FileSystemWatcher advice required please

[jimmyfishbean]

Hi,

I have a VB.Net Windows Service that monitors a varying number of
directories (that are read from an INI file). I set up a
FileSystemWatcher object to monitor each directory that is read from
the INI file and add each object to a collection.

The purpose of my service is to monitor the directories for any XML
files that are dropped into them. When a file is dropped, it is
firstly renamed by appending the extension '.lock' to the name of the
XML file. Secondly, the file is then processed by sending the contents
to a Web Service. Once the file has been completely processed and a
return value is received from the Web Service, the file is moved from
the directory to a 'Processed Files' folder (that is not monitored by a
FileSystemWatcher object).

I call a sub to process each directory, which loops through all files
in the directory (at one moment in time) and calls the web service for
each file.

When the service starts, any XML files in the 'monitored' are picked up
and processed without any erros/trouble. The problem starts if any
'new' XML files are dropped into the monitored directories when the
service is currently busy processing. I call the same sub that loops
through all files in a directory. Of course, there will be files
present in both calls to the sub, causing errors.

How can I tackle this? Is it reasonable to use a timer (I do not
currently use one). I did add a timer, but the number of handles and
memory kept increasing all the time (even when there was nothing to
process).

I am not concerned about the deletion of files or modification or
access. Simply addition/creation.

Any advice/guidance is greatly appreciated. Thanks.

Jimmy

Code snippet:

Private Sub setup()
...
While l <= UBound(aInputDirs)
Dim fsw As New FileSystemWatcher
fsw.Path = aInputDirs(l)
fsw.Filter = "*.xml"
fsw.IncludeSubdirectories = False
fsw.NotifyFilter = System.IO.NotifyFilters.LastWrite
AddHandler fsw.Changed, AddressOf OnChanged
fsw.EnableRaisingEvents = True

watcherCollection.Add(fsw)
l = l + 1
End While

l = 0
While l < UBound(aInputDirs)
ProcessDir(l)
l = l + 1
End While
...
End Sub


Private Shared Sub OnChanged(ByVal source As Object, ByVal e As
System.IO.FileSystemEventArgs)

'Dim strDir As String = e.Name

'1. work out the directory that has been changed (using the
full path/filename : e.Name)
Dim intLastSlash As Integer = e.FullPath.LastIndexOf("\")
Dim strDir As String = Left(e.FullPath, intLastSlash)


If Not bBusyProcessing Then
If Not e.Name = "XMLtoSOAP.ini" Then
If (File.GetAttributes(e.FullPath) And
FileAttributes.Directory) = FileAttributes.Directory Then
'Directory changed, created, or deleted.
Else
'File changed, created, or deleted.
Dim i As Integer = 0

Do While i < UBound(aInputDirs)
If aInputDirs(i) = strDir Then
ProcessDir(i)
Exit Do
End If

i = i + 1
Loop
End If
Else
'setup()
End If
End If

End Sub

Public Sub ProcessDir(ByRef lElement As Integer)
' Find all files in this directory and try to process them.
Dim fso As New Scripting.FileSystemObject
Dim oFile As Scripting.File
Dim strOrigFile As String
Dim stream As Scripting.TextStream
Dim bFileAlreadyOpen As Boolean
Dim cProcessedFiles As New Collection
Dim bMoreToProcess, bProcessedOne As Boolean

bMoreToProcess = True

While bMoreToProcess = True
bProcessedOne = False
For Each oFile In fso.GetFolder(aInputDirs(lElement)).Files

bBusyProcessing = True

'Make sure this file hasn't already been tried - if the
item is not in the collection an error is returned
On Error Resume Next
If cProcessedFiles.Count() <> 0 And
cProcessedFiles.Item(oFile.Name) <> oFile.Name Then
On Error GoTo 0
bFileAlreadyOpen = False
strOrigFile = oFile.Name
'Rename the file to see if it is still locked by
any process
On Error GoTo FileStillOpen

