Christian Geuer-Pollmann https://docs.microsoft.com/archive/blogs/chgeuer/feed.xml Tue, 16 Apr 2019 04:52:23 GMT en-US hourly 1 Avoiding unhealthy roles when configuring IIS with the ServerManager in the local Azure development fabric https://docs.microsoft.com/archive/blogs/chgeuer/avoiding-unhealthy-roles-when-configuring-iis-with-the-servermanager-in-the-local-azure-development-fabric Tue, 27 Sep 2011 13:11:05 GMT https://blogs.msdn.microsoft.com/chgeuer/2011/09/27/avoiding-unhealthy-roles-when-configuring-iis-with-the-servermanager-in-the-local-azure-development-fabric/ 10-second summary

In your Azure start-up code, you use the ServerManager class to modify your IIS settings. Some of your web role instances in the development fabric don’t come up and stay ‘unhealthy’. This article describes a possible cure for that.

Problem

In this article, I describe a solution to the problem where some of your Windows Azure web role instances in the development fabric get stuck in an unhealthy state, and thus do not start, when you use the ServerManager to tweak your Application Pool settings.

In our Windows Azure development project, we have a web role, which in turn has has multiple virtual applications (i.e. the CSDEF file contains many WebRole/Sites/Site/VirtualApplication elements). In our development environment, we use the ServerManager utility to change the identity under which the application pools run, so that they do not run under the "NETWORK SERVICE" account, but under a given user account (see Wade's article [https://www.wadewegner.com/2011/01/programmatically-changing-the-apppool-identity-in-a-windows-azure-web-role/#comment-4251] for details). Assuming we deploy 5 web role instances, and each has 4 virtual applications, we have to modify the settings for 5*(1+4)=25 application pools (it's 1+4, because in addition to the 4 virtual applications, we also need to we need to modify the actual web role itself).


  <WebRole name="Cloud.WebRole" vmsize="Small">
    <Sites>
      <Site name="Web">
        <VirtualApplication name="App1" physicalDirectory="..\Site.App1" />
        <VirtualApplication name="App2" physicalDirectory="..\Site.App2" />
        <VirtualApplication name="App3" physicalDirectory="..\Site.App3" />
        <VirtualApplication name="App4" physicalDirectory="..\Site.App4" />
        <Bindings>
          <Binding name="HttpPort80" endpointName="HttpPort80" />
          <Binding name="HttpsPort443" endpointName="HttpsPort443" />
        </Bindings>
      </Site>
    </Sites>

The term 'modifying a setting of an application pool' means that you use the type Microsoft.Web.Administration.ServerManager (from %WINDIR%\System32\inetsrv\Microsoft.Web.Administration.dll) to modify the application pools, and then call the serverManager.CommitChanges() method. When running multiple instances in your Windows Azure development fabric, your RoleEntryPoint.OnStart() method potentially run in parallel with other  RoleEntryPoint.OnStart(), and in the case of for ‘slow’-starting instances which are still being configured by the development fabric, you also run parallel to the fabric’s IisConfigurator.exe utility.

Why is that a problem? Well, in order to enact a configuration change, you need to call the serverManager.CommitChanges() method which essentially modifies a file in the local file system (namely "C:\Windows\system32\inetsrv\config\applicationHost.config"). And as you can imagine, this is the perfect opportunity for race conditions: Imagine a situation where one of your role instances (successfully) calls ServerManager.CommitChanges(), while the IisConfigurator.exe is in the process of configuring another role instance. Then IisConfigurator.exe fails to configure that other role (and crashes), that role is marked as ‘Unhealthy’ in the fabric and does not come off the ground. So, letting IisConfigurator.exe running into a race condition with your own code can ruin your day.

How the fix works

The CrossProcessBarrier

First of all, please keep in mind that this problem only occurs when running multiple web roles in the local development fabric. In a real deployment in a Windows Azure data center, your RoleEntryPoint.OnStart() is called after IisConfigurator.exe did it’s thing.

