Why does my new .Net 4.0 EF application randomly lock up?_问答_开发者

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 开发者_运维技巧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.