Professional ASP.NET 3.5 in C# and Visual Basic Part 153 pdf

Writing Events via Configuration: Running the Example Using the samplesection illustrated in the previous listings in this chapter, you can now write all errors as well as audits that fa

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<add name="EventLogProvider"

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

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

</providers>

The three attributes discussed so far are required attributes The rest are considered optional attributes TheminInstancesattribute defines the minimum number of times this Web event must occur before it is logged ThemaxLimitattribute defines the maximum number of instances of the defined Web event that can be recorded If instances are likely to occur because of some continuous loop, you might want to add

a value here TheminIntervalattribute denotes the minimum time allowed between log entries This

means that if theminIntervalis set to00:01:00and two Web events being monitored occur within 15 seconds of each other, the first one is recorded but the second instance is discarded because it falls within the 1-minute setting

Within the<rules>section, you can also see aprofileattribute defined in the<add />elements of the rules defined The value of this attribute comes from a definition that is supplied from the<profiles>

section of the<healthMonitoring>section This section is discussed next

<profiles>

The<profiles>section enables you to define some of the behaviors for Web event monitoring These

definitions are utilized by any number of rule definitions within the<rules>section An example use of the<profiles>section is illustrated in Listing 32-7

Listing 32-7: Using the<profiles> section

<system.web>

<! Code removed for clarity >

</eventMappings>

</providers>

<rules>

</rules>

<add name="Default" minInstances="1" maxLimit="Infinite"

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

Continued

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<add name="Critical" minInstances="1" maxLimit="Infinite"

</profiles>

</healthMonitoring>

</system.web>

</configuration>

As with the other sections, you add a profile definition by using the<add />element within the

<profiles>section Thenameattribute allows you to provide a friendly name that is then utilized from

the definitions placed within the<rules>section, as illustrated here:

<rules>

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

provider="EventLogProvider"

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

</rules>

The definitions in the<profiles>section also use the attributesminInstances,maxLimit, and

min-Interval These have the same meanings as if they were used directly in the<rules>section (see the

explanation in the previous section) The idea here, however, is that you can more centrally define these

values and use them across multiple rule definitions

Writing Events via Configuration: Running the Example

Using the sample<healthMonitoring>section (illustrated in the previous listings in this chapter), you

can now write all errors as well as audits that fail (failed logins) to the event log automatically

To test this construction in the<healthMonitoring>section, create a simple ASP.NET page that allows

you to divide two numbers and then show the result of the division on the screen An example ASP.NET

page is presented in Figure 32-11

Figure 32-11

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As you can see from this page, you can enter a single number in the first text box and another in the

second text box and press the calculate button This allows the two numbers to be divided The result

appears in a Label control on the page In this example, the code intentionally does not use any exception handling Therefore, if the end user tried to divide 5 by 0 (zero), an exception is thrown This event, in

turn, causes the exception to be written to the event log In fact, if you run a similar example and look in the event log, you find that the error has indeed been written as you have specified it should be within theweb.configfile The report from the event log is presented in Figure 32-12

Figure 32-12

Routing Events to SQL Server

Pushing Web events to the event log is something most Web applications do and is also something you should consider if you have overridden these built-in (and default) features Even more powerful than

writing them to the event log, however, is being able to write them to a database

Writing them to a database allows you to actually create a larger history, makes them more secure, and allows you to more easily retrieve the values and use them in any type of administration application that you might create

This capability was briefly introduced in Chapter 1 and is not that difficult to work with If you work

from the same<healthMonitoring>section created earlier in this chapter, writing the events to SQL

Server is as simple as adding some<add />elements to the various sections

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As shown in the previous<providers>section, a declaration actually exists for recording events into

SQL Server It is presented here again:

<add name="SqlWebEventProvider"

connectionStringName="LocalSqlServer"

maxEventDetailsLength="1073741823"

buffer="false" bufferMode="Notification"

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

<add name="WmiWebEventProvider"

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

</providers>

If you look over this bit of code, you see the definition to record events into SQL Server is presented in the

bold section within the<providers>section The section in bold shows a connection to the SQL Server

instance that is defined by theLocalSqlServerconnection string name You can find this connection

string in themachine.configfile, and you see that it points to an auto-generated SQL Server Express file

that ASP.NET can work with

<add name="LocalSqlServer" connectionString="data source=.\SQLEXPRESS;Integrated

Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true"

providerName="System.Data.SqlClient" />

</connectionStrings>

To work with Microsoft’s SQL Server 2005, you simply create a new connection string within your

ASP.NET application’sweb.configfile and reference the friendly name provided to this connection

from the<add />element of the<providers>section.

