IIS 6.0 (1) , PMP/MCSE [e-mail]

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IIS6.0?????????IIS 6.0??? (1)
? ?, PMP/MCSE ?????? yy_at_yuyong.net ????www.yuyong
.net
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????

• IIS 6.0?????
• Windows????
• IIS 6.0????
• HTTP.SYS
• IIS 6.0 New Isolation Mode
• WAS, Worker Processes and App Pools
• IIS 6.0?Reliability?Scalability?????

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IIS 6.0?????

• 99.999 Availability
• 5 9s availability through better isolation of
  code
• Increased Reliability
• Reliability through health monitoring and process
  recycling
• Improved Performance
• Performance improvements through kernel mode
  driver and response cache
• Enhanced Management
• Robust and Accessible configuration store via XML
  Metabase and WMI provider

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Windows????

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• Window???????

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Windows????
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IIS 6.0???
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IIS 6.0??????

• HTTP.SYS
• IIS 6.0 New Isolation Mode
• WAS, Worker Processes and App Pools

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HTTP.SYS

• What is it?
• Universal HTTP processor for Windows
• Always running
• Availability
• Isolation of Listener function
• Request queue management
• Performance Features
• Kernel-mode response cache
• One-time parsing of HTTP request

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The Internals of HTTP.SYS
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HTTP.SYS Functions

• The main role of HTTP.SYS is to listen for HTTP
  requests through TCPIP.SYS and return responses
  to the client however, it has other duties, such
  as
• Managing TCP connections.
• Validating HTTP requests
• Routing HTTP requests to the correct application
  pool.
• Caching of responses in kernel mode.
• Performing all text-based and centralized binary
  logging for the Web service (not ODBC).
• Implementing features such as connection limits,
  connection time-outs, queue-length limits, and
  bandwidth throttling for IIS.

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Https Cache Flow
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IIS 6.0 New Isolation Mode

• ?????????
• IIS 5.0????
• IIS 6.0???????????
• Worker process isolation mode
• IIS 5.0 isolation mode

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IIS 5.0????
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IIS 5.0 isolation mode
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Worker process isolation mode
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Worker Processes and App Pools

• Application Pool work-horse
• Handles requests routed to app pool
• Mini-web servers
• Contains all W3SVC functionality
• Loads ISAPIs both site filters and extensions
• Separates W3SVC from INETINFO

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W3ADMs Management Role

• W3ADM is responsible for controlling the lifetime
  of the worker processes
• When to start a worker process
• When to recycle a worker process if it is unable
  to process any more requests (becomes blocked).
• CPU monitoring is configured to stop an app pool
  after consuming too much CPU.
• Initiation of rapid-fail protection causes an
  application pool to stop.
• A configuration error caused by trying to use an
  incorrect identity causes an application pool to
  stop.
• A Windows administrator performs a demand stop or
  start on an application pool.
• In IIS5IM mode, W3ADM will try attempt to restart
  INETINFO if it crashes.

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Worker Process

• Contains a master DLL (W3CORE.DLL) that
  implements all request handling logic
• Requests are routed through HTTP.SYS to the
  worker process and W3SVC
• Is effectively administered and managed by W3SVC
• Can be loaded into INETINFO (IIS5IM) or W3WP.exe
  (WPIM)
• Serves only one app pool

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Application Pools

• A group of one or more URL namespaces served by a
  worker process
• Can be started and stopped like sites
• Can be configured for health detection,
  recycling, etc.
• Serve all content for a web app (vs. only ISAPI
  on IIS4/5)

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HTTP.SYS and Application Pools

• HTTP.SYS requests a worker process for the app
  pool if there is demand.
• If the app pool is not started, requests for the
  app pool will receive a Service Unavailable
  message.
• If a worker process has been shut down by W3ADM,
  then HTTP.SYS can restart it if the
  AppPoolAutoStart metabase property is set to TRUE
  (the default).

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Web Gardens

• An app pool served by more than one worker
  process is a web
• garden.
• To enable this, set the MaxProcess value gt 1.
• A benefit to Web gardens is that if one worker
  process gets bogged down (script engine hangs),
  there are other worker processes available to
  accept and process requests.

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Processor Affinity

• Setting processor affinity means assigning
  specific processes or applications to a specific
  processor.
• Controlling processor affinity can improve
  performance by reducing the number of processor
  cache flushes as threads move from one processor
  to another.
• Advanced configurations using Web gardens and
  processor affinity can be used on multi-processor
  computers where clusters of CPUs can be dedicated
  to specific application pools.

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Brief Overview .NET Application Domains vs.
Application Pools

• Application Domains
• Lightweight CLR unit of isolation
• One application domain per IIS application
• Combine with W3WP.exes to achieve high
  scalability and isolation
• ASP.NET manages application domains independently
• Recycled within a single process
• Can have private components, session variables ,
  etc.

