Hello,
I encountered a rare exception where adding listeners to an observable
value might break when they are added concurrently. This is due to
ExpressionHelper not being synchronized. I thought about how to fix this
on my side, but it is very difficult to do. As this is not a typical
platform thread issue, in my opinion it should be possible to add
listeners to one observable value from any thread without having to
think about any potential synchronization issues (which I can't solve
other than just running everything on one thread).
Even worse, due to the size and array being two different variables and
being incremented unsafely, once such a concurrent modification occurs,
this invalid state will persist permanently and will cause exceptions on
any further method call as well. The only solution is to restart the
application.
This is how a stack trace looks like when this occurs:
21:25:38:840 - error: Index 2 out of bounds for length 2
java.lang.ArrayIndexOutOfBoundsException: Index 2 out of bounds for length 2
at
com.sun.javafx.binding.ExpressionHelper$Generic.addListener(ExpressionHelper.java:248)
at
com.sun.javafx.binding.ExpressionHelper$Generic.addListener(ExpressionHelper.java:200)
at
com.sun.javafx.binding.ExpressionHelper.addListener(ExpressionHelper.java:65)
at
javafx.beans.binding.ObjectBinding.addListener(ObjectBinding.java:86)
at javafx.beans.binding.StringBinding.bind(StringBinding.java:114)
at javafx.beans.binding.Bindings$7.<init>(Bindings.java:428)
at javafx.beans.binding.Bindings.createStringBinding(Bindings.java:426)
at
io.xpipe.app.util.StoreStateFormat.shellEnvironment(StoreStateFormat.java:24)
at
io.xpipe.ext.proc.env.ShellEnvironmentStoreProvider.informationString(ShellEnvironmentStoreProvider.java:155)
at
io.xpipe.app.comp.store.StoreEntryWrapper.update(StoreEntryWrapper.java:228)
at
io.xpipe.app.comp.store.StoreViewState.lambda$updateContent$1(StoreViewState.java:147)
at java.lang.Iterable.forEach(Iterable.java:75)
at
io.xpipe.app.comp.store.StoreViewState.updateContent(StoreViewState.java:147)
at io.xpipe.app.comp.store.StoreViewState.init(StoreViewState.java:93)
at
io.xpipe.app.core.mode.BaseMode.lambda$onSwitchTo$1(BaseMode.java:109)
at io.xpipe.app.util.ThreadHelper.lambda$load$0(ThreadHelper.java:78)
at java.lang.Thread.run(Thread.java:1447)
21:25:38:847 - error: Index 3 out of bounds for length 2
java.lang.ArrayIndexOutOfBoundsException: Index 3 out of bounds for length 2
at
com.sun.javafx.binding.ExpressionHelper$Generic.addListener(ExpressionHelper.java:248)
at
com.sun.javafx.binding.ExpressionHelper$Generic.addListener(ExpressionHelper.java:200)
at
com.sun.javafx.binding.ExpressionHelper.addListener(ExpressionHelper.java:65)
at
javafx.beans.binding.ObjectBinding.addListener(ObjectBinding.java:86)
at javafx.beans.binding.StringBinding.bind(StringBinding.java:114)
at javafx.beans.binding.Bindings$7.<init>(Bindings.java:428)
at javafx.beans.binding.Bindings.createStringBinding(Bindings.java:426)
at
io.xpipe.app.util.StoreStateFormat.shellEnvironment(StoreStateFormat.java:24)
at
io.xpipe.ext.proc.env.ShellEnvironmentStoreProvider.informationString(ShellEnvironmentStoreProvider.java:155)
at
io.xpipe.app.comp.store.StoreEntryWrapper.update(StoreEntryWrapper.java:228)
at
io.xpipe.app.comp.store.StoreEntryWrapper.lambda$setupListeners$3(StoreEntryWrapper.java:143)
at
io.xpipe.app.util.PlatformThread.lambda$runLaterIfNeeded$0(PlatformThread.java:318)
at
com.sun.javafx.application.PlatformImpl.lambda$runLater$4(PlatformImpl.java:424)
at
com.sun.glass.ui.InvokeLaterDispatcher$Future.run$$$capture(InvokeLaterDispatcher.java:95)
at
com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java)
This full log goes up to index 50 out of bounds due to the recurring
nature of this exception.
Looking at the implementation of ExpressionHelper, I don't see any harm
in just synchronizing the methods, at least from my perspective. But I
guess that is up to the developers to decide. The only real solution I
have as an application developer is to perform all initialization on one
thread or just hope that this error is rare enough, both of which aren't
great options. So I hope that a potential synchronization of the
ExpressionHelper methods can be considered.
Best
Christopher Schnick
