UncaughtExceptionHandlerIntegration leaks memory

[xenomote]

Integration

sentry

Java Version

17

Version

7.6.0

Steps to Reproduce

Cannot be very specific because sentry SDK is being used by a plugin within a framework, and within that environment we cannot reproduce the issue unless we are receiving production traffic

Expected Result

no memory leak

Actual Result

the UncaughtExceptionHandlerIntegration appears to occupy the majority of the heap, eventually resulting in memory exhaustion and a crash.

On auditing the code it appears that

sentry-java/sentry/src/main/java/io/sentry/UncaughtExceptionHandlerIntegration.java

Lines 68 to 81 in 28c9a83

	final Thread.UncaughtExceptionHandler currentHandler =
	threadAdapter.getDefaultUncaughtExceptionHandler();
	if (currentHandler != null) {
	this.options
	.getLogger()
	.log(
	SentryLevel.DEBUG,
	"default UncaughtExceptionHandler class='"
	+ currentHandler.getClass().getName()
	+ "'");
	defaultExceptionHandler = currentHandler;
	}
	threadAdapter.setDefaultUncaughtExceptionHandler(this);

causes a stack to form, which prevents any of the exeption handlers from being GC'd and results in OOM. No idea why that register method is being called over and over again

we are planning to simply turn the UncaughtExceptionHandler off in the options to resolve this issue, but it's weird that the Sentry SDK apparently behaves this way by default

[romtsn]

I might be reading it wrong, but it looks like defaultExceptionHandler is already of instance UncaughtExceptionHandlerIntegration, which means someone set it before us manually, or the sdk has been initialized multiple times without calling Sentry.close() in between.

[xenomote]

Yes I agree with you Roman, that does seem to be the case

Sadly I can't really give any detail on how this would be the case because it's a library used by a plugin used by a framework, all of which I have no direct control over aside from config

From what I understand from debugging the whole stack, init should only be called once at framework startup when the plugin is initialised, and captureEvent is called for each event to be logged

I have no idea how or why the register method is being called multiple thousands of times, but my assumption would have been that init would be idempotent

[romtsn]

hm, but do you see that register is called multiple thousands of times actually?

My explanation would be that we just get into a infinite recursive call, because we delegate to defaultExceptionHandler here

sentry-java/sentry/src/main/java/io/sentry/UncaughtExceptionHandlerIntegration.java

Line 134 in 28c9a83

defaultExceptionHandler.uncaughtException(thread, thrown);

and since it's our own handler, we'll get into the loop.

One improvement from our side would be to just check if defaultExceptionHandler is not instance of UncaughtExceptionHandlerIntegration before delegating to it to avoid the loop, that should not hurt.