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OPC hangups and handle leaks

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28 Apr 2020 09:26 #8411 by support
QuickOPC uses a 3rd party library which could cause, under uncertain circumstances, a handle leak, in some older version. This is what is described in the forum topic you linked to, together with a suggested workaround (turning off the usage of that library). I cannot determine, from the forum topic, whether that has helped the customer.

We cannot influence what that 3rd party library does. But, we have since upgraded to a new version of it, and (at least in the test we have done), it appears that the problem in the library has been fixed. And we have no indication from anybody that they have handle leak problems in newer versions. Therefore, there is no known handle leak in the current QuickOPC.

Regards
The following user(s) said Thank You: jrcody38

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28 Apr 2020 09:00 #8410 by jrcody38
Replied by jrcody38 on topic OPC hangups and handle leaks
Hi,

Thanks for the quick response. Apologies If I wasn't clear on a few things in my initial message. I will give you a bit more information.

The application in question is written in c# and utilises QuickOPC. I have attached the OPC dll references.

The logs I have provided you with are captured from the System Management Console of our automation software platform software (Wonderware Archestra/inTouch) and for sure are not OPC client logs. The CIOPCServer.cpp error I sent in the first message is actually from our Archestra OI Gateway Server which manages the connection to the OPC Server but is itself not OPC code.

We have a applied the fix suggested by OPC and it has eliminated the handle leaks. This fix will be going through the usual testing processes and hopefully it will solve our problems in production but in the interim we are trying to get a greater understanding of what these problems are.

So my question is:

Can you provide any more information on the symptoms associated with Quick OPC handle leaks? If it is a known bug (which it surely must be), then do you have any records of symptoms and problems that other users have experienced with it? Handle leaks can be very tricky things to link specifically with unwanted application behaviour but any information the OPC team could provide on this would be much appreciated.


Thanks again,

Johnny
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27 Apr 2020 14:00 #8405 by support
Hello.

Ad 1 and ad 2. The errors on the image do not resemble anything that has to do with QuickOPC. They might be related to your (or other software) handling some QuickOPC-related exception - or not - but there is no way to tell, because nothing in the texts comes from QuickOPC. Specifically, I find it somewhat weird that the first message mentioned CIOPServer.cpp file - a) that's not our file, and b) is your software written in C++? That would be quite unusual for Windows Forms app. Also, the DAServerManager mentioned in the seconds message is not "ours". The bottom line is that there is practically nothing we can infer from these message alone.

Ad 3 and ad 4. Obviously, handle leak, if it coming from QuickOPC, would be a bug. Your first attempt should be to try the steps described in the forum article you linked to. If that does not help, next action would be to rebuild your app with latest QuickOPC and retest, to see if the problem goes away. If it does, upgrade (we do not support or fix version 5.35, sorry). If it does not, we will need to look at it further (looking for reproducible scenario first).

Best regards

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27 Apr 2020 09:32 #8402 by jrcody38
OPC hangups and handle leaks was created by jrcody38
Hi,

We are using the following setup.

OPC Quick Client v5.35.1173.1.
Wonderware inTouch for HMI
.NET Windows Forms application which references OPC Quick client.

We have been noting regular performance issues in production. Every two weeks or so, performance degradation is noted which leads to OPC event processing hang-ups in our .NET application we end up having to restart it.

What we have also noted is that there seems to be a handle leak stemming from use of the EasyDAClient object we use. From analysis, these leaks are coming from abandoned Mutex objects somewhere within the OPC code or in a dll which you use. This seems to conform to the below article.

www.opclabs.com/forum/general-issues/2123-handle-leak-memory...ing-opclabs-easyopc-dataaccess

The performance issues and hangups are quite subtle at times and sometimes our logs don't seem to give us too much information even though the performance of the system has significantly slowed and we need to restart it. I have provided some sample logs for you to assess. I have some questions in this regard:

1) Are the OPC client errors we are seeing directly related to the handle leak?
2) if not, can you provide any insight on the exception in question?
3) Are there any established symptoms of the handle leaks associated with the above referenced article on the leaks?


Attachments:
Sample OPC Client error message
Sample handle count snapshot of application. (Without handle leak it should run at about 500-600 handles).
Sample Mutant handle creation from Process Explorer
Sample abandoned Mutex information from WinDbg



Thanks,

Johnny
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