[CAMEL-20124] camel-netty - Fix ChannelHandlerFactories' usage of unsharable ByteArrayDecoder

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 4.0.4, 4.3.0
• Component/s: camel-netty
• Estimated Complexity: Unknown
• Assignee: Kengo Seki
• Reporter: Kengo Seki
• Created: 19/Nov/23 06:03
• Updated: 19/Nov/23 07:59
• Resolved: 19/Nov/23 07:59

Description

Recently I tried to set up a simple TCP proxy relaying any byte stream leveraging the Netty component, just like:

///usr/bin/env jbang "$0" "$@" ; exit $?
//DEPS org.apache.camel:camel-bom:4.2.0@pom
//DEPS org.apache.camel:camel-core
//DEPS org.apache.camel:camel-main
//DEPS org.apache.camel:camel-netty
//DEPS org.apache.camel:camel-support

import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.component.netty.ChannelHandlerFactories;
import org.apache.camel.main.Main;
import org.apache.camel.support.DefaultRegistry;

class proxy {

    public static void main(String... args) throws Exception {
        Main main = new Main();
        main.configure().addRoutesBuilder(new RouteBuilder() {
            public void configure() throws Exception {
                DefaultRegistry registry = (DefaultRegistry) getContext().getRegistry();
                registry.bind("bytesDecoder", ChannelHandlerFactories.newByteArrayDecoder("tcp"));
                registry.bind("bytesEncoder", ChannelHandlerFactories.newByteArrayEncoder("tcp"));

                from("netty:tcp://0.0.0.0:1234?decoders=#bytesDecoder&encoders=#bytesEncoder")
                    .to("netty:tcp://localhost:5678?decoders=#bytesDecoder&encoders=#bytesEncoder")
                    ;
            }
        });
        main.run();
    }
}

But sending data through this proxy fails with the following messages, and the client doesn't get any response:

WARNING: Failed to initialize a channel. Closing: [id: 0x45bcede1]
io.netty.channel.ChannelPipelineException: io.netty.handler.codec.bytes.ByteArrayDecoder is not a @Sharable handler, so can't be added or removed multiple times.
	at io.netty.channel.DefaultChannelPipeline.checkMultiplicity(DefaultChannelPipeline.java:600)
	at io.netty.channel.DefaultChannelPipeline.addLast(DefaultChannelPipeline.java:202)
	at io.netty.channel.DefaultChannelPipeline.addLast(DefaultChannelPipeline.java:195)
	at org.apache.camel.component.netty.DefaultClientInitializerFactory.addToPipeline(DefaultClientInitializerFactory.java:102)
	at org.apache.camel.component.netty.DefaultClientInitializerFactory.initChannel(DefaultClientInitializerFactory.java:72)
...

This is because ChannelHandlerFactories wraps ByteArrayDecoder with ShareableChannelHandlerFactory, but it's not actually sharable (doesn't have a @ChannelHandler.Sharable annotation).
A factory class that returns a new ByteArrayDecoder instance for each newByteArrayDecoder() call is required here, as the document explained.

Issue Links

• links to: GitHub Pull Request #12072