File System Watcher Over Network - vb.net

I am using standalone application vb.net(2.0) and using filesysystem watcher class to find any new xml coming into that specified directory then application take that file and continue the process but the direcotry have been located in network machine,
Now my problem is
once the path is not available it mean the shared path server going to offline, then my application not intemate me, how could i chage my code,
any one have idea, please share to me
Thanks in Advance
Nanda.A

If you're listening for changes on a directory and it becomes unavailable (like the server being restarted), the FileSystemWatcher will throw an Exception. It provides a OnError event that you can listen for and you can decide how to handle the problem.
I have an application that runs multiple watchers and when one errors the application will handle the error by looping every 30 seconds attempting to connect again. It also keeps a running total of the number of times it has tried to connect unsuccessfully and eventually will give up (after about an hour).
Here's the general idea in VB.Net:
''' <summary>
''' This event is called when an error occurs with the file watcher. Most likely the directory being watched is no longer available (probably from a server reboot.)
''' </summary>
Protected Sub Scan_Error(ByVal Source As FileSystemWatcher, ByVal E As ErrorEventArgs)
'// Stop listening
Source.EnableRaisingEvents = False
'// Maximum attempts before shutting down (one hour)
Dim Max_Attempts As Integer = 120
Dim Timeout As Integer = 30000
Dim I As Integer = 0
'// Attempt to listen - if fail, wait and try again in 30 seconds.
While Source.EnableRaisingEvents = False And I < Max_Attempts
I += 1
Try
Source.EnableRaisingEvents = True
Catch
Source.EnableRaisingEvents = False
System.Threading.Thread.Sleep(Timeout)
End Try
End While
End Sub

