I have recently rolled out a new ASP .Net application. This application uses .Net 4.0 and the Entity Framework 4. It is a "basic" CRUD application. I almost exclusively used the EntityDataSource for Data Access.
The users have reported "ocassional freezing" of the application (they all use IE 8). If the user closes his browser and starts back up, the app is fine. It happens maybe once or twice per day total, usually to the heavy users. (So, I have been leaning toward memory leack or some other kind of resource limitation.)
Until just a little while ago, I have never seen this happen. It dosn't leave anything in the Event Log on the client PC nor Server. Also, there is nothing in the IIS error logs or the SQL logs.
A little while ago, I finally got it to happen. I was switching all of my EntityDataSources to use a single Object Context per page. I downloaded the EF Profiler (which seems to be a great product) and it pointed out that I am using multiple object contexts on many of my pages, due to the fact that many of them have more than one EntityDataSource. So, I was cleaning all this up and testing each page, when lo and behold....IE stopped loading pages!
At first, the page started loading slowly (and this was a page that I had already modified to use a single Object Context, so although I still believe I need to implement this "singleton" pattern throughout all my pages, I guess it isn't the culprit! Anyway..), then at some point I received:
Message: Sys.WebForms.PageRequestManagerTimeoutException: The server request timed out.
Still, nothing in the Event Log. I also checked the IIS web logs and I don't see anything, but they are pretty tough to read with the naked eye, I may have to download a parser to make sure there is nothing in there.
Anyway, I decided to start up another window and navigate to my app, and sure enough that window worked fine, no problems. I went back to the windows that stopped responding, refreshed it, waited... went to the home page of my app (which is basically just some static html.. and nothing.. ). Next, I opened a new tab in the window that is currently frozen and that tab works fine. So, I go back to the window that can no longer load pages from my app and try some other web sites.... espn.com loads fine, msn.com loads fine, I then enter the URL for my app home page (and tried some other pages in my app) and NOTHING. IIS doesn't even log the attempts in its Log Files (its like IE has just decided not to do anymore "gets" for my localhost!). Finally, after waiting for a while (while I was typing this post) I now have this error message in that window:
Internet Explorer cannot display the webpage. What you can try: The problem can be caused by a variety of issues, including: BLAH BLAH BLAH...
So, I jump back to that window and it can still browse Internet sites just fine. But, once again when I try to go to any of the pages in my app, I get NOTHING (spinning blue circle in the tab). So, once again I start a new tab in that same browser and I can browse around my application just fine.
What has my app done to this browser instance that will no longer let it load any of its pages (in fact, it seems like it isn't even doing a GET on any of the apps pages, since there is nothing new in the IIS logs...except for when I load the pages in these other tabs and/or browser windows that work fine, so the logging is still working...)? I will be forever indebted to the person that can help me figure this out. I am not sure it will do much good, but I am going to leave this browser window up on the chance that someone can tell me some things to try to diagnose this problem. It feel like I am THIS close to figuring it out. I finally have a window up that is misbehaving. I am afraid to close the window or do a new build on the app until I get some good input on things to try....
I should add that when this happened to me, I was running on my local PC, so I was the only user and only had one window open to the app..
Although, I am completely stumped!
We had the same issue and seemed to fix it by adding the following JavaScript to all pages with ajax:
window.onunload = abortRequest;
function abortRequest() {
Sys.WebForms.PageRequestManager.getInstance().abortPostBack();
}
I hope this helps!
sounds like a request just takes too long to execute. A web-browser is only allowed to keep two concurrent connections to a single webserver unless you utilize http pipelining (which isn't well supported anyway). However, My experience is that this is per browser, not per tab.
This is why nothing shows up in your logs, because your browser never initiate a request because it is waiting for the page to finish loading before it can fetch another page. I would start looking into the last request initiated before the lockup, it is probably that page that locks for some reason and never finishes.
ASP.NET utilizes only one thread as long as all request are sequential. As soon as you fire up two request simultaneously, a new thread is initiated (Init() on HttpApplication is invoked), and that can cause intermittent errors if you do funky stuff on Init().
If you think this is related to EF, you might read up on how to avoid locking in multi-threaded environment (because a web application is very much multi-threaded however this usually kicks in a production environment).
Ugh, I feel your pain - I hate these types of issues. Here's my divide-n-conquer process when something like this is happening (adapted somewhat to your case):
Step 1 - Environment Visibility
Get yourself set up so you can roughly see inside your systems. Set up Performance Monitor, and add a couple of important counters (IIS Current Requests, ASP.NET Current Requests, SQL Server - Active Transactions). The idea here with the "active requests/transactions" counters is you want to find out which part of the system is holding on to the request.
Additionally, add counters for total request time in IIS and the DB (so you can see it climbing as something is hanging on).