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Reliability Best PracticesIsolating Apps in
Application Pools

• Can create one or more application pools
• Each served by one or more W3WP.exes.
• Each W3WP.exe serves only one pool.
• Reqs routed directly to pool by HTTP.sys
• Isolate applications based on
• Site/Customer
• Functionality
• Reliability
• Application version (as long as each has separate
  URL)
• Best Practices
• Timeout Pool put misbehaving applications in a
  more restrictive pool
• Leaks ? throttle back memory usage
• Crashes ? enable Rapid Fail Protection.
• Isolate critical applications in their own pool
• MS.COM best practice separate ASP and ASP.net
  applications

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Reliability Best PracticesPinging Auto Health
Detection

• Pinging
• Periodic check to ensure at least 1 thread is
  available to do work
• Can set Frequency of Ping, response time per pool
• Orphaning -gt if ping fails, can take action
• REPORT_UNHEALTHY
• ISAPI SSF
• Used with Ping to request a recycle if
  unhealthy
• ASPNET used in conjunction w/ResponseDeadlockInter
  val
• Best Practices
• Use Pinging to ensure IIS w3wp and ASPNET have
  threads available to do work
• Check NT App Log for Warnings from W3SVC-WP

Event Type Warning Event Source W3SVC-WP Event
Category None Event ID 2262 Date 5/4/2003 Tim
e 10233 PM Computer ltCOMPUTERNAMEgt Descrip
tion ISAPI 'C\aspnet_isapi.dll' reported
itself as unhealthy for the following reason
'Deadlock detected'.
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Reliability Best PracticesPeriodic Process
Recycling

• What is it?
• Periodically restart applications based on
• Default Uptime
• of requests
• Scheduled time
• Memory consumption (virtual memory and actual
  used memory)
• On-demand
• Why use it?
• Refresh apps to ensure availability
• Prevent bad apps from taking over the system
• Session/App State
• In-proc state is lost when process is terminated
• Use OOP Session State management (ASPNET_STATE,
  SQL) to persist state!

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Reliability Best PracticesOverlapping Recycle
Ready for Recycle
user
kernel
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Reliability Best PracticesOverlapping Recycle
Ready for Recycle
user
kernel
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Reliability Best PracticesOverlapping Recycle
ready
user
kernel
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Reliability Best PracticesOverlapping Recycle
Shut down
user
kernel
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Reliability Best PracticesOverlapping Recycle
user
kernel
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RecyclingOverlapping vs. Non-Overlapping

• Overlapping Recycle
• Terminates only old process after new process
  starts
• Possible for apps to be instantiated multiple
  times

• Non-Overlapping Recycle
• Terminates old process first
• Then starts new process to replace it
• Reduces multi-instance problems

BOTH still queue requests in the kernel No
interruption in service!
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Reliability Best PracticesRecycling Best
Practices

• Overlapping Recommendations
• Use Overlapping (default) wherever possible
• If unable to use Overlapping
• Increase AppPools AppPoolQueueLimit if youre
  getting 503s (QueueFull error in HTTPERR log)
• CAUTION doing so will consume more memory when
  queuing.
• Recycling Recommendations
• Disable (default) Uptime-based recycling for .NET
  App-hosting Pools
• Monitor w3wp.exe private bytes, look for plateau.
• gt 800mb Increases risk of .net OutOfMemory
  Exceptions
• Use iisapp.vbs to map PID to pool
• Use PeriodicRestartPrivateMemory to control
  memory usage
• Max PeriodicRestartPrivateMemory value for pools
  hosting .NET apps should be MIN(800mb, 60
  physical ram)

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Scalability Best PracticesHTTP.SYS Kernel Caching
HTTP.SYS API
HTTP.SYS
Send Response
Listener
Req. Queue
Req. Queue
Req. Queue
Namespace Mapper
Response Cache
HTTP Engine
HTTP Parser
TCP/IP
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Scalability Best PracticesHTTP.SYS Kernel Caching
HTTP.SYS API
HTTP.SYS
Send Response
Listener
Req. Queue
Req. Queue
Req. Queue
Namespace Mapper
Response Cache
HTTP Engine
HTTP Parser
TCP/IP
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Scalability Best PracticesHTTP.SYS Kernel Caching
HTTP.SYS API
HTTP.SYS
Send Response
Listener
Req. Queue
Req. Queue
Req. Queue
Namespace Mapper
Response Cache
HTTP Engine
HTTP Parser
TCP/IP
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Scalability Best PracticesHTTP.SYS Kernel Caching
HTTP.SYS API
HTTP.SYS
Send Response
Listener
Req. Queue
Req. Queue
Req. Queue
Namespace Mapper
Response Cache
HTTP Engine
HTTP Parser
TCP/IP
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Scalability Best PracticesHTTP.SYS Kernel Cache,
part 2

