ASP'NET 2'0 Black Belt

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(No Transcript)
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ASP.NET 2.0 Black Belt

• Improving performance

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Overview

• Performance improvements with ASP.NET 2.0
• Asynchronous request handling
• SQL caching
• Client callbacks (if time permits)
• Summary
• Questions and answers

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Introducing

• Class-A
• Kennisprovider
• Microsoft development
• Training
• Coaching
• Alex Thissen
• Trainer/coach
• http//www.alexthissen.nl

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Why this session?

• Web Server performance is critical!
• Determined by combination of hardware and
  software
• Good or bad use of ASP.NET greatly influences
  performance
• Achieve better performance by
• Good programming practice
• Taking advantage of features in ASP.NET 2.0

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Asynchronous request handling
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The need for asynchronous ASP.NET

• Long running operations performed during handling
  of page request can degrade performance
• Shorter requests will take much longer than
  necessary
• On average throughput will be lower
• Asynchronous ASP.NET to the rescue
• Page request can be handled asynchronously
• Do not wait for long running operations to
  complete
• Spawn long operations on different threads

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Thread pools in .NET and ASP.NET

• .NET uses a pool of threads per process
• Pool has two types of threads
• Worker threads (default 100 in pool)
• IO completion port threads (default 100 in pool)
• Change defaults with calls to ThreadPool.SetMax/Mi
  nThreads
• Several .NET classes use IO threads
• Sockets, Web Service Proxies, WebRequest,
  FileStream

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ASP.NET threads

• ASP.NET uses 20 worker and 20 IO threads by
  default
• A minimum number of threads is reserved to handle
  callbacks from async operations
• Performance gain by switching from worker to IO
  threads
• Avoid draining worker threads in pool

ltprocessModel maxWorkerThreads "20"
minWorkerThreads "1" maxIoThreads "20"
minIoThreads "1" /gt lthttpRuntime
minFreeThreads "threads" minFreeLocalRequestFre
eThreads "threads" ... /gt
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ASP.NET architecture
worker processaspnet_wp.exe (IIS4,5) or w3wp.exe
(IIS6)
ASP.NET runtime in .NET CLR
inetinfo.exe (IIS 4 and 5)
HttpApplication\vdir1
aspnet_isapi.dll(native code)
HTTP pipeline
HttpApplication\vdir2
http.sys kernel mode driver(IIS 6)
aspnet_isapi.dll(native code)
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IHttpAsyncHandler interface

• Asynchronous web pages implement
  IHttpAsyncHandler interface
• Request threads are returned to pool right after
  async operation is started on other thread
• Implementing IHttpAsyncHandler is NOT a trivial
  or easy task

public interface IHttpAsyncHandler IHttpHandler
IAsyncResult BeginProcessRequest(HttpContext
context, AsyncCallback cb, object extraData)
void EndProcessRequest(IAsyncResult result)
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Asynchronous pages in ASP.NET 2.0

• Add asynctrue to _at_Page directive or ltpagesgt
  element in web.config
• Pass delegates for start and completion of
  asynchronous operation in AddOnPreRenderCompleteAs
  ync method
• Register event handler for PreRenderComplete

private void Page_Load(object sender, EventArgs
e) this.AddOnPreRenderCompleteAsync( new
BeginEventHandler(BeginAsynchronousOperation),
new EndEventHandler(EndAsynchronousOperation))
this.PreRenderComplete new
EventHandler(LongRunningAsync_PreRenderComplete)

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Effects during page lifecycle
Client

request page

LoadComplete
PreRender
PreRenderComplete
Thread 1
SaveViewState
Render
send response

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Effects during page lifecycle

Client
request page

Thread 1
LoadComplete
PreRender
IAsyncResult
PreRenderComplete
SaveViewState
Render
Thread 2
send response

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Synchronous performance
100 concurrent users
20 concurrent users
50 concurrent users
10 concurrent users
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Asynchronous performance
50 concurrent users
20 concurrent users
10 concurrent users

• 100 concurrent users

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Downside of async pages

• Async pages have no timeout
• Not really meant to perform several async
  operations
• Does not flow impersonation information, current
  HttpContext or culture to end handlers
• Hard to pass some form of state to async threads
• Requires at least High trust

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Asynchronous tasks

• In ASP.NET 2.0 you can add async tasks to page
  request handling
• Flow contextual information
• Pass state to async handler
• Have timeout value and timeout handler
• Register tasks before PreRenderComplete
• Registered tasks get executed automatically
• Tasks are executed only once
• ExecuteRegisteredAsyncTasks will only run tasks
  that have not executed before