On your client PC, set up Fiddler.
Step 2 - Reproduce Issue
Usually at this point, the application realizes you can see it and starts behaving perfectly. ;) Stop and make sure you can still reproduce the issue.
Step 3 - Take the DB out of the equation
Create 4 pages in your application:
Static HTML file (.htm) that will NOT go through the ASP.NET runtime engine. This is your baseline for raw IIS.
ASPX page with no tricks (no database access, no processing, just a simple page that ASP.NET can spit out)
ASPX page with one simple database call (of some size, maybe do a single big query or something)
ASPX page with some complex transactions (multiple queries, etc)
Step 4 - Reproduce and measure
Since this issue will probably be pretty obvious once you can see it, find the bottleneck with your performance counters and Fiddler. Your issue sounds like you could have an intermittent connectivity issue (either between client and web server or web server/SQL), especially if IE is giving you the "page cannot be displayed" error, but you should see that in Fiddler. On the server side, you should see one of those performance counters hanging.
well, sounds like the app is waiting for a database operation to complete but is locked, probably because of another operation.
Try using the SQL profiler to trace the activity, and isolate what processes are running for a long time.
You can differentiate the requests using the SPID column in the trace view, it contains a unique ID number for each session from your App.
I have new information regarding this issue.
The application uses Integrated Authentication. This causes every reqest to come back (twice) with access denied, before IE send the credentials.
I can't help but wonder if this is what could be causing the "time outs".
I implemented an Ajax "Loading" animation on every page that prevents the user from clicking a button until the previous request is completed and that has GREATLY diminished the amount of "freezes" the users are experiencing.
Although, it still happens somewhat often.
Related
I have a very strange situation here with CEF Sharp x86 (67 with latest cef.redist 3.3497.1841), but originally reported with v49. It's very crazy, so I'm just looking, maybe somebody have stumbled upon anything similar. We host WPF ChromiumWebBrowser inside WinForms UserControl (via ElementHost) and it's running inside 3rd party application, with which it does not interact in any way (so it's a plugin to this host application). For about 100 or so users everything is ok, but for a single person this happens: webpage loads and displays correctly, but the ChromiumWebBrowser.IsBrowserInitialized flag is always false.
Now, by 'user' I don't mean Windows account, just a user in totally unrelated 3rd party application, logging-in against 3rd party userid/password verification - unrelated to any windows settings. So as crazy as it sounds we've tried it on multiple computers on multiple windows accounts, using different user ids for the application, and the result is still the same - for this one userid there is a problem, for others - all ok.
I wonder if anyone has had such crazy experience with CEF. I'm betting on some bug in .NET layer, as the actual browser works fine - webpage is rendered, you can browse normally. Also this has sth to do with CEF run as plugin to this exact 3rd party app - if I run a test winform app with same setup - user control -> element host -> WPF ChromiumWebBrowser, all is ok. CEF log is not much help, no errors other than in OK situation.
I'm not attaching any code or logs, I don't think it'd be helpful in this case. Just for more background the plugin has been around for almost 3 years with not a single bug reported, except this case. Just to make it clear - I need this flag to be true to be able to inject JS calls into the plugin.
Ok, so it turned out to be a case of opening 2 instances of browser within single process. One browser window was initializing and working fine, second was was displaying page, but reporting 'not initialized'. It became clear only when I went to customer and actually saw the scenario, because they did not report that they opened 2nd instance. I this case, they don't need 2nd instance, so that was the fix, maybe there is an error I our code, I'll follow up this issue once we do more through analysis.
Is there one kind soul out there who has the time to help me figure out why my application is intermittently hanging (and hopefully how to fix it)? I'm running a web program from VS2015 that accesses a SQL Server database. Sometimes I'll click on a link on my webpage and everything works fine. Other times, though, the little circle just spins forever, and it never comes back. It doesn't seem to be related to the database because one time I caught it hanging on a call to XmlSerializer serializer = new XmlSerializer(type);
I'm running the website in IIS Express on localhost on a Windows 10 laptop (16GB & plenty of disk). I also have ReSharper if anyone thinks that can help me diagnose the problem. I've been fighting with this for days and have no idea what else to do but hope that someone here will have pity on me.
Re: D Stanley's comments: "Do you have any logging? Can you run it in the debugger to see where it's hanging? Is there anything in the system event logs?"
There is logging, but only on caught exceptions. Nothing that will help the hang situation. I can run it in the debugger, but when it's hung I can't see where it's hung (it's in External Code). The Event Log does report a "perflib" error when I run the program. I can post that info if you think it would help.
More info. I installed Fiddler. When the application is hung, Fiddler is still going to town. The "Process" it's showing is "scriptedsandbox64", which is doing I/O and consuming CPU time.
