In IIS there are two areas (well, more than two) where recycling can occur:
Under the "Process Model" section → "Idle Timeout" (default 20 minutes)
and
Under the "Recycle" section → "Regular Time Interval" (default 1740 minutes)
My questions are:
What are the differences between the two methods?
What are the negative implications of settings them to 0?
Idle Timeout is if no action has been asked from your web app, it the process will drop and release everything from memory
Recycle is a forced action on the application where your processed is closed and started again, for memory leaking purposes and system health
The negative impact of both is usually the use of your Session and Application state is lost if you mess with Recycle to a faster time.(logged in users etc will be logged out, if they where about to "check out" all would have been lost" that's why recycle is at such a large time out value, idle timeout doesn't matter because nobody is logged in anyway and figure 20 minutes an no action they are not still "shopping"
The positive would be get rid of the idle time out as your website will respond faster on its "first" response if its not a highly active site where a user would have to wait for it to load if you have 1 user every 20 minutes lets say. So a website that get his less then 1 time in 20 minutes actually you would want to increase this value as the website has to load up again from scratch for each user. but if you set this to 0 over a long time, any memory leaks in code could over a certain amount of time, entirely take over the server.
From here:
One way to conserve system resources is to configure idle time-out
settings for the worker processes in an application pool. When these
settings are configured, a worker process will shut down after a
specified period of inactivity. The default value for idle time-out is
20 minutes.
Also check Why is the IIS default app pool recycle set to 1740 minutes?
If you have a just a few sites on your server and you want them to
always load fast then set this to zero. Otherwise, when you have 20
minutes without any traffic then the app pool will terminate so that
it can start up again on the next visit. The problem is that the first
visit to an app pool needs 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 your application needs
to be loaded. That can take a few seconds. Therefore I set that to 0
every chance I have, unless it’s for a server that hosts a lot of
sites that don’t always need to be running.
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.
I have inherited a desktop app that makes calls to a series of Web Services on IIS. The web services (also) have to be able to run timed processes, independently (without having the client on). Hence they all have timers.
The web service timers were shutting down (memory leak?) so we set the Idle time out to 0 and timers stay on.
Related
I have an IIS website which connects to MySQL. I have a link in the website which do the intensive calculation. When this link is triggered, it uses around 20% of CPU resource. Then, if I click other links, the other links are responding very slow. Until the link that does calculation finished, then other links responding time will resume. I am curious why only 20% CPU is used, but the other links still respond slowly. It seems the calculation link occupies the CPU resource. But isn't it different link are run in parallel, how it should be affected by intensive calculation of one link? How can I improve that, or should I tune something in IIS of my code?
Increase the maximum number of worker processes in your IIS application pool for your website. This will enable the server handle multiple requests at the same time. Below is how.
Open IIS Manager and Navigate to Application pools.
Right click the application pool for your website and select Advanced Settings.
In the Advanced Settings Dialog Box under Process Model, change the value of maximum worker processes to 10. [You may enter another number (greater than or less than 10)] 1 is default and means only one worker process will be started to handle all your requests. Meaning that only one request will be processed at a time.
Click Ok to save your changes
Restart your application pool [Not mandatory but advised]
Thats all. Your Website should now be able to process multiple requests at the same time
I've been trying to diagnose an issue pertaining to thousands of hung/stuck EndRequest requests in IIS. This is becoming a large problem for us as we're hitting the concurrent connection cap after about a week or two and have to recycle the whole application pool to clear the request list.
Because this is a live application, I have limited troubleshooting options, so anything that would halt or bring down the application pool I am not allowed to do.
IIS Information
Concurrent connection cap is set to its maximum of 65535.
Configuration debug in the web config is set to false and we have a
timeout set at 110 seconds.
Windows Server 2012 R2 Version 6.2 (Build 9200)
IIS Version 8.5.9600.16384
The long running requests have 0 data transfer, checked with
WireShark.
I'm pretty much at a loss on why these aren't timing out. I've set all the appropriate settings - the ones I could find from MSDN and other sources. We have a very, very hard time replicating this on our development environment so it's been blind testing for the most part. I've found articles and such on other state hangs, but I cannnot find anything on why a request in the EndRequest state will not time out.
Advanced Settings Page:
https://postimg.org/image/gxec32kmt/
Application Pool Requests Page:
https://postimg.org/image/qupcw57o5/
Web Config:
https://postimg.org/image/5xt4rh1xh/
Update 1
I did a bit of digging into our fallback that is supposed to close connections after an hour of no usage. We seem to currently have 10,153 sessions still active with a last active time of 3 days ago. I've stepped through this function quite a bit and it seems to be working as intended. It goes through the list of sessions and anyone over an hour of inactivity has their WebSocketHandler.Close() method called. However it seems some sessions are refusing to close after the method is being called. We have logging in place to tell us if any exceptions are being thrown during the run but it seems as though it's running as expected.
This was my mistake. I was running against an old sessions data pull. A current pull of the session data shows no sessions running greater then their specified time. This means that the WebSocketHandler.Close() was called on them and they were removed from our in-memory list.