'create a copy of the original file to revert back
to if in changerootnode mode
If bChangeRootNode Then
If Not fso.FolderExists(aInputDirs(lElement) &
"\Temp") Then
fso.CreateFolder(aInputDirs(lElement) &
"\Temp")
End If

fso.CopyFile(oFile.Path, aInputDirs(lElement) &
"\Temp\" & oFile.Name)
sCurrFile = aInputDirs(lElement) & "\Temp\" &
oFile.Name
End If

fso.MoveFile(oFile.Path, oFile.Path & ".lock")
On Error GoTo 0
If Not bFileAlreadyOpen Then
ProcessFile(lElement, strOrigFile)
End If
'Store the file in a collection for exclusion in
the lower loop
cProcessedFiles.Add(strOrigFile, strOrigFile)
bProcessedOne = True
End If

bBusyProcessing = False
Next oFile
bMoreToProcess = bProcessedOne
End While

fso = Nothing

Exit Sub

FileStillOpen:
bFileAlreadyOpen = True
Resume Next

End Sub

'NOTE: Sub ProcessFile calls the web service

 

[Kevin Spencer]

Okay, you have a FileSystemWatcher which, I assume, is monitoring the
"Created" event. When a file is created, the FileSystemEventArgs passed with
the event contains the path of the file created. You can use this
information to move the file to the new location. No need to create a list
of files to move. Process each one at a time.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
We got a sick zebra a hat,
you ultimate tuna.

 

[jimmyfishbean]

Thanks for that Kevin. I have tried your suggestion.

However, if I drop more than 1 file into the DROP folders, only the
first file is passed to the OnChanged sub. Therefore I can only move 1
file (unless I call a sub that moves all files from the DROP folder to
a temp folder). Am I correct to assume that only 1 event is triggered
regardless of the number of files dropped into the directory? It would
be a lot easier/better if a separate event was triggered for each file.

If I try to move all files in the DROP folder in the OnChanged sub,
only 1 gets moved (as the application thinks that only one file is
there at the time the event was triggered). Do I need to use a timer
here to periodically check the fodler? I do not want to, and thought
the whole purpose of the filesystemwatcher was to provide functionality
that would allow each and every file droppped to trigger an event. I
take it I have it all so wrong...

My new OnChanged sub:

Private Shared Sub OnChanged(ByVal source As Object, ByVal e As
System.IO.FileSystemEventArgs)
Dim intLastSlash As Integer = e.FullPath.LastIndexOf("\")
Dim strDir As String = Left(e.FullPath, intLastSlash)
Dim fso As New Scripting.FileSystemObject
Dim oFile As Scripting.File
Dim file As File

If Not e.Name = "XMLtoSOAP.ini" Then
If (File.GetAttributes(e.FullPath) And
FileAttributes.Directory) = FileAttributes.Directory Then
'Directory changed, created, or deleted.
Else
'File changed, created, or deleted.
'move the files to a temp location
If Not Directory.Exists(strDir & "\Temp") Then
Directory.CreateDirectory(strDir & "\Temp")

If File.Exists(strDir & "\Temp\" & e.Name) Then
file.Delete(strDir & "\Temp\" & e.Name)
End If

'now move the file(s)
For Each oFile In fso.GetFolder(strDir).Files
oFile.Move(strDir & "\Temp\" & e.Name)
Next
End If
End If
End If
End Sub

The problem is that I never know how many files will be dropped into
the DROP folder at one time. There may be just a single one, there may
be 20 and ther may be 20, followed by another 30 straight afterwards.

Thanks.
Jimmy

 

[jimmyfishbean]

The sub should read:

Private Shared Sub OnChanged(ByVal source As Object, ByVal e As
System.IO.FileSystemEventArgs)
Dim intLastSlash As Integer = e.FullPath.LastIndexOf("\")
Dim strDir As String = Left(e.FullPath, intLastSlash)
Dim fso As New Scripting.FileSystemObject
Dim oFile As Scripting.File
Dim file As File

On Error Resume Next

If Not e.Name = "XMLtoSOAP.ini" Then
If (file.GetAttributes(e.FullPath) And
FileAttributes.Directory) = FileAttributes.Directory Then
'Directory changed, created, or deleted.
Else
'File changed, created, or deleted.
'move the files to a temp location
If Not Directory.Exists(strDir & "\Temp") Then
Directory.CreateDirectory(strDir & "\Temp")

End If

If file.Exists(strDir & "\Temp\" & e.Name) Then
file.Delete(strDir & "\Temp\" & e.Name)
End If

'now move the file(s)
For Each oFile In fso.GetFolder(strDir).Files
oFile.Move(strDir & "\Temp\" & e.Name)
Next
End If
End If

End Sub

Cheers.

