Add forked mode to Play

[pauldraper]

lt's relatively easy (e.g. #3799) to introduce memory leaks in application reloading. Or have misbeaving application run out of other resources (run out of file descriptors, sockets) or have globalness (loading a native library, setting a system property, registering URL handlers).

The classloader reload is superior for speed, but it would be nice to have the choice to stop and restart an process, for robustness.

There was sbt-fork-run-plugin but it hasn't worked for some time, and was recently removed altogeher.

[richdougherty]

Agreed, I would like forked mode too!

The idea I have for dev mode is to have some sort of thin proxy server that holds the HTTP/HTTPS ports open and then forwards traffic to the user's application. The proxy server forwards traffic if the application compiles OK or shows an error message otherwise. However, this is quite a lot of work…