I'm working on a Windows application (not WinForms, not Console, not WinService), is just a project with an entry class.
What is the best way, in .NET, to stop an application from exiting the Main method?
I know I can achieve this in console with Console.Read() or I can use EvenWaitHandle.WaitOne() and never call Set().
Is there a better way of doing this?
Thanks for the help in advance.
UPDATE:
This is an overview of the application.
I need to start independent processes (some exe) on demand, containing wcf service. WCF service should listen idefinetly and that is why I need this functionality. The most similar approach I can find is IIS (many w3wp processes running at the same time).
w3svc.exe (IIS windows service) starts many instances of w3wp.exe depending on the number of configured app pools and the requests, it receives.
In my application I want to keep up the processes representing w3wp.exe in the IIS infrastructure, not w3svc. What is the kind of message loop that would keep alive w3wp in .NET?
You can do that in sooo many ways. I personally like this one, as it is very readable and self explanatory:
Process.GetCurrentProcess().WaitForExit();
IIS is a windows service which is why it runs like this. You might look at other options like a single service where you can invoke it via an api and tell it to start another thread or listener. Starting new instances of applications isn't the best option. Typically windows applications have a messagepump, which is a while loop I think...which would prevent it from exiting.
However, you can also follow the example here, which I believe does not close the formless window:
Run Formless Notification User Control?
while(true)
{
// to make it less CPU intensive
Thread.Sleep(1000);
}
Of course, any solution you can think of will not prevent the forceful termination of application by killing its process.
In your update you say that the program is starting several other programs using Process. (It happens to be 'yourself' but that doesn't matter.)
If the program has already done that it doesn't sound like it has any more to do. That process ending won't kill all of the processes it spawned.
You can use the process.WaitForExit() to wait for the processes that you spawn to all exit, rather than just spinning doing nothing, if for some reason you really need to keep the process alive. If there is something that it actually needs to do after spawning the other processes then you'd need to tell us what that is, because if there is something you should be waiting on an event of some sort, which is something you haven't brought up.
Edit: you claim that all the process is doing is "listening". Define that task. If you have a blocking GetNextRequest method then you simply have: while(true){GetNextRequest();}. If it's non blocking, then use use a BlockingCollection<MyRequests> in which the receive method/event hanlder adds a new item to the collection and the main thread had a while loop just like I mentioned before reading from the blocking collection. The point is that you shouldn't ever just sit there and do nothing; you process is doing something, so do that in a while(!done) or while(true) loop. If the method isn't blocking, it's a reasonably well defined problem to solve; just wrap it in a blocking method call.
System.Threading.Thread.Sleep(millisenconds);
Related
We have a .NET console app that has many foreground threads.
If we kill the process using Task Manager or issuing killjob, kill from the command line in windows, is there a way by which we can gracefully shut down the application (adding manged code within the .net console app), something like having a function being called say TodoBeforeShutdown() that disposes objects, closes any open connections, etc.
P.S. - I read the other threads and they all suggested different ways to kill the process, rather than my specific question, what is the best way we can handle a terminate process, within the .NET managed code.
Thanks in advance.
Unfortunately, there is no event raised that you can handle whenever a process is killed.You can think of killing a process like cutting off the power to the computer—no matter what code you have designed to run on system shutdown, if the computer doesn't shut down gracefully or properly, that code is not going to run.
When you kill a process using Task Manager, it calls the Win32 TerminateProcess function, which unconditionally forces the process (including all of its owned threads) to exit. The execution of all threads/processes is halted, and all pending I/O requests are canceled. Your program is effectively dead. The TerminateProcess function does not invoke the shutdown sequence provided by the CLR, so your managed app would not even have any idea that is was being shut down.
You suggest that you're concerned about disposing objects whenever your application's process is terminated, but there are a couple of things worth pointing out here:
Always strive to minimize the amount of damage that could be done. Dispose of your objects as early as possible, whenever you are finished with them. Don't wait until later. At any given time, when your program's process is terminated, you should only be keeping the bare minimum number of objects around, which will leave fewer possibilities for leaks.
The operating system will generally clean up and free most of these resources (i.e., handles, etc.) upon termination.
Finally, it should go without saying that process termination in this way is truly an exceptional condition—even if some resources leak, that's to be expected. You're not supposed to shut an app down this way any more than you're supposed to kill necessary Windows system processes (even though you can when running as an Administrator).
