I'm in the process of designing an application that will run on a headless Windows CE 6.0 device. The idea is to make an application that will be started at startup and run until powered off. (Basically it will look like a service, but an application is easier to debug without the complete hassle to stop/deploy/start/attach to process procedure)
My concern is what will happen during development. If I debug/deploy the application I see no way of closing it in a friendly and easy way. (Feel free to suggest if this can be done in a better/user friendly way) I will just stop the debugger and the result will be WSACleanup is not called.
Now, the question. What is the consequence of not calling WSACleanup? Will I be able to start and run the winsock application again using the debugger? Or will there be a resource leak preventing me to do so?
Thanks in advance,
Jef
I think that Harry Johnston comment is correct.
Even if your application has no UI you can find a way to close it gracefully. I suppose that you have one or more threads in loops, you can add a named manual reset event that is checked (or can be used for waits instead of Sleep()) inside the loop condition and build a small application that opens the event using the same name, sets it and quits. This would force also your service app to close.
It may not be needed for debugging, but it may be useful also if you'll need to update your software and this requires that your main service is not running.
Related
well this has been bugging me for a couple of days on and off. I am at a clients site where they have a number of bespoke, written in house, services running on a Windows 2008R2 IIS server. The problem is that a couple of these services keep hanging, they are stuck in a “Stopping” state and the only way to kill them off is to open process explorer and kill the threads. Before anyone says anything about using ‘runas’, or logging on as the local admin, or the service owner, etc we’ve been through all of that.
The problem lies with the executable itselfs. The development team, in another country are going to look at this but it will take 4-5 months minimum, and we’re not certain they’ll get it right then.
I have a Powershell script to check the services on a regular basis which has the ability to ensure the services are running and if not, the force a stop and restart of the service, then it sends an email to confirm the actions. However with these specific services mentioned it can do nothing. They can’t be killed in task manager, taskkill, or process explorer (unless one kills the threads) it just says access denied. It is possible to change the permissions in process explorer and kill it but that’s a lengthier process than killing the threads.
To make things a little more difficult I can’t use the process name as on this server there are two other websites using an exe with the same name, just in a different folder.
What I’m after is a way to find and kill the threads of a processID, which I’ve already obtained via the script I have, so the rest of the script can complete the task of restarting the said service. At the moment this service dies on an inconsistent basis throughout the day and night, and the support guys have to RDP onto the server, open process explorer, find the offending process and kill the threads off then restart the services. A bit too much hassle for these already over worked guys especially if we can get powershell to do it automatically.
Hope someone can help on this. Thanks in advance.
Low level thread handling is likely to require native Win32 API usage. Powershell might help with P/Invoke, but the process is going to be complex. For starters, find out if the following tools can be used to identify the stuck thread. Maybe you can combine this info with some Sysinternals tools like handle.exe to find out what really blocks the thread.
The .Net framework has some tools available via System.Diagnostics.Process namespace. A list for threads for named process is available like so,
$ps = [diagnostics.process]::getProcessesByName("iexplore")
$p = $ps[0]
$p.Threads[0]
Full documentation is in MSDN. There is no method for killing a thread, but this should be kind of starting point for identifying the stuck one.
Another a way is to use WMI to get win32_thread data like so,
$threads = gwmi win32_thread
The output is quite different and some filtering is needed. Some examples are available. Another a WMI solution attempt might be based on Win32_process that has Terminate method.
I am new to mobile website development, and facing this issue where I want to refresh data on the website in every 30 sec which is invoked from the client side and server provides the data in response. Problem is when I close the browser or when the browser goes in background it stops working. Is there any thing we can do to make this thing possible?
Have a look at the Android Developers - Processes and Threads guide. You'll get a deeper introduction to how process life-cycles work and what the difference is between the states for background- and foreground processes.
You could embed your web app in a WebView. This way you could deal with the closing browser case: you could provide a means to "exit" the app that involves closing only your container activity. That way the timers you have registered in javascript will still be running in the 'WebViewCoreThread'. This is an undesirable behavior and a source of problems, but you can take advantage of it if you want (just make sure you don't run UI-related code there). I've never tested this in Kit Kat (which uses a different WebView based on Chrome) but works for previous versions, as I described here.
Now the user can always close any app. Even without user interaction, the OS can kill your app on low memory. So just give up on long-running apps that never end, because the OS is designed in such a way this is simply not possible.
You could go native and schedule Alarms using the AlarmManager.
Just checked this out on the Android KitKat WebView and as per Mister Smith's comments the javascript will continue executing in the background until the Activity is killed off:
Just tested with this running in a WebView:
http://jsbin.com/EwEjIyaY/3/edit
My gut instinct is that if the user has moved your application into the background, there seems little value in performing updates every 30 seconds, it makes more sense to just start updating again once the user opens the device up and cache what information you currently have available to you.
As far as Chrome for Android goes the same is happening, as Chrome falls into the background the javascript is still running.
If you are experiencing different behaviour then what exactly are you seeing and can you give us an example?
I'm currently working on a solution that has two projects, a console and a form application. The console application is the main entry point to my application, and from the console the user would run the form application.
The problem is, when the user boots the form application the rest of the business logic (from the console app) won't run until the form is closed. My first thought was to use a background worker for the form, but the business logic in the form project already uses a background worker (and I only have two CPUs...). Perhaps this could be my ignorance for multithreading, but is there a way to do this?
Any thoughts are much appreciated!
