I have been working on a ARKit/ SceneKit app. I have been getting this particular Scenekit Error, which doesn't crash the app right away, however on repeated usage after a certain point, the app crashes.
[SceneKit] Error: inconsistency in scene graph found in C3DNode
finalize
I have used the usual ways to create nodes and remove them from parent, etc. And more importantly, I have created several other modules (within the same app) without ever encountering such an error. I have been trying to close this issue for the past two days, however I couldn't get any clue.
Following are what I have tried:
Checking allocations of SCNNodes (in Instruments) hoping rather that
some nodes would persist, but this is not the case.
Removing any method which changes the SCNMaterial of a node, hoping the possibly changes in material property might have some
issue.
Removing any node which are being regenerated in my app, hoping that possibly generating lot of nodes might create this issue.
Comparing this module against other modules within my app, which are based on the same logic to check whether I might have changed something within this module. But to no avail.
Removing all logics of AddAudioNode() and in fact all audio nodes themselves, since I saw in my allocations within Instrument.trace that they are persistent and are not being removed on node removal. But this also didn't help.
Granted this module is supposedly more complex with incrementally more number of nodes, however I am not able to understand what direction to strike in to investigate this Error.
I have not found anything existing on the net/ SO on this issue. The only option I am left with to raise a TSI with Apple, though it would cost me 1 TSI, which I have left, and they are expensive, these TSIs! Hence, I really hope if someone is able to throw some light on this and let me know how to approach this bug, it would be very helpful. Anything you require from the code, I can add in, but then the whole codebase is pretty humongous to post here. Hence, snippets as much as applicable.
I have encounted this error when my code was trying to remove nodes on a background thread, so I recommend checking that you are on the main thread with Thread.isMainThread when debugging to ensure you are on the main thread. Something like SCNAction.run(block) actually launches your code in a background thread, which is where I encountered this error. Basically the background thread removed from parent while at the same time the main thread was trying to do something with the node, which cause the scene graph to change before the node finished its process.
Related
I am building an app which list a set of files. When the user performs an action to one of the files, the action is process intensive (performs multiple ajax requests, updates an offline sqlite database, performs various checks on the file, etc). The user can trigger the said action on multiple files at a time.
The problem is that when the action is performed on more than one file, it blocks the UI. Digging down into the issue, removing certain part of the action (i.e. if I remove the section that performs a verification of the file size, type, and calculate the meta when missing, etc), it wears down the effect of UI lock, though it is still there.
From what I read so far, it is suggested to extract such logic out of the main process i.e. to have a separate process to handle those. The proposed solutions I've read are
use worker thread
create a child process
create a server
I've been struggling to understand and come up with a working example for each. I came across this module named piscina which says to generate workers (my understanding it is a wrapper to create worker thread?).
On the repo here I've setup an example which simulates the issue I have. So if I trigger multiple instances of the action by pressing the "Test" button at the bottom. And then try to increment the count at the top, I can experience the UI lock/lags. It takes approximately 10-15 clicks on the "Test" button to replicate. I can also hear the CPU fan increasing when performing this.
Are there any projects/examples around which gives a simplified implementation on how to mitigate or work around this problem?
EDIT
After #tromgy suggestions I've performed the following updates/test:
Adjusting the await run to a regular promise did seem to solve the issue.
But triggering multiple instances simultaneously, for example, 20, still causes UI lock. Attempting the same on my actual project causes memory heap errors.
I tried moving the Piscina instance outside, rather than creating a new instance on each event, it solves the memory leap, but not the UI lock/lag/freeze issue.
I've tried converting invoke to an actual event, the UI issue still persist.
I have been debugging an app for a while and am ready to upload it to app store. However, I still get occasional crashes that are hard to duplicate or debug--for example when pushing buttons in weird sequences. If I write these sequences down, I can debug but inevitably it happens when I haven't written it down and these can be difficult to replicate.
I know I need to just call it a day and leave future bug fixes for next release. I have removed all the abort() statements I had in testing. However, occasionally rather than getting a crash that lets you just close the app and reopen, I get one that makes it impossible to open the app without reinstalling. For example, this just happened, with a
'NSGenericException', reason: '*** Collection <__NSCFSet: 0x174a41b90> was mutated while being enumerated.'
This resulted from switching VCs during a background sync to the cloud.
I can live with crashes where you just need to reopen but not with ones that render the app unusable. Are there any guidelines for types of crashes to help you focus on the really fatal ones?
Or is there anything you can do to keep crashes from bricking app?
