[Dubbo- netty4 nettyclienthandler should trigger heartbeat handler] fix heartbeat when channel active

[zonghaishang]

What is the purpose of the change

set heartbeat flag when client channel active (netty4), issue: #1996

Brief changelog

1. org.apache.dubbo.remoting.transport.netty4.NettyClientHandler#channelActive
2. org.apache.dubbo.remoting.transport.netty4.NettyClientHandler#channelInactive
   trigger handler event.

Verifying this change

Enable netty4 transporter, client connect to remote server, org.apache.dubbo.remoting.exchange.support.header.HeaderExchangeHandler#connected should be triggered.

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[zonghaishang]

@qinliujie Please help to review this pr, thanks.

[codecov-io]

Codecov Report

Merging #1997 into master will increase coverage by 0.03%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #1997      +/-   ##
============================================
+ Coverage     50.94%   50.98%   +0.03%     
- Complexity     4773     4775       +2     
============================================
  Files           562      562              
  Lines         25218    25221       +3     
  Branches       4449     4449              
============================================
+ Hits          12848    12859      +11     
+ Misses        10439    10432       -7     
+ Partials       1931     1930       -1

Impacted Files	Coverage Δ	Complexity Δ
.../remoting/transport/netty4/NettyServerHandler.java	71.42% <ø> (-0.8%)	6 <0> (ø)
.../remoting/transport/netty4/NettyClientHandler.java	63.63% <100%> (+5.01%)	5 <2> (ø)	⬇️
...onfig/spring/extension/SpringExtensionFactory.java	73.07% <0%> (-11.54%)	8% <0%> (ø)
...bo/remoting/transport/netty/NettyCodecAdapter.java	53.12% <0%> (-1.57%)	3% <0%> (ø)
.../dubbo/remoting/transport/netty4/NettyChannel.java	65% <0%> (-1.25%)	22% <0%> (-1%)
...a/org/apache/dubbo/monitor/dubbo/DubboMonitor.java	89.71% <0%> (+1.86%)	15% <0%> (ø)	⬇️
...rpc/protocol/dubbo/telnet/InvokeTelnetHandler.java	55.69% <0%> (+3.79%)	13% <0%> (+3%)	⬆️
...ubbo/rpc/protocol/dubbo/ChannelWrappedInvoker.java	50% <0%> (+4.16%)	3% <0%> (ø)	⬇️
...apache/dubbo/rpc/protocol/dubbo/FutureAdapter.java	48.38% <0%> (+19.35%)	3% <0%> (ø)	⬇️

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[qinliujie]

@zonghaishang it is ok,but I have a question,can we remove com.alibaba.dubbo.remoting.transport.netty4.NettyClientHandler#disconnect method?By querying the netty api document, I find that it is useless. The disconnect method is invoked only when the user intend to disconnect network and is not called when the network connection is broken.So I think channelInactive method is enough

[zonghaishang]

@qinliujie

I confirmed your question and found the basis from the netty project：

channelOpen, channelBound, and channelConnected have been merged to channelActive. channelDisconnected, channelUnbound, and channelClosed have been merged to channelInactive. Likewise, Channel.isBound() and isConnected() have been merged to isActive().

More detail can refer here: https://github.com/netty/netty/wiki/New-and-noteworthy-in-4.0
Em... we can safely remove the disconnect method

[qinliujie]

@zonghaishang well done!! @chickenlj please review again~