risefront

code.pfad.fr/risefront is a package for gracefully upgrading the server behing a tcp connection with zero-downtime (without disturbing running transfers or dropping incoming requests).

Inspired by overseer, but re-engineered to also work on windows!

Documentation and examples on code.pfad.fr/risefront

The name is meant to be the opposite of fallback (since it switches to a new executable when asked to do so).

Underlying logic

When you start multiple instances of a program wrapped in risefront:

• the first one (the parent o) will actually listen to the addresses and call Run
• when a second instance (child A) is started, it detects that a parent is already running
  • it creates some random sockets to locally listen to
  • it informs the parent, that it wants to take over
  • it calls Run with those "proxy listeners"
  • from now on, the parent will forward all new connections to those "proxy listeners"
• if a third instance is started (child B), the same steps happen and the second instance (child A) will exit after handling its last request