So on your laptop, you want to ensure that only one process at a time uses the ServerManager class. Your RoleEntryPoint.OnStart() code should run when IisConfigurator.exe has fully finished it’s business. So we ‘simply’ need to wait in the OnStart() code of each role, until …, yeah, hm, until when exactly? When all OnStart() methods are ‘at the same point’, that’s the right time when IisConfigurator is done.

In the Task Parallel Library, there is a nice construct called System.Threading.Barrier, which defines how many ‘participants’ should wait for each other, and when all participants reach the barrier, it releases them at once. Unfortunately, System.Threading.Barrier is for tasks and threads within the same process, and doesn’t work across different processes on Windows. So we need something that mimics a barrier, but uses Windows synchronization primitives which work across processes.

We developed a small utility type called CrossProcessBarrier. It uses global Mutex objects so synchronize across processes, and provides all we need. To enlist multiple participants in a cross-process barrier, we need some sort of identifier for each participant. Each participant needs to know the identifiers of the other participants. Based on these identifiers, each instance of the CrossProcessBarrier checks whether the others are already running (via a Mutex), and – once they all exist – releases the waiting thread. For a sample, see the unit test for the CrossProcessBarrier.

The ServerManagerBarrier

After having this cross-process synchronization primitive, the remaining step is to use that in our WebRole. The ServerManagerBarrier.ApplyServerManagerActions(Action<ServerManager> a) method allows you to pass in an Action<ServerManager> delegate in which you can safely apply the modifications you want to apply to IIS7. So that method (1) ensures you’re not trashing IIsConfigurator.exe, and (2) ensures your different web roles do not collide.

An example

The example similar to what Wade Wegner does in his article on “Programmatically Changing the AppPool Identity in a Windows Azure Web Role”.

var appPoolUser = "EUROPE\\chgeuer";
var appPoolPass = "top$secr3tPa55w0rd";

Action<ServerManager> updateIdentity = (serverManager) =>
{
    var sitename = RoleEnvironment.CurrentRoleInstance.Id + "_Web";
    var appPoolNames = serverManager.Sites[sitename].Applications.Select(app => app.ApplicationPoolName).ToList();

    foreach (var appPoolName in appPoolNames)
    {
        var pool = serverManager.ApplicationPools[appPoolName];

        pool.ProcessModel.IdentityType = ProcessModelIdentityType.SpecificUser;
        pool.ProcessModel.UserName = appPoolUser;
        pool.ProcessModel.Password = appPoolPass;
    }
    serverManager.CommitChanges();
};

ServerManagerBarrier.ApplyServerManagerActions(updateIdentity);

 

How do I get it?

In your development project: Nuget!

The NugetPackage WindowsAzure.DevelopmentFabric.IISConfigurator.Syncronizer brings the library down right into your web role. Check out the sample in the TweakIdentityWhenRunningInCorpnet() method on how to use it.

Source….

If you prefer source, grab it here: https://github.com/chgeuer/azureiisconfiguratorsync 

Feedback…

I’m interested to hear your thoughts, questions, concerns…

]]> How to host and use a DependencyObject in a threaded Console app https://docs.microsoft.com/archive/blogs/chgeuer/how-to-host-and-use-a-dependencyobject-in-a-threaded-console-app Thu, 15 Jan 2009 03:24:28 GMT https://blogs.msdn.microsoft.com/chgeuer/2009/01/15/how-to-host-and-use-a-dependencyobject-in-a-threaded-console-app/ Recently, I developed some business objects that I needed to use both in WPF world (with vanilla data binding), as well as within a WCF web service. Of course, from the WPF books we learn that a DependenyProperty can only be directly accessed from the thread where it was created. So the implementation does that in the appropriate thread. The problem I still had was that my messages were dispatched to my business object, but that they remained in the queue with a DispatcherOperationStatus Pending. Thanks to the guys from the WPF team (Dwayne Need and a bunch of other folks) and their "did you actually start the Dispatcher?" question, here's a small sample. Maybe it helps ...