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Async tasks

• Single unit of work encapsulated by PageAsyncTask
  class
• Constructor takes three delegates
• BeginEventHandler start async operation here
• EndEventHandler complete async operation
• TimeoutHandler called when task times out
• Tasks can execute in parallel for better
  concurrency
• Page execution halts until all tasks have
  completed or timed out

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Configuration of async tasks

• Default timeout of async tasks is 45 seconds
• Change timeout in _at_Page directive or ltpagesgt
  element in web.config
• Page itself does not have to be asynchronous
• But sync page will block until all async tasks
  have completed or timed out

lt_at_Page Asynctrue AsyncTimeout60
gt ltsystem.webgtltpages asyncTimeout60 /gt
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Things to remember

• IIS 5.1 on Windows XP has default setting of 10
  concurrent requests
• Gives 403.9 errors if exceeded
• Increase by editing metabase key
  LM/W3SVC/MaxConnections (40 hardcoded limit)
• BUG All requests are handled by IO threads
• On IIS5 and in ASP.NET 1.0 and 1.1 (without SP1)
  install hotfix from KB 821156
• ASP.NET 1.1SP1 and 2.0 require registry setting
  HKLM\Software\Microsoft\ASP.NET\UseWorkerThreadsO
  nIIS5 to 1 (DWORD)

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Fixing IIS5.1ASP.NET bug

• Before IO threads used

After worker threads used
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SQL caching
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Caching in ASP.NET

• ASP.NET has rich caching mechanism
• Automatic cache management
• Scavenging of cache if necessary
• Declarative caching in controls and directives
• Programmatic caching with Cache API
• ASP.NET 2.0 adds new features
• SQL Cache support
• Cache profiles
• More declarative control over cache management

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SQL Caching basics

• Caching data retrieved from database can avoid
  lots of trips to database server
• Putting data in cache is easy use Cache API
• Determining when to get fresh data is hard part
• Cached items should be invalidated when
  underlying data changes
• Two mechanisms are available to determine
  changes
• Polling mechanism periodically checking if data
  has changed
• Query notifications (new in SQL Server 2005)

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Polling mechanism

• ASP.NET runtime polls for database changes on a
  specified interval
• Can be used with SQL Server 7, 2000 and 2005
• Triggers on table of interest react to changes by
  INSERT, UPDATE and DELETE
• Trigger runs sproc to increase Change ID in a
  special table AspNet_SqlCacheTablesForChangeNotifi
  cation

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Preparing database for polling

• Enable polling on database
• Creates poll table and stored procedures
• Enable polling on specific table
• Creates triggers and adds entry in poll table

aspnet_regsql.exe E d Northwind ed
aspnet_regsql.exe -E -d Northwind -t Categories
-et
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SQL caching configuration
ltconfigurationgt ltconnectionStringsgt ltadd
name"NorthwindConnectionString"connectionString"
" providerName"System.Data.SqlClient" /gt
lt/connectionStringsgt ltsystem.webgt ltcachinggt
ltsqlCacheDependency enabled"true"
pollTime"1000"gt ltdatabasesgt ltadd
name"Northwind" connectionStringName"Nort
hwindConnectionString"/gt lt/databasesgt
lt/sqlCacheDependencygt lt/cachinggt
lt/system.webgt lt/configurationgt
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SQL 2005 Notification architecture
ASP.NET
SQL Server
SqlCommand
Cache
Northwind
TCP Port 1433
Notification Delivery Service
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Preparing for SQL2005 notifications

• Enable Service Broker on database
• Enable caching in web.config

ALTER DATABASE Northwind SET ENABLE_BROKER GO
ltconfigurationgt ltsystem.webgt ltcachinggt
ltsqlCacheDependency enabled"true" /gt
lt/cachinggt lt/system.webgt lt/configurationgt
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Start listening to notifications

• Call SqlDependency.Start with connection string
• Creates a new queue and a new service with GUIDs
  in name
• Once per connection string in lifetime of an
  application, typically global.asax
• Remember to call SqlDependency.Stop

void Application_Start(object sender, EventArgs
e) SqlDependency.Start(connectionString) voi
d Application_End(object sender, EventArgs e)
SqlDependency.Stop(connectionString)
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Output Caching with SQL dependencies

• Page output cache can be dependent on query
  results retrieved from SQL Server
• SqlDependency attribute specifies invalidation
  mechanism
• CommandNotification for query notification
• Semi-colon separated list for polling
• Automatically adds dependency to SqlCommand
  objects used in code

