Scenario: I've an n-Tier enterprise ASP.NET application deployed using Web Deployment Projects. All tiers produce independent assemblies that is consumed by the ASP.NET application.
Problem: When I run the app. for the first time after deployment it takes lot of time to load dependent assemblies in memory. But once loaded its lighting fast app. In case if there are no users accessing the app, IIS unloads the assemblies from the memory and when a user tried to access the app on a later instance it goes on loading all the assemblies once again taking the same amount of time to load as it takes to do so for the first time.
I'm looking for a solution that enables me to keep my assemblies loaded into memory persistently overriding the volatile nature of assemblies towards memory residency.
Or any other solution that lets my users happily use the app resolving the mentioned problem.
In IIS 6, go to the Application Pools section, and right-click > Properties on the pool which hosts the ASP.NET application in question. Go to the Performance tab and uncheck "Shutdown worker processes after being idle for:"
In IIS 7, go to the Connections pane and find Application Pools, and select Advanced Settings for the pool which hosts your application. Find the "Idle Timeout" property and set it to "0" (this disables it).
The default is 20 minutes of inactivity. By unchecking the box, once your AppDomain is loaded by the worker process, it will never die (unless you kill the process or something of course). By default, IIS will recycle the process when it reaches some limit, such as a memory cap, but it will also start a new one and "phase over" all incoming requests until the old one is unused, so as to minimize disruption.
I've also written a small c# class which will keep your ASP.NET application alive (alternate archived version) under normal circumstances. Since it runs within the application, obviously it can't stop IIS or anything else from explicitly killing the process, but it will keep the application "hot", e.g. the app will never go idle long enough for IIS to decide to shut it off.
If you do not have direct control over your IIS configuration (shared host, for example) your best bet is to have a small application running on a separate system - say, an always-on workstation - which hits your site every x minutes to keep the application pool from timing out. Nothing fancy - a simple WebRequest and a while() loop in a console application will do.
One of the advantages of ASP .net is the posibility to create static (shared) instances of objects.
To avoid the necessity of an external process you can create an static timer in (per example) global.asax which calls for a page on the domain with a simple WebRequest. On this way the site keeps alive himself until a manual reset of the pool is done.
I wrote a little C# console application that keeps my 4 sites alive every 10 mins via windows task scheduler. Life is once again good. We do not run the app from 2-5am just so the serves can do any cleanups of memory, if it even matters. for our sites there is rarely anyone on at those hours anyway.
Related
Is there a way to recycle and afterwards reload an application pool?
My problem has been slow performance when logging in to my web application. I found out that the "Idle Time-out(minutes)" was sat to 20 by default. This caused the application to terminate when idle so that it can start up again on the next visit. After searching the web i found out that this value could be sat to 0 so it won't terminate. However, the first visit after recycling, an app pool have to create a new w3wp.exe worker process which is slow because the app pool needs to be created, ASP.NET or another framework needs to be loaded, and then the application needs to be loaded. Source right here
This means that every time the app recycles, the first visitor have to wait longer then the other visitors when logging in, doing some stuff and log out.
The web application is using the ISS from Dynamics AX 2009.
Sorry I thought you are working on IIS 7.5
But there was a beta for this in IIS7 actually.
I think you are looking something along the lines of this
A warmup module for IIS 7.5
"IIS Application Initialization for IIS 7.5 enables website administrators to improve the responsiveness of their Web sites by loading the Web applications before the first request arrives. By proactively loading and initializing all the dependencies such as database connections, compilation of ASP.NET code, and loading of modules, IT Professionals can ensure their Web sites are responsive at all times even if their Web sites use a custom request pipeline or if the Application Pool is recycled. While an application is being initialized, IIS can also be configured to return an alternate response such as static content as a placeholder or "splash page" until an application has completed its initialization tasks."
Download Link
http://www.iis.net/downloads/microsoft/application-initialization
And also have a look at this; which basically talks about using warm up classes which comes with ASPNET 4
http://weblogs.asp.net/gunnarpeipman/archive/2010/01/31/asp-net-4-0-how-to-use-application-warm-up-class.aspx
Checkout the suspend option.
IIS now has
Idle Time-out Action : Suspend setting
Suspending is just freezes the process and it is much more efficient than the destroying the process. Because it uses the same process and does not create another one after waking up.
How to identify the web application on the default application pool that that use the a huge amount of memory?
