I am using a .dll from Ingeardrivers.com. I realize this question would more appropriately be asked on that site and have posted to there as well but more people on here makes my chances of it getting answered better.
I am a novice programmer and this is my first experience with threading. Basically I have two main loops in my program, and when I run each loop as the 'main thread' by itself - they both work fine individually. The problem is when I am starting two threads and running the main loop inside these threads, at some point in the loop they both are trying to use the Ingear.net dll and when one loop already has created an instance of the class, the second loop just sits on the constructor and doesn't do anything.
Does anyone have any suggestions on how to resolve?
I'd recommend firstly that you check with the vendor to see if the library is thread safe.
But in the mean time you could try creating a single instance of the class and passing it to your two threads/loops as part of the constructor (or setting a property with it).
It'll most likely not work, but you won't know until you try.
The add-on is thread safe -
I was manually disconnecting the controller each time via 'controllername.disconnect()'
For some reason this didn't actually close the connection and I was maxed out on CIP connections. When I removed that, the controller somehow knew to disconnect by itself.
Strange but it works.
Related
I've got a long-running loop which involves a fair amount of UI functions. This loop therefore must be run on the main thread. However, I also want to display progress of this task, so this must also run on the main thread as displaying the current progress would involve updating the UI. I am really struggling to find a way of allowing the UI to update with current progress on the main thread when the main loop is also running on the main thread. What happens is that the UI is frozen during the loop and then updates to show that the process is finished when it's done.
This is not for a production app, it's for a personal project that will never be release. So it is of no concern that the UI is frozen from a UX perspective. If the solution involves putting the processing in the background then this refactoring is fine, but I'm not sure how to do it when a lot of the heavy lifting during this loop involves UI stuff too.
Isn't it funny how you sometimes come up with a solution just after posting the question?! The key seemed to be rather than using a for loop for the processing, instead putting the processing function inside a separate method and repeatedly calling it, passing the array of objects to process to it. Doing this, you can call the function using [self performSelector:withObject:afterDelay:]. Even if you provide a value of zero for the delay, it causes the method to be called on the next run loop. This means you can update the UI, process the next item, and repeat this process until the array of items is empty. Here's my completed solution. If anybody knows a better way I'd still love to hear it, but for now this is at least working!
Edit - I packaged this solution up into a class of its own to make it easier to manage, and put it on my Github. Maybe it will help somebody else out :)
Edit 2 - made the processing class more flexible by making it run loops instead of iterating through arrays. You can of course use it to iterate through an array yourself, as per the example in the readme. But if you're not working with an array, you can just run the loop runCount times and do whatever you need to do in the processingBlock.
https://github.com/mashers/BackgroundLoopProcessor
I would like to create a wxPython app such that:
If I run a second instance of that app (e.g., call the Python script from the shell a second time), no new instance should be created.
Instead, the toplevel frame of the already running instance should be raised and focussed.
The first point can be easily implemented by wx.SingleInstanceChecker (see the example code there), but at least the example code only gives a way for making the second instance of the app abort, but not raise the existing app's main frame.
I am using wxPython-Phoenix with Python 3.
Claritication: I would much prefer an out-of-the-box solution like wx.SingleInstanceChecker (that is, not implement my own locking and IPC solution).
You can use any kind of IPC to send a message asking the other program to do whatever needs to be done (just raise its top level window or maybe handle the command line options passed to the second instance). In C++ there are wxConnection and the related wxServer and wxClient classes that can be used for this, but I'm not sure if they're wrapped by wxPython -- however you could use any Python IPC module instead, if they aren't.
As has been pointed out, the "correct" way to do this is IPC because you have a new process that is supposed to affect a change (raise and focus) in another process.
What you seem to want is to take advantage of the IPC channel that wx.SingleInstanceChecker is already using to do your work. Unfortunately, you can't. That class is implemented in the wxWidgets c++ code and therefore there are no Python bindings to the internal workings of the class.
However, you can probably abuse wx.SingleInstanceChecker to do what you want. In your program, you can set up a timer at some rapid interval (say, 250ms) that will constantly check IsAnotherRunning() from your main process. Therefore, when your second process starts up, the first will notice and can raise itself to the front. You would just have to wait for a little bit in the secondary process before it exits, to give the first time to notice.