If this is your regular plan to shut down your console application, you need to find another plan.
In short: You can't!Killing a process is exactly the opposite of a gracefull exit.If you are running Foreground Threads, sending a wm_exit won't shut down your app. Since you have a console app, you could simply redirect the console input to send an "exit" to your process.Further I think you could change the app to service (instead of a console application), this would offer you exactly what you are looking for -> interface for gracefull exit based on windows build-in tools/commands.
I am currently trying to write a windows form application (in C#) that can start and stop multiple Java processes (with parameters to run a specific jar file).
I have no problem starting each process; however I need to find a way to make the application close all of them when it exits, regardless of which way (being an unknown amount of java processes), that I run in an individual worker thread each to avoid tying up the main thread while the application is running (and catching the processes outputs).
I had a look at this one: Close another process when application is closing
but it does not seem to work for my purpose (it doesn't close the processes).
it does not seem to work for my purpose.. (it doesn't close the processes).
But what does it do? Does it close the Java window(s) at least? Do your Java applications even have windows?
In general,
If possible (i.e. if you build the Java application yourself) you should set up a mechanism between your C# and Java application(s) to gracefully signal the Java application(s) to shut down (socket, etc.)
Failing that, you may still be able to gracefully shut down your Java application(s), if they are graphical, by sending WM_CLOSE. This is what the Process.CloseMainWindow/Process.Close approach that you tried (and failed) does. If your Java applications are console applications, you can try closing its/their standard input and/or simulating ^C instead.
Finally, when all else fails, use Process.Kill to terminate your Java child process(es) -- ungracefully. You may want your controlling process to first try 1. or 2. above, wait until either all child processes have exited or until a short period of time (e.g. 3s) has elapsed, and only then proceed with Process.Kill on whatever processes have not exited already.
procrss.kill The Kill method is an excellent way to cause a Process to meet a violent and swift end. The Kill method can throw some exceptions. But it often does not and usually will accomplish your desired objective—which is somewhere between cold-blooded murder and a swift and painless execution.
I am developing a high performance App that is causing the main process to seemingly stop responding and crash - from time to time - due to overload (I get the Close Application Dialog so the App never exits per se, just freezes, which is annoying)
I welcome any clean way to pro grammatically detect when the App is frozen, so I can use a BAT (or else) to automatically Kill the process and Restart.
Of course, this is a temporary fix while auditing the App, but it comes very handy in the meanwhile.
TieBreaker : BTW, Is there a way to override windows' Exception Screen and just quit the App ???
This is mostly annoying feature most of the time.
EDIT :
FOR GOD'S SAKE : the app IS freaking freezing, THOUGH every single task run in BG Workers and threads !!! And I specified that in comments. Come'on, I am not that dumb. Just that your app runs BG workers does not imply it never freezes ! And As I said, please JUST answer my question, I am not looking for lessons on how to design my App, that I am already working on and I know what has to be done. As specified MANY times, I just need a fix on the server in the meantime.
Thank you.
I'll say it if noone else will :) Make a separate forms app that does-
Process[] prs = Process.GetProcesses();
foreach (Process pr in prs)
{
if (!pr.Responding)
{
try
{
pr.Kill();
}
catch { }
}
}
//then to restart-
var process = new Process
{
StartInfo = new ProcessStartInfo
{
FileName = #"C:\yourapp.exe"
}
};
process.Start();
Obviously oversimplified.
We handle this in a service by having the main service exe be little more than a shell that launches the child threads.
The child threads are then responsible for reporting back to the parent thread whenever they can to record the last date/time they were "seen".
On a regular interval, the service app checks the list of child processes and, if one hasn't been seen for a predetermined period of time (i.e. 2 minutes), but did not report that it had closed down, the parent process will first try to join the thread and shut it down gracefully (usually fails) and then, if that didn't work, aborts the thread.
We have used this approach successfully for many years, starting when an OCR service that we were running would hang constantly due to bugs in the OCR software.
Move all CPU instensive tasks off of the GUI and invoke back to the gui to report any statuses.
The main app should never freeze. I wrote an app that generated over 500 threads (all at once) and managed them as they asynchronously (.net 2) processed multiple database calls. I believe you need to systematically move all processes to a thread safe situation and remove any direct GUI calls.
