Every SlapOs machine has a "watchdog" process which is monitoring other processes and calls "bang" to master (either a real slapos.org master or local slapproxy one).
The purpose of bang is to infor master a process died so it can do whatever needed so next call to slapos node instance really do start it.
Bang is called whenever:
In theory, buildout is run all the time, repeatedly and is
supposed to have 0 execution time (theoretical model). But since that
would take 100% of CPU, we have to call it less often. So, we find ways
to call it less often.
buildout is called
buildout is actually called by slapgrid. Slapgrid itself is called
every Y (in theory, Y = 0, but in reality 1 minute). So, slapgrid is
Currently bang has to go through the master. It is possible
in future to consider a short cut that does not go through the master.
But I (JP) am not sure yet that it is a good idea. It is probably simpler and
cleaner to run slapproxy locally if one needs full autonomy.