[ISSUE #1879] Prevent blocked by group transfer service

[duhenglucky]

What is the purpose of the change

close issue

Brief changelog

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Verifying this change

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[coveralls]

Coverage decreased (-0.01%) to 50.933% when pulling 14969aa on duhenglucky:issue_1879 into 1558e05 on apache:develop.

[rushsky518]

Run example org.apache.rocketmq.example.quickstart.Producer to send a msg.

for debug, i add a sout here

@Override
public void asyncProcessRequest(ChannelHandlerContext ctx, RemotingCommand request, RemotingResponseCallback responseCallback) throws Exception {
	asyncProcessRequest(ctx, request).thenAcceptAsync(
			r -> {
				System.out.println(r);
				responseCallback.callback(r);
			},
			this.brokerController.getSendMessageExecutor());
}

debug result:

1. org.apache.rocketmq.broker.processor.SendMessageProcessor#handlePutMessageResult is invoked in GroupCommitService thread.

{
  System.out.println(r);
  responseCallback.callback(r);
}

is invoked in SendMessageThread_1, and r is null

[duhenglucky]

Run example org.apache.rocketmq.example.quickstart.Producer to send a msg.

for debug, i add a sout here

@Override
public void asyncProcessRequest(ChannelHandlerContext ctx, RemotingCommand request, RemotingResponseCallback responseCallback) throws Exception {
	asyncProcessRequest(ctx, request).thenAcceptAsync(
			r -> {
				System.out.println(r);
				responseCallback.callback(r);
			},
			this.brokerController.getSendMessageExecutor());
}

debug result:

1. org.apache.rocketmq.broker.processor.SendMessageProcessor#handlePutMessageResult is invoked in GroupCommitService thread.

{
  System.out.println(r);
  responseCallback.callback(r);
}

is invoked in SendMessageThread_1, and r is null

r is null just because of the succeed send message response returned to the client directly by org.apache.rocketmq.broker.processor.AbstractSendMessageProcessor#doResponse in org.apache.rocketmq.broker.processor.SendMessageProcessor#handlePutMessageResult method and these responses will not be processed by AfterRPCHook, the code here is a little confusing

[rushsky518]

Run example org.apache.rocketmq.example.quickstart.Producer to send a msg.
for debug, i add a sout here

@Override
public void asyncProcessRequest(ChannelHandlerContext ctx, RemotingCommand request, RemotingResponseCallback responseCallback) throws Exception {
	asyncProcessRequest(ctx, request).thenAcceptAsync(
			r -> {
				System.out.println(r);
				responseCallback.callback(r);
			},
			this.brokerController.getSendMessageExecutor());
}

debug result:

1. org.apache.rocketmq.broker.processor.SendMessageProcessor#handlePutMessageResult is invoked in GroupCommitService thread.

{
  System.out.println(r);
  responseCallback.callback(r);
}

is invoked in SendMessageThread_1, and r is null

r is null just because of the succeed send message response returned to the client directly by org.apache.rocketmq.broker.processor.AbstractSendMessageProcessor#doResponse in org.apache.rocketmq.broker.processor.SendMessageProcessor#handlePutMessageResult method and these responses will not be processed by AfterRPCHook, the code here is a little confusing

Yes, that's why i apply thenApplyAsync method on SendMessageProcessor#handlePutMessageResult, it returns the real response

[duhenglucky]

Run example org.apache.rocketmq.example.quickstart.Producer to send a msg.
for debug, i add a sout here

@Override
public void asyncProcessRequest(ChannelHandlerContext ctx, RemotingCommand request, RemotingResponseCallback responseCallback) throws Exception {
	asyncProcessRequest(ctx, request).thenAcceptAsync(
			r -> {
				System.out.println(r);
				responseCallback.callback(r);
			},
			this.brokerController.getSendMessageExecutor());
}

debug result:

1. org.apache.rocketmq.broker.processor.SendMessageProcessor#handlePutMessageResult is invoked in GroupCommitService thread.

{
  System.out.println(r);
  responseCallback.callback(r);
}

is invoked in SendMessageThread_1, and r is null

r is null just because of the succeed send message response returned to the client directly by org.apache.rocketmq.broker.processor.AbstractSendMessageProcessor#doResponse in org.apache.rocketmq.broker.processor.SendMessageProcessor#handlePutMessageResult method and these responses will not be processed by AfterRPCHook, the code here is a little confusing

Yes, that's why i apply thenApplyAsync method on SendMessageProcessor#handlePutMessageResult, it returns the real response

yep, actually ctx.writeAndFlush is also a blocking operation, let us polish it in your PR.