 

[Kevin Spencer]

Hi Jimmy,

Why are you using OnChange? If you remember my first reply, I told you that
I assumed you were using the OnCreated event. This is because you said that
the files were being "dropped" into the directory. This causes a Create
event to occur, and that should be the only event that you need to listen
for.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
We got a sick zebra a hat,
you ultimate tuna.

 

[jimmyfishbean]

Hi Kevin,

I am monitoring just for the OnCreated event as you have suggested:

fsw.IncludeSubdirectories = False
fsw.NotifyFilter = System.IO.NotifyFilters.LastWrite
fsw.NotifyFilter = System.IO.NotifyFilters.FileName
fsw.NotifyFilter = System.IO.NotifyFilters.LastAccess

AddHandler fsw.Changed, AddressOf OnCreated
AddHandler fsw.Created, AddressOf OnCreated 'not recommended see the
link at top this while loop

In my OnCreated sub, I try to move all files that have been dropped
into the DROP folder to a different folder where they will be
processed. I would expect all files to be moved:

If Not Directory.Exists(strDir & "\Temp") Then
Directory.CreateDirectory(strDir & "\Temp")
End If

If File.Exists(strDir & "\Temp\" & e.Name) Then
File.Delete(strDir & "\Temp\" & e.Name)
End If

'now move the file(s)
For Each oFile In fso.GetFolder(strDir).Files
oFile.Move(strDir & "\Temp\" & e.Name)
bFileMoved = True
Next

However, only one file gets moved to the Temp folder. It seems as if
the OnCreated event gets called when the first file is identified as
being created, and when I try to move all files in the folder, the
filesystem thinks there is only the one file (i.e. the one that
triggered the event). Therefore, I have had to implement a timer that
will read the DROP folder, and move the remaining files periodically.
To me this is defeating the objective of the FileSystemWatcher.

To make matters worse ;P, the memory/no of handles used by my
application is forever increasing. I am closing objects and setting
them to nothing, as well as calling GC.Collect() in each sub.

Is this really how the FileSystemWatcher works? Can you please suggest
a more elegant/efficient way of achieving my aim? Much appreciated.

Jimmy

 

[Kevin Spencer]

Hi Jimmy,

The Created event occurs once per each file created. In addition, I see that
you're attaching the same event handler to the Changed event. This was not
what I suggested. To quote my earlier replies:

First reply:

"When a file is created, the FileSystemEventArgs passed with the event
contains the path of the file created. You can use this
information to move the file to the new location.No need to create a list of
files to move. **Process each one at a time.**"

Second reply:

"Why are you using OnChange? If you remember my first reply, I told you that
I assumed you were using the OnCreated event. This is because you said that
the files were being "dropped" into the directory. This causes a Create
event to occur, and that should be the only event that you need to listen
for."

You know, my mother used to tell me about people who loved her recipes for
one thing or another. But they would come back and tell her that when they
used her recipe, it just didn't taste as good as my mother's. Invariably,
she found out that they had "improvised" a bit on her recipe, and that this
was the reason it didn't taste the same!

I'm thinking that perhaps you are misunderstanding something about these
files being dropped into the folder, because of a question you asked earlier
in this thread:

"Am I correct to assume that only 1 event is triggered regardless of the
number of files dropped into the directory? It would
be a lot easier/better if a separate event was triggered for each file."

At the time you were asking about the Change event, but I believe you
misunderstand the idea of "dropping multiple files" in general. When you
drop multiple files into a folder, they are created one at a time. It
happens so fast that it may look like it's doing more than one at a time,
but it's not.

Also, multiple events are fired during different types of IO operations.
Take a note of this Note from the SDK:

"Common file system operations might raise more than one event. For example,
when a file is moved from one directory to another, several OnChanged and
some OnCreated and OnDeleted events might be raised. Moving a file is a
complex operation that consists of multiple simple operations, therefore
raising multiple events. Likewise, some applications (for example,
anti-virus software) might cause additional file system events that are
detected by FileSystemWatcher."

