Why AddConcurrentHandlers will panic after connecting to NSQD or NSQ Lookupd？

[maplessssy]

When I read go-nsq source code,I found AddConcurrentHandlers will panic after connecting to NSQD or NSQ Lookupd
Can someone explain why it is so designed?
thx

[ploxiln]

It is just trying to enforce a strict order: add handlers, connect. Connect methods will also fail if no handlers were added first. (That aspect is probably more important, you probably want to ensure a goroutine is already waiting on the unbuffered incomingMessages channel before the conn tries to send on it.)

I guess it panics instead of just returning an error, because a correctly written program will definitely never get this error, so callers may be in the habit of not checking for the error. If starting over again I think we would not do it this way, but there's not a big-enough benefit to changing now.

[maplessssy]

ok, enforce a strict order is simple and clear. I just think that in some scenarios we may need to dynamically modify the ConcurrentHandlers at runtime to manage consumer concurrent processing power, but maybe there's not a big-enough benefit.