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Page output caching

• Use _at_OutputCache directive to set up output
  caching with a dependency to command
• SQL Server 2005
• SQL Server 7 and 2000

lt_at_ OutputCache Duration"60" VaryByParam"None"
SqlDependency"CommandNotification" gt
lt_at_ OutputCache Duration"60" VaryByParam"None"
SqlDependency"NorthwindProductsPubsAuthors" gt
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DataSource controls

• SqlDataSource control offers SqlCacheDependency
  property
• Only for SQL Server databases
• Works same way as page output caching

ltaspSqlDataSource ID"SqlDataSource1"
runat"server" ConnectionString"lt
ConnectionStringsNorthwindConnection
gt" EnableCaching"True" CacheDuration"10"Cache
ExpirationPolicy"Sliding"SelectCommand"SELECT
ProductID, ProductName, QuantityPerUnit FROM
dbo.Products" SqlCacheDependency"CommandNotificat
ion"gt lt/aspSqlDataSourcegt
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DataSource controls

• ObjectDataSource control does not support
  notifications
• Add caching logic with SqlCacheDependency inside
  of Select method
• Resort to polling

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SqlCacheDependency class

• Output cache and data source controls create an
  instance of SqlCacheDependency
• You can use SqlCacheDependency directly

SqlCommand command new SqlCommand(sql,
connection) SqlCacheDependency dependency new
SqlCacheDependency(command) Response.AddCacheDepe
ndency(dependency)-- or -- Cache.Insert("key",
someDataSet, dependency)
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ADO.NET 2.0 and Query Notifications

• SqlClient managed provider has support for Query
  Notifications in SQL Server 2005
• Two important classes for Query Notifications
• SqlDependency class for easy wiring
• SqlNotificationRequest

SqlDependency dependency new SqlDependency(comma
nd) dependency.OnChanged new
OnChangedEventHandler(DataChanged) SqlDataReader
reader command.ExecuteReader( ) void
DataChanged(object sender, SqlNotificationEventArg
s args)
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Troubleshooting

• Special rules apply for SELECT statements
• Must use explicit column names
• You cannot use SELECT
• Specify schema name for db objects
• Example SELECT FROM dbo.Customers
• More rules apply, see MSDN
• Database compatibility level must be 90 or higher
  sp_dbcmptlevel Northwind, 90
• SQL Server Service cannot run under Local System
  account
• Add dependency to command before executing it

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Troubleshooting

• ASP.NET identity that is not dbo should have
  enough rights
• Requires attached instance, not User Instance of
  SQL Server Express
• SQL CLR must be enabled

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SQL Caching recommendations

• Use wisely infrequently changing data, e.g.
  read-mostly lookup tables
• For middle tier scenarios you might want to
  specify your own service and queue
• SqlNotificationRequest for more control and
  custom handling of notifications
• Check out SqlCacheDependencyAdmin for
  administrative tasks related to polling

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Client callbacks
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Client callbacks

• A client callback is a out-of-band call to the
  web server
• Server round-trip "behind-the-scenes"
• No page refresh or complete page round-trip
• Can perform actions at the server and optionally
  retrieve data and update UI
• Improves friendliness and responsiveness of the
  user interface
• Callbacks are made asynchronously by default
• Perceived (not actual) performance is improved

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Client callbacks, AJAX and Atlas

• AJAX Asynchronous JavaScript and XML
• Atlas is Microsoft framework for Web 2.0
  applications
• Browser compatible client-side libraries for
  object-orientation and
• Web Server controls for declaratively emitting
  markup and script for client callbacks
• ASP.NET Client callbacks is like light-weight
  AJAX
• No XML is transferred between client and server
• No script libraries or server controls

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Callback flow of information
Server-side
Client-side
WebResource script
Web page
WebForm1.aspx
include
onClick
Page state
ltscriptgt lt/scriptgt
DoCallback
ltscriptgtlt/scriptgt
HTTP POST
RaiseCallbackEvent GetCallbackResult
MSXML3.XMLHTTP
Callback
ltscriptgtlt/scriptgt
onReadyStateChange
ltscriptgtlt/scriptgt
ltscriptgtlt/scriptgt
Timeout
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Client-side script

• Client-side JavaScript starts roundtrip to server
  
• Three functions DoCallback, CallbackComplete,
  ExecuteCallback
• ASP.NET callback script is included as a Web
  Resource
• Embedded Resource made available for download
  through HTTP handler AssemblyResourceLoader
• Special URL WebResource.axd?dt

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Data exchange

• Data is posted back as regular URL-encoded form
  data, not necessarily XML
• Contains ViewState, Event validation data,
  callback ID and param
• Response contains response and new Event
  validation data