I have a web application, using Spring-Boot. There is now a need for this application to use a custom dll (in house build dll file). There is nothing wrong with this dll, as we use it on our other applications, and have no problems with it.
To load the library in this new web application I'm writing, I have added the dll file to the procrun directory. This directory is on the library path, so that makes sense.
During startup I put in code to immediately load the dll, and also test some of its functionality. This works fine.
However, I have a timer, that schedules the execution of some functions, which may or may not include function calls to the dll.
At some point, about 10 minutes or so into execution, the service unexpected and seemingly without any valid reason, stops.
Although I try/catch exceptions at the appropriate logical places in code, there are no relevant log entries printed.
The Event Log shows something that reminds me of a null pointer exception:
Another bread crumb is that the event log will print something about the dll_unload. (see picture)
I need some help figuring out why the service is failing/stopping.
Kind Regards.
EDIT: After about three days of debugging and scratching my head, I came upon a forum thread that explained that this problem has something to do with the manner in which the system releases the memory during garbage collection. It seems that the dll in question was being unloaded by the garbage collector, even though it could still be called at some time later - which of course was the cause of the service falling over.
To solve the problem, I put in a timer that would call a method in the dll at three minute intervals (on my system this would not impact performance). I know this solution is a hack, but it works for me.
I'm trying to pass data which is continuously changed from the inside of one While loop to the inside of another While loop of a sub-vi. The main program on the left is constantly reading new data and the program on the right is adding 1 to the new value. My issue is that I cannot input new values to a While loop which is already running and thus my sub-vi is never updated. I've tried a global variable ("write" from the main program control and then "read" into the sub-vi) but that doesn't work either (same result as if the main were just passing data into the sub).
I apparently don't have enough reputation to post a picture of my program but I'm basically trying to run parallel loops (almost inside each other). Can anyone lend me an experienced hand?
The most common problem with while loops are based on lack of knowledge how exactly does the while loop work in LabVIEW.
First of all the information will be given outside the loop only if the condition terminal (right down corner of the loop) will be flagged as true.
If you want to pass the data earlier (while the loop is running) you have to choose easiest option:
Use queue (is the most common and well working). I can elaborate how this one work in practise if you want, or just try to run an example from LabVIEW help.
local/shared variables - you can define in your own library variables and pass the data by READ/WRITE option.
Please try to upload some documentation to an external server (as you are blocked here), and post a link, and then I could help you with a specific example.
Help»Find Examples. Search for "queue". Pick out an example with parallel loops.
You might want to look into Queues or Notifiers as means of passing data between running loops.
I'm developing a DirectShow CSource capture filter. It works fine, but when I close the program that is using the filter (in this case I'm testing with VLC, but the same happens with other programs), the program crashes (if I'm debugging it in Visual Studio then a breakpoint is triggered).
I've been hunting down this problem for some time now and found that both, my source filter and my source stream are not being released; this is, their reference counter is 1 at the end of the program, DllCanUnloadNow() function reports that there are 2 objects still in use, and, when CoUninitialize() is invoked, the program crashes.
I'm pretty sure that the reference counters are being handled correctly since I'm using the base classes implementation. The only unusual thing in my software that I can think of is that I'm using my own version of DllGetClassObject(): I configured the .DEF file to have MyDllGetClassObject() exported instead of DllGetClassObject() so I could insert some code before invoking the default implementation. I don't think this is a problem since I've checked that the reference counter of all objects I return at the end of MyDllGetClassObject() is 1.
I guess I'm missing something about the lifecycle of the filter, but can't figure out what (this is the very first capture filter I'm developing). Any suggestion?
Thank you in advance,
Guillermo
I finally figured out what was going on. The static method InitializeInstance in my source filter is invoked with bLoading == false and rclsid == <the GUID of my filter> at process shutdown. That seems to be the appropriate place to release that remaining reference counter from the filter instance.
I got the key idea of how important is to release all COM objects before CoUninitialize some time ago from another post on StackOverflow entitled DirectShow code crashes after exit (PushSourceDesktop sample). All I needed was just a little bit more knowledge on DirectShow filters lifecycle.
Anyway, thank you for your efforts, Roman, I know how vague this thread sounded from the beginning :)