Professional ASP.NET 3.5 in C# and Visual Basic Part 152 ppt

Using the health monitoring system enables you to use the event logging for Web events such as failed logins, application starts and stops, or any unhandled exceptions.. You define where

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void DisplayInstances(PerformanceCounterCategory pcc)

{

List<string> listPcc = new List<string>();

foreach (string item in pcc.GetInstanceNames())

{

listPcc.Add(item.ToString());

}

listPcc.Sort();

DropDownList3.DataSource = listPcc;

DropDownList3.DataBind();

}

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)

{

PerformanceCounterCategory pcc;

pcc = new PerformanceCounterCategory(DropDownList1.SelectedItem.Text);

DropDownList2.Items.Clear();

DropDownList3.Items.Clear();

DisplayCounters(pcc);

}

protected void Button1_Click(object sender, EventArgs e)

{

PerformanceCounter pc;

if (DropDownList3.Items.Count > 0)

{

pc = new PerformanceCounter(DropDownList1.SelectedItem.Text, DropDownList2.SelectedItem.Text, DropDownList3.SelectedItem.Text);

}

else

{

pc = new PerformanceCounter(DropDownList1.SelectedItem.Text, DropDownList2.SelectedItem.Text);

}

Label1.Text = "<b>Latest Value:</b> " + pc.NextValue().ToString();

}

</script>

To make this work, you have to deal with only a couple of performance-counter objects such as the

PerformanceCounterCategoryand thePerformanceCounterobjects The first drop-down list is

pop-ulated with all the categories available These values are first placed in aList(Of String)object that

enables you to call aSort()method and also allows you to remove any categories you aren’t interested

in by using theRemove()method before binding to the DropDown list control

The category selected in the first down list drives what is displayed in the second and third drop-down lists The second drop-drop-down list displays a list of counters that are available for a particular

category You might tend to think that the third drop-down list of instances is based upon the counter

that is selected, but instances are set at the category level

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When the button on the page is clicked, a new instance of thePerformanceCounterobject is created and,

as you can see from the example, it can be instantiated in several ways The first constructor takes just

a category name and a counter name, whereas the second constructor takes these two items plus the

instance name utilized After aPerformanceCounteris created, theNextValue()method pulls a sample

from the specified item, thus producing the results that are illustrated in Figure 32-7

Application Tracing

ASP.NET does an excellent job of displaying trace information either directly on the requested pages of

your ASP.NET application or in a trace log that can be found athttp://[server]/[application]/trace

.axd Sample screenshots of both of these scenarios appear in Figure 32-8

Figure 32-8

You can get a lot of detailed information on working with tracing for instrumentation in Chapter 24

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Understanding Health Monitoring

One of the more exciting instrumentation capabilities provided by ASP.NET is the health monitoring sys-tem introduced with ASP.NET 2.0 ASP.NET health monitoring is built around various health monitoring

events (which are referred to as Web events) occurring in your application Using the health monitoring

system enables you to use the event logging for Web events such as failed logins, application starts and stops, or any unhandled exceptions The event logging can occur in more than one place; therefore, you can log to the event log or even back to a database In addition to this disk-based logging, you can also use the system to e-mail health monitoring information

By default, the health monitoring system is already enabled All default errors and failure audits are

logged into the event logs on your behalf For instance, throwing an error produces an entry in the event log, as illustrated in Figure 32-9

Figure 32-9

By default, these errors are registered in the event logs, but you can also record these events in a couple of other places You define where you record these event messages through the various providers available

to the health monitoring system These providers are briefly covered next

The Health Monitoring Provider Model

Quite a bit of information about what a provider model is and how the health monitoring system works with providers is covered in Chapter 12, but a short review of the providers available to the health mon-itoring system is warranted here as well

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The health monitoring system has the most built-in providers in ASP.NET A diagram of the available

providers is shown in Figure 32-10

Figure 32-10

Seven providers are available to the health monitoring system right out of the box:

❑ System.Web.Management.EventLogWebEventProvider: Enables you to use the ASP.NET health

monitoring system to record security operation errors and all other errors into the Windows

event log

❑ System.Web.Management.SimpleMailWebEventProvider: Allows you to use the ASP.NET health

monitoring system to send error information in an e-mail

❑ System.Web.Management.TemplatedMailWebEventProvider: Similar to the

SimpleMailWeb-EventProvider, theTemplatedMailWebEventProviderclass this provider lets you send error

information in a templated e-mail Templates are defined using a standard.aspxpage

❑ System.Web.Management.SqlWebEventProvider: Enables you to use the ASP.NET health

mon-itoring system to store error information in SQL Server Like the other SQL providers for the

other systems in ASP.NET, theSqlWebEventProviderstores error information in SQL Server