EDIT
My application pool contains many apps, and i can't separate or stop them, can i know what resources are used for some specific application in my multi-application application pool?
I've needed to do this in the past as well for web servers running more than one application pool. As per this article: "If you need to identify which application pool is associated with a particular w3wp.exe process, open an Administrative Command Prompt, switch into the %windir%\System32\inetsrv folder (cd %windir%\System32\inetsrv) and run appcmd list wp. This will show the process identifier (PID) of the w3wp.exe process in quotes. You can match that PID with the PID available in Task Manager."
This is exactly what I did.
You can do it using Performance monitor, open it, then click "Add Counter" then choose "Asp.Net Applications" or "ASP.Net Apps vx.xxxxx", then select your counter.
I think that in IIS, if you have multiple web apps sharing 1 app pool, the w3wp.exe process will isolate each web site into its own AppDomain. If you are using .NET 4, it looks like there is some performance metrics that can be read per AppDomain.
This means that you might be able to add some code in your applications that dump out the stats of their own AppDomain, which you can then aggregate and report on.
I haven't tried this myself, but it seems like it might help...
A really simple form of doing this may be to just in your Application_Start() method, set AppDomain.MonitoringIsEnabled = true;
Then have a "stats.aspx" page that dumps AppDomain.CurrentDomain.MonitoringTotalProcessorTime and whatever other stats, to a label.
We are using IIS7 to host an asp.net web-based application.
In this environment administrators and developers can deploy code to the application on a regular basis.
The new code or app goes as a DLL to the ASP.NET bin folder. Upon deployment of the new DLL, IIS restarts the process, impacting (slowing down) all online users.
Is there a way to configure IIS to run the process in the background and once ready make the switch from old state into new without impacting the users?!
Thanks in advance for your feedback!
IIS already does this, that's what recycling is all about. IT's loading the DLL's while the old version of the application is still running. only after this is completed the recycling is complete.
However loading the DLL's is only part of getting web applications ready, there might also be initial loads like loading/caching the user db etc.
These actions are not part of the recycle process, they happen after all DLL's reloaded and the recycling is already completed.
A while back I ran into this issue with an application that had a huge startup time due to heavy db activity/caching during startup. So I was interested if there is some functionality that allows us to execute code before the recycle is marked as completed, so that the application is first considered recycled when everything is ready to run. Basically what I wanted is some kind of staging functionality.
I was in contact with the IIS team regarding this issue, sadly they told me that no such functionality exists, nor is it planned.
To solve this you could try do the following:
Use alternating deploys:
You setup 2 Websites with separate application pools. One of them is the LIVE website the other one is the STAGED website. If you want to deploy changed you simply deploy to the STAGED website. After everything is loaded/cached etc. you switch the URL settings of the web applications to reroute incoming requests from the LIVE to the STAGED one. So the LIVE one becomes the new STAGED and the other way around. The next deploy would then go to the new STAGED again and so on.
UPDATE
Apparently they have created a IIS Module that provides this functionality by now:
IIS Application Warm-Up Module for IIS 7.5
The IIS team has released the first beta test version of the
Application Warm-Up Module for IIS 7.5. This makes warming up your
applications even easier than previously described. Instead of writing
custom code, you specify the URLs of resources to execute before the
Web application accepts requests from the network. This warm-up occurs
during startup of the IIS service (if you configured the IIS
application pool as AlwaysRunning) and when an IIS worker process
recycles. During recycle, the old IIS worker process continues to
execute requests until the newly spawned worker process is fully
warmed up, so that applications experience no interruptions or other
issues due to unprimed caches. Note that this module works with any
version of ASP.NET, starting with version 2.0.
For more information, see Application Warm-Up on the IIS.net Web site.
For a walkthrough that illustrates how to use the warm-up feature, see
Getting Started with the IIS 7.5 Application Warm-Up Module on the
IIS.net Web site.
See:
http://www.asp.net/whitepapers/aspnet4
If you use ASP.NET 4 Auto Start feature:
You can still choose to auto-recycle the worker processes from time to
time. When you do that, though, the app will immediately restart and
your warm up code will execute (unlike today - where you have to wait
for the next request to-do that).
The main difference between Warm Up and Auto Start feature is that the Warm Up Module is part of the recycling process. Rather than blocking the application for requests, while running the init code.
Only thing you get by using the Auto Start feature is that you don't have to wait for a user to hit the page, which does not help your case.
