On Wednesday 29 September 2004 19:07, Lars Ellenberg wrote:
> / 2004-09-29 14:58:47 +0200
>
> \ Philipp Reisner:
> > > [...]
> > >
> > > >     Currently this covers only the states, and outlines the
> > > > transitions. It should help to define the actions to be taken on
> > > > every possible "input" to the DRBD internal "state machine".
> > >
> > > While reading through this giant e-mail I lost my confidence that it
> > > could be a good idea to have a "central" state switching function in
> > > DRBD, but of course I will see what this discussions gives...
> >
> > Thought about this a bit more... and came to the conclusion that it
> > would be a good idea. What do you think of this skeleton -
> > pseude code (it compiles actually).
>
> I think it probably should come out more like a real state machine,
> with a defined set of possible INPUTS,
> a defined set of states (which should not have the same detail depth as
> the actual drbd internal state set with all its different attributes),
> a set of actions, and a defined state[INPUT] => action => newstate
> matrix.
>
> maybe that is overkill.

Currently I want to go the way that was outlined with the new_st.c
skeleton.

Regarding: only worker should do state changes.
  We have quite a lot of inputs that are asynchronous by their nature.
  E.g. Disk fails. It does not make any sense to synchronize an advance
  in the disk-state state-machine with anything.

While it makes a lot of sense to synchronize changes to the node
state machine. 

At first I drew a directed graph of the cstates we have in 
drbd-0.7 (see cstates-7.ps)

You will immediately realize that the differentiation between
Unconfigured and StandAllone is a leftover from drbd-0.6

Then I drew directed graphs of the "state machines" as I see
them for drbd-0.8

conn-states-8.ps, disk-states-8.ps, node-states-8.ps (has 2 pages)

PS: The program is graphviz

-Philipp
-- 
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