Christian

namespace Microsoft.EMIC.ChGeuer.BlogSample
{
    using System;
    using System.Windows;
    using System.Threading;
    using System.Windows.Threading;
    using System.Diagnostics;
 
    public class HostingDependencyObjectInOwnApplicationRepro
    {
        [STAThread]
        static void Main(string[] args)
        {
            Thread.CurrentThread.Name = "MyServiceHostApplication";
 
            Dispatcher d = Dispatcher.CurrentDispatcher;
 
            SomeDataObject data = new SomeDataObject() { Id = "Foo" };
            data.DataChanged += new DataChangedEventHandler(ProgramDataChanged);
 
            Console.WriteLine(data.DoStuff("New value 1"));
 
            new Thread((ThreadStart)delegate()
            {
                // This is the thread that ocntinuously works with the data,
                // like a WCF service
                Thread.CurrentThread.Name = "MyWCFService";
 
                for (var i = 0; i < 10; i++)
                {
                    Thread.Sleep(500);
 
                    var res = data.DoStuff(string.Format("New value {0}", i));
                    if (res == null)
                    {
                        break;
                    }
                    Console.WriteLine("The result from the thread is '{0}'", res);
                }
            }).Start();
 
            Dispatcher mainDispatcher = Dispatcher.CurrentDispatcher;
            new Thread((ThreadStart)delegate()
            {
                Console.WriteLine("Press <Return> to close the application");
                Console.ReadLine();
                AppShutdownDispatcher(mainDispatcher);
            }).Start();
 
            Dispatcher.Run();
        }
 
        public static void AppShutdownDispatcher(Dispatcher theMainDispatcher)
        {
            if (theMainDispatcher.CheckAccess())
            {
                theMainDispatcher.InvokeShutdown();
            }
            else
            {
                Dispatcher.CurrentDispatcher.Invoke(DispatcherPriority.Send, (Action)(() => 
                {
                    theMainDispatcher.InvokeShutdown(); 
                }));
            }
        }
 
        static void ProgramDataChanged(object sender, DataChangedEventArgs e)
        {
            Console.WriteLine("Data changed to {0}", e.NewValue);
        }
    }
 
    public delegate void DataChangedEventHandler(object sender, DataChangedEventArgs e);
 
    public class DataChangedEventArgs : EventArgs
    {
        internal DataChangedEventArgs(string newValue)
        {
            this.NewValue = newValue;
        }
 
        public string NewValue { get; private set; }
    }
 
    public class SomeDataObject : DependencyObject
    {
        public SomeDataObject() 
        {
            this.Dispatcher.Hooks.OperationPosted += new DispatcherHookEventHandler(DispatcherOperationPosted);
        }
 
        public event DataChangedEventHandler DataChanged;
 
        public static readonly DependencyProperty IdProperty =
            DependencyProperty.Register("Id", typeof(string), typeof(SomeDataObject),
            new PropertyMetadata() { DefaultValue = string.Empty, PropertyChangedCallback = OnDataChanged });
 
        public string Id
        {
            get { return (string)this.GetValue(SomeDataObject.IdProperty); }
            set { this.SetValue(SomeDataObject.IdProperty, value); }
        }
 
        private static void OnDataChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            Debug.Assert(sender is SomeDataObject);
 
            DataChangedEventHandler handler = ((SomeDataObject)sender).DataChanged;
 
            if (handler != null)
            {
                handler(sender, new DataChangedEventArgs((string)e.NewValue));
            }
        }
 
        private void DispatcherOperationPosted(object sender, DispatcherHookEventArgs e)
        {
            Console.Out.WriteLine("Posted operation with prio {0}", e.Operation.Priority.ToString());
 
            e.Dispatcher.UnhandledException += new DispatcherUnhandledExceptionEventHandler(Dispatcher_UnhandledException);
        }
 
        void Dispatcher_UnhandledException(object sender, DispatcherUnhandledExceptionEventArgs e)
        {
            Console.Error.WriteLine("Unhandled {0}", e.Exception.GetType().Name);
        }
 
        public string DoStuff(string someNewValue)
        {
            Console.WriteLine("Called by {0}", Thread.CurrentThread.Name);
            if (this.Dispatcher.HasShutdownStarted)
            {
                return null;
            }
 
            if (this.Dispatcher.CheckAccess())
            {
                this.Id = someNewValue;
                return this.Id + " computed";
            }
            else
            {
                Func<string, string> doIt = (arg) =>
                {
                    this.Id = arg;
                    return this.Id + " computed";
                };
 