Related

Weird Issue With Windows Service - Service Timing Out

Hi there I have piece of legacy (VS2010) Windows Service code that I have imported into VS2017 and is causing me severe frustration. This code has worked well for about the last 6 years, however when I carry out the install and attempt to start the service the SCM comes back with a timeout error. The OnStart code is as follows:
Protected Overrides Sub OnStart(ByVal args() As String)
'Instaniate the timer for the service
_serviceTimer = New Threading.Timer(New Threading.TimerCallback(AddressOf Tick), Nothing, 60000, 60000)
End Sub
The call back is:
Private Sub Tick(ByVal state As Object)
'Switch off the timer event whilst the code executes
_serviceTimer.Change(System.Threading.Timeout.Infinite, System.Threading.Timeout.Infinite)
If Not _started Then
Startup()
_started = True
End If
Call ServerProcess()
'Re-enable the timer now that application code has completed
_serviceTimer.Change(_longInterval, _longInterval)
End Sub
I originally had the Startup process in the OnStart method, however removed it as an attempt at resolving this issue, however it has not made any difference. Method Startup is as follows:
Public Sub Startup()
Try
'Source these settings from the local config file
_appDataFolder = Utilities.GetSetting("AppDataRoot")
_configPathMapped = _appDataFolder & Utilities.GetSetting("ConfigPathMapped")
_logPath = _appDataFolder & "\" & utl.GetSetting("LogPath")
'Instaniate the timer for the service - Commented out after moving startup code from OnStart method
' _serviceTimer = New Threading.Timer(New Threading.TimerCallback(AddressOf Tick), Nothing, Timeout.Infinite, Timeout.Infinite)
'Initialise logging architecture
_logger = New aslLog.Logger(_configPathMapped & "nlog.config", _logPath, My.Application.Info.ProductName, My.Application.Info.Version.ToString)
_logger.SendLog("Started PSALERTS Schedule Server Service", NLog.LogLevel.Info, _serviceTimer, _checkInterval, Nothing)
'Determine if the cloned config files exists in the mapped config file folder
'We clone these files to a writable destination to allow us to overcome write restrictions ot the C: drive on the SPEN PTI Desktop model
If Not System.IO.File.Exists(_configPathMapped & "psaservermachine.config") Then
'Clone the app.config file in the config folder as psaservermachine.config
Utilities.CloneFile(_programFileLocation & "PSALERTSScheduleServer.exe.config", _configPathMapped & "psaservermachine.config")
End If
If Not System.IO.File.Exists(_configPathMapped & "nlog.config") Then
'Clone the nlog.config file
Utilities.CloneFile(_programFileLocation & "PSALERTSScheduleServer.exe.config", _configPathMapped & "nlog.config")
End If
'Determine the Oracle TNS Environment
'Check for the existence of the environment variable 'TNS_ADMIN'
If Environment.GetEnvironmentVariable("TNS_ADMIN") IsNot Nothing Then
'If TNS_ADMIN exists then we can continue with the application session
Else
Dim oraTnsPath As String = ""
'If it doesn't exist then we need to determine the Oracle information from the PATH environment variable
oraTnsPath = GetOraTnsPath()
If oraTnsPath <> "" Then
'Then create the TNS_ADMIN environment variable
Environment.SetEnvironmentVariable("TNS_ADMIN", oraTnsPath)
Else
'If no oracle client information exists then raise an error to this effect and exit the app
'informing the user that they need to install the Oracle client in order to use PSALERTS
Beep()
Throw New PSALERTSOracleConfigException(
"PSALERTS Oracle Configuration Error. PSALERTS Did not find a valid Oracle Client." & vbCrLf & vbCrLf &
"Please install a valid Oracle Client and try again." & vbCrLf & vbCrLf &
"If a valid Oracle Client is installed then ensure that the PATH environment variable contains an entry for the Oracle Client." & vbCrLf & vbCrLf &
"For example - TNS_ADMIN=C:\oracle\12.1.0\Client_lite\NETWORK\ADMIN"
)
End If
End If
'Register the application
If Not Registered() Then
'Register the application
Register()
End If
If Registered() Then
'Clean/close any stray Excel processes from previous debug session
If _debugModeOn Then
CleanUpRedundantProcesses("EXCEL", "PSALERTS")
End If
'instantiate fresh excel session
_myXLApp = New Excel.Application
'Get the timer interval settings
_longInterval = CType(utl.GetSettingServerMachine(_configPath, "appSettings", "LongIntervalMillis"), Integer)
_initInterval = CType(utl.GetSettingServerMachine(_configPath, "appSettings", "InitialIntervalMillis"), Integer)
_refreshInterval = CType(utl.GetSettingServerMachine(_configPath, "appSettings", "InitialIntervalMillis"), Integer)
'Re-start the timer with periodic signalling as per the specified check interval
_serviceTimer.Change(_initInterval, _initInterval)
Else
_started = False
End If
Catch ex As Exception
_logger.SendLog("PSALERTS Schedule Server startup failure.", NLog.LogLevel.Error, ex)
Finally
End Try
End Sub
I use a similar technique for a number of similar services and they are running fine. Would appreciate some insight from any Windows Service gurus out there. Oh, I use WiX to carry out the install, again this is a well worn template for a number of similar such applications.
Kind Regards
Paul J.
Core: The very most typical errors:
Config problems: connection strings, faulty paths, etc...
Boot startup problem (good list - from FAQ)
Wrong password / login account when running as a real user with password.
Files missing or runtimes missing.
Permission problems (ACL / NT Privilege missing).
Maybe check this answer before the below.
UPDATE: Maybe have a look at this previous answer. Service startup timing issue. Also check my ad-hoc answer there in the same page.
Debugger: Other than that - nothing like stepping through the code with a debugger. I haven't done that in a long time. Deploy debug binaries and try? Windows 10 now hides messages from services - not sure how that affects debuggers: No more switching to Session 0.
I am not a service guru, but a deployment specialist. I'll just provide some links and see if that helps. Maybe I have not fully understood the whole problem. I tend to focus on the deployment side and not so much development side.
Ideas List / Debugging Check List: These are "ideas lists" for what could be wrong for applications in general - not just services (two first lists are similar - created some time apart):
Crash on launch
Desktop application won't launch
General purpose WiX / MSI links
Yes, these lists are very generic - too large to digest. Just skim the first two I think.
Debugging Tools: Also a reminder of the most useful service debugging tools: Event Viewer, Task Manager, Services.msc, Process Explorer (system internals), The NET command and SC.exe.
Good Service FAQ: https://www.coretechnologies.com/WindowsServices/FAQ.html
Your startup method should fire up a background worker and quickly return to the SCM that it has started. There is a system wide default setting of 30 seconds but honestly a proper service should respond in a few seconds.
Looking though your code, your connection to the database is probably the long pole causing the problem.

