NPE while trying to invoke the method HttpMethod.name()

[nictas]

Hi,

I'm using the Netty client through Reactor Netty and the Cloud Foundry Java client in order to communicate with a Cloud Foundry controller. Usually everything works fine, but sometimes I get the following NullPointerException:

Caused by: java.lang.NullPointerException: while trying to invoke the method io.netty.handler.codec.http.HttpMethod.name() of a null object loaded from local variable 'method'
	at io.netty.handler.codec.http.HttpClientCodec$Decoder.isContentAlwaysEmpty(HttpClientCodec.java:236)
	at io.netty.handler.codec.http.HttpObjectDecoder.readHeaders(HttpObjectDecoder.java:609)
	at io.netty.handler.codec.http.HttpObjectDecoder.decode(HttpObjectDecoder.java:218)
	at io.netty.handler.codec.http.HttpClientCodec$Decoder.decode(HttpClientCodec.java:202)
	at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:502)
	at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:441)
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:278)
	at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:253)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352)
	at io.netty.handler.ssl.SslHandler.unwrap(SslHandler.java:1478)
	at io.netty.handler.ssl.SslHandler.decodeJdkCompatible(SslHandler.java:1227)
	at io.netty.handler.ssl.SslHandler.decode(SslHandler.java:1274)
	at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:502)
	at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:441)
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:278)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:352)
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1408)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:360)
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:930)
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:796)
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:432)
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:333)
	at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:906)
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	... 1 more

The exception occurs on different requests and it's also not that easily reproducible - 3 occurrences in 20000 HTTP requests.

Steps to reproduce

N/A. My hope is that you'll know the issue when you see the stack trace.

Minimal yet complete reproducer code (or URL to code)

I don't have a unit test that reproduces the issue ATM. If you need one, I'll try to write something.

Netty version

Reactor Netty 0.8.10.RELEASE + Netty 4.1.29.Final

JVM version (e.g. java -version)

java version "1.8.0_212"
Java(TM) SE Runtime Environment (build 8.1.055)

OS version (e.g. uname -a)

Linux 4f05ab19-01cd-458d-6c4f-93d3 4.15.0-55-generic #60~16.04.2-Ubuntu SMP Thu Jul 4 09:03:09 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

[nictas]

Big thanks for the fix @normanmaurer!