Warn about "Received Write command before Register command".

[ShawnYun]

• Akka.Net version - 1.4.2
• Windows 10 x64
• When I updated to akka1.4.2，warn appeared. But in Akka1.3.16, there is no warn.

[Aaronontheweb]

cc @IgorFedchenko - this question might be up your alley

[IgorFedchenko]

@Aaronontheweb Indeed, thanks

@ShawnYun This is one of the logging system improvements we added into new release. What it means is that internal TcpConnection actor received Tcp.Write before he has received Tcp.Register command. So basically as described here you are usually sending Tcp.Register command with connection handler IActorRef, which will then receive data from socket (and other stuff like failure reports and ack messages). And here Tcp.Write arrives before anybody was registered as a "handler" on your side.

This is marked as Warning (not Error) since we are just buffering such writes (unlike dropping them as it was before v1.4), and then flushing buffer once your Tcp.Register message is arrived. So basically all is working, no data loss occurs.
But yet, there might be some race condition that may result in sending Write before Register. Or Register and Write are sent from different actors, which breaks messages ordering guarantee.

[ShawnYun]

@IgorFedchenko Thanks! Very professional answer.