I have built and started an OPC UA embedded Openmodelica server with the BouncingBall model like so:
$ omc +s path/to/model
$ ./BouncingBall -embeddedServer=opc-ua -rt=1
Now I'm trying to interact with it using an OPCUA client. However, I don't understand how I'm supposed to interact with the server properly. As far as I know this is undocumented.
The most promising approach seems to be to set enableStopTime to false and run to true. Then the simulation seems to run indefinitely and the values seem to make sense. It seems I'm only able to extract the values in real time however. While running, when I set run to false it seems that the server enters an erroneous state and it refuses to give any values back.
If I restart the executable and instead set step to true nothing seems to change and after trying to set step to true a second time the server becomes unresponsive. The -rt=1 option doesn't seem to matter. Seems like it enters the same state as above (1).
(After restart) If I leave enableStopTime to be true and set run to true the simulation runs to stop and then the server quits with message The simulation finished successfully. Maybe this is intended. Kind of seems odd. Would make sense to be able to restart the simulation or trigger it with new options.
What I would hope to be able to do: Start and stop simulation as well as rewind to a certain point to check the value at that point. It seems to me that the API "affords" this functionality and it could probably be provided by hackingly wrapping the executable and API. Are the above bugs or intended? What is the intended way to interact with an OPC UA server in these cases?
The OpenModelica compiler version is 1.16.0~1-g84b4a71
Please try the latest nightly build
It includes the following commit.
That might solve it. I believe things worked without subscriptions before, since I could never reproduce this without them.
(By the way, do people go on our git commit feed and try to reproduce bugs fixed in the last 24 hours; we quite often get questions that were just recently fixed)
Related
I have been trying to fuzz using both AFL and Libfuzzer. One of the distinct differences that I have come across is that when the AFL is executed, it runs continuously unless it is manually stopped by the developer.
On the other hand, Libfuzzer stops the fuzzing process when a bug is identified.I know that it allow the addition of parallel fuzzing through the jobs=N command, however those processes still stop when a bug is identified.
Is there any reason behind this behavior?
Also, is there any command that allows the Libfuzzer to run continuously unless the developer stops the fuzzing process?
This question is old but I also was in need to run libFuzzer without stopping.
It can be accomplished with the flags -fork=<N of jobs> combined with -ignore_crashes=1.
Be aware that now Ctrl+C doesn't work anymore. It is considered as a crash and just spawns a new job. But I think this is a bug, see here.
I have a multiplayer project which has some forever loops with checking code inside of them.
The problem is, multiple computers might process this and change crabx or craby due to lag in the variables dvotes, uvotes, lvotes, or rvotes. Only one machine should change this, though.
This can be easily solved by giving each player an ID like many people do in SQL. I would just check if the ID is 1, and that would be the "operating machine". I would then do all of these checks on that one machine. It would do things a Scratch server would do if you could program it...
The problem with this is that there is no way to detect when a player leaves the game. There is no block that is called "on exit" or "on stop button pressed". How would I go about doing this? I have seen people have a button which people click to exit, but some people will not click it/not even see it.
Thanks in advance!
Option 1
I've never been especially successful with cloud data myself, but I've heard the theory on this before:
Essentially, each player gets a "counter". Their computer then constantly increases that counter. If the counter ever stops increasing (which will be detected by the other computers, who are all looking after one another), the project will know that the user has left and one of the computers will take care of removing their ID and other data.
Obviously, this is much easier said than done. (As I said, I've never gotten complex cloud data to work well for myself, but I've seen it done successfully and explained.)
Option 2
Alternatively, you might be better off taking advantage of this cloud api created by MegaApuTurkUltra. I find that stealing from others tends to be the best way of solving problems when it comes to code. ;)
I try to use txt-records to share information between multiple devices. Therefore I am using bonjour/avahi. The server-side works fine as wireshark proofs. Information is added to the txt-record and sent out using MDNS.
