Re: How Unix manages processes in userland

[John Nemeth <jnemeth%cue.bc.ca@localhost>]

On Dec 7,  1:37am, Roy Marples wrote:
} On 07/12/2013 1:33, John Nemeth wrote:
} > On Dec 7,  1:26am, Roy Marples wrote:
} > } On 07/12/2013 1:08, Aaron B. wrote:
} > } > As a sysadmin, I often care less about the internal details, and 
} > more
} > } > about what a system provides. What I want to see:
} > } >
} > } > 1) Easy to define/install a new service
} > } > 2) Easy to manipulate a service (enable/disable/restart/etc)
} > } > 3) Easy to query a service's state.
} > } >
} > } > IMHO, #3 is the ticky part. People often assume things are 'up' or
} > } > 'down' and ignore the scope of all the other failures in between.
} > }
} > } Well, from a service management perspective it's either up or down.
} > } It may have an intermediate state of starting, but that still falls 
} > in
} > } the down category.
} > 
} >      Not quite.  If it's down, you may want to do a restart.
} > However, if it is currently starting, then you want to give it time
} > to complete the startup process before doing a restart.  And, of
} > course, if it fails to come up after a few restart attempts, you
} > want to mark it as failed, stop doing restarts, and bring it to
} > the attention of an administrator.
} 
} What you describe are actions.
} I was defining states, sorry if that wasn't clear :)

     Well, in that case, starting should be a state.  Actions are
simply forced state transitions.  You don't want to force a transition
from down to up (i.e. restart), if it is currently starting (assuming
it hasn't missed a startup timeout).

}-- End of excerpt from Roy Marples