Fixing LEAK: ByteBuf.release() when using circuit breaker with netty http producer

[samratdhillon]

Fixes https://issues.apache.org/jira/browse/CAMEL-16418

LEAK: ByteBuf.release() results when using circuit breaker with netty http producer

Using circuit breaker pattern with camel netty http will result in memory leaks. Netty will report ByteBuff leak as noted in the below stack trace. This can be reproduced very easily with a simple route definition (code sample attached). Note that the leak has nothing to do with actual circuit breaker timeouts and will result irrespectively and every time the netty http producer is called. Also it occurs with implementation of camel-reslience4j and camel-microprofile

LEAK: ByteBuf.release() was not called before it's garbage-collected. See https://netty.io/wiki/reference-counted-objects.html for more information.
Recent access records:
#1:

#2:
io.netty.buffer.AdvancedLeakAwareCompositeByteBuf.retain(AdvancedLeakAwareCompositeByteBuf.java:36)
org.apache.camel.component.netty.http.NettyHttpProducer$NettyHttpProducerCallback.done(NettyHttpProducer.java:123)
org.apache.camel.component.netty.NettyProducer$NettyProducerCallback.done(NettyProducer.java:555)
org.apache.camel.component.netty.handlers.ClientChannelHandler.channelRead0(ClientChannelHandler.java:229)
io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:99)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436)
io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324)
io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:296)
io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:719)
io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655)
io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581)
io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
java.base/java.lang.Thread.run(Thread.java:834)

[samratdhillon]

Sample to reproduce the problem

`public class CamelRoute extends RouteBuilder{
@OverRide
public void configure() throws Exception {

    restConfiguration()
    .component("netty-http")
    .host("0.0.0.0")
    .port(8081)
    .bindingMode(RestBindingMode.json);

    rest().get("/demo").produces("text/plain").route()
    .transform()
    .constant("demo page");

    rest().get("/demo/get").route()
    .circuitBreaker()
    .resilience4jConfiguration().timeoutEnabled(true).timeoutDuration(10000)
    .end()
    .log(LoggingLevel.INFO, "incoming request")
    .to("rest:get:demo?host=localhost:8081")
    .onFallback().transform().constant("timeout")
    .end();
}

}`

[davsclaus]

If you want to help backport this to 3.7.x, then you should take the commits from master branch and adjust the merge conflict and submit a new PR against the 3.7.x branch

[samratdhillon]

@davsclaus PR #5274 has been created which backports this fix into 3.7.x