__EVENTTARGET__EVENTARGUMENT__VIEWSTATE2FwEP
Ah4Hb25jbGljawUgR2V0SGVsbG9aXb3JabdcsxMiwgJ2w1__C
ALLBACKID__Page__CALLBACKPARAM12__EVENTVALIDA
TION2FwEWAwL2BraDpAgL72B4SRCAKM54rGBpFe3rPMr2H
7QsP2vv4x4ojYDdL2
14/wEWDgLh94yAQServer Time is 13035
AM LengthEventValidationDataResponse
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Client callback enabled pages

• Pages that can handler client callbacks implement
  System.Web.UI.ICallbackEventHandler
• RaiseCallbackEvent receives client-side data
• Response is generated in GetCallbackResult
• Split into two methods to allow for asynchronous
  pages or tasks

public interface ICallbackEventHandler void
RaiseCallbackEvent(string eventArgument)
string GetCallbackResult( )
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Altered page lifecycle

• Page lifecycle is different for callbacks
• Check withPage.IsCallback property

Client
Init
LoadState
request page
ProcessPostData
Load
2nd ProcessPostData
Change events
Postback events
PreRender/Complete
send response
Render
Unload
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Altered page lifecycle

• Page lifecycle is different for callbacks
• Check withPage.IsCallback property

Client
Init
LoadState
request page
ProcessPostData
Load
2nd ProcessPostData
Change events
RaiseCallbackEvent
send response
GetCallbackResult
Unload
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Putting callbacks together

• Create JavaScript functions for
• Firing callback
• Use server-side code or include from .js file
• Create call with a call to ClientScriptManager
  GetCallbackEventReference method
• Handling callback
• Error handling (optionally)
• Register client script blocks or includes
• Choose client-side event to call function
• Wire up HTML DOM event handler

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Passing arguments to server

• Retrieve values of controls through HTML DOM
• Choose an appropriate form of marshalling and/or
  encoding for complex data

ltselect name"ProvincieLijst" id"ProvincieLijst"
onchange"HaalFlitsers(GetListValue(ProvincieLijst
), null)"gt
ltscript type"text/javascript"gtlt!-- function
HaalFlitsers(args, context) WebForm_DoCallback('
__Page',args,HaalFlitsersCallback,"",HaalFlitsersE
rror,true)// --gt lt/scriptgt
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Context of callback

• Context does not travels back and forth between
  client and server
• Maintained at client
• Use context to
• Keep track of multiple active async callbacks
• Context can be null, simple datatype (e.g.
  string) or object

var context new Object() context.Param1
context.Param2 WebForm_DoCallback('__Page'
,args,OnCallBack,context,OnCallBackError,true)
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Error handling

• Exception thrown during page lifecycle will
  result in error scenario on client
• Exception is caught and message is propagated to
  client (prefixed 'e')
• Register a error function
• Requires you to specify async behavior boolean in
  call to GetCallbackEventReference

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Client callbacks from controls

• Some controls in ASP.NET 2.0 use Client callbacks
• GridView, TreeView and DetailsView
• Controls that call back need to implement
  ICallbackEventHandler
• Optionally ICallbackContainer
• Provides a formalized way for controls to
  retrieve callback script for buttons

public interface ICallbackContainer string
GetCallbackScript(IButtonControl button,
string argument)
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Event validation

• ASP.NET 2.0 validates events on post/callback
• Not just any control can cause postback and send
  arguments
• Avoid setting lt_at_Page EnableEventValidation"Fals
  e" gt
• Register values for event validation inside
  GetCallbackResult
• Still cannot read directly from control. Use
  Request object instead.

ClientScript.RegisterForEventValidation("ListBox1"
, index.ToString( ))
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Browser compatibility

• Works with
• Internet Explorer with MSXML 3.0
• Mozilla and Opera style browsers
• Non-IE browsers do not use XmlHttp object
• Script determines XmlHttp does not exist
• Creates a hidden IFrame for every request
• Data is submitted to server via normal HTTP POST
  and form.submit()

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Review

• Performance of ASP.NET web applications can be
  drastically improved by using new ASP.NET 2.0
  features
• Asynchronous pages and task relieve threads
  making overall response times better
• SQL Caching avoids unnecessary roundtrips to
  database server and provides easy cache
  invalidation based on data changes
• Client callback provides lightweight AJAX
  functionality and improves perceived performance

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Questions

• ?

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SDC 2006
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Question 1

• What is the name of the property that was
  previously called SmartNavigation?

MaintainScrollPositionOnPostback
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Question 2

• How do you take a Web application offline with a
  single page?

Place app_offline.htm in root of application
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Question 3

• What is the hardcoded (!) limit of concurrent
  requests on IIS 5.1 in Windows XP?

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