Although this SQL Server instance is declared and defined, it is not utilized by any of the rules that you

have established Looking at the previous sections, you can see that within the<rules>section of the

health monitoring section of theweb.config, only two rules exist: a rule to write all errors to the event

log and another rule to write failure audits to the event log To add a new rule to write errors (all errors

again) to SQL Server, you use the construction shown in Listing 32-8

Listing 32-8: Creating a rule to write events to SQL Server

<system.web>

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</eventMappings>

</providers>

<rules>

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

provider="EventLogProvider"

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

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

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

<add name="All Errors SQL Server" eventName="All Errors"

provider="SqlWebEventProvider"

</rules>

</healthMonitoring>

</system.web>

</configuration>

To be able to write to SQL Server, you must create a new<add />element within the<rules>section of the document The friendly name provided via thenameattribute must be unique in the list of defined

rules or you encounter an error In this case, the name of the rule isAll Errors SQL Serverand like

theAll Errors Defaultrule, it points to the event mapping ofAll Errorsas shown via the

event-Nameattribute Theproviderattribute then points to the SQL Server definition contained within the

<providers>section In this case, it isSqlWebEventProvider

With all this in place, run the ASP.NET page (shown earlier) that allows you to throw an error by dividing

by zero If you run this page a couple of times, you see that ASP.NET has automatically created an

ASPNETDB.MDFfile in your project (if you didn’t already have one)

You can then open the SQL Server Express Edition database and expand the Tables node in the Server

Explorer of Visual Studio In this list of available tables, you find a new table calledaspnet_WebEvent_ Events Right-click this table and select Show Table Data from the menu This gives you something

similar to what is illustrated in Figure 32-13

As you can see from this figure, the entire event is now stored within SQL Server (it is the first and only event at the moment) One of the nice things about this example is that not only is this event recorded to the database, but it is also written to the event log because you can use more than a single provider for each event You can just as easily use a provider that comes fromMailWebEventProviderand send the error out as an e-mail message

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Figure 32-13

Buffering Web Events

When you start working with Web events that you want to write to a database (such as SQL Server) or

sent via an e-mail, you soon realize that doing so can really lock up your database or result in a huge

amount of e-mail (especially if your application is sent into some perpetual loop of errors) For this

reason, you can see why these providers inherit fromBufferedWebEventProvider

BufferedWebEventProviderdoes exactly what it says — it buffers (or queues) your collected Web events

before performing the specified action upon them The reason you might want to buffer is to eliminate

the possibility of your database being pounded or your e-mail box being flooded

Definitions of how the buffering should occur are located in the<bufferModes>section within the

<healthMonitoring>section of theweb.configfile An example of the<bufferModes>section is

pre-sented in Listing 32-9

Listing 32-9: Using the<bufferModes> section

<system.web>

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<add name="Critical Notification" maxBufferSize="100" maxFlushSize="20"

urgentFlushThreshold="1" regularFlushInterval="Infinite"

urgentFlushInterval="00:01:00"

maxBufferThreads="1" />

<add name="Notification" maxBufferSize="300" maxFlushSize="20"

urgentFlushThreshold="1" regularFlushInterval="Infinite"

<add name="Analysis" maxBufferSize="1000" maxFlushSize="100"

urgentFlushThreshold="100" regularFlushInterval="00:05:00"

urgentFlushInterval="00:01:00" maxBufferThreads="1" />

<add name="Logging" maxBufferSize="1000" maxFlushSize="200"

urgentFlushThreshold="800"

regularFlushInterval="00:30:00" urgentFlushInterval="00:05:00"