Addhandler [process].Exited makes windows service to stop

Recently I've created a windows service which can help to trace the process start time and exit time, but I found that whenever the addhandler [process].exited executed, the windows service will stop
Here are my codes for the handler
For Each chrome_p As Process In NewChromeProccess
chrome_p.EnableRaisingEvents = True
AddHandler chrome_p.Exited,
Sub()
Using sw As StreamWriter = New StreamWriter(AppDomain.CurrentDomain.BaseDirectory + "\MonitoringApplication.txt", True)
ChromeEndTime.Add(chrome_p.ExitTime)
sw.WriteLine($"Process: {chrome_p.ProcessName}, Exit Time: {chrome_p.ExitTime}")
End Using
End Sub
Next
The description for Event ID 0 from source Service1 cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer.
If the event originated on another computer, the display information had to be saved with the event.
The following information was included with the event:
Service cannot be started. An instance of the service is already running
After some investigation I think the problem you are encountering is due to the line
sw.WriteLine($"Process: {chrome_p.ProcessName}, Exit Time: {chrome_p.ExitTime}")
And, specifically, the chrome_p.ProcessName part. When I had the line as you wrote it above, I was getting the error message: Process has exited, so the requested information is not available. Switching that out with a string constant, I get the line Process: chrome_p.ProcessName, Exit Time: 5/2/2019 8:05:46 PM in the text log file.

ManagementException: Not found

I have a program which runs on some wearable terminals in our warehouse. These terminals connect via remote desktop to our server which actually hosts and runs this program.
This program takes a scan of product, launches another program (if it isn't already running for the current user) which handles some processing, then does some additional processing once finished. One issue I'm running into is checking if the second program is already running. I've tried a lot of different code but this is what I settled on as it seemed to work perfectly fine.
Private Function CheckPrintLabelRunning() As Boolean
Dim selectQuery As String = "Select * From Win32_Process Where Name = 'vbPrintLabel.exe'"
Dim searcher As New System.Management.ManagementObjectSearcher(selectQuery)
Dim processList As System.Management.ManagementObjectCollection = searcher.[Get]()
For Each obj As System.Management.ManagementObject In processList
Dim argList As String() = New String() {String.Empty, String.Empty}
Dim returnVal As Integer = Convert.ToInt32(obj.InvokeMethod("GetOwner", argList))
If returnVal = 0 Then
If argList(0).ToString.ToUpper = Environment.UserName.ToUpper Then
Return True
End If
End If
Next
Return False
End Function
On Thursday, while the users were using the application on the terminals, the following error message popped up in my error logs. This application has seemingly been closing itself down, hitting the main form's FormClosing event (indicating that it isn't a full crash, but something that is handled inappropriately or an environment crash perhaps?). Here is the exception:
System.Management.ManagementException: Not found
at System.Management.ManagementException.ThrowWithExtendedInfo(ManagementStatus errorCode)
at System.Management.ManagementObject.InvokeMethod(String methodName, ManagementBaseObject inParameters, InvokeMethodOptions options)
at System.Management.ManagementObject.InvokeMethod(String methodName, Object[] args)
at vbFullCasePicking.frmFullCasePicking.CheckPrintLabelRunning()
at vbFullCasePicking.frmFullCasePicking.StartPrintLabelListener()
at vbFullCasePicking.frmFullCasePicking.PrintLabel(Boolean blnSMPLabels, String strCartonID)
I would like to point out that in this particular issue, the application did not close itself down, but I am still curious about this error as it's the first I've seen it of all the months this has been in use.
EDIT: More info...the server the application runs on is Windows Server 2003. This issue has not generated any event log entries of any kind as far as we can see.
EDIT 2: I completely forgot about this, but I have a previous question regarding this issue. I was initially querying all the processes which seemed to cause errors when multiple users would try to query at the same time. This is likely the same issue, then, just with a much smaller window. Any input is greatly appreciated.