Update 2
NETSTAT using netstat -s on pastebin: https://pastebin.com/embed_js/qBbZ4gJ1
Update 3
Correction to update 1. Can a connection close be called and fail? If so, then we're accidentally orphaning the reference to the connection in our server. I would still expect the IIS timeout to kick in however, there must be some catches to it collecting requests.
In asp.net, the default session time out is 20 minutes. Suppose if i am changing the session time out period to 2 hours or greater than of its, then will it cause any performance issue on server side?
I would like to know Is there any limitations or disadvantages of using maximum session out time in asp.net?
Please guide me to get out of this issue?
Sessions are maintained on server for each user. Increase in session time out will prevent the Server from releasing memory allocated to inactive session.
I would like to know Is there any limitations or disadvantages of
using maximum session out time in asp.net?
HttpSessionState.Timeout Property
The Timeout property cannot be set to a value greater than 525,600
minutes (1 year). The default value is 20 minutes.
Disadvantage:
You will have performance issues if you have large number of users and with increase in session timeout, your inactive sessions will remain in Web server memory which may cause application pool to recycle, which would result in loosing all sessions for all users.
If you are you using IIS6 or greater then depending on your Application Pool settings it may affect how frequently the w3wp process is recycled. When the app pool is recycled your sessions will be lost unless you use out-of-process session state management or sql as a session state host.
If you increase the timeout to two hours individual users wont lose their session as often, but it increases the odds that all users browsing the site will occasionally get logged off when the process is recycled.
Increasing the session time means that a web page left idle is less likely to time out (such as if the user goes to lunch leaving the web page open). However, this takes up more server resources, since, as Habib says, the server must store the user information during this time.
It can also be is a security risk. If the user closes the web page rather than logs out, it increases the window for a CSRF attack.
The best thing to do is understand how your users use the web page. If pages must be kept open for long periods, look at a periodic callback or refresh for the page. Alternatively, if the site is security sensitive, consider logging the user out automatically after a period of inactivity.
Take in consideration that if your trying to raise the timeout value in a shared hosting environment you will fail as they block you from this by set that value in the machine.config file and hat takes precedent, you will need to use SQL Session 's for that and you will be free to change that timeout time as you please.
They also normally restart the AppPool every often to unblock any malicious or bad code that could block other websites, and every time the AppPool restart, here goes all your sessions (not if you use SQL Sessions instead, of course)...
In the other hand, if your hosting the web application yourself, aside of the size in memory (remember that Im assuming that you are saying user sessions and as the name says, are per user, per application you would use Application Sessions). If you consider this memory increase, nothing, not even performance would be diminish.
Intro
I am developing a web application using ASP.NET MVC 3, C#, targeting IIS 7.0+. We have a number of long-running async requests (utilizing AsyncController/Async action features). I also use HttpRuntime.Cache quite often (and in some non-standard way which doesn't really matter here).
Question
Can IIS application pool be suddenly recycled if there are active long-running requests present? I want to prevent that behavior if possible as I don't want to lose data from cache.
Do I really need to use some persistent storage (i.e. Database) to overcome possible issues?
Normally IIS won't recycle an application which has pending requests for it due to period of inactivity. But IIS could recycle your application if you hit memory or CPU tresholds. But this is something that you could configure in your IIS management console.
When a recycle is triggered there is a "shutdown time limit" that defaults to 90 seconds. That's how long processes have to finish before they will be shutdown forcibly. This is configurable through IIS, you likely want to increase this to a large value in addition to removing non-desired recycle triggers (memory, CPU, time, schedule, requests, etc.)
I have a website hosted under IIS 7 on Window 2008 x64. IIS is running in 64 bit mode and the site has its own Application Pool 64 bit etc. The website appears to run fine most of the time and then all of a sudden each hour it freezes the users request. They don't get a timeout message, it just hangs and appears to wait for about 2-3 minutes before returning the page.
I have monitored the Worker Process on that application pool during and see the processor is at a very steady 25%. Memory is fine and not increasing in any scary way.
I have setup Failed Request Tracing to show me every issue where a request takes more than 30 seconds and yes it records it but with no errors.
Other websites in different application pools on the same server are working fine during the outage.
Any suggestion of how I might debug this issue?
Do you have IIS set to recycle worker processes on that application pool on a given schedule? You indicate you monitored it, but you didn't indicate whether or not you found it to be recycling excessively, just that the memory allocated wasn't increasing in an untoward way.
Do the IIS logs show anything unusual during the time period? Try an app like Fiddler to help debug requests to the web server.
Turn out we were using a control called i-Load to resize images. It has a function to delete temp files after 3 hours. This was locking the IO and causing out entire web-app to halt. Switch it off and all work fine now. Hope this helps someone.
Does the Application depend on a Database that has some Job running every hour?
In case the DB is under heavy load, it would take longer for the queries to execute on your DB and therefor take longer for your web-app to process the pages.
Yes IO process can block the application pool pending thread once not completed other one. So create another thread of IO process and proper handle the cancel token source.