Change effective on 01 May 2012
When stopping or restarting dynos, unix signal
SIGTERM now goes to all processes in the dyno, not just the first process. This provides a graceful shutdown for Resque workers and Play Framework apps (among others), avoiding spurious R12 (Exit timeout) errors.
During a brief transition period, you can revert to the old behavior with the sigterm-all Heroku Labs feature.