I get this message too often and think that it is not usual, how i can fix this issue?
A worker process with process id of '8052' serving application pool 'mywebsite.com' has requested a recycle because it reached its private
bytes memory limit.
Hi this is not an expire because of a timeout, it's an application pool recycle due to memory limit. Usually very bad.
if you have full control of your ASP.NET application I suggest you profile it carefully and detect where you are allocating and not releasing / disposing a lot of memory.
It might help to understand what are the common use cases users are going through more often and start investigating those.
Are you loading a lot of byte[] in memory for file downloads?
are yoou keeping too many references in the Session?
once we had a similar problem and we found out only after several weeks that we were storing a reference to pages in the Session so all visited pages were kept in memory all the times. Not easy to find but once we corrected this the problem was solved.
You probably have a memory leak. There are many possible causes, possibly session or request instances registered with static events. Operations that are trying to load too much data into memory, session timeouts set too long etc.
You need to do some profiling to identify the cause.
Of course its also possible you just don't enough memory for the number of users and need to scale, but it's highly unlikely unless you have a lot of traffic.
Maybe your application use a lot of memory? Regarding to this post you have reached allowed memory size for application and IIS restarts the application pool.
Related
I have a web application that uses ASP.NET with "InProc" session handling. Normally, everything works fine, but a few hundred requests each day take significantly longer to run than normal. In the IIS logs, I can see that these pages (which usually require 2-5 seconds to run) are running for 20+ seconds.
I enabled Failed Request Tracing in Verbose mode, and found that the delay is happening in the AspNetSessionData section. In the example shown below, there was a 39-second gap between AspNetSessionDataBegin and AspNetSessionDataEnd.
I'm not sure what to do next. I can't find any reason for this delay, and I can't find any more logging features that could be enabled to tell me what's happening here. Does anyone know why this is happening, or have any suggestions for additional steps I can take to find the problem?
My app usually stores 1-5MB in session for each user, mostly cached data for searches. The server has plenty of available memory, and only runs about 50 users.
It could be caused by lock contention for the session state. Take a look at the last paragraph of MSDN's ASP.NET Session State Overview. See also K. Scott Allen's helpful post on this subject.
If a page is annotated with EnableSessionState="True" (or inherits the web.config default), then all requests for that page will acquire a write lock on the session state. All other requests that use session state -- even if they do not acquire a write lock -- are blocked until that request finishes.
If a page is annotated with EnableSessionState="ReadOnly", then the page will not acquire a write lock and so will not block other requests. (Though it may be blocked by another request holding the write lock.)
To eliminate this lock contention, you may want to implement your own [finer grained] locking around the HttpContext.Cache object or static WeakReferences. The latter is probably more efficient. (See pp. 118-122 of Ultra-Fast ASP.NET by Richard Kiessig.)
There is chance your are running up against the maximum amount of memory that Application Pool is allowed to consume, which causes a restart of the Application Pool (which would account for the delay you are seeing in accessing the session). The amount of memory on the server doesn't impact the amount of memory ASP.NET can use, this is controlled in the machine.config in the memoryLimit property and in IIS 6.0 later in IIS itself using the "Maximum memory used" property. Beyond that, have you considered alternatives to each user using 5 MB of session memory? This will not scale well at all and can cause a lot of issues while under load. Might caching be a more effective solution? Do the searches take so long that you need to do this, could the SQL/Database Setup be optimized to speed up your queries?
I have a number of ASP.NET (4.0) web applications that appear to leak (a small amount) of memory during each request. It is such a small amount, that for most use-cases, it will not grow to become a problem for weeks or even months at a time. I generally try to be good with closing any connections managed by the application, avoiding state-variables (or instance variables for my singleton), etc.
My question is this - is this normal behavior for ASP.NET applications? I had turned off the default (IIS 7) behavior of recycling the app pool after 20 minutes of being idle. I do this since the application takes a few minutes to build its internal cache, and I want to avoid negatively impacting the user experience (and having them wait for the application to start when they issue the request).
I am aware this could be mitigated by serializing the cache or speeding up the cache generation process but my question has more to do with the principle of it: I personally consider relying on the IIS auto-recycle feature as a bandaid approach. Am I wrong? am I just not seeing the garbage collector at work because the application's memory usage is not high enough compared to the amount of available memory? or should I dig deeper into the memory issues?
Any insight would be appreciated.
Unfortunately it is normal, though mostly dues to shoddy application writers than anything else.
IIS by default configures newly created application pools to recycle every 1740 minutes for this reason.
As you said, this is a band-aid. A well written application that clears up all of its resources (including dangling event handlers), shouldn't leak at all.
See this blog post about the subject.
When adding items using the default insert method Insert(key, value) and as such using the default behavior of HttpRuntime.Cache, when does the scavenging take place?
The limit on the application pool that hosts my application is 0 (unlimited)... but I see no way to find out how big the cache can get before scavenging occurs? The problem is I am caching a potentially very large amount of data but I have limited memory on the server and I want to avoid recycling of the app pool.
I am asking in the context of IIS6 and IIS7.
Thank you.
The short answer is that the cache begins to scavenge at Cache.EffectivePrivateBytesLimit.
The default limit is calculated using a number of factors, and generally should keep your process from excessive recycling. Ideally an application won't be affected by a recycle, but I realize there are many reasons why that isn't always possible. If needed, you should be able to set memory limits for the cache in coordination with the app pool recycle settings.
Thomas Marquardt from the asp.net team wrote a very interesting post explaining the details.
Lets say that you are using a shared hosting plan and your application stores lots of objects
in the application state.