See the Gu's blog post:
http://weblogs.asp.net/scottgu/archive/2009/09/15/auto-start-asp-net-applications-vs-2010-and-net-4-0-series.aspx
UPDATE 2:
Sadly the Warmup Module has been discontinued for IIS 7/7.5:
http://forums.iis.net/t/1176740.aspx
It will be part of IIS8 though (It's now called Application Initialization Module):
http://weblogs.asp.net/owscott/archive/2012/03/01/what-s-new-in-iis-8.aspx
UPDATE 3:
As pointed out in the comments the Warmup Module resurfaced for IIS 7.5 as Application Initialization Module for IIS 7.5 after IIS 8 was released:
http://www.iis.net/downloads/microsoft/application-initialization
The first part of ntziolis answer is a wee bit inaccurate. The worker process isn't being recycled or restarted, it just keeps running. If this were the case, then in shared pool environments you would have sites knocked out every time a new one was deployed.
When you deploy a new ASP.NET application it's the site's "Application Domain" within the worker process is torn down, not the pool process.
In addition pool recycling is a completely separate concept to deployment
At this point in time in the commercial life of ASP.NET, during a deployment, a site will be in an inconsistent state until all of the site is deployed. There is still no good story about this from Microsoft at this time for single site on a single server deployments.
This is why ASP.NET has the special App_Offline.htm page. It's there so you can enable that page, deploy and then turn it off.
The second part of ntziolis answer is nearly correct but you don't need two sites or two application pools. You just need two file system folders that switch between being the physical folders for the site...if you're on a single server and not behind a load balancer or ARR.
If your sites were on a web server behind a load-balancer or ARR then having two different sites would make sense, you could route requests from one site to the other and round-robin on each deploy.
Obviously if there is a large amount of user generated content (uploaded files and the like) then you'd map a virtual directory in your site to a common location for this data.
In larger scale deployments where your app is running across (for example) a load-balanced environment you can do more sophisticated deployments.
For related questions please see:
How Do I deploy an application to IIS while that web application is running
Publishing/uploading new DLL to IIS: website goes down whilst uploading
Is smooth deployment possible with componentized ASP.NET MVC apps?
What is difference between application domain and application pool?
I have read many articles regarding these two terminology. but still unable to get proper understanding about them.
Please elaborate it with simple description.
Thanks
IIS process is w3wp;
Every application pool in IIS use it's own process;
AppPool1 uses process 3784, AppPool2 uses process 5044
Different applications in Asp.net will use different
AppDomain;
AppTest1 and AppTest2 are in different AppDomain, but in
the same process.
What's the point to use them?
Application pool and AppDomain , both of them can provide
isolations, but use different approaches. Application pool
use the process to isolate the applications which works
without .NET. But AppDomain is another isolation methods
provided by .NET.
If your server host thousands of web sites, you wont use
thousands of the application pool to isolate the web sites,
just because, too many processes running will kill the os.
However, sometime you need application pool. One of the
advantages for application pool is that you can config the
identity for application pool. Also you have more flexible
options to recycle the application pool. At least right now,
IIS didn't provide explicit options to recycle the appdomain.
An application pool is a group of one or more URLs of
different Web applications and Web sites. Any Web directory
or virtual directory can be assigned to an application pool.
Every application within an application pool shares the same
worker process executable, W3wp.exe, the worker process that
services one application pool is separated from the worker
process that services another [Like starting MS Word and
opening many word documents]. Each separate worker process
provides a process boundary so that when an application is
assigned to one application pool, problems in other
application pools do not affect the application. This
ensures that if a worker process fails, it does not affect
the applications running in other application pools. [i.e]
for Eg., If word document is having issue it should not
logically affect your Excel Sheet isn’t it.
application domain is a mechanism (similar to a process in
an operating system) used to isolate executed software
applications from one another so that they do not affect
each other. [i.e] opening of MS WORD doesn’t affect MS EXCEL
you can open and close both the applications any time since
there is no dependency between the applications. Each
application domain has its own virtual address space which
scopes the resources for the application domain using that
address space.
Thanks to this link
I am trying to figure out what exactly is Appdomain recycling?
When a aspx page is requested for the first time from a DotNet application, i understand that an appdomain for that app is created, and required assemblies are loaded into that appdomain, and the request will be served.
Now, if the web.config file or the contents of the bin folder, etc are modified, the appdomain will be "recycled".