Your objective is to handle as few as necessary to get the job done.
Otherwise, you may have one event handler trying to perform the same IO
operation as another "at the sem time," and run into beaucoups trouble.

So, here's what I want you to do. Handle *only* the Created event. Don't
worry about NotifyFilter. For the OnChange event handler, the default
(LastWrite | FileName | DirectoryName) is perfect. In your OnChange
override, simply move the file specified in the FileSystemEventArgs.FullPath
member passed. The OnChange event handler method will be called for *each*
file dropped into the folder. Remember, *one* at a time!

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
We got a sick zebra a hat,
you ultimate tuna.

 

[Michael D. Ober]

Here's a complete VB 2005 application that monitors a directory tree and
processes files that are ready to process. I defined ready to process as a
non-zero byte size file that hasn't had a change in file size for at least
one minute. I think I have indented the correctly - to verify the indents,
copy into a VB 2005 project and use the IDE's indenter.

Mike.

'============================================================

Option Compare Text
Option Explicit On
Option Strict On

Imports System.IO
Imports System.Threading

Module ArchiveImportLoader
Private ArchiveImport As String
Private FilesToProcess As ProcessFiles
Private fsw As FileSystemWatcher
Private Declare Function GetConsoleWindow Lib "kernel32.dll" () As IntPtr
Private Declare Function ShowWindow Lib "user32.dll" (ByVal hwnd As IntPtr,
ByVal nCmdShow As Int32) As Int32
Private Const SW_SHOWMINNOACTIVE As Int32 = 7

Public Sub Main()
Dim NoVersion As New Collection
logs.WriteLog(My.Application.Info.Title & " Starting")
Console.Title = AppName()
Thread.CurrentThread.Name = "MAIN"
' Read environment
ArchiveImport = OSInterface.iniWrapper.ReadString("ArchiveManager",
"ImportRoot", "wakefield.ini")
Dim ArchiveRoot As String =
OSInterface.iniWrapper.ReadString("ArchiveManager", "Root", "wakefield.ini")
For Each v As String In
Split(OSInterface.iniWrapper.ReadString("ArchiveManager", "NoVersion",
"wakefield.ini"), "|")
NoVersion.Add("*" & v)
Next
' Ensure the import directory exists
WriteLog("Creating File System Watcher on '" & ArchiveImport & "'")
My.Computer.FileSystem.CreateDirectory(ArchiveImport)
' Start the worker thread and configure the FSW subsystem
FilesToProcess = New ProcessFiles(ArchiveImport, ArchiveRoot, NoVersion)
ConfigureFSW()
' Configuration done; Minimize the window
WriteLog("Initialization Complete")
Thread.Sleep(New TimeSpan(0, 0, 5))
ShowWindow(GetConsoleWindow(), SW_SHOWMINNOACTIVE)
' Go to sleep, but periodically wakeup and check for missed files
Dim SleepPeriod As TimeSpan = New TimeSpan(0, 15, 0)
Do While True
Console.WriteLine(Now.ToString & vbTab & Thread.CurrentThread.Name & ":
Checking for Missed Files")
ProcessTree()
Thread.Sleep(SleepPeriod)
Loop
End Sub

Private Sub ProcessTree()
Try
My.Computer.FileSystem.CreateDirectory(ArchiveImport)
For Each fName As String In
My.Computer.FileSystem.GetFiles(ArchiveImport,
FileIO.SearchOption.SearchAllSubDirectories)
FilesToProcess.Add(fName)
Next
Catch ex As Exception
WriteLog(ex.ToString)
End Try
End Sub

