"Lionel Schiepers" <l*@bvdep.com> wrote in message
news:u6mAobSlGHA.1664@TK2MSFTNGP03.phx.gbl...
> We have a multithreaded service written in .NET 2.0 that is running
> 24h/24. This service checks nearly 250 another servers to log statisticals
> data acquired via WMI, SNMP, PerformanceCounter...
>
> We use XOsoft for the fail over of our SQL Server databases (active,
> passive but the clients are always using the same name to connect to the
> elected active server) but we always have problems when the active server
> change because the PerformanceCounter objects use a cache located to the
> class PerformanceCounterLib internal to the .NET framework. This cache
> contains the categories available for each server name. Because the
> servers are not identical, the categories of a server cannot be reused for
> the other one and we catch these exceptions after a fail over.
>
> [2006/06/21 13:05:16.1935] Pdh Failed for xxx..bvdep.net
> System.InvalidOperationException: Could not Read Category Index: 3616.
>   at System.Diagnostics.CategorySample..ctor(Byte[] data, CategoryEntry
> entry, PerformanceCounterLib library)
>   at System.Diagnostics.PerformanceCounterLib.GetCategorySample(String
> category)
>   at System.Diagnostics.PerformanceCounterLib.GetCategorySample(String
> machine, String category)
>   at System.Diagnostics.PerformanceCounter.NextSample()
>   at ServerPatrol.Agent.Components.Specialized.Pdh.Invoke(ResultPipeline
> results, TargetDTO target, String& resultDescription)
>
>
> It exists the method PerformanceCounter.CloseSharedResources() that clears
> the cache but for all servers which is not interesting for us because we
> have all the time between 1.000 and 3.000 open performance counters
> dispatched to ~250 servers. I'm not even sure it's possible because the
> service is always running between 10 and 60 threads at the same time and
> the implementation of CloseSharedResources doesn't seem to be thread safe.
>
> Is there any tricks to correct this kind of problem?
>
> I have two solutions but I prefer not to use them until a better one.
>
>
> 1. Put the PerformanceCounters associated to a server in a dedicated
> application domain. That way, I can call CloseSharedResources without
> loosing the data of the other servers. I don't like this solution because:
>    - I don't want to manage the lifetime of my objects between the
> application domain
>    - I don't want an application with ~250 application domains.
>    - Debugging is harder.
>
> 2. Directly removing the concerned cached entries via reflection (because
> the class is internal). I used Reflector to write the following code but I
> don't like this solution because the internal implementation could change
> between different version of the .NET Framework.
>
>    System.Reflection.Assembly assembly =
> System.Reflection.Assembly.GetAssembly(typeof(PerformanceCounter));
>    Type type =
> assembly.GetType("System.Diagnostics.PerformanceCounterLib");
>    System.Reflection.FieldInfo fi = type.GetField(
>        "libraryTable",
>        System.Reflection.BindingFlags.Static |
> System.Reflection.BindingFlags.NonPublic);
>
>    Hashtable dictionary = fi.GetValue(null) as Hashtable;
>    if (null == dictionary)
>        return;
>    System.Globalization.CultureInfo culture = new
> System.Globalization.CultureInfo(9);
>    string key =
> server.ToLower(System.Globalization.CultureInfo.InvariantCulture) + ":" +
> culture.LCID.ToString("X3",
> System.Globalization.CultureInfo.InvariantCulture);
>    object o = dictionary[key];
>    if (null != o)
>    {
>        System.Reflection.MethodInfo mi = o.GetType().GetMethod("Close",
> System.Reflection.BindingFlags.Instance |
> System.Reflection.BindingFlags.NonPublic);
>        mi.Invoke(o, new object[0]);
>        dictionary.Remove(key);
>    }
>
> Thanks in advance.
>
> Lionel Schiepers (ls at bvdep.com),
> Bureau van Dijk Electronic Publishing
> Belgium.
>
>