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:

• called explicitly (by a promise for example, by a service itself)
• a process watched by the watchdog becomes in a state that is not the one it is supposed to be

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

• every X (this can be configured at the profile level)
• if promises are not all satisfied
• if requested services are not available
• as the result of bang

buildout is actually called by slapgrid. Slapgrid itself is called every Y (in theory, Y = 0, but in reality 1 minute). So, slapgrid is called:

• at lease every minute
• right after a slapgrid call if something happened in the previous call (ex. request of new service, failing promise) with an increasing delay to reduce CPU load