I suggest you add lots more log messages to your code, something like:
DateTime.Now.ToString("o") "Starting xxx"
DateTime.Now.ToString("o") "Finished xxx"
where xxx is a name for some chunk of code. You suspect the problem is in external code, so wrap all those calls.
You can then see where the application spends excessive time. Once you have found the right area, then perhaps add more logging to focus in on the problem.
The answer to my hanging problem was to use Local IIS instead of IIS Express. Once I figured out how to set up the website for localhost and began running with Local IIS my hangs disappeared.
I want to monitor changes in background in complex web application. This is one-page application with many scripts and so on. I need to be logged in to have access to data I want to monitor.
I tried to use webrequest, but I think that the application is to complex to do it that way. There is also a problem with authentication.
I also tried WebBrowser component, but web application is telling me, that this browser is too old and I should get newer one.
Perfect solution would:
Open this web application in chrome (or some other modern browser) in background
Save the page to memory
Extract values using something like HtmlAgilityPack
While this will be happening I want to normally use the computer (so opening chrome window is not a good solution for me).
Is there any way to achieve something like that?
if you can cope with an extra browser running, have a look at SeleniumHQ. with its webdriver-backed selenium you can start a dedicated browser instance and perform user actions by coding in high-level programming languages like java. it should not interfere your manual work at all, but will take up the same amount of memory and cpu time your "real" browser would.
if the web application has no captcha and does not object to automated script accessing it, you could also login in a background program by sending appropriate HTTP requests and parse the response. python's urllib2 would be my first choice.
if you dont want any additional processes running, you could also create a browser plugin, that autorefreshs and parses a certain open tab every few seconds.
So I've been trying to figure out why the application pool keeps crashing every now and then, and I've pinpointed the page that is cau seems to be causing the issue.
When I open the site in the browser, and visit the Shipping cart page (after adding stuff to the cart), the entire browser becomes unresponsive, and I open Task Manager, and see that IE (browser) is using 99% CPU, so I right-click > Create DUMP > Try to read DUMP but WinDBG does not seem to like DMP files; won't read them.
So I move on, and try to figure it out without the dump files. I fire up Visual Studio, open the site in question, and then follow the same process (add stuff to cart, then visit cart page). And to my surprise, everything is OK.
Not sure what to do now. Any suggestions? How would you determine the cause of the hanging, when everything runs perfectly, locally - and when everything used to run perfectly online, but no longer runs fine online?
If the browser becomes unresponsive and eats 99% CPU, that's a client side problem; it most likely doesn't have anything to do with IIS or your server side code.
Could it be that you have some javascript in your page is buggy and goes into a busy loop? I think it's worth a shot to test this (use either IE's developer tools (F12), Visual Studio's javascript debugging functionality, or FireFox in combination with FireBug).
Edit
It strikes me as odd that your AppPool crashes, and in doing so, causes the web browser to turn non-responsive. With non-responsive, do you really mean that the browser itself stops working (i.e. navigating a page back or going to another url such as google.com is impossible?)
Anyway, if you think the problems occur on the server-side, you could try the following things (in order of increasing effort):
After an AppPool crash, check the windows event log (run 'eventvwr' from a command prompt) and see what information that gives you.
View the IIS log (you might have to turn it on first), see if it contains any weird request patterns, such as your page getting hammered)
Run your website from IIS, but attach a debugger from Visual Studio (under Tools, Attach to process - include only managed code) to the IIS worker process (usually w3wp.exe). If your page throws an exception, VS should be able to catch it.
Add more tracing to your page, the Global.asax's Application_Error seems like a particularly good candidate.
I wrote a webcrawler which calls a web page in a do while loop amount 3 seconds
totally there are 7000 sites... i parse the data and save it in my DB.
sometimes because the script is loading for a long time, i got a timeout in browser,
but in background i continues. I see that on my database.
Can I prevent this?.. Now it's just possible if I stop webserver.
Thank you and best regards.
Your web page is kicking off a server-side process. Killing your browser or closing it is not going to stop this. It sounds to me like a web page to control this is the wrong approach, and you should be looking at a connected form of application like a WinForms/WPF app. There would be ways to get this to work with ASP.NET, but they are not going to be simple. I think you have just chosen the wrong technology.
Starting an intensive, long running process like this from a web page is almost never a good idea. There are lots of reasons, but the main ones are :
1) If you get a timeout in the browser (this is your scenario) the data you have harvested may not be displayed.
2) What happens if you hit refresh in the browser? Will it attepmt to start the whole process again? this is an easy target for an attacker, if he wants to tie up all your server resources.
3) Is the data you are crawling really likely to change to such an extent that you need "live" crawling? 99% of cases would be served just as well with a background timed job running the crawl, and your front end just displaying the contents of the database.
I would seriously recommend you rethink your crawling strategy to something more controllable and stable.