My question is, at the end of the recycling process, will the appdomain be loaded with assemblies and ready to serve the next request? or a page has to be requested to trigger the assemblies to load?.
Well, I think the thread was getting smoothly to a final conclusion, but in the end, it was otherwise.
I'll try to answer the question based on my understanding and leveraging what i've just read about in other web sites.
First of all, I myself try to avoid the term recycle other than for Application Pools since this may render someone confused. Now, getting to process, pools and AppDomain, I see the picture as follows:
An Application Pool is, in short, a region of memory that is maintained up and running by a process called W3WP.exe, aka Worker Process. Recycling an Application Pool means bringing that process down, eliminating it from memory and then originating a brand new Worker Process, with a newly assigned process ID.
Regarding Application Domains, I see it as subsets of memory regions, within the aforementioned region that plays the role of a container. In other words, the process in memory, W3WP.exe in this case, is a macro memory region for applications that stores subset regions, called Application Domains. Having said that, one process in memory may store different Application Domains, one for each application that is assigned to run within a given Application Pool.
When it comes to recycling, as I initially told, it's something that I myself reserve only for Application Pools. For AppDomains, I prefer using the term 'restart', in order to avoid misconception. Based on this, restarting a AppDomain means starting over a given application with the newly added settings, such as refreshing the existing configuration. That happens within the boundaries of that sub-region of memory, called AppDomain, that ultimately lies within the process associated with a respective Application Pool. Those new settings may come from files such as
web.config,
machine.config,
global.asax,
Bin directory,
App_Code,
and there may be others.
AppDomain are isolated from each other, that makes total sense. If not so, if changes to a web.config, let's say, of application 1, requited recycle of the pool, all other applications assigned to that pool would get restarted, what was definitely not desired by Microsoft and by anyone else.
Summarizing my point,
Process (W3WP.exe)
AppDomain 1
AppDomain 2
AppDomain 3
AppDomain n
n = the number of assigned applications to the Application Pool managed by the given W3WP.exe
Processes are memory regions isolated from one another
AppDomains are sub-memory regions isolated from one another, within the same process
Global IIS settings changes may require Application Pool recycle (killing and starting a new Worker Process, W3WP.exe)
Application-wide settings changes AppDomains concerns, and they may get restarted after changes in some specific files such as the ones outline above
For further information, I recommend:
http://blogs.msdn.com/b/david.wang/archive/2006/03/12/thoughts-on-iis-configuration-changes-and-when-it-takes-effect.aspx
What causes an application pool in IIS to recycle?
http://blogs.msdn.com/b/tess/archive/2006/08/02/asp-net-case-study-lost-session-variables-and-appdomain-recycles.aspx
Regards from Brazil!
Take a look at this - that might explain it:
http://weblogs.asp.net/owscott/archive/2006/02/21/ASP.NET-v2.0-2D00-AppDomain-recycles_2C00_-more-common-than-before.aspx#440333
In general. What is called "first hit" on an ASP.NET Website is usually taking longer time, due to compilation, and creation of an AppDomain.
Whenever you deploy a site - make sure to use the "Publish Website" function in Visual Studio, to pre-compile your website. Then the "first hit" penalty is reduced. And remember to set the configuration to Release, and not Debug!
Recycle shuts down the process hosting the appdomain. You'll notice that the PID changes when you recycle it.
Unloading the AppDomin simply unloads all of the assemblies in the AppDomain, which can then be reused.
The important thing to remember is that once the CLR is loaded into a process, it can't be removed. So if you needed to do something as soon as the CLR is loaded, then simply unloading the AppDomain won't help, because the CLR won't be reloaded.
Also not that IIS isn't the only process which can host the AppDomain - any process can, and you don't always want to kill the whole process just to unload your assemblies.
If your pages are "updatable," they must be compiled before use. That means, yes, on first request the assemblies are loaded, compiled, and made ready for accessing. Whenever these files are changed (even some virus software can trigger this by changing the modified date of the files!), the appdomain gets recycled.
You can configure your web application to not be updatable. Everything gets compiled into DLLs, and you won't see any .ASPX or .CS files in the virtual directory. It makes your code harder to update (need to put some additional text on your webpage? Recompile time!), but it increases the availability of your web app.
However, this still won't prevent your web app from being recycled if any of the files are altered. For example, if you edit web.config, your appdomain will recycle even if its compiled.