FileSystemWatchers and CacheDependency

  • Thread starter Thread starter Guest
  • Start date Start date
G

Guest

Hi,
I am developing an application that requires me to set up file system
watchers on directories on a network drive, as well as set up
CacheDependencies in the same location for my System.Web.Caching.Cache. When
i set up the file watchers and then create the cache dependency i receive an
Exception (AccessViolationError - Attempted to read or write protected
memory). I have included a the stack trace from the exception at the end of
this post. This only occurs when i am creating a large number of file
watchers ( i have found the the for my PC i can only create 48!). The
following is a sample application i built which consistantly throws the
exception( note that when i copy the directory structe from the network drive
to a local drive the function works flawlessly ).

List<FileSystemWatcher> watchers = new List<FileSystemWatcher>();
foreach( string directory in Directory.GetDirectories(
@"\\itchy\imagelink\Books\V3Books" ) )
{
FileSystemWatcher watcher = new FileSystemWatcher( directory );
watcher.Deleted += new FileSystemEventHandler( watcher_Deleted );
watcher.Created += new FileSystemEventHandler( watcher_Created );
watcher.Renamed += new RenamedEventHandler( watcher_Renamed );
watcher.Changed += new FileSystemEventHandler( watcher_Changed );
watcher.EnableRaisingEvents = true;
watchers.Add( watcher );
}
CacheDependency depencency2 = new CacheDependency(
@"\\itchy\imagelink\Books\V3Books\man.lst" );


Partial Stack Trace:

at System.Web.UnsafeNativeMethods.RaiseFileMonitoringEventlogEvent(String
eventInfo, String path, String appVirtualPath, Int32 hr)
at System.Web.FileChangesMonitor.CreateFileMonitoringException(Int32 hr,
String path)
at System.Web.DirMonCompletion..ctor(DirectoryMonitor dirMon, String dir,
Boolean watchSubtree, UInt32 notifyFilter)
at System.Web.DirectoryMonitor.StartMonitoring()
at System.Web.DirectoryMonitor.StartMonitoringFile(String file,
FileChangeEventHandler callback, String alias)
at System.Web.FileChangesMonitor.StartMonitoringPath(String alias,
FileChangeEventHandler callback, FileAttributesData& fad)
at System.Web.Caching.CacheDependency.Init(Boolean isPublic, String[]
filenamesArg, String[] cachekeysArg, CacheDependency dependency, DateTime
utcStart)
at System.Web.Caching.CacheDependency..ctor(String filename, DateTime start)
at System.Web.Caching.CacheDependency..ctor(String filename)
at WindowsApplication4.Form1.LoadTargetFolder() in
D:\MyProjects\WindowsApplication4\WindowsApplication4\Form1.cs:line 52
at WindowsApplication4.Program.Main() in
D:\MyProjects\WindowsApplication4\WindowsApplication4\Program.cs:line 17
at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence
assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext,
ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()

Thanks,
Daniel
 
daniel,

Not really answering your question but I am wondering why you don't just
create one FileSystemWatcher on "\\itchy\imagelink\Books\V3Books" and set the
IncludeSubdirectories property?

Another option might be to map a drive to "\\itchy\imagelink\Books\V3Books"
and then enumerate the directories through the mapped drive.

Michael

daniel said:
Hi,
I am developing an application that requires me to set up file system
watchers on directories on a network drive, as well as set up
CacheDependencies in the same location for my System.Web.Caching.Cache. When
i set up the file watchers and then create the cache dependency i receive an
Exception (AccessViolationError - Attempted to read or write protected
memory). I have included a the stack trace from the exception at the end of
this post. This only occurs when i am creating a large number of file
watchers ( i have found the the for my PC i can only create 48!). The
following is a sample application i built which consistantly throws the
exception( note that when i copy the directory structe from the network drive
to a local drive the function works flawlessly ).

List<FileSystemWatcher> watchers = new List<FileSystemWatcher>();
foreach( string directory in Directory.GetDirectories(
@"\\itchy\imagelink\Books\V3Books" ) )
{
FileSystemWatcher watcher = new FileSystemWatcher( directory );
watcher.Deleted += new FileSystemEventHandler( watcher_Deleted );
watcher.Created += new FileSystemEventHandler( watcher_Created );
watcher.Renamed += new RenamedEventHandler( watcher_Renamed );
watcher.Changed += new FileSystemEventHandler( watcher_Changed );
watcher.EnableRaisingEvents = true;
watchers.Add( watcher );
}
CacheDependency depencency2 = new CacheDependency(
@"\\itchy\imagelink\Books\V3Books\man.lst" );