Express Edition by default

❑ System.Web.Management.TraceWebEventProvider: Enables you to use the ASP.NET health

monitoring system to send error information to the ASP.NET page tracing system

❑ System.Web.Management.IisTraceWebEventProvider–: Provides you with the capability to use

the ASP.NET health monitoring system to send error information to the IIS tracing system

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❑ System.Web.Management.WmiWebEventProvider: Enables you to connect the ASP.NET health

monitoring system to the Windows Management Instrumentation (WMI) event provider

Health Monitoring Configuration

By default, theEventLogWebEventProviderobject is what is utilized for all errors and failure audits

These rules are defined along with the providers and what Web events to trap in the rootweb.config

file found atC:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\CONFIG All the information for the

health monitoring section is defined within the<healthMonitoring>section of this file Even though

these items are defined in the rootweb.configfile, you can also override these settings and define them yourself in your application’sweb.configfile

To define the health monitoring capabilities and behaviors in yourweb.configfile, place a <healthMon-itoring>section within the < system.web > section of your configuration file:

<system.web>

</healthMonitoring>

</system.web>

</configuration>

The<healthMonitoring>section can include a number of subsections, including the following:

❑ <bufferModes>

❑ <eventMappings>

❑ <profiles>

❑ <providers>

❑ <rules>

You next look at some of the core sections and how you can use these sections to define health monitoring tasks in your application’sweb.configfile

<eventMappings>

The<eventMappings>section of the health monitoring system allows you to define friendly names for

specific events that can be captured You can declare a number of events in this section, but doing so

doesn’t mean that they are utilized automatically Remember that when placing events in this section,

you are just simply defining them in this configuration file for reuse in other sections Listing 32-4 shows

an example of event mapping

Listing 32-4: Using the<eventMappings> section

<system.web>

Continued

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<add name="All Events"

type="System.Web.Management.WebBaseEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

startEventCode="0" endEventCode="2147483647" />

<add name="Heartbeats"

type="System.Web.Management.WebHeartbeatEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

<add name="Application Lifetime Events"

type="System.Web.Management.WebApplicationLifetimeEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

<add name="Request Processing Events"

type="System.Web.Management.WebRequestEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

<add name="All Errors"

type="System.Web.Management.WebBaseErrorEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

<add name="Infrastructure Errors"

type="System.Web.Management.WebErrorEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

<add name="Request Processing Errors"

type="System.Web.Management.WebRequestErrorEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

<add name="All Audits"

type="System.Web.Management.WebAuditEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

<add name="Failure Audits"

type="System.Web.Management.WebFailureAuditEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

<add name="Success Audits"

type="System.Web.Management.WebSuccessAuditEvent,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

</eventMappings>

</healthMonitoring>

</system.web>

</configuration>

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From this section, you can see that a number of different event types are defined within this

<eventMappings>section Not all these definitions are required, just the ones you are interested in work-ing with Because these definitions are important, look at how the first one is listed:

<add name="All Events"

type="System.Web.Management.WebBaseEvent,System.Web,

Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

The<add>element takes a number of different attributes The first,name, allows you to give a

user-friendly name that can be used later in one of the other sections of the document In this case, the user-friendly name provided isAll Events

The next attribute is thetypeattribute This enables you to define the NET event object with which this event mapping is associated In this case, it is the base event used by all the other event types as a base class Although the object definition with thetypeattribute is shown on multiple lines in this book, you should define it on a single line in order for it to work All the possible Web events it might associate

with are found in theSystem.Web.Managementnamespace

Each Web Event that is recorded has a code associated with it, and you can use thestartEventCode

attribute to define a starting point for this code definition In the preceding example, the event code starts

at0and increments from there until it reaches the number defined in theendEventCodeattribute In this case, the ending event code is2147483647

The following table defines each event type you can find in theSystem.Web.Managementnamespace

Web Event

You can, therefore, use this instance within the<eventMappings>

section in order to create a definition to capture all events

intervals instead of every time they occur

WebApplicationLifetimeEvent This event defines Web events that occur on the scale of the

application and its lifecycle These types of events include application starts and stops as well as compilation starts and stops

and include items such as when a transaction for a request is committed or aborted

that deal with error types You can, therefore, use this instance within the<eventMappings>section to create a definition to capture all error events

errors or any compilation or parsing errors

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Web Event

aborted or requests are larger than allowable as defined by the

maxRequestLengthattribute in the configuration file It also includes any validation errors or any unhandled exceptions

deal with login attempts These attempts can either fail or succeed You can use this instance within the<eventMappings>

section to write a definition to capture all login attempts

attempts

Now that all the error definitions are in place within the<eventMappings>section, the next step is to

further define the structure your health monitoring system will take by detailing the<providers>section,

which is also found within the<healthMonitoring>section

<providers>

As you saw earlier in Figure 32-10, seven different providers that you can use within the health

moni-toring system are available to you out of the box By default, ASP.NET records these events to the event

logs using theEventLogWebEventProvider, but you can also modify the provider model so that it uses

any of the other providers available You can also build your own custom providers so you can record

these Web events to any data store you want

You can find more information on building custom providers in Chapter 13.

