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Posted to commits@cordova.apache.org by GitBox <gi...@apache.org> on 2020/03/10 08:32:46 UTC
[GitHub] [cordova-android] HansKrywaa opened a new issue #924: Crash Report:
ConcurrentModificationException
HansKrywaa opened a new issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924
# Bug Report
## Problem
We mentioned some Crash Reports from our App, build with `cordova-android@8.1.0`. Crashlog:
**java.util.ConcurrentModificationException: java.util.ConcurrentModificationException**
```
java.util.LinkedHashMap$LinkedHashIterator.nextNode LinkedHashMap.java:775
java.util.LinkedHashMap$LinkedValueIterator.next LinkedHashMap.java:803
org.apache.cordova.PluginManager.onResume PluginManager.java:262
org.apache.cordova.CordovaWebViewImpl.handleResume CordovaWebViewImpl.java:452
org.apache.cordova.CordovaActivity.onResume CordovaActivity.java:277
android.app.Instrumentation.callActivityOnResume Instrumentation.java:1465
android.app.Activity.performResume Activity.java:8203
android.app.ActivityThread.performResumeActivity ActivityThread.java:4757
android.app.ActivityThread.handleResumeActivity ActivityThread.java:4810
android.app.servertransaction.ResumeActivityItem.execute ResumeActivityItem.java:52
android.app.servertransaction.TransactionExecutor.executeLifecycleState TransactionExecutor.java:190
android.app.servertransaction.TransactionExecutor.execute TransactionExecutor.java:105
android.app.ActivityThread$H.handleMessage ActivityThread.java:2373
android.os.Handler.dispatchMessage Handler.java:107
android.os.Looper.loop Looper.java:213
android.app.ActivityThread.main ActivityThread.java:8147
java.lang.reflect.Method.invoke Method.java
com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run RuntimeInit.java:513
com.android.internal.os.ZygoteInit.main ZygoteInit.java:1101
```
### Environment, Platform, Device
<!-- In what environment, on what platform or on which device are you experiencing the issue? -->
From Crashlog this happens to a Mate 20 Pro with Android 9 and a Galaxy Note10+ with Android 10 too.
### Maybe related Issue?
- #912
Please fix this 😊
## Checklist
<!-- Please check the boxes by putting an x in the [ ] like so: [x] -->
- [X] I searched for existing GitHub issues
- [X] I updated all Cordova tooling to most recent version
- [X] I included all the necessary information above
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[GitHub] [cordova-android] HansKrywaa commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
HansKrywaa commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613461405
The App is a „big" one, from one of the biggest Insurances from Germany. I'm the developer, but i can't just say: Yes we make it like this, if we don't know how the performance is losing. 🤔
But in general this sounds like a good idea, is this fork much work for you?
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[GitHub] [cordova-android] breautek commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
breautek commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-612698912
Nah... the content of your app doesn't sound like it fit well with my theory... How often do you see these crashes in your crashlytics?
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[GitHub] [cordova-android] HansKrywaa commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
HansKrywaa commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613423950
It happen like 30 Times now 🤔
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[GitHub] [cordova-android] breautek commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
breautek commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613745852
@HansKrywaa I have a branch at https://github.com/breautek/cordova-android/commits/concurrent-plugin-manager-8.1
I would advise you to fork `cordova-android` and merge my branch into your own fork (that way you have complete control)
Then you can install the platform via
`cordova platform add https://github./com/yourgitrepo.git#your-branch`
Just like any `cordova-android` update, you'll need to remove the platform first by doing:
`cordova platform remove android`
You can look at the change set at https://github.com/breautek/cordova-android/commit/bfda452a09ba26412e0f527f6af1957379d89453
Upon further reading, it looks like I didn't need to wrap everything inside a `synchronized` block, **unless** if you use the iterators, which the codebase does not. So using `Collections.synchronizedMap` should be enough, but again, hard to say for certain when we lack a reproducible test case.
I saw no significant performance impact with my test app, but obviously my test app wasn't a real production app. It was just the cordova hello world app with all of the apache plugins installed. I'll leave it up to you if you see any significant performance impacts on your app, which would represent a real-world scenario.
Given how frequent the crash appears to occur... with any luck, you won't see the crash for the next 30 days or so...? :crossed_fingers:
Please do keep me updated.
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[GitHub] [cordova-android] HansKrywaa commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
HansKrywaa commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-612619725
Hey @breautek ,
thanks for your explanation.
