what happens in an application server (tomcat etc.

Question

If a client cancel its request, the application server is suposed to throw the following error :

java.net.SocketException: Connection reset by peer: socket write error

But what is exactly happening ?

Let's say I'm doing a very expensive operation on the server side, and I'm writing some data to the outputstream everytime my server service get a new result (kind of streaming). In the middle of this operation, the client cancel the request. What happens ?

The operation stops, because the socket throws this error when the connection closed ? If it's not stopped, what happens to the data flushed in the outputstream after that ?

Thanks

Answer 1

I can't tell what Tomcat is doing but here is what happens:

1. the client closed the socket gracefully (then the server is notified about the close and closes its side of the connection too, in which case any buffered data ready to be sent is lost);

2. the client cut the socket brutally (then the server is NOT notified and it will detect the connection loss after a timeout or at the first attempt to send data - this will fail).

So, if your streaming is "constant", the server will always be 'protected' against undetected lost connections (the first send attempt will clean-up the area).

If this streaming is not constant, then you should make room for a timeout, or use TCP Keep-Alives to make sure that the connection state is tested on a regulary basis.

Hope it helps.