You should just fix this problem. Since you have this crashlog with that error message, you know which method can raise the problem, so you've got a good head start on fixing it, even if the problem manifests itself inconsistently and/or in a variety of ways.
But the occasional crash may not seem like too much of an inconvenience to you, but it is the quickest way to 1-star reviews and unhappy customers. I suspect you will quickly regret distributing an app with known, easily reproduced crashes.
But, a few observations:
It sounds like your background update process is mutating your model objects used by the main thread.
If possible, I'd suggest being careful to simply do not change any of your model objects in the background thread, but rather populate a local variable and when you're ready to update the UI accordingly, dispatch both the model update and UI refresh to the main thread.
If you cannot do this for some reason, you have to synchronize all interaction of model updates with some mechanism such as locks, GCD serial queue, reader-writer model, etc. This is slightly more complicated approach, but can be done.
I would advise temporarily editing your target's "scheme" and turn on the thread sanitizer:
It may possibly help you identify and more easily reproduce these sorts of problems. And the more easily you can reproduce the problem, the more easily you will be able to fix the issue.
You say:
Or is there anything you can do to keep crashes from bricking app?
It sounds like the "save" operation is somehow leaving the results in persistent storage in an internally inconsistent manner. Any one of the following would help, though I'd suggest you do all three if possible):
At the risk of repeating myself, fix the crash (it's always better to eliminate the source of the problem than try to program around manifestations of the problem);
Depending upon how you're saving your results, you may be able to employ an atomic save operation, so that if it fails half way, it won't leave it in an inconsistent state; we can't advise how you should do that without seeing code snippet illustrating how you're saving the results, but it's often an option;
Make sure that, if the "load" process that reads the persistent storage can fail, that it does so gracefully, rather than crashing; see if you can get it in this state where the app is failing during start-up, and then carefully debug what's going on in the start-up process that is causing the app to fail with this particular set of data in persistent storage. In the "devices" section, there is an option to download the data associated with an app, so you can carefully diagnose what's going on.
I have been developing an iOS app that utilizes the CloudKit feature available for Apple Developers. I've found it to be a wonderful resource, especially since the very day I started designing my backend, the service I was intending to use (Parse) announced it was shutting down. It's very appealing due to it's small learning curve, but I'm starting to notice some annoying little issues here and there so I'm seeking out some experts for advice and help. I posted another CloudKit question a couple days ago, which is still occurring: CloudKit Delete Self Option Not Working. But I want to limit this to a different issue that may be related.
Problem ~ Ever since I started using CloudKit I have noticed that whenever I manually try to edit (delete an entry, remove or add part of a list, even add a DeleteSelf option to a CKReference after creation), and then try to save the change, I get an error message and cannot proceed. Here is a screenshot of the error window that appears:
It's frustrating because anytime I want to manipulate a record to perform some sort of test, I either have to go do it through my app, or just delete the record entirely and create a new one (that I am able to do without issue). I have been just working around this issue for over a month now because it wasn't fatal to my progress. However, I am starting to think that this could be related to my other CloudKit issues, and maybe if I could get some advice on how to fix it I could also solve my other problems. I have file numerous bug reports with Apple, but haven't received a response or seen any changes.
I'd also like to mention that for a very long time now (at least a few days), I've noticed down in the bottom left hand corner of my Dashboard that it is consistently saying that it's "Reindexing Development Data". I remember at first that wasn't an issue, I would get that notification after making a change but it'd go away after the operation is complete. Now it seems to be stuck somewhere inside the process. And this is a chronic issue, it's saying this all the time, even right when I log into my dashboard.
Here is what I'm talking about:
As time goes on I find more small issues with CloudKit, I'm concerned that once I go into production more problems could start manifesting and then I could have a serious issue. I'd love to stick with CloudKit and avoid the learning curve of a different service like Amazon Web Services, but I also don't want to set myself up for failure.
Can anyone help me with this issue, or has anyone else experienced it on a regular basis? Thanks for the advice and help!
Pierce,
I found myself in a similar situation; the issue seemed to be linked to Assets; I had an Asset in my record definition. I and several other I noted reported the re-indexing issue on the apple support website and after about a month it eventually disappeared.
Have you tried resting your database schema completely, snapshot the definition; since you zap it completely and than reset, see inset.
Ultimately I simply created a new project, linked it to cloud kit and use the new container in my original app.
I'm having an issue with an umbraco site of mine: For some reason some of the nodes are timing out when I try to click on them in the back-end of the site.
