Spring WebClient memory leak on DataBufferLimitException

We are using spring-webflux:5.3.1. When we hit data buffer limit and get DataBufferLimitException we see the following in the logs and in the monitoring shows us something that looks like a memory leak.

13:45:20.076 [reactor-http-nio-2] ERROR reactor.netty.channel.ChannelOperationsHandler - [id: 0x8ea65ae1, L:/127.0.0.1:53820 ! R:localhost/127.0.0.1:53819] Error was received while reading the incoming data. The connection will be closed.
io.netty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1
    at io.netty.util.internal.ReferenceCountUpdater.toLiveRealRefCnt(ReferenceCountUpdater.java:74)
    at io.netty.util.internal.ReferenceCountUpdater.release(ReferenceCountUpdater.java:138)
    at io.netty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:100)
    at io.netty.handler.codec.http.DefaultHttpContent.release(DefaultHttpContent.java:92)
    at io.netty.util.ReferenceCountUtil.release(ReferenceCountUtil.java:88)
    at reactor.netty.channel.FluxReceive.onInboundNext(FluxReceive.java:349)
    at reactor.netty.channel.ChannelOperations.onInboundNext(ChannelOperations.java:381)
    at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:656)
    at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:94)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
    at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
    at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436)
    at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324)
    at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:296)
    at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
    at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
    at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:719)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.base/java.lang.Thread.run(Thread.java:832)

It's easy to simulate by decreasing maxInMemorySize

val webClient = WebClient
      .builder()
      .codecs { configurer -> configurer.defaultCodecs().maxInMemorySize(20) }
      .build()

webClient.get().uri("http://localhost:${port()}").retrieve().bodyToMono(String::class.java).block()

Comment From: rstoyanchev

I think this is a duplicate of #26060. If you are able to try to with 5.3.2-SNAPSHOT to confirm, that would be great.

Comment From: lukas-krecan

I confirm, the ERROR message is not logged in 5.3.2-SNAPSHOT. Thanks