instance definition is not clear

[Filirom1]

start_instance(s) and stop_instance(s) add provision job (as run_command and handle_git_command)

scale_instance and create_release set retired on instances.

create_instance insert a new instance.

I think there is a confusion between two different concepts:

• resistant erosion processes
• dynos

Resistant erosion processes (REP) are setup by the user with the ps command.

• ps:scale web=2, --> create 2 REP
• ps:scale web=0 -> destroy every REP of type web
• ps:stop --> destroy every REP
• ps:restart --> do not touch the REP, and restart the dyno
• set idle --> do not touch the REP, and stop the dyno
• http request but REP is idle --> do not touch the REP, and start the dyno
• midnight restart -> do not touch the REP, and restart the dyno
• application crash --> store crash info in the REP and start a new dyno if number of crash is not too much.
• dynohost crash --> do not touch the REP, and start new dynos

The role of an REP is to make sure a dyno is started even if crash happens.

May be useful for #7