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I was wondering if someone has a clue of what is happening here, and could point me in the right direction.

Ok ..lets put the code in context.

I have ajax methods (jquery) like this:

$xmlHttp("/Api/GetWaitingMessages", { count: 20 })
    .always(processResult);

($xmlHttp simply wraps a jQuery defered, and some basic $ajax options)

And in our healthmonitoring back-office i see things like this:

Exception information:
Exception type: System.ArgumentException
Exception message: The parameters dictionary contains a null entry for parameter 'count' of non-nullable type 'System.Int32' for method 'System.Web.Mvc.ActionResult GetWaitingMessages(Int32)' in 'AjaxController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter.
Parameter name: parameters

Now the thing is, i placed some traces & try/catches (for testing) to make sure that jQuery never calls GetWaitingMessages with an empty or undefined "count", but as far as the healthmonitoring exeptions go: GetWaitingMessages was instantiated and passed null as a parameter. (from what i understand, MVC instantiates methods via reflection)

btw: the error only happens like maybe 1 out of many thousands of requests

The signature of GetWaitingMessages is:

public virtual ActionResult GetWaitingMessages(int count)
{
    ....
}

So i suppose, mvc shouldn't even hit the method since there should be no signature match..

Does MVC have problems with high traffic websites (ie. multi-threading problems) ?

The site mentioned above is running on a cluster of 5 web-farm servers with Network Load Balancing and IP affinity.

Each server gets around 1500 request/sec at peak times.

The site is using url rewriting to map domains to areas (ie test.com will simply insert /test into the url) since it's a skinable & multilingual white label site.

Some more details on site configuration:

The controller that serves ajax requests is decorated with

[SessionState(SessionStateBehavior.Disabled)]

HttpModules that where considered useless where removed since we need to run: runAllManagedModulesForAllRequests="true" in MVC. I could have set runAllManagedModulesForAllRequests="false", and then try to figure out what to add, in which order, but found it simpler to just remove what i know is not essential.

<remove name="AnonymousIdentification" />
<remove name="Profile" />
<remove name="WindowsAuthentication" />
<remove name="UrlMappingsModule" />
<remove name="FileAuthorization" />
<remove name="RoleManager" />
<remove name="Session" />
<remove name="UrlAuthorization" />
<remove name="ScriptModule-4.0" />
<remove name="FormsAuthentication" />

The following are all activated and configured in the web.config

<pages validateRequest="false" enableEventValidation="false" enableViewStateMac="true" clientIDMode="Static">   

and also:
urlCompression
staticContent
caching
outputCache

EDIT : just analyzed my trace logs a bit more. When the error occurs, i see (Content-Length: 8), which corresponds to (count=20). However i do not see any query parameters in the logs. I dumped the HttpInputStream to the logs, and it's completely empty ..but like i just mentioned, the logs also say that Content-Length = 8, so something is very wrong here.

Could IIS (eventually url rewriting) be mixing up it's stuff somewhere along the way ?

-

Any help would be greatly appreciated ..i'm ripping my hair out trying to understand what could possibly be going wrong here.

Thanks, Robert

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3
  • Commenting here since that Q was deleted: "I'm sure i didn't misread it (not that i agree) ..also can't find the link. But if you search google "async 50ms"" -- right, if you google for "async 50ms" you will find bunch of threads about Async/Await and 50ms, which has nothing to do with multithread programming :-) "The async and await keywords don't cause additional threads to be created" (c) msdn.microsoft.com/en-us/library/vstudio/… Commented Jul 8, 2013 at 4:43
  • When using async/await you are logically using functions with a return type of Task/Task<type>, which are creating threads. So while the keywords don't mean multi-threading themselves, they can only be used in a mutli-threading context anyways (Task<>). Commented Jul 8, 2013 at 14:20
  • Sorry for being insistant, but i haven't seen a async/await combo yet that doesn't await a Task<> Commented Jul 8, 2013 at 14:23

3 Answers 3

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0

What type of a request does your xmlHttp issues to a server (GET, POST or something else)?

What is the definition of GetWaitingMessages action method?

It might very well be the case of mismatching accepted verbs or argument names.

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2 Comments

All ajax request are POST, and the server variables in the healthmonitoring trace show that the request for the failed method was in POST too, so that seems fine.
What i did try, is to put an if on the ajax requests, to make sure that no request leaves if count != 20, however the request does go, so i assume count=20, yet the error will still occur. So i assume the error must be on the server-side. GetWaitingMessages() was just one example of many other methods impacted by this behavior :(
0

I have a feeling that this could be a problem with MVC not being able to bind to your 'count' parameter. By default, it expects the parameter to be named 'id'.

You can try the following:

  1. Modify your GetWaitingMessages action to define it with a parameter called 'id' instead of 'count'
  2. Create a custom model binding as described in the accepted answer to the stackoverflow question at asp.net mvc routing id parameter

Hope this helps

EDIT: Just saw your reply to another answer stating that the action is a POST. In which case, binding may not be an issue.

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1 Comment

The problem does not happen systematically, but more like 1 out of who knows how many thousands of requests.. But yeah, and thanks, i will see if this changes anything !
0

Just for testing try this to see if there is any problem .

public virtual ActionResult GetWaitingMessages(FormCollection form)
{
  var count=Int32.Parse(form["count"]);

  ....
}

Of course it will throw if the count field isn't set. If it always works correctly then the problem is with routing or model binding.

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9 Comments

Put the test online just after seeing your reply, and got my first couple of errors. Whats weird is that my trace shows "Content-Length: 8", which corresponds perfectly with form parameters (count=20). Do you think its likely or very improbable that url rewriting might be playing funny tricks here ? Thanks
Are you using IIS 7+? I prefer to handle url rewriting in the application. Currently I'm developing a multitenant skinable application and I've implemented my own url rewriting to map the a request to a common route format "tenant/controller/action'. It was a very tricky piece of code, but so far in my tests it works ok (however it isn't tested in a real highly concurrent situation yet)
yes, we are on 2008 r2 (i added some config settings to my 1st post). Our old site was using custom rewriting and ajaxPro (but it had similar errors where ajaxPro was instantiating methods with null parameters). I just got done rewriting everything to work with MVC to be able to take advantage of the inheritance we get with areas and shared folders (for skins), native serialization offered by mvc controllers (ajax), model binding/validation, and all the other goodies of course.
Try another stuff. When count seems to be missing log everything about the request. If jquery sends everyting right and asp.net doesn't receive the actually params, I suspect some filtering is going on, perhaps a problem with the load balancer?!
I do log everything, this is the result: 1) GetWaitingMessages was called with null. 2) Content-Length: 8, shows up in the log. Which corresponds perfectly with the parameter normally passed to GetWaitingMessages: -> count=20. And when i dump the parameters actually passed to GetWaitingMessages, i get count=null. So i'm kinda lost.. :)
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