• Benefits
• Much faster to serve response no transition to
  user mode
• 15k req/s from Kernel Cache vs. 1.3k req/s from
  ASPNET output cache
• Lighter load on CPU (though more kernel CPU time)
• Using it in ASP.net
• Complete responses can be cached by
• REMEMBER your application wont see subsequent
  requests for this URL after caching once.
• Standard cache flush semantics apply
• If on UNC, be sure to have MaxCmds set high
  enough
• Otherwise ? failed to start monitoring changes
  to directory \\svr\share\webcontent

lt_at_ OutputCache LocationServer gt
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Scalability Best PracticesHTTP.SYS Kernel Cache,
part 2

• Things that would prevent a response from being
  cached by HTTP.sys
• Requests requiring Authentication (AUTHENTICATE)
• Filters installed that are not cache-aware
  (FilterEnableCache FALSE default)
• Process gets recycled all cache entries for
  that process are flushed
• Content changes

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Scalability Best PracticesIdle Timeout and
Demand Start

• Idle Timeout
• Time out and shut down idle processes if process
  is idle for given period of time
• Frees resources for active applications
• Apps still available even if worker process idles
  out and is shut down!
• Demand Start
• Start worker process only if theres demand for
  the App Pool
• DemandStartThreshold only start/run a max of x
  w3wp.exe processes on the server at any time
• Best Practices
• Use Idle Timeout to free up resources for other
  heavy-use applications
• W3wp.exe uses 20mb private bytes w/ASPNET loaded
  (no applications)
• w/HelloWorld (30 concurrent conns) you go up to
  30mb
• Consider disabling idle timeout if app startup
  takes a long time
• More Pools ? consider using more aggressive
  IdleTimeout to recover memory quicker

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Scalability Best PracticesIIS 6 Web Gardens and
Processor Affinity

• Web Gardens
• App Pool w/ gt 1 worker process
• Connection-based routing w/in Garden
• Not processor based (can enable on 1 CPU
  server)
• Processor Affinitization
• Bind app pool process/es to 1 or more CPUs
• Mask-based configuration

Web Garden application pool
W3SVC
HTTP.SYS
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Scalability Best PracticesWeb Gardens and
Processor Affinity BPs

• Web Garden Best Practices
• Not beneficial in most cases only good for
  following specialized applications
• Application is multi-instanceable
• Application is not CPU-intensive
• Application has synchronous high latency backend
  (or sync high latency anywhere)
• Affinity Best Practices
• Affinitize pool to a POD (or hemisphere)
• In general, 4CPU is optimal case for affinity
• Try affinitizing NICs to CPUs too (distribute NIC
  interrupts)
• Done using SMPAffinitized True using
  SMPProcessorAffinityMask

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Scalability Best PracticesWeb Gardens and
Processor Affinity BPs

• Web Garden Best Practices
• Not beneficial in most cases only good for
  following specialized apps
• Application is multi-instanceable
• Application is non-CPU intensive
• Application has synchronous high latency backend
  (or sync high latency anywhere)
• Affinity Best Practices
• Affinitize pool to a POD (or hemisphere)
• In general, 4CPU is optimal case for affinity
• Try affinitizing NICs to CPUs too (distribute NIC
  interrupts)
• Done using SMPAffinitized True using
  SMPProcessorAffinityMask

ltIIsApplicationPool Location "/LM/W3SVC/AppPool
s/BuildingBlock0" //Procs 0-3 SMPAffinitized"TR
UE" SMPProcessorAffinityMask28"15" gt
ltIIsApplicationPool Location
"/LM/W3SVC/AppPools/BuildingBlock1" //Procs 4-7
SMPAffinitized"TRUE" SMPProcessorAffinityMask
"240" gt
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Scalability Best PracticesControlling Resource
Usage

• Use IIS Memory Recycling (private bytes
  PeriodicRestartPrivateMemory)
• Watch for w3wp.exe private bytes exceeding 800mb
• ASPNET OutOfMemory Exceptions attributed to
  address space fragmentation
• Reduce PeriodicRestartPrivateMemory to recycle
  sooner to prevent this from occurring (start at
  just under 800mb)
• CPU Throttling
• Use Windows System Resource Manager (Windows
  Server 2003 Ent and Data Center only) to control
  CPU usage
• Put mission critical applications in their own
  pools, and create WSRM policies for those pools
  to ensure they get CPU when they need it

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????

• MSDN Webcast IIS Architecture Overview
• IIS 6.0 ???
• TechNet Webcast Have Your Cake and Eat It, Too
  Understanding How ASP.NET Works with IIS 6.0
• TechNet Webcast The Ins and Outs of Web Service
  Extensions in IIS 6.0
• TechNet Webcast HTTP.sys Inside and Out
• IIS6 Reskit Book (downloadable book)
• CHAPTER_2_IIS_6.0_Architecture.doc

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