If they start taking too much memory does this mean that the server will just remove them?
If not what will happen then? What happens when the server has no memory left? Can you still store objects into the application or session state?
I am asking this because i am planning on developing a big site that will rely on the application state, and it will be crucial that the objects stored there don't get destroyed.
What i am afraid of is that at a certain point i might have too many objects in the application state and they might get removed to free up memory.
There are three different thresholds:
The total size of your app exceeds the maximum process size on your machine (really only applicable with an x86 OS). In that case, you'll start getting out of memory errors at first, generally followed very quickly by a process crash.
Your process, along with everything else running on the machine, no longer fits in physical memory. In that case, the machine will start to page, generally resulting in extremely poor performance.
Your process exceeds the memory limit imposed by IIS on itself, via IIS Manager. In that case, the process will be killed and restarted, as with a regular AppPool recycle.
With the Application object, entries are not automatically removed if you approach any of the above thresholds. With the Cache object, they can be removed, depending on the priority you assign.
As others have said, over-using the Application object isn't generally a good idea, because it's not scalable. If you were ever to add a second load-balanced server, keeping the info in sync from one server to another becomes very challenging, among other things.
What happens when any application takes up too much memory on a computer?
It causes the server to run everything really slowly. Even the other sites that share the computer.
It's not a good idea to store that much in application state. Use your config file and/or the database.
It sounds like you have a memory leak, the process keeps leaking memory until it crushes with an out-of-memory condition and is then automatically restarted by the server.
1.5GB is about the maximum amount of memory a 32 bit process can allocate before running out of address space.
Somethings to look for:
Do you do your own caching? when are
items removed from the cache?
Is there somewhere data is added to a
collection every once in a while but
never removed?
Do you call Dispose on every object
that implements IDisposable?
Do you access any non-managed code at
all (COM objects or using DllImport)
or allocate non-managed memory (using
the Marshal class for example)?
anything that is allocated there is
never freed by the garbage collector,
you have to free it yourself.
Do you use 3rd party libraries or any
code from 3rd parties? it can have
any of the problems in the list too.
If you use the Cache object instead of the Application object, you can minimize problems of running out of memory. If the memory utilization of the ASP.Net worker process approaches the point at which the process will be bounced automatically (the recycle limit), the memory in Cache will be scavenged. Items that haven't been used for a while are removed first, potentially preventing the process from recycling. If the data is stored in Application, ASP.Net can do nothing to prevent the process from recycling, and all app state will be lost.
However, you do need to have a way of repopulating the Cache object. You could do that by persisting the cached data in a database, as others have proposed.
Here's a short article with a good code example for handling Cache.
And here's a video of how to use Cache.
Anything stored in application state should be refreshable, and needs to be saved in current status in files or database. If nothing else happens, IIS restarts worker processes at least once a day, so nothing in application state will be there forever.
If you do run out of memory, you'll probably get an out of memory exception. You can also monitor memory usage, but in a shared host environment, that may not be enough information to avoid problems. And you may get the worker process recycled as an "involuntary" fix.
When you say that it's crucial that objects stored in application state don't get destroyed, it sounds like you're setting yourself up for trouble.
I think you should use session instead of the application sate and stored that session into sql server database. So once your application user end its session that will release your memory.
If you want more specific answer then please provide the more information about your application.
My first time really getting into caching with .NET so wanted to run a couple of scenarios by you.
Question 1: Many expensive objects
I've got some small objects (simple int/string properties) which are pretty expensive to instantiate. These are user statistic objects which each user may have 1 - 10 of. Is it good or bad practice to fill up the cache with these fellas?
Question 2: Few cheap regularly used objects
Also got a few objects (again small) which are used many times on every page load. Is the cache designed to be accessed so regularly?
Fanks!
stackoverflow: Cracking question suggestion tool btw.
1) I would cache them. You can always set CacheItemPriority.Low if you are worrying about the cache 'filling up'
2) Yes the cache is designed to be accessed regularly. It can lead to huge performance improvements.
The answer to both of your questions is to cache them aggressively if you can.
Objects that are expensive to instantiate yet relatively static (that is unchanging) throughout the application's life ought to be cached. Even relatively inexpensive objects should be cached if you can improve performance by doing so.
You may find yourself running into problems when you need to invalidate the cache when any of these objects become stale or obsolete. Cache invalidation can be a difficult problem especially in a multi-server environment.
I don't think there is any problem with hitting the cache too frequently...
Overall asp.net Caching is fairly intelligent int terms of deciding what to keep and generally managing space. As a rule though I wouldn't depend on the cache to store information, only use it as an alternative to hitting disk or DB. User objects may be better served by session state.
https://web.archive.org/web/20211020111559/https://aspnet.4guysfromrolla.com/articles/100902-1.aspx
is a great article explaining the built in capabilities of .net caching.
Let's address the question in your title - when caching is too much.
It's too much if you are putting so much in the cache that it is pushing other things away. If the web sites on the server in total is using more memory than there is physical memory, they will push each other out into the virtual memory that is stored on disk. That will practically mean that you are caching some of the objects on disk instead of in memory, which is a lot slower.
It's too much if you are putting so many objects in the cache that they push each other out, so that you rarely get to use any of the objects in the cache before they go away.
So, generally you can cache a lot before you reach the limit where there is no point in putting anything more in the cache.
When determine what's most benificial to cache, consider where the bottle necks are. If you for example have a database server with a lot more capacity than the web server, caching the database results doesn't save so much resources. Getting data from the database takes time, but it doesn't use much resources on the web server while waiting for it, so it will not affect the throughput much.