Develop Reference

How to capture Exceptions from threads I have no direct access to?

I have developed a Windows Service capable of running a few plugins. Due to its nature, when developing Windows Services, the Start and Stop methods should run and return as fast as possible. The Start method runs Start methods from all plugins, which also should not block the execution. In this example, both plugins instantiate a Threading.Timer, which run in background.
The execution order happens as follows. The arrows indicate what runs in a different thread:
-> MyService.Start -> pA.Start -> pb.Start -> return
\_> DoWork() \
\_> DoWork()
Since both DoWork() are running inside a Timer, if an Exception happens, I am unable to catch it. This could easily be avoided if I could modify PluginA and PluginB, but I can't.
Any suggestion on what I could do to avoid this issue? Thanks in advance.
The following code is an oversimplification of the real code:
public class MyService
{
private PluginA pA = new PluginA();
private PluginB pB = new PluginB();
// Windows Service runs Start when the service starts. It must return ASAP
public void Start()
{
// try..catch doesn't capture PluginB's exception
pA.Start();
pB.Start();
}
// Windows Service runs Stop when the service Stops. It must return ASAP
public void Stop()
{
pA.Stop();
pB.Stop();
}
}
// I have no control over how this is developed
public class PluginA
{
private Timer _timer;
public void Start()
{
_timer = new Timer(
(e) => DoWork(),
null,
TimeSpan.Zero,
TimeSpan.FromSeconds(10));
}
private void DoWork()
{
File.AppendAllText(
"C:/log.txt",
"hello" + Environment.NewLine);
}
public void Stop()
{
_timer.Change(Timeout.Infinite, 0);
}
}
// I have no control over how this is developed
public class PluginB
{
private Timer _timer;
public void Start()
{
_timer = new Timer(
(e) => DoWork(),
null,
TimeSpan.Zero,
TimeSpan.FromSeconds(10));
}
private void DoWork()
{
File.AppendAllText(
"C:/log.txt",
"Goodbye" + Environment.NewLine);
throw new Exception("Goodbye");
}
public void Stop()
{
_timer.Change(Timeout.Infinite, 0);
}
}

You can also use the AppDomain.UnhandledException Event.
Please note that you can't recover from such an exception.

Debugging and logging windows service

I am learning basics of windows service. I have created a very simple one.
using System.ServiceProcess;
namespace WindowsServiceBasic
{
public partial class OmerService : ServiceBase
{
public OmerService()
{
InitializeComponent();
}
protected override void OnStart(string[] args)
{
System.Diagnostics.Debugger.Launch();
WriteLog("START");
}
protected override void OnStop()
{
System.Diagnostics.Debugger.Launch();
WriteLog("STOP");
}
private void WriteLog(string durum)
{
eventLog1.WriteEntry(performanceCounter1.RawValue.ToString());
}
}
}
using System;
using System.IO;
using System.ServiceProcess;
namespace WindowsServiceBasic
{
internal static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
private static void Main()
{
AppDomain.CurrentDomain.UnhandledException += CurrentDomain_UnhandledException;
ServiceBase[] ServicesToRun;
ServicesToRun = new ServiceBase[]
{
new OmerService()
};
ServiceBase.Run(ServicesToRun);
}
private static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
{
if (e != null && e.ExceptionObject != null)
{
string createText = e.ToString();
File.WriteAllText(#"c:\omerlog.txt", createText);
}
}
}
}
The first time my service (AServis) starts successfully but when I click the restart it crashes. Since my service is very simple It should have been worked properly. I try to log the error, put try catch but I could not find anything. I am trying to attach process, it debugs stop event but after stop debug suddenly finishes and start process crashes. Could you please help me what is the reason and how can I debug and log error.
Thanks in advance

I saw that it was stuck in
public OmerService()
{
InitializeComponent();
}
I could see the issue adding System.Diagnostics.Debugger.Launch(); statement.
public OmerService()
{
System.Diagnostics.Debugger.Launch();
InitializeComponent();
}

The standard trick I use in this situation is to add a call to System.Diagnostics.Debugger.Break in my start up code. Now, when you start the service as normal (through the Service Control Manager (SCM)), the call to the Break will cause Windows to launch the JIT debugger, which should prompt you to choose the debugger you wish to attach to the process (e.g., Visual Studio), which will then enable you to debug your code as normal.
Also see this: Easier way to debug a Windows service.

Start service on other machine: service on Local Computer started and then stopped

I created a C# windows service and installed it successfully on my local developer machine (it works well).
Now I'm trying to install the service on a different machine.
I copied the "Release" folder to the new machine and installed the service.
When I start the service on the new machine I get the following error:
"service on Local Computer started and then stopped. Some services stop automatically if they are not in use by other services or programs."
I don't get any message to the Application event log, I even added debug message as the first line of the program, but i see nothing in the Event Viewer (as if the code doesn't start at all). :/
What have i done wrong?