ADDENDUM How did I run 500+ threads:
Usage of smart locks done from the beginning on all shared data locations. See my blog articlesSmart Resource Locking in C# .Net for Thread Safe CodeC# MultiThreading Using ThreadPool, Anonymous Delegates and Locks
Interface created which specified an action operation with data, error status as a properties.
Threading base class created (for classes in #4 and #5) which created, started and cleaned up thread opertions. No business logic, just a method of handling threading in one location.
Class created based on interface in #2 and also derived from step #3. Class via the interface was required to get data and place data (thread safe via localized lock) and report its status. Class also designed to give up thread cycle if no work done to be done via thread.Sleep(0) instead of busy waiting.
Manager class created (which ran on its own thread and derived from #3).It launched 1-N #4 classes to do work. Each of those instances was placed into a working list.
Manager class simply browsed the working list for instances which reported their work was done if it was done it moved the instance to the done work. Manager class also kept records of the status (thread safe via locks) to exposed properties (as well as any reported errors by the children instances). Manager gave up thread cycle after each run and slept for 250 milleseconds before starting again.
GUI thread had working timers which dealt with getting specific status from the manager. They would extract the data from the manager's properties and invoke back the GUI to target a control (gridview) which reported all statuses and errors.
By doing that, I was able to achieve individual threads doing specific work and if a process ran into a problem it reported it, or it reported success or failure. Those messages bubbled up to the manager which bubbled up to the timers which bubbled up to the GUI. The gui handled no business logic except to start the mananager and timers.
I get that this doesn't help your situation right now and I feel your pain. But until you are able to seperate out the business logic from the GUI and handle error situations in the threads (background workers) and bubble them up to the GUI, you will still have this frustration with the current code.
If something is locking that is a sign that business logic is too tightly coupled with GUI operation and that has to be divorced before you will get the performance you want from the GUI.
HTH
I've got a windows service with only two methods - one private method DoWork(), and an exposed method which calls DoWork method. I want to achieve the following:
Windows service runs DoWork() method every 6 hours
An external program can also invoke the exposed method which calls DoWork() method. If the service is already running that method called from the service, DoWork() will again be invoked after the current method ends.
What's the best approach to this problem? Thanks!
An alternative approach would be to make use of a console application which can be scheduled by Windows task scheduler to run every 6 hours. In that case you don't waste resources to keep the Windows service running the entire time but only consume resources when needed.
For your second question: when you take the console app approach you can have it called by making use of Process.Start for example.
If the purpose of your application is only to run a specific task every six hours, you might be better off creating a command line application and creating a scheduled task that Windows runs automatically. Obviously, you could then manually start this application.
If you're still convinced you need a service (and honestly, from what I've seen so far, it sounds like you don't), you should look into using a Timer, but choose your timer carefully and read this article to get a better understanding of the timers built into .NET (Hint: Pay close attention to System.Timers.Timer).
To prevent reentry if another method tries to call DoWork() while the process is in the middle of performing its operation, look into using either a Mutex or a Semaphore.
there are benefits and drawbacks either way. my inclination with those options is to choose the windows service because it makes your deployment easier. scheduling things with the windows task scheduler is scriptable and can be automated for deployment to a new machine/environment, but it's still a little more nonstandard than just deploying and installing a windows service. you also need to make sure with task scheduler it is running under an account that can make the webservice call and that you aren't going to have problems with passwords expiring and your scheduled tasks suddenly not running. with a windows service, though, you need to have some sort of checking in place to make sure it is always running and that if it restarts that you don't lose hte state that lets it know when it should run next.
another option you could consider is using nservicebus sagas. sagas are really intended for more than just scheduling tasks (they persist state for workflow type processes that last for more than the duration of a single request/message), but they have a nice way of handling periodic or time-based processes (which is a big part of long running workflows). in that a saga can request that it get back a message from a timeout manager at a time it requests. using nservicebus is a bigger architectural question and probably well beyond the scope of what you are asking here, but sagas have become how i think about periodic processes and it comes with the added benefit of being able to manage some persistent state for your process (which may or may not be a concern) and gives you a reason to think about some architectural questions that perhaps you haven't considered before.
you can create a console application for your purpose. You can schedule the application to run every 6 hours. The console will have a default method called on application start. you can call your routine from this method. Hope this helps!!
