BlockHound integration causes blocking on netty FastThreadLocalRunnable

Expected behavior

Other applications with BlockHound integration shouldn’t fail with internal netty blocking on FastThreadLocalRunnable.

Actual behavior

BlockHound integration added the following https://github.com/netty/netty/pull/9687/files#diff-2652ecd7677e7e42648c274b05543377R75 marking FastThreadLocalRunnable as blocking. Spring Cloud Gateway also has BlockHound integration and it causes the following error

java.lang.Error: sun.misc.Unsafe#park
	at reactor.blockhound.integration.CustomBlockHoundIntegration.lambda$applyTo$0(CustomBlockHoundIntegration.java:29)
	at reactor.blockhound.BlockHound$Builder.lambda$install$6(BlockHound.java:318)
	at reactor.blockhound.BlockHoundRuntime.checkBlocking(BlockHoundRuntime.java:46)
	at sun.misc.Unsafe.park(Unsafe.java)
	at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
	at java.util.concurrent.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:467)
	at io.netty.util.concurrent.GlobalEventExecutor.takeTask(GlobalEventExecutor.java:95)
	at io.netty.util.concurrent.GlobalEventExecutor$TaskRunner.run(GlobalEventExecutor.java:239)
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.lang.Thread.run(Thread.java:748)

I had to add an exception to pass

 builder.allowBlockingCallsInside(
		"io.netty.util.concurrent.FastThreadLocalRunnable", "run");

builder.allowBlockingCallsInside(“io.netty.util.concurrent.GlobalEventExecutor”, “takeTask”); didn’t work because of NPE exceptions that resulted.

i.n.u.c.SingleThreadEventExecutor : Unexpected exception from an event executor: java.lang.IllegalMonitorStateException: null
 at java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:151) ~[na:na]
 at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1261) ~[na:na]
 at java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:457) ~[na:na]
 at java.util.concurrent.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:474) ~[na:na]
 at io.netty.util.concurrent.SingleThreadEventExecutor.takeTask(SingleThreadEventExecutor.java:256) ~[netty-common-4.1.45.Final.jar:4.1.45.Final]
 at io.netty.util.concurrent.DefaultEventExecutor.run(DefaultEventExecutor.java:64) ~[netty-common-4.1.45.Final.jar:4.1.45.Final]
 at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989) ~[netty-common-4.1.45.Final.jar:4.1.45.Final]
 at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) [netty-common-4.1.45.Final.jar:4.1.45.Final]
 at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) [netty-common-4.1.45.Final.jar:4.1.45.Final]
 at java.lang.Thread.run(Thread.java:748) 

Steps to reproduce

Minimal yet complete reproducer code (or URL to code)

It’s not minimal, but https://github.com/spring-cloud/spring-cloud-gateway/tree/2.1.x

./mvnw clean install.

Netty version

4.1.44.final

JVM version (e.g. java -version)

openjdk version “1.8.0_232” OpenJDK Runtime Environment (AdoptOpenJDK)(build 1.8.0_232-b09) OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.232-b09, mixed mode)

OS version (e.g. uname -a)

Linux sgibb-dell 5.3.0-26-generic #28-Ubuntu SMP Wed Dec 18 05:37:46 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

/cc @bsideup @violetagg

[violetagg]

@spencergibb I tried spring-cloud-gateway build with https://github.com/netty/netty/pull/10020/files#diff-2652ecd7677e7e42648c274b05543377R78-R85 and I think it is OK now. Can you check with this configuration?

@normanmaurer @bsideup Can you check PR #10020

[normanmaurer]

@bsideup cool… I think @spencergibb said that whitelist GlobalEventExecutor#takeTask did not work in his report.