"started and then stopped" message usually appears when your server throws an exception during start up. Which could be for many reasons, including invalid paths and inability to write to the Application Event Log due to missing source or insufficient privileges.
I usually include an option to run my service as a console app.
Which allows me to display any exceptions using Console.WriteLine.
Following assumes your service extends from System.ServiceProcess.ServiceBase.
partial class MyService : ServiceBase
{
private static void Main(string[] args)
{
MyService svc = new MyService();
if (Environment.UserInteractive)
RunConsole(args, svc);
else
Run(svc);
}
public MyService()
{
InitializeComponent();
}
protected static bool KeepRunning { get; set; }
protected override void OnStart(string[] args)
{
StartServiceHost();
}
protected override void OnStop()
{
StopServiceHost();
}
protected override void OnShutdown()
{
StopServiceHost();
base.OnShutdown();
}
private static void RunConsole(string[] args, ConverterService svc)
{
// need to hold on to Ctrl+C, otherwise StopServiceHost() never gets called
Console.CancelKeyPress += (sender, e) => ShutDown(svc);
KeepRunning = true;
svc.OnStart(args);
Console.WriteLine("Press <Ctrl+C> to exit.");
while (KeepRunning)
{
Console.ReadLine();
}
}
private void StartServiceHost()
{
// start your service
}
private void StopServiceHost()
{
// stop your service
}
private static void ShutDown(MyService svc)
{
Console.WriteLine("exiting...");
svc.OnStop();
KeepRunning = false;
}
}

Well, I've found the problem:
I used password decryption with DataProctionScope.LocalMachine.
So when I changed the machine- the decryption failed.
I had to re-encrypt the passwords on the local machine and then the decryption worked fine.
Thank you for your responds!
*The eventlog debugging didn't work because of my fault.

Self-install of WInService

I've googled this one
but when i'm trying to apply it i get an error. So install/uninstall works fine, but service itself just doesn't start and after timeout it says that service doesn't respond. I don't know why. When i'm attaching to process it even doesn't enter into Main() method, static constructors and so on. I've used this addon for attach.
public static void Main()
{
AppDomain.CurrentDomain.UnhandledException += OnException;
if (Environment.UserInteractive)
{
AskUserForInstall();
}
else
{
ServiceBase.Run(new NotificatorService());
}
}
Service is also very simple:
using System.ServiceProcess;
using System.Windows;
namespace AZNotificator
{
public partial class NotificatorService : ServiceBase
{
static NotificatorService()
{
int x = 5;
}
public NotificatorService()
{
InitializeComponent();
}
protected override void OnStart(string[] args)
{
MessageBox.Show("Hello");
}
protected override void OnStop()
{
}
}
}

You can not call MessageBox.Show("Hello"); from the windows service since the service does not have the GUI.
If you want to do some interaction from the windows service have a look at this article
http://msdn.microsoft.com/en-us/library/ms683502(VS.85).aspx
So remove MessageBox.Show("Hello"); from your OnStart method and your service should start just fine.

Open a mutex shared with a service

I have a service that creates a thread with a loop that should run until the mutex is signalled by another process. I have the following in my service code
private readonly Mutex _applicationRunning = new Mutex(false, #"Global\HsteMaintenanceRunning");
protected override void OnStart(string[] args)
{
new Thread(x => StartRunningThread()).Start();
}
internal void StartRunningThread()
{
while (_applicationRunning.WaitOne(1000))
{
FileTidyUp.DeleteExpiredFile();
_applicationRunning.ReleaseMutex();
Thread.Sleep(1000);
}
}
Now I have a console application that should claim the mutex and force the while loop to be exited
var applicationRunning = Mutex.OpenExisting(#"Global\HsteMaintenanceRunning");
if (applicationRunning.WaitOne(15000))
{
Console.Write("Stopping");
applicationRunning.ReleaseMutex();
Thread.Sleep(10000);
}
When the console application tries to open the mutex I get the error "The wait completed due to an abandoned mutex." Whats wrong here?

I recommend that you use the Service's built-in stop signal rather than a mutex. The mutex class is more appropriate for managing exclusive access to a shared resource, which is not what's going on here. You could also use a system event but since services already have a built-in mechanism for signaling when they're stopping, why not use it?
Your service's code would look like this:
bool _stopping = false;
Thread _backgroundThread;
protected override void OnStart(string[] args)
{
_backgroundThread = new Thread(x => StartRunningThread());
_backgroundThread.Start();
}
protected override void OnStop()
{
_stopping = true;
_backgroundThread.Join(); // wait for background thread to exit
}
internal void StartRunningThread()
{
while (!stopping)
{
FileTidyUp.DeleteExpiredFile();
Thread.Sleep(1000);
}
}
Then, your console application would need to use the framework's ServiceController class to send the shut down message to your service:
using System.ServiceProcess;
...
using (var controller = new ServiceController("myservicename")) {
controller.Stop();
controller.WaitForStatus(ServiceControllerStatus.Stopped, TimeSpan.FromSeconds(15.0));
}