What I need to know:
I would like to detect when a the main thread (process?) terminates so that I can ensure certain actions are performed before it is terminated.
What I have found myself:
I found the events AppDomain.DomainUnload and AppDomain.ProcessExit. AppDomain.DomainUnload seems to work with non-applications like MbUnit. AppDomain.ProcessExit seems to work with applications but there is a 3 second time limit which I really don't like. Is there more ways to detect when an AppDomain / process terminates?
Background:
I am looking for such an event to ensure my log is persistet to file when the application terminates. The actual logging runs on another thread using a producer-consumer pattern where it is very likely that log entries might queue up in memory and I need to ensure this queue is saved to file when the application terminates.
Is there anything else I should be aware of?
Update:
Changed the above to reflect what I have found out myself. I am not happy with the 3 second time limit during ProcessExit. The MSDN documentation does say though that it can be extended:
The total execution time of all
ProcessExit event handlers is limited,
just as the total execution time of
all finalizers is limited at process
shutdown. The default is three
seconds, which can be overridden by an
unmanaged host.
Does anyone know how to override the default?
More ideas are also highly appreciated!
Follow up:
I have posted a follow up question to this.
You should have an entry point for your application. Normally you can do there some logging when all tasks are terminated:
static void Main()
{
try
{
Application.Run( .... );
}
finally
{
// logging ...
}
}
What exactly do you want to find out?
When the process terminates? (Just because the AppDomain is unloaded doesn't necessarily mean that the entire process is terminating)
When the main thread terminates (If there are other non-background threads, the main thread can terminate without the process terminating (or AppDomain unloading)
So they're not quite the same thing.
Anyway, it is generally dangerous to have log messages buffered in memory at all. What happens if someone turns off the power? Or if I terminate your process through Task Manager? All your log messages are gone. So often, you'll want unbuffered writes in your log, to get messages pushed to disk immediately.
Anyway, another (more robust) approach might be to run the logger itself in a non-background thread. That way, even if the rest of the application terminates, the logger won't, so the process is kept alive. Then you just have to set some flag when the rest of the app terminates, to let the logger know that it too should close once it has written out all pending log messages.
It still won't save you from the case where the system loses power or someone forcibly termianates the process on the OS-level, but it will handle all cases where the application closes normally, and gives you unlimited time to perform clean-up actions (since the process isn't actually terminating yet, it's still got one live thread)
ie. guaranteed to be called and have unlimited time to finish?
Unfortunately, NO option is going to have unlimited time, and be guaranteed. There is no way to enforce this, as many things can happen. Somebody tripping over the power cord or a forced termination of your program will prevent any option from giving you adequate time to handle things.
In general, putting your logic at the end of the Main routine is probably the most reasonable option, since that gives you complete freedom in handling your termination events. You have no time constraints there, and can have the processing take as much time as needed.
There are no guarantees that this will run, though, since a forceful termination of your program may bypass this entirely.
Based on the documentation, it looks like the default application domain (the one your Main method is probably running in) will not receive the DomainUnload event.
I don't know a built-in event that would do what you expect.
You could define your own custom event, have interested parties register with it, and fire off the event just before you return from Main().
I don't know how old this thread is, but I've had a similar problem whcih was a little tough for me to solve.
I had a WinForms application that was not firing any of the above forementioned events when a user logged out. Wraaping the Application.Run() in a try finally didn't work either.
Now to get around this you would have to using PInvoke into Win32 API's to achieve this. Well you did prior to .NET 2.0 anyways. Luckly MS introduced a new class called SystemEvents. With this class you can catch a SessionEnd event. This event allows you to cleanup when the OS want to terminate your app. There is no .NET time limit o this event it appears, although the OS will eventually kill your app if you take too long. This is a little more than 3 seconds, although 3 seconds should be plenty of time to cleanup.
Secondly my other problem was I wanted my worker thread to terminate the main thread once it was finished its work. With an Application.Run() this was hard to achieve. What I ended up doing was calling Application.Run() with a shared Application context. The thread is then able to call ApplicationContext.ThreadExit() to force the Application.Run to return. This seems to work quite nicely.
Hope this helps someone.
Regards
NozFX