Cheers
Well, this is pretty unusual. In general, it doesn't make a lot of sense to provide the user with a nice GUI and still leave a console window up and interactive.
But yes, calling Application.Run() or Form.ShowDialog() is going to block the thread. It has to, the message loop needs to be running to keep the GUI alive. If you do this, be sure to put the [STAThread] attribute on the Main() method.
The only other decent alternative is to start a thread. This isn't a problem, a UI thread doesn't burn any CPU cycles. Code only ever runs when the user does something, it's otherwise idle 99% of the time. Be sure to call the thread's SetApartmentState() method before you start it, STA is required.
We are having a web application build using asp.net 3.5 & SQL server as database which is quite big and used by around 300 super users for managing around 5000 staffs.
Now we are implementing SMS functionality into the application which means the users will be able to send and receive SMS. Every two minute the SMS server of the third party is pinged to check whether there are any new messages. Also SMS are hold in queue and send every time interval of 15 to 30 minutes.
I want this checking and sending process to run in the background of the application all the time, even if the user closes the browser window.
I need some advice on how do I do this?
Will using thread will achieve this or do I need to create a windows service for it or are there any other options?
More information:
I want to execute a task in a timer, what will happen if I close the browser window, the task wont be completed isn't it so.
For example I am saving 10 records to the database in a time interval of 5 minutes, which means every 5 minutes when the timer tick event fires, a record is inserted into the database.
How do I run this task if I close the browser window?
I tried looking at windows service but how do I pass a generic collection of data to it for processing.
There really is no thread or service choice, a service can (and usually is!) multi threaded, a thread can start a service.
There are three basic choices you can:-
Somehow start another thread running when a user logs in -- this is probably a very poor choice for what you want, as you cannot really keep it running once the user session is lost.
Write a fully fledged windows service which is starts on OS startup and continues running unitl the server is shutdown. You can make this dependant on the SQLserver service, so it starts after the DB is available. This is the "best" solution but may be overkill for your purposes. Aslo you need to know the services API to write it properly as you need to respond correctly to shutdown and status requests.
You can schedule your task periodically using either the Windows schedular, or, preferably the schedular which is built in to SQLServer, I think this would be the most suitable option for your needs.
Distinguish between what the browser is doing and what's happening server-side.
Your Web App is sitting server-side waiting for requests from whatever browsers may be running, and servicing those requests, in servicing those requests I guess it may well put messages on a queue and have a look in a database for any new messages.
You want the daemon processor, which talks to the third-party SMS, to be triggered by time rather than by browser function. Either of your suggestions would work:
A competely independent service could run and work against the queues and database.
Your web app, which I assume is already a service, could spawn a thread
In either case we have a few technical questions of avoiding any race conditions between the browser-request processing and the daemon - but databases and queueing systems can deal with that.
So I would decide between stand-alone daemon and background thread like this:
Which is easier to implement? I'm a Java EE developer, I know in my app server I have an API for specifying code to be run according to a timer, the API deals with the threading issues. So for me that's very easy. I don't know what you have available. Timers are not quite as trivial as they may appear - so having a reliable API is beneficial. If this was a more complex requirement, where the daemon code were gnarly and might possibly interfere with the WebApp code then I might prefer to keep it conspicuously separate.
Which is easier to deploy and administer? Deploy separate Web App and daemon, or deploy one thing. In the Java EE world we could have a single Enterprise Application with all the code, so that's a single thing to deploy, start and control.
One other thing to consider: Scaling and Resilience. You might choose to have more than one copy of your web app running, either to provide fail-over capabilities or just because you need the extra power. In which case how many daemons would you have? Would it be a problem to have two daemons running? You might need some extra code to mediate between two daemons, for example log in the database the time of last work, each daemon can say "Oh, my buddy balready did the 10:30 job, I'll go back to sleep"
How do you disable closing an application when it is not responding and just wait till it recovers back?
What you're asking is not just impossible (any user with sufficient priviledges can terminate a process...no matter what OS), it's a horrible User Experience (UX) decision.
Think about it from the User's point of view. You're sitting there looking at an application. The application doesn't appear to be doing anything and isn't providing you any visual feedback that it is doing work. You'd think the application was hung and you'd restart it.
You could do anything from showing a scrolling progress bar to having the long running process update some piece of information on the UI thread (think of an installer in mid-install...it's constantly telling you which files it's putting where rather than just making you wait). In any case, you should be providing some visual feedback to the user so they know your application is still running.
Have the GUI work in a separate thread so that it is (hopefully) never "not responding".
If this is a question about programming, your program should never be in that state since you've tied up the GUI thread somehow. And you can't (and shouldn't) stop Windows or the user from closing your program. They've detected your code is rubbish and have every right to forcefully toss it out of their valuable address space.
In any case, your program's too busy doing other stuff - if it can't respond to the user, it probably can't waste time protecting itself either.
At some point, developers need to get it through their thick skulls that the computer belongs to the user, not them.
Of course, if you're talking about how to configure Windows to prevent this (such as on your PC), then this question belongs on serverfault.
Don't. No matter how important you think your application is, your users' ability to control their own systems is more important.
You can always terminate applications from task manager if you have the privileges. You can just disable or not show the system menu options that has the close icon and close menu option in the application window but that is not going to prevent the user from terminating it from task manager as mentioned before. Instead, I would just show some busy processing icon in the application so the user understands what is going on.
Only thing you can do is disable the close button. Users can still kill it from task manager or similar tool, to way around that. You could make killing it harder by launching it as a privileged process, but that comes with many more problems of its own.