Motivation:
When always triggered fireChannelWritabilityChanged() directly when the update the pending bytes in the ChannelOutboundBuffer was made from within the EventLoop. This is problematic as this can cause some re-entrance issue if the user has a custom ChannelOutboundHandler that does multiple writes from within the write(...) method and also has a handler that will intercept the channelWritabilityChanged event and trigger another write when the Channel is writable. This can also easily happen if the user just use a MessageToMessageEncoder subclass and triggers a write from channelWritabilityChanged().
Modification:
- Always invoke the fireChannelWritabilityChanged() later on the EventLoop.
- Only trigger the fireChannelWritabilityChanged() if the channel is still active.
- when write(...) is called from outside the EventLoop we only increase the pending bytes in the outbound buffer (so that Channel.isWritable() is updated directly) but not cause a fireChannelWritabilityChanged(). The fireChannelWritabilityChanged() is then triggered once the task is picked up by the EventLoop as usual.
Result:
No more re-entrance possible because of writes from within channelWritabilityChanged(...) method.
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