventProvider-derivative named
BufferedWebEventProvider that adds buffering support. SqlWebEventProvider
derives from BufferedWebEventProvider and improves performance by "batching"
Web events and committing them to the database en masse.
BufferedWebEventProvider is prototyped as follows:
public abstract class BufferedWebEventProvider : WebEventProvider
{
// Properties
public bool UseBuffering { get; }
public string BufferMode { get; }
// Virtual methods
public override void Initialize (string name, NameValueCollection
config);
public override void ProcessEvent (WebBaseEvent raisedEvent);
public override void Flush ();
// Abstract methods
public abstract void ProcessEventFlush (WebEventBufferFlushInfo flushInfo);
}
SqlWebEventProvider
SqlWebEventProvider is the Microsoft Web event provider for SQL Server
databases. It logs Web events in the provider database, using the schema
documented in "Data Schema," and it uses the stored procedure documented in
"Data Access." Knowledge of the database schema is hidden in the stored
procedure, so that porting SqlWebEventProvider to other database types requires
little more than modifying the stored procedure. (Depending on the targeted
database type, the ADO.NET code used to call the stored procedure might have to
change, too. The Microsoft Oracle NET provider, for example, uses a different
syntax for named parameters.)
The ultimate reference for SqlWebEventProvider is the SqlWebEventProvider
source code, which is found in SqlWebEventProvider.cs. The sections that follow
highlight key aspects of SqlWebEventProvider's design and operation.
Provider Initialization
Initialization occurs in SqlWebEventProvider.Initialize, which is called one
timewhen the provider is loadedby ASP.NET. SqlWebEventProvider.Initialize
processes the connectionStringName and maxDetailsEventLength configuration
attributes. Then, it calls base.Initialize to process other supported
configuration attributes such, as useBuffering, and throw an exception if
unrecognized configuration attributes remain.
SqlWebEventProvider.Initialize reads the connection string identified by the
connectionStringName attribute from the <connectionStrings> configuration
section, and caches it in a private field. It throws a
ConfigurationErrorsException if the attribute is empty or nonexistent, if the
attribute references a nonexistent connection string, or if the connection
string doesn't use integrated security.
Data Access
SqlWebEventProvider performs all database accesses through the stored procedure
named aspnet_WebEvent_LogEvent (Table 7-2). That stored procedure is a simple
one consisting of a single INSERT statement that initializes the fields of the
new record with the input parameters generated by
SqlWebEventProvider.FillParams
Processing Web Events
When a Web event is raised, the Web events subsystem calls the ProcessEvent
method of each Web event provider mapped to that event type. If buffering is
not enabled, SqlWebEventProvider.ProcessEvent records the Web event in the
provider database, by calling the helper method WriteToSQL. If buffering is
enabled, SqlWebEventProvider.ProcessEvent buffers the Web event by calling the
base class's ProcessEvent method. The following is the source code for
SqlWebEventProvider.ProcessEvent, with diagnostic code removed for clarity:
public override void ProcessEvent(WebBaseEvent eventRaised)
{
if (UseBuffering)
{ base.ProcessEvent(eventRaised); }
else
{ WriteToSQL(new WebBaseEventCollection(eventRaised), 0, new
DateTime(0)); }
}
If buffering is enabled, the Web events subsystem calls the provider's
ProcessEventFlush method to flush buffered Web events. ProcessEventFlush's job
is to read buffered Web events from the event buffer, and commit them to the
database. SqlWebEventProvider.ProcessEventFlush calls WriteToSQL to log the
buffered events. as follows:
public override void ProcessEventFlush (WebEventBufferFlushInfo flushInfo)
{
WriteToSQL(flushInfo.Events,
flushInfo.EventsDiscardedSinceLastNotification, flushInfo.LastNotificationUtc);
}
SqlWebEventProvider.WriteToSQL contains the logic for recording Web events in
the provider database. WriteToSQL calls FillParams to generate the parameters
written to the database, and then calls the stored procedure
aspnet_WebEvent_LogEvent to write the parameters to the provider database.
WriteToSql is capable of writing one Web event or multiple Web events, and it
contains built-in logic for delaying retries for at least 30 seconds (or the
number of seconds specified by the commandTimeout configuration attribute)
after a failed attempt to write to the database.
Differences Between the Published Source Code and the .NET Framework's
SqlWebEventProvider
The published source code for SqlWebEventProvider differs from the .NET
Framework version in the following respects:
· Declarative and imperative CAS checks were commented out. Because
the source code can be compiled standalone, and thus will run as user code
rather than trusted code in the global assembly cache, the CAS checks are not
necessary.
· The published version includes a derived event type called
MyWebBaseEvent that is used for manipulating events in the provider. The NET
Framework provider uses the base WebBaseEvent class directly, because the .NET
Framework provider is able to call internal WebBaseEvent methods.
Swapnil (Swaps)
http://swapsnet.spaces.live.com/
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