Private Sub ConfigureFSW()
WriteLog("ConfigureFSW: Configure File System Watcher on '" &
ArchiveImport & "'")
My.Computer.FileSystem.CreateDirectory(ArchiveImport)
If Not fsw Is Nothing Then
WriteLog(vbTab & "Lost Previous File System Watcher system context,
removing from application")
With fsw
.EnableRaisingEvents = False
RemoveHandler .Changed, AddressOf OnFSWChanged
RemoveHandler .Error, AddressOf OnFSWError
End With
fsw = Nothing
End If
WriteLog(vbTab & "Create New File System Watcher on '" & ArchiveImport &
"'")
fsw = New FileSystemWatcher(ArchiveImport, "*")
With fsw
.NotifyFilter = NotifyFilters.Size
.IncludeSubdirectories = True
AddHandler .Changed, AddressOf OnFSWChanged
AddHandler .Error, AddressOf OnFSWError
.EnableRaisingEvents = True
End With
End Sub

Private Sub OnFSWChanged(ByVal sender As Object, ByVal e As
FileSystemEventArgs)
' Specify what is done when a file is changed, created, or deleted.
On Error Resume Next
Thread.CurrentThread.Name = "FSWChanged"
FilesToProcess.Add(e.FullPath)
End Sub

Private Sub OnFSWError(ByVal sender As Object, ByVal e As ErrorEventArgs)
On Error Resume Next
Thread.CurrentThread.Name = "FSWError"
WriteLog(TypeName(sender) & vbNewLine & e.ToString)
ConfigureFSW()
ProcessTree()
End Sub

Public Sub WriteLog(ByVal msg As String)
On Error Resume Next
Dim tName As String = Thread.CurrentThread.Name
If tName <> "" Then msg = tName & ": " & msg
Console.WriteLine(Now.ToString & vbTab & msg)
logs.WriteLog(msg)
End Sub
End Module

Public Class ProcessFiles
Inherits Collections.ObjectModel.KeyedCollection(Of String, FileToMove)

Private ThreadLock As New SynchronizationContext
Private NewFile As New AutoResetEvent(False)
' Set up the WorkerThread last as the sync objects need to exist
Private WorkerThread As New Thread(AddressOf Worker)

' One object can be passed to a new worker thread when it starts; the
FileControl class is that object
Private Class FileControl
Public ImportRoot As String
Public ArchiveRoot As String
Public NoVersion As New Collection
End Class

Protected Overrides Function GetKeyForItem(ByVal item As FileToMove) As
String
Return item.Key
End Function

Public Sub New(ByVal CopyFrom As String, ByVal CopyTo As String, ByVal
cNoVersions As Collection)
Dim fc As New FileControl
WriteLog("Creating new ProcessFiles container.")
With fc
.ImportRoot = CopyFrom
.ArchiveRoot = CopyTo
For Each str As String In cNoVersions
.NoVersion.Add(str, str)
Next
End With
WorkerThread.IsBackground = True ' Allow the program to exit at any time
WorkerThread.Name = "Mover" ' Used to track log entries
WorkerThread.Start(fc)
End Sub

Public Shadows Sub Add(ByVal File As String)
Try
Dim fm As New FileToMove(File)
SyncLock ThreadLock
If Not Contains(fm.Key) Then
MyBase.Add(fm)
WriteLog("Found '" & File & "'")
End If
End SyncLock
Catch ex As Exception
WriteLog(ex.ToString)
End Try
' Always trigger this just in case there are files waiting for movement
NewFile.Set()
End Sub

