VS2013 publish Web deployment task failed The file is in use

Question

I am using VS2013 Premium to publish a site to Windows Server 2012. All files publish ok except these: SqlServerTypes\\x64\\msvcr100.dll

SqlServerTypes\\x64\\SqlSer

Answer 1

I have found the reason why the solution at http://blogs.msdn.com/b/webdev/archive/2013/10/30/web-publishing-updates-for-app-offline-and-usechecksum.aspx did not work for the original poster, and I have a workaround.

The issue with the EnableMSDeployAppOffline approach is that it only recycles the app domain hosting the application. It does not recycle the app pool worker process (w3wp.exe) which the app domain lives in.

Tearing down and recreating the app domain will not affect the Sql Server Spatial dlls in question. Those dlls are unmanaged code which are manually loaded via interop LoadLibray calls. Therefore the dlls live outside the purview of the app domain.

In order to release the files locks, which the app pool process puts on them, you need to either recycle the app pool, or unload the dlls from memory manually.

The Microsoft.SqlServer.Types nuget package ships a class which is used to load the Spatial dlls called SqlServerTypes.Utilities. You can modify the LoadNativeAssemblies method to unload the unmanaged dlls when the app domain is unloaded. With this modification when msdeploy copys the app_offline.htm the app domain will unload and then unload the managed dlls as well.

[DllImport("kernel32.dll", SetLastError = true)]
internal extern static bool FreeLibrary(IntPtr hModule);

private static IntPtr _msvcrPtr = IntPtr.Zero;
private static IntPtr _spatialPtr = IntPtr.Zero;

public static void LoadNativeAssemblies(string rootApplicationPath)
{
    if (_msvcrPtr != IntPtr.Zero || _spatialPtr != IntPtr.Zero)
        throw new Exception("LoadNativeAssemblies already called.");

    var nativeBinaryPath = IntPtr.Size > 4
        ? Path.Combine(rootApplicationPath, @"SqlServerTypes\x64\")
        : Path.Combine(rootApplicationPath, @"SqlServerTypes\x86\");

    _msvcrPtr = LoadNativeAssembly(nativeBinaryPath, "msvcr100.dll");
    _spatialPtr = LoadNativeAssembly(nativeBinaryPath, "SqlServerSpatial110.dll");

    AppDomain.CurrentDomain.DomainUnload += (sender, e) =>
    {
        if (_msvcrPtr != IntPtr.Zero)
        {
            FreeLibrary(_msvcrPtr);
            _msvcrPtr = IntPtr.Zero;
        }

        if (_spatialPtr != IntPtr.Zero)
        {
            FreeLibrary(_spatialPtr);
            _spatialPtr = IntPtr.Zero;
         }
    };
}

There is one caveat with this approach. It assumes your application is the only one running in the worker process that is using the Spatial dlls. Since app pools can host multiple applications the file locks will not be released if another application has also loaded them. This will prevent your deploy from working with the same file locked error.