Providers are declared within the<providers>section, which is nested within the

<healthMonitor-ing>section of the document Within the rootweb.configfile found atC:\WINDOWS\Microsoft.NET\

Framework\v2.0.50727\CONFIG, you find a short list of declared providers You can also declare other

providers in your application’sweb.configfile as presented in Listing 32-5

Listing 32-5: Using the<providers> section

<system.web>

<! Code removed for clarity >

</eventMappings>

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<add name="EventLogProvider"

type="System.Web.Management.EventLogWebEventProvider,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a" />

<add name="SqlWebEventProvider"

connectionStringName="LocalSqlServer"

maxEventDetailsLength="1073741823"

buffer="false" bufferMode="Notification"

type="System.Web.Management.SqlWebEventProvider,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a" />

<add name="WmiWebEventProvider"

type="System.Web.Management.WmiWebEventProvider,System.Web, Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a" />

</providers>

</healthMonitoring>

</system.web>

</configuration>

In this example, you see three separate health monitoring providers declared in theweb.configfile A

provider is defined for storing Web events in the event logs, another for storing in SQL Server, and finally another for the Windows Management Instrumentation (WMI) system

By declaring these providers within the<providers>section of theweb.configfile, you don’t ensure

that these providers are actually utilized Instead, they are simply defined and ready for you to use You

specify which providers to use within the<rules>section of the<healthMonitoring>section, which is defined shortly

You can add defined providers by using the<add />element within the<providers>section Within the

<add />element, you find a series of available attributes The first one is thenameattribute This allows you to provide a friendly name to the defined provider instance that you will use later when specifying the provider to actually use The name can be anything you want Thetypeattribute allows you to

define the class used for the provider In some cases, this is all you need (for example, for the event log provider) If you are working with a database-linked provider, however, you must further define things like theconnectionStringattribute along with thebufferandbufferModeattributes These are covered

in more detail later

After your providers are defined in the<healthMonitoring>section of the document, the next step is to determine which Web events to work with and which provider(s) should be utilized in the monitoring of these events Both these operations are accomplished from within the<rules>section

<rules>

The<rules>section allows you to define the Web events to monitor and the providers to tie them to

when one of the monitored Web events is actually triggered When you are using the health

mon-itoring system, you can actually assign multiple providers to watch for the same Web events This

means that you can store the same Web event in both the event logs and in SQL Server That is pretty

powerful Listing 32-6 provides an example of using the<rules>section within your application’s

web.configfile

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Listing 32-6: Using the<rules> section

<system.web>

</eventMappings>

</providers>

<rules>

<add name="All Errors Default" eventName="All Errors"

provider="EventLogProvider"

profile="Default" minInstances="1" maxLimit="Infinite"

minInterval="00:01:00" custom="" />

<add name="Failure Audits Default" eventName="Failure Audits"

provider="EventLogProvider" profile="Default" minInstances="1"

maxLimit="Infinite" minInterval="00:01:00" custom="" />

</rules>

</healthMonitoring>

</system.web>

</configuration>

In this example, two types of Web events are being recorded You specify rules (the Web events to

mon-itor) by using the<add />element within the<rules>section Thenameattribute allows you to provide

a friendly name for the rule definition TheeventNameis an important attribute because it takes a value

of the Web event to monitor These names are the friendly names that you defined earlier within the

<eventMappings>section of the<healthMonitoring>section The first<add />element provides a

defi-nition of monitoring forAll Errorsvia theeventNameattribute Looking back, you can see that this was,

indeed, defined in the<eventMappings>section

<add name="All Errors"

type="System.Web.Management.WebBaseErrorEvent,System.Web,

Version=2.0.0.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a"

</eventMappings>

After specifying which Web event to work with through theeventNameattribute, the next step is to define

which provider to use for this Web event You do this using theproviderattribute In the case of the first

<add />element, theEventLogProvideris utilized Again, this is the friendly name that was used for the

provider definition in the <providers> section, as shown here:

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