Private Sub Worker(ByVal obj As Object)
Dim fc As FileControl = CType(obj, FileControl)
Dim FilesRemaining As String
Dim LocalServer As String = My.Computer.Name
' The target file names will always be in UNC format. Local Server will be
used to replace the actual targ
' for the local copy that will get backed up to tape during incremental
backups.
Do While Left$(LocalServer, 1) = "\"
LocalServer = Mid$(LocalServer, 2)
Loop
LocalServer = "\\" & TrailSlash(LocalServer) ' Format is now
"\\<servername>\"
' This thread never exits
Do While True
' Wait for a file to be added to the list
NewFile.WaitOne()
Do While Count > 0
FilesRemaining = ""
Dim WaitTime As TimeSpan = FileToMove.OneMinute
Dim index As Integer = Count - 1
Try
Do While index >= 0
Dim f As FileToMove = Item(index)
Dim msg As String = ""
Try
If f.SizeStable Then
Dim FileBase As String = Mid$(f.FileName, InStrRev(f.FileName,
"\") + 1)
Dim DestFile As String = Replace(f.FileName, fc.ImportRoot &
"\", fc.ArchiveRoot & "\")
Dim UseVersioning As Boolean = True
For Each template As String In fc.NoVersion
If FileBase Like template Then
UseVersioning = False
Exit For
End If
Next
If UseVersioning AndAlso File.Exists(DestFile) Then
Dim i As Integer = InStrRev(DestFile, ".")
Dim FileExt As String = ""
If i > 0 Then
FileBase = Left$(DestFile, i - 1)
FileExt = Mid$(DestFile, i)
Else
FileBase = DestFile
End If
i = 0
Do
i += 1
DestFile = FileBase & "_" & i.ToString & FileExt
Loop While File.Exists(DestFile)
End If
' Move the source file
Try
' Copy to the local archives first; always override the
destination
Dim LocalDest As String = Replace(DestFile, "\\hermes\",
LocalServer)
Try
My.Computer.FileSystem.CopyFile(f.FileName, LocalDest)
Catch ex As Exception
logs.WriteLog("Unable to copy '" & f.FileName & "' to '" &
LocalDest & "'")
End Try
My.Computer.FileSystem.MoveFile(f.FileName, DestFile, True)
msg &= vbNewLine & "Moving '" & f.FileName & "' => '" &
DestFile
SyncLock ThreadLock
Remove(f.Key)
End SyncLock
Catch ex As Exception
msg &= vbNewLine & "Exception Processing: " & f.FileName &
vbNewLine & ex.ToString
If FilesRemaining <> "" Then FilesRemaining &= vbNewLine
FilesRemaining &= f.FileName
End Try
Else
If FilesRemaining <> "" Then FilesRemaining &= vbNewLine
FilesRemaining &= f.FileName
End If
Catch ex As FileNotFoundException
SyncLock ThreadLock
Remove(f.FileName)
End SyncLock
Catch ex As Exception
If FilesRemaining <> "" Then FilesRemaining &= vbNewLine
FilesRemaining &= f.FileName
msg &= vbNewLine & "Exception Processing: " & f.FileName &
vbNewLine & ex.ToString
Finally
If f.NextCheck < WaitTime Then WaitTime = f.NextCheck
End Try
If msg <> "" Then WriteLog(msg)
' Decrement index to get the next item. This always works as deleting
an item will leave the bottom index the same
index -= 1
Loop
Catch ex As Exception
WriteLog(ex.ToString)
End Try
If Count > 0 Then
WriteLog("Files Left: " & Count.ToString & vbNewLine & FilesRemaining)
WriteLog("Sleep Until: " & (Now + WaitTime).ToString)
Thread.Sleep(WaitTime)
WriteLog("Sleep Done: " & Now.ToString)
End If
Loop
Loop
End Sub
End Class

Public Class FileToMove
Private mFileName As String
Private utcLastChecked As Date
Private mLastSize As Long = 0
Public Shared ReadOnly OneMinute As TimeSpan = New TimeSpan(0, 1, 0)
Private Shared ReadOnly OneHour As TimeSpan = New TimeSpan(1, 0, 0)

Public Sub New(ByVal FileName As String)
mFileName = FileName
UpdateSize()
utcLastChecked =
My.Computer.FileSystem.GetFileInfo(mFileName).LastWriteTime.ToUniversalTime
End Sub

Public ReadOnly Property Key() As String
Get
Return mFileName
End Get
End Property

Public ReadOnly Property FileName() As String
Get
Return mFileName
End Get
End Property

Private Shared ReadOnly Property utcNow() As Date
Get
Return Now.ToUniversalTime
End Get
End Property

Private Sub UpdateSize()
UpdateSize(My.Computer.FileSystem.GetFileInfo(mFileName).Length)
End Sub

Private Sub UpdateSize(ByVal NewSize As Long)
mLastSize = NewSize
utcLastChecked = utcNow
End Sub