The front-end works fine and there aren't any slowdown issues there, however I'm unable to edit these same nodes in the back-end as the system seems to just hang. This is making it incredibly difficult to debug as I have no idea what properties are actually causing the problems here. What's strange is I can create a node of the same document type and enter in some dummy values and that works fine, yet I can't seem to edit the existing nodes.
I've tried republishing the entire site, republishing the individual nodes, deleting the umbraco.config file and nothing has worked up to this point.
What's also interesting is that if I close down the browser the system seems to stop hanging and I can log in and try again.
Has anyone encountered this before or know where to begin?
Thanks
I have encountered something similar. The longer you work with Umbraco the slower it becomes and if you check the memory usage in Chrome's task manager, you can see that certain actions upon nodes bump the memory usage up a little further. The answer is just to close down the tab and open a new one.
I have reported this and Umbraco cannot replicate this. However, I do think that this is possibly due to maybe a package installed into Umbraco, maybe uComponents. It's very difficult to pin point.
Update:
If you can access some nodes but not others, then this is actually slightly easier to debug. I would check what similarities the nodes that timeout have.
Are they all of the same document type?
Do they all use the same data type?
I would guess that the nodes in question are using a data type that is performing an operation when the node is loading, and that operation is timing out. For example, do you have any data types that load data from the database, like enums? Do you have any datatypes that load data from a web service?
Do you have any usercontrol data types wrapped in the UserControlWrapper data type? These would be somewhere to check.
Finally, check:
The databases [umbracoLog] table. Any Umbraco-specific errors will be listed there.
Check the computer's event viewer. This will show any unhandled errors.
My money's on a database timeout.
I am getting this AV message about 3 to 5 seconds after the applications close as expected:
Exception EAccessViolation in module rtl160.bpl at 00073225. Access violation at address 500A3225 in module 'rtl160.bpl'. Read of address 00000004.
These (20) applications are very similar in that they are IBX business applications. About half of them did not cause the AV to occur.
These applications were ported from Delphi-xe and they worked flawlessly for a long time. No changes were made to the projects in the port. Both 32 and 64 bit builds gave the same results.
Is this a bug in some library's finalization section freeing a resource or something?
I am using Delphi-XE2 Update 3.
Would appreciate the help.
Try using madExcept / EurekaLog etc. - they give you detailed stack trace on AV. This is not always a panacea, but can point you to the problem.
Access Violations are by their nature already very troublesome beasts since they deal with invalid pointers in memory. One that occurs a while after an application shuts down is even worse because that's when your app is in "cleanup" mode. You're could be dealing with something that went wrong much earlier in the application, but is only exposing itself at shutdown.
General Tips:
Try to always undo things in the reverse order you did them. E.g.
Create A, Create B ... Destroy B, Destroy A
Connect to Database, Open Dataset ... Close Dataset, Disconnect from Database
Even making sure you've done all the above before shutting down can help tremendously.
Any threads that are still running while your application is running can cause problems.
Preferably ensure all your child threads are properly terminated before final shutdown.
Refer back to Closing datasets above. Depending on what you're doing, some database components will create their own threads.
If you're using COM, try ensure ComObj is high up in the initialization sequence (I.e. place it as high as possible in your DPR).
Delphi finalizes units in the reverse order that they were initialized.
And you don't want ComObj to finalize before other things that are dependent on ComObj have also done so.
If you're using interface references, make sure you resolve circular reference issues.
Some of these problems can be tricky to find, but you can do the following:
Setup a source-code "sandbox" environment (you're going to chuck all your changes as soon as you've found the problem).
Figure out the simplest set of steps required to guarantee the error. (Start app and immediately shutdown would be ideal.)
Then you're going to comment-out delete wipe out chunks of code between tests and basically follow a divide and conquer approach to:
rip out code
test
if the problem persists, repeat. Else roll-back and rip out a different chunk of code.
eventually your code base will be small enough to pinpoint likely problems which can be tackled with targeted testing.
I've had this kind of access violation problem on occasion with old Delphi or C++Builder projects. Today I had it with C++Builder. At the time of the crash, by looking in the Debug -> Call Stack window, I can see that it's happening inside a call to fflush, called by __exit_streams and _exit.
I'm not sure what is causing it, since it's so deep in the Borland library code, but it seems to come and go at random when the code changes. And it seems to be more common with multi-form applications.
This time the error went away when I just added a new button on the main form. A button which is just there, has no event handlers and does not do anything. I think that any random change to the code, classes, variables etc rearranges the memory layout when you relink the application, and that either triggers or untriggers the error.
For now, I just leave the new button on the form, set it to "not visible" so that there's no visible change. As it seems to work, it's good enough solution for me at this time.