Problem: I'm encountering an IllegalReferenceCountException in production. The issue occurs when I attempt to log the original response body before deserialization fails.

1. how can I debug this error?
2. could you explain what's the error?

Env

• Spring WebFlux (Spring Boot 3.4.3)
• Netty + Reactor + Coroutine(Kotlin)
• Kotlin

Suspicious Code The following custom Decoder is intended to log the response body when deserialization fails.

@Bean
fun webClientCustomizer(): WebClientCustomizer {
    return WebClientCustomizer { webClientBuilder: WebClient.Builder ->
        val delegate = Jackson2JsonDecoder(JacksonMapperFactory.createObjectMapper())
        val loggingJackson2JsonDecoder = LoggingJacksonDecoder(delegate)

        webClientBuilder.clientConnector(ReactorClientHttpConnector(HttpClient.create()))
            .exchangeStrategies(
                ExchangeStrategies.builder().codecs {
                    it.defaultCodecs().jackson2JsonDecoder(loggingJackson2JsonDecoder)
                }.build(),
            )
    }
}

private class LoggingJacksonDecoder(
        private val delegate: Jackson2JsonDecoder,
    ) : Jackson2JsonDecoder(delegate.objectMapper) {

        override fun decode(dataBuffer: DataBuffer, targetType: ResolvableType, mimeType: MimeType?, hints: MutableMap<String, Any>?): Any {
            try {
                DataBufferUtils.retain(dataBuffer)
                return super.decode(dataBuffer, targetType, mimeType, hints)
            } catch (e: DecodingException) {
                dataBuffer.readPosition(0)
                val sourceString = dataBuffer.toString(Charsets.UTF_8)
                throw DecodingException("JacksonDecodingError. source=$sourceString", e)
            } finally {
                DataBufferUtils.release(dataBuffer)
            }
        }
    }

Stack Trace

An exception has been observed post termination, use DEBUG level to see the full stack: ioty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1 

[e7001a4d-1, L:/***.**.**.**:43618 - R:secret/**.*.***.***:80] Error was received while reading the incoming data. The connection will be closed.

ioty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1
    at ioty.util.internal.ReferenceCountUpdater.toLiveRealRefCnt(ReferenceCountUpdater.java:83)
    at ioty.util.internal.ReferenceCountUpdater.release(ReferenceCountUpdater.java:148)
    at ioty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:101)
    at ioty.handler.codec.http.DefaultHttpContent.release(DefaultHttpContent.java:92)
    at ioty.util.ReferenceCountUtil.release(ReferenceCountUtil.java:90)
    at reactorty.channel.FluxReceive.onInboundNext(FluxReceive.java:380)
    at reactorty.channel.ChannelOperations.onInboundNext(ChannelOperations.java:435)
    at reactorty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:841)
    at reactorty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:115)
    at ioty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
    at ioty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    at ioty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
    at ioty.handler.timeout.IdleStateHandler.channelRead(IdleStateHandler.java:289)
    at ioty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
    at ioty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    at ioty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
    at ioty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436)
    at ioty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346)
    at ioty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318)
    at ioty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
    at ioty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
    at ioty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    at ioty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
    at ioty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1357)
    at ioty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
    at ioty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
    at ioty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:868)
    at ioty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:799)
    at ioty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:501)
    at ioty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:399)
    at ioty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:998)
    at ioty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
    at ioty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.base/java.lang.Thread.run(Thread.java:1583)

try bufferSize exceed problem -> already adjust and the error doesn't occurred.

expected RefCountError doesn't occurred.