How to find 64-bit process info using a 32-bit process

I have a 32 bit application that shells a second application that can be 32 or 64-bit depending upon the computer it's running on.
I only want one instance of the second application to run at a time, and I need the first application to prevent the second from being launched more than once.
I want to be able to use GetProcessesByName to obtain the running processes. This seems to work fine. It's when I attempt to obtain the module data to find out what folder the second application was run from that things fall apart.
Does anyone have a suggestion for identifying 64-bit processes and their folder of origin from a 32-bit application?
Thank you,
SH
You can use the WMI API (System.Management namespace) for this, specifically the ManagementObjectSearcher. The example below shows to get the process id and full command line from all running notepad instances.
Imports System.Management
Module Module1
Sub Main()
Dim wmi = New ManagementObjectSearcher("SELECT ProcessId, CommandLine FROM Win32_Process WHERE CommandLine LIKE ""%notepad%""")
Dim result = wmi.Get().OfType(Of ManagementObject)()
For Each r In result
Console.WriteLine("Process ID: {0}, Command Line: {1}" r("ProcessId"), r("CommandLine"))
Next
End Sub
End Module
I think it could be easier if you set a Mutex when launching second app.
In main app you could do this: if Mutex doesn't exist you run second app (which creates Mutex when run and release it when closing), otherwise you skip...
EDITED:
You can't edit second app to insert the creation of a mutex, ok.
But you can do this in main app:
Create a background worker BackgroudWorker wrk
Set a private bool to true: bool running = false
Execute wrk when you want the new app run: if (running) return; running = true;
wrk creates a Process and waits for its end
when wrk ends running = false
Just an idea...
EDITED AGAIN:
If you close first app and reopen it, user is able to run second app again.
So you could do this:
Create a background worker BackgroudWorker wrk
Write a tmp file (on NTFS it can be empty)
Execute wrk when you want the new app run:
if your tmp file exists then exit;
wrk creates a Process and waits for its end
when wrk ends deletes tmp file
With this method, even if user quits your first app, tmp file remains on hdd; so when user runs first app again, second app will not be executed.
Remeber that if user is smart enough to undestand this, he could manully delete file and the trick is done.
Finally: are you sure user cannot run directly second app?

Reset IIS on multiple servers at once instead of looping through

I am trying to reset IIS on a set of servers all at one time instead of looping through and resetting each one individually, but I can't seem to figure out how to do it. Could someone please give me an example? Thank you
I am using System.Diagnostics
With m_Process.StartInfo
.FileName = strFileName
.Arguments = String.Format("{0}{1}", server, strArguements)
.UseShellExecute = False
.CreateNoWindow = True
.RedirectStandardError = True
.RedirectStandardOutput = True
End With
I've seen a few questions today with similar conditions ("instead of looping") and I've been trying to figure out what the big deal is about looping. Since iisreset (what I am guessing is assigned to strFileName in your example) takes a single machine name, you are out of luck in that department.
I would assume that iisreset connects to the SCM on the target server and does a restart of the IIS Admin and dependent services.
I suppose you could roll your own iisreset.exe that took multiple servers on the command line, but internal to that you would have to use some kind of iteration.
Could you maybe explain why you can't or don't want to loop?
At some level you have to loop over the list of servers and send some message to each to instruct them to reset. Whether you do that by running iisreset with each server name or by some other means, you can't really make the loop go away.
However, if you're just saying that you want to start resetting all the servers as fast as possible rather than waiting for the first to finish resetting before you start resetting the second, it looks like you already have that. When you call m_Process.Start(), it should return as soon as the new iisreset process has started. As far as I can see, it doesn't block and wait until iisreset exits. Therefore, your iisreset processes should already run in parallel.
If I understand what you're asking, you're okay looping throught he servers, but you just don't want to wait for each server to complete before proceeding to the next one. Since ProcessStartInfo doesn't allow any way to detach from a process you're starting (be nice if it did), you can do it like this (obviously, missing your parameters and such):
Imports System.Threading
Class Restarter
Sub Main()
Dim ServerList As New List(Of String)
For Each server As String In ServerList
ThreadPool.QueueUserWorkItem(AddressOf RestartServer, server)
Next
End Sub
Sub RestartServer(ByVal Server As String)
Dim m_Process As System.Diagnostics.Process
With m_Process.StartInfo
.FileName = strFileName
.Arguments = String.Format("{0}{1}", Server, strArguements)
.UseShellExecute = False
.CreateNoWindow = True
.RedirectStandardError = True
.RedirectStandardOutput = True
End With
m_Process.Start()
End Sub
End Class