Partial Stack Trace:

at System.Web.UnsafeNativeMethods.RaiseFileMonitoringEventlogEvent(String
eventInfo, String path, String appVirtualPath, Int32 hr)
at System.Web.FileChangesMonitor.CreateFileMonitoringException(Int32 hr,
String path)
at System.Web.DirMonCompletion..ctor(DirectoryMonitor dirMon, String dir,
Boolean watchSubtree, UInt32 notifyFilter)
at System.Web.DirectoryMonitor.StartMonitoring()
at System.Web.DirectoryMonitor.StartMonitoringFile(String file,
FileChangeEventHandler callback, String alias)
at System.Web.FileChangesMonitor.StartMonitoringPath(String alias,
FileChangeEventHandler callback, FileAttributesData& fad)
at System.Web.Caching.CacheDependency.Init(Boolean isPublic, String[]
filenamesArg, String[] cachekeysArg, CacheDependency dependency, DateTime
utcStart)
at System.Web.Caching.CacheDependency..ctor(String filename, DateTime start)
at System.Web.Caching.CacheDependency..ctor(String filename)
at WindowsApplication4.Form1.LoadTargetFolder() in
D:\MyProjects\WindowsApplication4\WindowsApplication4\Form1.cs:line 52
at WindowsApplication4.Program.Main() in
D:\MyProjects\WindowsApplication4\WindowsApplication4\Program.cs:line 17
at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence
assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext,
ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()

Thanks,
Daniel
Click to expand...
 
Michael,

The number of file watchers that causes the crash seems to be completely
intermitant, my example may be a bit overly complex but i hav also tried
having just one file watcher on the network directory and some times it
crashes sometimes it doesn't. It also seems to make no difference whether it
is a mapped network drive or not.

Also, the number of filewatchers differs between locations that i map to..
on some network paths i can create several file watchers before a crash, on
other servers only one...

I have tried a mapping to servers with various operating systems including
windows xp, win 2000 and 2003 all with the same results.

Regards
Daniel

Michael said:
daniel,

Not really answering your question but I am wondering why you don't just
create one FileSystemWatcher on "\\itchy\imagelink\Books\V3Books" and set the
IncludeSubdirectories property?

Another option might be to map a drive to "\\itchy\imagelink\Books\V3Books"
and then enumerate the directories through the mapped drive.

Michael

daniel said:
Hi,
I am developing an application that requires me to set up file system
watchers on directories on a network drive, as well as set up
CacheDependencies in the same location for my System.Web.Caching.Cache. When
i set up the file watchers and then create the cache dependency i receive an
Exception (AccessViolationError - Attempted to read or write protected
memory). I have included a the stack trace from the exception at the end of
this post. This only occurs when i am creating a large number of file
watchers ( i have found the the for my PC i can only create 48!). The
following is a sample application i built which consistantly throws the
exception( note that when i copy the directory structe from the network drive
to a local drive the function works flawlessly ).

List<FileSystemWatcher> watchers = new List<FileSystemWatcher>();
foreach( string directory in Directory.GetDirectories(
@"\\itchy\imagelink\Books\V3Books" ) )
{
FileSystemWatcher watcher = new FileSystemWatcher( directory );
watcher.Deleted += new FileSystemEventHandler( watcher_Deleted );
watcher.Created += new FileSystemEventHandler( watcher_Created );
watcher.Renamed += new RenamedEventHandler( watcher_Renamed );
watcher.Changed += new FileSystemEventHandler( watcher_Changed );
watcher.EnableRaisingEvents = true;
watchers.Add( watcher );
}
CacheDependency depencency2 = new CacheDependency(
@"\\itchy\imagelink\Books\V3Books\man.lst" );


Partial Stack Trace:

at System.Web.UnsafeNativeMethods.RaiseFileMonitoringEventlogEvent(String
eventInfo, String path, String appVirtualPath, Int32 hr)
at System.Web.FileChangesMonitor.CreateFileMonitoringException(Int32 hr,
String path)
at System.Web.DirMonCompletion..ctor(DirectoryMonitor dirMon, String dir,
Boolean watchSubtree, UInt32 notifyFilter)
at System.Web.DirectoryMonitor.StartMonitoring()
at System.Web.DirectoryMonitor.StartMonitoringFile(String file,
FileChangeEventHandler callback, String alias)
at System.Web.FileChangesMonitor.StartMonitoringPath(String alias,
FileChangeEventHandler callback, FileAttributesData& fad)
at System.Web.Caching.CacheDependency.Init(Boolean isPublic, String[]
filenamesArg, String[] cachekeysArg, CacheDependency dependency, DateTime
utcStart)
at System.Web.Caching.CacheDependency..ctor(String filename, DateTime start)
at System.Web.Caching.CacheDependency..ctor(String filename)
at WindowsApplication4.Form1.LoadTargetFolder() in
D:\MyProjects\WindowsApplication4\WindowsApplication4\Form1.cs:line 52
at WindowsApplication4.Program.Main() in
D:\MyProjects\WindowsApplication4\WindowsApplication4\Program.cs:line 17
at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence
assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext,
ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()

Thanks,
Daniel
Click to expand...
Click to expand...
 
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