</bufferModes>

</eventMappings>

</providers>

<rules>

</rules>

</profiles>

</healthMonitoring>

</system.web>

</configuration>

In this code, you can see four buffer modes defined Each mode has a friendly name defined using the

nameattribute For each mode, a number of different attribute can be applied To examine these attributes, take a closer look at theLoggingbuffer mode

<add name="Logging"

maxBufferSize="1000"

maxFlushSize="200"

urgentFlushThreshold="800"

regularFlushInterval="00:30:00"

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This buffer mode is called Logging and, based on the values assigned to its attributes, any provider using

this buffer mode sends the messages to the database or via e-mail every 30 minutes This is also referred

to as flushing the Web events The time period of 30 minutes is defined using theregularFlushInterval

attribute Therefore, every 30 minutes, ASP.NET sends 200 messages to the database (or via e-mail) It will

not send more than 200 messages at a time because of what is specified in themaxFlushSizeattribute

Well, what happens if more than 200 messages are waiting within that 30-minute time period? ASP.NET

still sends only 200 messages every 30 minutes and holds additional messages when the number exceeds

200 The maximum number of message held in the queue cannot exceed 1,000 messages This number

is set through themaxBufferSizeattribute However, after the total in the queue hits 800 messages,

ASP.NET starts flushing the messages every 5 minutes instead of every 30 minutes The change in

fre-quency of messages is determined by theurgentFlushThresholdattribute, and the time interval used

to send messages when theurgentFlushThresholdis hit is determined by theurgentFlushInterval

attribute

After you have defined the buffering modes you want to use, the next step is to apply them To analyze

the process, look back on how theSqlWebEventProvideris declared

<add name="SqlWebEventProvider"

connectionStringName="LocalSqlServer"

maxEventDetailsLength="1073741823"

buffer="false" bufferMode="Notification"

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

<add name="WmiWebEventProvider"

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

</providers>

Again, this event is shown in bold First, the most important attribute is thebufferattribute By default,

buffering of messages is turned off This is done by setting thebufferattribute tofalse ThebufferMode

attribute allows you to assign one of the defined buffer modes created within the<bufferModes>section

In this case, theNotificationbuffer mode is referenced Changing the buffer attribute totrueenables

the events to be sent only to SQL Server according to the time intervals defined by theNotification

buffer mode

E-mailing Web Events

When monitoring a server for Web events, you are not always going to be networked into a server or

actively monitoring it every second This doesn’t mean that you won’t want to know immediately if

something is going very wrong with your ASP.NET application For this reason, you will find the

Sim-pleMailWebEventProviderand theTemplatedMailWebEventProviderobjects quite beneficial

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Using the SimpleMailProvider

TheSimpleMailWebEventProvidersends Web events as a simple text e-mail, as shown in Figure 32-14

Figure 32-14

To set up this provider, you place an additional<add />element within the<providers>section, as

illustrated in Listing 32-10

Listing 32-10: Adding a SimpleMailWebEventProvider instance

<add name="SimpleMailProvider"

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

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

from="website@company.com"

to="admin@company.com"

cc="adminLevel2@company.com"

bcc="director@company.com"

bodyHeader="Warning!"

bodyFooter="Please investigate ASAP."

subjectPrefix="Action required."

buffer="false"

maxEventLength="4096"

maxMessagesPerNotification="1" />

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After the provider is added, you also add a rule that uses this provider in some fashion (as you do with

all the other providers) This is done by referencing theSimpleMailWebEventProvidername within the

provider attribute of the<add />element contained in the<rules>section

For this to work, be sure that you set up the SMTP capabilities correctly in yourweb.configfile An

example is presented in Listing 32-11

Listing 32-11: Setting up SMTP in the web.config file

<system.web>

</system.web>

<system.net>

<network host="localhost"

port="25"

defaultCredentials="true"

/>

</smtp>

</mailSettings>

</system.net>

</configuration>

If you do not have a quick way of setting up SMTP and still want to test this, you can also have ASP.NET

create e-mail messages and store them to disk by setting up the<smtp>section as illustrated in

Listing 32-12

Listing 32-12: Another option for setting up the SMTP section

<system.web>

</system.web>

<system.net>

</smtp>

</mailSettings>

</system.net>

</configuration>

In this scenario, the e-mails will be just placed within theC:\root directory

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