IIS - 503 service unavailable error - Asked By nishant gautam on 02-Feb-10 02:38 PM

I am on a shared hosting service. These days I am getting 503 error quite frequently. I am not able to know the exact reason. how could I Know the exact reason why it is happening?

I know about rapid fail protection which cause application pool to shut down for a particular number of error in a fixed time. but what type of error these can be for example these are not html errors obviously, not complilation error, then what type of errors/failures can cause application pool shutdown.
I have installed blog on my site and generaly when i view blog pages I get 503 error so what type of error/failure we could think of which can cause application pool to shutdown....

Application pool 'schoolsearch.in v2.0 (Classic)' exceeded its job limit settings.

could you tell me how it could exceed job limit settings...? does this mean something in code is eating up too much resources..??

i have  a java script which runs continuously on home page of my site. except that I dont have anything which runs after every few minutes...

I am using global.asax file in which I am using

  Private Const DummyPageUrl As String = "http://www.schoolsearch.in/hiturl.aspx"
    'Private Const CONNECTION_STRING As String = "Data Source=(local);Initial Catalog=tempdb;Integrated Security=SSPI;"
    Private Const LOG_FILE As String = "c:\temp\Cachecallback.txt"
    Private Const MSMQ_NAME As String = ".\private$\ASPNETService"
    Private Const DummyCacheItemKey As String = "GagaGuguGigi"
    Private Const DummyCacheItemKey2 As String = "huhuhuhhuhu"

    Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("con").ToString)
    Public Shared _JobQueue As New ArrayList()

    ''' <summary>
    ''' Required designer variable.
    ''' </summary>
    Private components As System.ComponentModel.IContainer = Nothing

    'Public Sub New()
    '    InitializeComponent()
    'End Sub
   
   
    Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
        ' Code that runs on application startup
        RegisterCacheEntry()
    End Sub
   
    ''' <summary>
    ''' Register a cache entry which expires in 1 minute and gives us a callback.
    ''' </summary>
    ''' <returns></returns>
    Private Sub RegisterCacheEntry()
        ' Prevent duplicate key addition
        If HttpContext.Current.Cache(DummyCacheItemKey) IsNot Nothing Then
            Exit Sub
        End If
           
        HttpContext.Current.Cache.Add(DummyCacheItemKey, "Test", Nothing, DateTime.MaxValue, TimeSpan.FromDays(1), CacheItemPriority.NotRemovable, _
         New CacheItemRemovedCallback(AddressOf CacheItemRemovedCallback))
        
         'HttpContext.Current.Cache.Add(DummyCacheItemKey2, "Test", Nothing, DateTime.MaxValue, TimeSpan.FromMinutes(10), CacheItemPriority.NotRemovable, _
         'New CacheItemRemovedCallback(AddressOf CacheItemRemovedCallback2))
    End Sub
        
         'Public Sub CacheItemRemovedCallback2(ByVal key As String, ByVal value As Object, ByVal reason As CacheItemRemovedReason)
         '       System.Diagnostics.Debug.WriteLine("Cache item callback2: " & DateTime.Now.ToString())
         '       hitpage()
         'End Sub


 I have commented all these and even deleted global.asax file . could that be a reason

Amount of data stored in the data Cache could also be a reason, if I am not wrong. Did you try running it after commenting the caching part?

The whole  cache part is already commented....

 have a quick question regarding variables.

Q-1)All variables which I create in a VB file (even public variables , all datasets ) gets destroyed and cleared after page is executed (means page is displayed)  ????

Q-2)variable inside function gets destroyed once function is complete so I dont need to worry but what about public variable which I declare in class scope (so that I can use them in .aspx also) do they also get destroyed once page execution is complete.??

Q-3) while executing any page suppose I am retrieving some data from backend and storing in dataset, could that data be so large that memory threshold gets crossed and application pool gets shutdown..?but in this case 503 error should come only on a  


I am trying dotnet profiler also to keep a track of memory usage. I am running same code on my local machine with dotnet profiler.
live instance and live memory usage remains same but total instances and total memory usage keeps increasing.

some statisctics- when I go from page1 to page2  again to page1 then to page2 and the to page1

                                          page1        page2               page1            page2                page1
total instance                    62,976        84,421              84,316            82,185,               86,720
live instance                      61,620        74,314              75,545            74,845                76,126
Total memory(bytes)        4,096,751    5,829,198        8,183,464        6,300,569        7,512,323
live memory(bytes)           3,705,235    4,437,829        4,871,300        4,478,517        4,603,951

earlier I was using       
 Response.Cache.SetExpires(DateTime.Now.AddDays(1))
 in page 2(statistics are posted after removing this line)