The problem occurs on the client side, where the daemon/service does not seem to get the information change all the time. It is stuck with information that is already outdated and does not automatically update it when I try to resolve the service again.
On the client side I am using DNSServiceResolve in combination with a callback function where I call TXTRecordContainsKey and TXTRecordGetValuePtr to make sure the data is available before use. This all works fine except that, as already mentioned, the information is not always updated.
Am I missing something, or are there any additional API-function calls that I can use to force the daemon to update its record except DNSServiceResolve?
Thank you in advance.
Solved, always make sure you deaktivate your firewall when dealing with such strange problems...
This completely solved my issue.
To set the seem, I'm an experienced developer and have coded many languages over the years, including a good bit of Perl back in late 90's early 00's. Since then I haven't touched Perl, but now have a client who wants some changes making to an existing open source project built using Perl5 and Catalyst. I've quickly worked through the Catalyst tutorials, read a few books online and am now starting to feel my way.
I have the existing project up and running on a clean Debian Wheezy VM and am testing the code an my changes using the Catalyst Development Server.
While working through the tutorials and writing a few test apps, the development server would always output a lot of useful information when run, such as the configured routes etc.. But under this project, when I run the server I don't get a lot of output. I don't even get messages sent to $c->log->debug();
I run the server with the following command:
perl ./script/asnn_panel_server.pl -d -r
Which outputs the following:
HTTP::Server::PSGI: Accepting connections at http://0:3000/
I can access the server and the application is running fine.
In a test controller action I can try the following lines:
$c->log->debug("A test debug message");
print "A test print message\n";
The debug log message does not appear in my development server output, but the print line does. So I know the call to $c->log->debug() is not blowing up, because the next line is executing, but where is it going?
So essentially I feel I 'could' get more useful output from the Catalyst Development server, but am not.
I have googles but can't find anything of relevance. Sorry if I'm going in the wrong direction here, I do know what I doing in general, but have a lot to pick up here in a short amount of time!
I suspect my issues might be specific to the open source project I'm working on, but there's not a lot of help to be had from that direction. Could anyone give me any pointers as to what to investigate?
UPDATE : I now realise that the application is using log4perl, which is configured to send $c->log->debug() to syslog. I still don't know why the Catalyst Development server isn't providing much output.
:wq
For anyone coming upon this later, if you want to see the developer debug stream (stuff about the routes and classes and models your application is using, etc you need to be in debug mode, which you can do easily by setting CATALYST_DEBUG=1 in your env (I often start my app like "CATALYST_DEBUG=1 perl -Ilib script/myapp_server.pl"
There is sadly a difference between debug as a log level and debugging mode. The way catalyst works is that if you are in debugging mode (via CATALYST_DEBUG=1, or any of the other documented ways this gets turned on) all this debugging stream gets sent to the log, most of it logged at the debug level (again debug as a log level is distinct from debugging developer mode :( ) So you need both debugging mode and your logger should be set to listen at the debug level.
If you use the default catalyst log, it is debug level by default, so doing CATALYST_DEBUG=1 is all you need. If you use a different logger be sure to enable debug log level for your development setup, if you wish to see those developer stream logs.
Messages sent to $c->log->debug() are generally disabled in production environments. If it doesn't seem to matter whether you start your scripts with or without the -d switch, then I'd suggest something downstream in the sequence is setting the environment variable CATALYST_DEBUG to 0 or undef unilaterally.
That said, you should be able to see the output of $c->log->info() or $c->log->warn() calls. The answer to that question should help you determine if the problem is log4perl or Catalyst related.
Hopefully that will get you on your way.
I was working on something for a client today when I found a way to break some functionality in our program.
(The code is really legacy code, it's been in development for about 10 years and I've only been working here for about a year.)
It didn't cause an error, or cause the program to crash, but if a user was using the program and duplicated the behavior I'm pretty sure they'd be holding up their "WTF?" flag.