About our App: It's a App where you can companionship someone, so basically it's a lot about Background Location and Websockets. I also used a Plugin which allows me to run in the Background, with a Method do disable the WebView Optimization: https://github.com/HansKrywaa/cordova-plugin-advanced-background-mode
Can i give you any more Information?
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[GitHub] [cordova-android] HansKrywaa commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
HansKrywaa commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613471483
I currently won't have the time 😕 Please message me if you are ready, so i can try it out and maybe use it in the next Release. Will we be able to test performance somehow?
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[GitHub] [cordova-android] timbru31 commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
timbru31 commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613443387
We know this issue happens, without a proper way to reproduce it, it is however very difficult to debug, fix and confirm the fix. :(
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[GitHub] [cordova-android] HansKrywaa commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
HansKrywaa commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613837805
Thanks for your work, i will do like you told. I'm not sure when we will build the next Release Version, but i will use the Fork in this and ping you here for your Information! 😊
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[GitHub] [cordova-android] breautek commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
breautek commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-612563876
I believe this is caused because we access these `LinkedHashMap` objects potentially from different threads and these hash maps are not thread safe.
> Note that this implementation is not synchronized. If multiple threads access a linked hash map concurrently, and at least one of the threads modifies the map structurally, it must be synchronized externally. This is typically accomplished by synchronizing on some object that naturally encapsulates the map. If no such object exists, the map should be "wrapped" using the Collections.synchronizedMap method. This is best done at creation time, to prevent accidental unsynchronized access to the map:
Map m = Collections.synchronizedMap(new LinkedHashMap(...));
https://docs.oracle.com/javase/8/docs/api/java/util/LinkedHashMap.html
However it will be very hard to be confident unless if we can reproduce this reliability. In the above callstacks, it seems to be occurring on the iteration of plugins on responding to a pause or resume event. Unfortunately this isn't necessary the error, it's just tells us that the hash map has changed while we were iterating.
@HansKrywaa can you tell me a little bit of your app? My wild theory is this is related to maybe the webview being unloaded/killed but that would only make sense if your app goes into the background to load up something memory intensive (such as the camera app). Normally under this situation, the webview is suppose to load back up (but the webview environment would be refreshed). I'm thinking there might be a race condition there...
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[GitHub] [cordova-android] breautek commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
breautek commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613470397
I don't think it's that much work, I think it's literally just wrapping our Linked Hash Maps inside a [synchronizedMap](https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html#synchronizedMap(java.util.Map)) and using the wrapping the map iterations inside a `synchronized` block.
I'll probably start this tonight, or if you like to tackle this yourself, feel free.
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[GitHub] [cordova-android] breautek edited a comment on issue #924: Crash
Report: ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
breautek edited a comment on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613476176
I think all iterations of the plugin map needs to be synchronized, so logically I think I believe if you have a large number of plugins, you'll see a bigger impact. I'll test by installing all the apache plugins + maybe a few more and try to compare apps on cordova-android@8.1 vs the fork.
This is all just speculation, so we'll see just how big of the impact is. The impact could be insignificant altogether as well, for all we know...
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[GitHub] [cordova-android] breautek commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
breautek commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613476176
I think all iterations of the plugin map needs to be synchronized, so logically I think I believe if you have a large number of plugins, you'll see a bigger impact. I'll test by installing all the apache plugins + maybe a few more and try to compare apps on cordova-android@8.1 vs the fork.
This is all just speculation, so we'll see just how big of the impact is.
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[GitHub] [cordova-android] breautek commented on issue #924: Crash Report:
ConcurrentModificationException
Posted by GitBox <gi...@apache.org>.
breautek commented on issue #924: Crash Report: ConcurrentModificationException
URL: https://github.com/apache/cordova-android/issues/924#issuecomment-613457396
To be clear he was just simply responding to my question haha...
If it only happened 30 times since you opened the issue, that's approximately 1 occurrence per day... which means the chances of intentionally triggering the bug naturally will likely be extremely difficult.
I have a feeling that there are potential race conditions in the resume/pause lifecycles but we will likely need a controlled test case to prove it...
Or if you're willing... I can branch off of 8.1 and implement `synchronizedMap` and you can fork my branch. We'll see if the problem goes away. If it is a race condition, the java docs appears to suggest that `synchronizedMap` should fix it by ensuring synchronised access to our plugin maps. I'm assuming this is at a performance cost though and I'm not sure how significant that would be...
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