Public ReadOnly Property SizeStable() As Boolean
Get
If mLastSize = 0 Then
If utcNow -
My.Computer.FileSystem.GetFileInfo(mFileName).CreationTime.ToUniversalTime >
OneHour Then
My.Computer.FileSystem.DeleteFile(mFileName)
Throw New FileNotFoundException("File still empty after one hour")
End If
UpdateSize()
Return False
End If
Dim CurrentSize As Long =
My.Computer.FileSystem.GetFileInfo(mFileName).Length
If mLastSize = CurrentSize AndAlso _
(utcNow - utcLastChecked) > OneMinute AndAlso _
(utcNow -
My.Computer.FileSystem.GetFileInfo(mFileName).LastWriteTime.ToUniversalTime)

OneMinute Then

Return True
Else
UpdateSize(CurrentSize)
Return False
End If
End Get
End Property

Public ReadOnly Property NextCheck() As TimeSpan
Get
Dim ts As TimeSpan = utcNow - utcLastChecked
Debug.Print(ts.ToString)
If ts > OneMinute Then Return New TimeSpan(0)
Debug.Print((OneMinute - ts).ToString)
Return OneMinute - ts
End Get
End Property
End Class

'===================================================================

 

[jimmyfishbean]

Hi Kevin,

Thanks for the guidance (and patience). I'm on the right track now
thanks to you. Think the explanantion with the recipes did it!!

Despite only monitoring 2 directories, my application/service seems to
use up to 25 - 30 MB of memory usage (the handles go up to 250 +). Is
this a common burden with the FileSystemWatcher, or is it likely to be
due to inefficient code? The VB.Net application I have created has
actually been upgraded from VB6 to .Net. The VB6 application used
several directory monitoring API calls (i.e.
FindFirstChangeNotification, FindNextChangeNotification,
MsgWaitForMultipleObjects, etc). When processing the same number of
files as the VB.Net application, the memory usage would reach no more
than 13 MB (with 150 + handles). Thanks once again Kevin.

Hi Mike,

Thanks for the code. Before I deploy code from your application, may I
ask roughly how much memory the application uses and whether it reaches
the high levels (30MB) of my (inefficient ;P) windows service
application? Cheers,

Jimmy

 

[jimmyfishbean]

May I point out that despite upgrading my VB6 project to VB.Net, I was
unable to get the directory monitoring API calls to work, hence the use
of the FileSystemWatcher component. If someone has been able to make
use of the API calls then please let me know. Thanks.

Jimmy

 

[Michael D. Ober]

On a server that has been up since Feb 3rd, the code I posted has run for 10
minutes total and is currently using about 11Mb of VM allocation and a
physical memory footprint of 1 Mb. Numbers are from the server's Task
Manager and event viewer.

Mike.

 

[Michael D. Ober]

I'm not sure you really want to use the API for this. The FSW in .NET 2.0
appears to be a "smart" wrapper around the API. By "smart" I mean that it
checks to ensure the file that triggered the API calls meets the file
template requirements you gave the FSW object before returning. FSW also
resets the API for the next event so you don't have to remember to do this
yourself. (The VB 2005 code I posted was originally written in VC++ 6 and
not having to do these two items dumped a page of code.)

Mike.

 

[Kevin Spencer]

Hi Jimmy,

The .Net Framework tends to use a lot more memory than a VB6 or C++ native
app would. This is because of the built-in memory management. As long as you
are disposing anything that needs disposing (such as the FileSystemWatcher
class, when you stop monitoring), you shouldn't worry about it. Garbage
Collection will take care of it. The .Net Framework tends to cache for a
long time, but it is very reliable. I'm assuming you're only using one
instance of the FileSystemWatcher?

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
We got a sick zebra a hat,
you ultimate tuna.

 

[Michael D. Ober]

Kevin,

Jimmy will need two instances of the FileSystemWatcher since he is
monitoring two directories. Unless the directories are under a common
parent, in which case he can monitor the parent. In either case, the
footprint shouldn't be a big as he is seeing.

Mike Ober.

 

[Michael D. Ober]

Let me clarify - the code I posted started when the server came up the
evening of the 3rd and has used 10 minutes of CPU time since then.

Mike Ober.

 

[Kevin Spencer]

Hi Michael,

I should have said "1 per drop directory."

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
We got a sick zebra a hat,
you ultimate tuna.

 

[jimmyfishbean]

Kevin, Mike,

My app is now working ;P, and as efficient as it possibly can. Thanks
guys.

Jimmy