In our program we have named fields (textboxes) and static text (labels) that can be linked with the textboxes. When the textbox is not filled in the label(s) that were linked to them disappear.
The functionality that I broke was, when you change the name of a textbox that already has one label or more linked to it, and save the file, without re-associating the one or more labels associated with the textbox, the formerly-associated labels appear when the textbox is blank.
Now my thinking on the matter is that a simple observer pattern could have solved this problem in the first place, but then I didn't write the code.
I was thinking that if I could dig up more situations like this with the guys in my shop, that maybe I could talk them into considering unit testing, decoupling, applying patterns where they are called for and the like.
So for this reason I was wondering if anyone had any tips for finding broken (but not error causing) functionality in any sort of app (web-based, desktop, etc...)
For an app to fail usability, it has to have a defined set of expected behaviors.
"Is this textbox SUPPOSED to do nothing when the enter key is pressed?" Maybe it is, maybe it isn't. I've seen apps where a tester/reviewer reports something that they ASSUME should work another way, when in actuality the client specifically asked that they DON'T want the form submitted on a return key press, but only a submit button click.
So basically you have to define proper behaviour before you can determine incorrect behavior.
Hire some testers.
If it has an interface, then one of my favorite unconventional test is putting 5-10 year old children in front of it. You'd be surprised what they can come up with (especially the younger ones). While this may sound like a joke, it isn't -- it really works, because children don't have the mindset of only going through "mindset" paths.
And yeah, children are the experts in "breaking things" xP.
Code inspections, i.e. reading the source code: if you had taken time to read/inspect the source code, looking for "smells" or even just looking for code whose behaviour you don't immediately understand and agree with, you might have been holding up your "WTF?" flag too.
Test, test, test.
Do unexpected things. Start doing one task and switch another to see if anything goes haywire. Use the back button when you're not supposed to. Open it in two windows. Let it time out.
Test in all browsers, especially IE.
You can find database connections/sessions aren't released by:
working out the minimum number of connections you need to do something
setting resource limits to that minimum number
ensuring one "run" of the scenario that should use exactly that number (and release it afterwards)
then run it again a few times... do you run out of connections?
I used to work in a company where programmers regularly used to forget to de-allocate db connections. The standard answer was to reduce the resource to a minimum to see if there's a leak - and to try to work out where it is by restarting the system and running different scenarios repeatedly.
The first hour of code review, with the first reviewer, will do the most to find quality problems. But here's the thing: You don't need to convince people of quality problems. You need to convince them of the value of fixing bugs, and of rewriting only when the present quality absolutely justifies it.
I've dealt with some seriously bad code in my time. But you can't just rewrite. You need a spec before you can even tell if the rewrite is an improvement.
Sometimes, you have to infer the spec from the code and then check it against some human somewhere. But by the time you've done that, you understand the code as written and are now better prepared to repair than to rewrite -- most of the time.
Repair proceeds by a process of small behavior-preserving modifications that render the spec more clear in the code. Then, when you find something that looks wrong, you don't just change it. You ask around until you find the person responsible for that decision, and you get them to show you where in the spec it says that behavior X is correct. (This conversation can take many forms.) If you're lucky, they'll tell you that behavior X is in fact incorrect, and then you've earned your pay.
assert()
Also unit testing with coverage analysis.
This is particular to the Visual Studio IDE, although it probably also applies to others:
During testing, always at some point run in the debugger with "Break when an exception is thrown" turned on.
This can often help expose exceptions which are incorrectly being silently caught and which represent bugs, but otherwise may not be evident.
Code reviews should always also include reviews of the unit test code.
The problem is that with ad-hoc testing it's impossible to know how much or how well a developer has tested their code. So, you're at the mercy of different developers definition of the word "done".
If you include reviews of the unit test code at the same time you review the production code you should have a good idea of whether the code is really complete; in that "complete" includes "tested". Not just "Hey, I'll throw it over the wall to the testers!".