Debugger fails to load variable values due to java.lang.OutOfMemoryError

[marecabo]

The Java debugger fails to show locals after a large object is created in the current scope.

Environment

• Operating System: Windows 10 1909 18363.1734 x64
• JDK version: OpenJDK 16.0.2
• Visual Studio Code version: 1.59.1
• Java extension version: 0.81.0
• Java Debugger extension version: 0.35.0

Steps To Reproduce

1. Debug a class and set a break point after a line, where a large object is created in the current scope.

SomeClassContainingAMap variable = this.getSomethingWithAVeryLargeMapOfComplexObjectsInside();

Launch Command

>  c:; cd 'c:\path\to\folder'; & 'c:\Users\user\.vscode\extensions\vscjava.vscode-java-debug-0.35.0\scripts\launcher.bat' 'C:\jdk-16.0.2\bin\java.exe' '-agentlib:jdwp=transport=dt_socket,server=n,suspend=y,address=localhost:53340' '-Xmx24G' '-ea' '-XX:+ShowCodeDetailsInExceptionMessages' '-Dfile.encoding=UTF-8' '@C:\Users\user\AppData\Local\Temp\cp_c5uy9eqnavixxyehhdl84kqui.argfile' 'my.run.class' 

Log

WARNING: Using incubator modules: jdk.incubator.foreign, jdk.incubator.vector
[Error - 6:03:17 PM] Aug 27, 2021, 6:03:17 PM [error response][variables]: Java heap space
Java heap space
java.lang.OutOfMemoryError: Java heap space
	at java.base/java.util.Arrays.copyOf(Arrays.java:3536)
	at java.base/java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:228)
	at java.base/java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:802)
	at java.base/java.lang.StringBuilder.append(StringBuilder.java:242)
	at org.eclipse.jdi.internal.jdwp.JdwpString.read(JdwpString.java:40)
	at org.eclipse.jdi.internal.MirrorImpl.readString(MirrorImpl.java:455)
	at org.eclipse.jdi.internal.StringReferenceImpl.value(StringReferenceImpl.java:65)
	at com.microsoft.java.debug.core.adapter.formatter.StringObjectFormatter.toString(StringObjectFormatter.java:46)
	at com.microsoft.java.debug.core.adapter.variables.VariableFormatter.valueToString(VariableFormatter.java:92)
	at com.microsoft.java.debug.core.adapter.variables.VariableDetailUtils.computeToStringValue(VariableDetailUtils.java:89)
	at com.microsoft.java.debug.core.adapter.variables.VariableDetailUtils.formatDetailsValue(VariableDetailUtils.java:53)
	at com.microsoft.java.debug.core.adapter.handler.VariablesRequestHandler.handle(VariablesRequestHandler.java:286)
	at com.microsoft.java.debug.core.adapter.DebugAdapter.lambda$dispatchRequest$0(DebugAdapter.java:89)
	at com.microsoft.java.debug.core.adapter.DebugAdapter$$Lambda$641/0x00000008013915a0.apply(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture.uniComposeStage(CompletableFuture.java:1183)
	at java.base/java.util.concurrent.CompletableFuture.thenCompose(CompletableFuture.java:2305)
	at com.microsoft.java.debug.core.adapter.DebugAdapter.dispatchRequest(DebugAdapter.java:88)
	at com.microsoft.java.debug.core.adapter.ProtocolServer.dispatchRequest(ProtocolServer.java:118)
	at com.microsoft.java.debug.core.protocol.AbstractProtocolServer.lambda$new$0(AbstractProtocolServer.java:78)
	at com.microsoft.java.debug.core.protocol.AbstractProtocolServer$$Lambda$632/0x000000080137cb70.accept(Unknown Source)
	at io.reactivex.internal.observers.LambdaObserver.onNext(LambdaObserver.java:60)
	at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.drainNormal(ObservableObserveOn.java:200)
	at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.run(ObservableObserveOn.java:252)
	at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:61)
	at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:52)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
	at java.base/java.lang.Thread.run(Thread.java:831)

[Error - 6:03:26 PM] Aug 27, 2021, 6:03:26 PM [error response][evaluate]: Java heap space
Java heap space
java.lang.OutOfMemoryError: Java heap space
	at java.base/java.util.Arrays.copyOf(Arrays.java:3536)
	at java.base/java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:228)
	at java.base/java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:802)
	at java.base/java.lang.StringBuilder.append(StringBuilder.java:242)
	at org.eclipse.jdi.internal.jdwp.JdwpString.read(JdwpString.java:40)
	at org.eclipse.jdi.internal.MirrorImpl.readString(MirrorImpl.java:455)
	at org.eclipse.jdi.internal.StringReferenceImpl.value(StringReferenceImpl.java:65)
	at com.microsoft.java.debug.core.adapter.formatter.StringObjectFormatter.toString(StringObjectFormatter.java:46)
	at com.microsoft.java.debug.core.adapter.variables.VariableFormatter.valueToString(VariableFormatter.java:92)
	at com.microsoft.java.debug.core.adapter.variables.VariableDetailUtils.computeToStringValue(VariableDetailUtils.java:89)
	at com.microsoft.java.debug.core.adapter.variables.VariableDetailUtils.formatDetailsValue(VariableDetailUtils.java:53)
	at com.microsoft.java.debug.core.adapter.handler.EvaluateRequestHandler.lambda$handle$0(EvaluateRequestHandler.java:122)
	at com.microsoft.java.debug.core.adapter.handler.EvaluateRequestHandler$$Lambda$723/0x0000000801428ab8.get(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1764)
	at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1756)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:295)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1016)
	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1665)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1598)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)

[Error - 6:03:29 PM] Aug 27, 2021, 6:03:29 PM [error response][evaluate]: Java heap space
Java heap space
java.lang.OutOfMemoryError: Java heap space

Current Result

With a running debugging session, this is shown on the variables pane of the debugger side bar. Also, no values of variables are shown while hovering over them.

Expected Result

Showing locals and providing variable value hovers should still work even if large objects are created.

Additional Informations

If I'm allowed to speculate here: The log suggests that something is copied which might not be wise with very large objects. Running the class without debugger works totally fine.

Thank you for your work for bringing Java support to VS Code.

[testforstephen]

From the logs, the exception appears that when the Variables view tries to evaluate toString() value of a large object. I also observed that when the local variable contains a large HashMap object, it takes a long time to display the Variables view.

Current workaround is to disable "toString()" view.