                // return (string)this.Dispatcher.Invoke(DispatcherPriority.Send, 
                //      TimeSpan.FromMilliseconds(500), doIt, someNewValue);
                
                DispatcherOperation op = base.Dispatcher.BeginInvoke(DispatcherPriority.Send, doIt, someNewValue);
 
                var status = op.Wait(TimeSpan.FromMilliseconds(500));
                Console.WriteLine("Status: " + status.ToString());
 
                if (status == DispatcherOperationStatus.Completed)
                {
                    return (string)op.Result;
                }
                else if (status == DispatcherOperationStatus.Aborted)
                {
                    return "Cancelling";
                }
                else
                {
                    throw new Exception("Houston, we have a problem");
                }
            }
        }
    }
}
]]> X509 certificate tool https://docs.microsoft.com/archive/blogs/chgeuer/x509-certificate-tool Tue, 16 Dec 2008 09:56:19 GMT https://blogs.msdn.microsoft.com/chgeuer/2008/12/16/x509-certificate-tool/ I noticed that Jason's (https://blogs.msdn.com/thehoggblog/archive/2007/08/20/swiss-army-knife-of-x-509-certificate-tools.aspx) and Justin's (https://blogs.msdn.com/justinjsmith/archive/2007/07/10/new-wcf-security-examples.aspx) blog entries refer to an old location at https://wcf.netfx3.com that seems to be down. I figured out that the tool is now available for download from the WCF community samples here: 

https://code.msdn.microsoft.com/Project/Download/FileDownload.aspx?ProjectName=netfxsamples&DownloadId=3395

]]> My old Ph.D. thesis online https://docs.microsoft.com/archive/blogs/chgeuer/my-old-ph-d-thesis-online Mon, 27 Mar 2006 07:44:00 GMT https://blogs.msdn.microsoft.com/chgeuer/2006/03/27/my-old-ph-d-thesis-online/ A colleague asked me about XML Signature, and I just remenbered that my old Ph.D. thesis ("Confidentiality of XML documents by pool encryption") is online, which contains (besides theoretical nonsense) a nice introduction to XML Signature in chapter 4.2...

 

]]> WS-Policy and WS-PolicyAttachment are updated https://docs.microsoft.com/archive/blogs/chgeuer/ws-policy-and-ws-policyattachment-are-updated Fri, 10 Mar 2006 06:52:00 GMT https://blogs.msdn.microsoft.com/chgeuer/2006/03/10/ws-policy-and-ws-policyattachment-are-updated/ WS-Policy and WS-PolicyAttachment are republished:

https://specs.xmlsoap.org/ws/2004/09/policy/

]]> We're (still) hiring https://docs.microsoft.com/archive/blogs/chgeuer/were-still-hiring Fri, 10 Mar 2006 06:40:00 GMT https://blogs.msdn.microsoft.com/chgeuer/2006/03/10/were-still-hiring/ We (European Microsoft Innovation Center) are still looking for new colleagues, software devs and program managers, all preferrably with a researchy touch:

https://www.microsoft.com/emea/emic/joboffers.mspx

]]> Finally I found our interview videos https://docs.microsoft.com/archive/blogs/chgeuer/finally-i-found-our-interview-videos Fri, 08 Jul 2005 06:42:00 GMT https://blogs.msdn.microsoft.com/chgeuer/2005/07/08/finally-i-found-our-interview-videos/ Videos interviews from EMIC employees (European Microsoft Innovation Center) are here: ]]>