On Tue, 2009-04-14 at 14:05 +0200, Dietmar Maurer wrote: > So CPG provide a framework to implement distributed finite state > machines (DFSM). But there is no standard way to get the initial state > of the DFSM. Almost all applications need to get the initial state, so I > wonder if it would make sense to provide a service which solves that > problem (at least as a example). > > My current solution is: > > I introduce a CPG mode, which is either: > > DFSM_MODE_SYNC ... CPG is syncing state. only state synchronization > messages allowed. Other messages are > delayed/queued. > > DFSM_MODE_WORK ... STATE is synced accross all members - normal > operation. Queued > messages are delivered when we reach this state. > > When a new node joins, CPG immediately change mode to > DFSM_MODE_SYNC. Then all members send their state. > > When a node received the states of all members, it computes the new > state by merging all received states (dfsm_state_merge_fn), and > finally switches mode to DFSM_MODE_WORK. > > Does that make sense? >
Cool idea if it wasn't totally integrated with CPG but instead some external service which people could use in addition to CPG. It would make a great addition as a service engine or c library using CPG. Regards -steve > - Dietmar > > > > On Thu, Apr 09, 2009 at 09:00:08PM +0200, Dietmar Maurer wrote: > > > > If new, normal read/write messages to the replicated state > continue > > while > > > > the new node is syncing the pre-existing state, the new node needs > > to save > > > > those operations to apply after it's synced. > > > > > > Ah, that probably works. But can lead to very high memory usage if > > traffic > > > is high. > > > > If that's a problem you could block normal activity during the sync > > period. > > > > > Is somebody really using that? If so, is there some code available > > > (for safe/replay)? > > > > There is no general purpose code. dlm_controld is an example of a > > program > > doing something like this, http://git.fedorahosted.org/git/dlm.git > > > > It uses cpg to replicate state of posix locks, uses checkpoints to > sync > > existing lock state to new nodes, and saves messages on a new node > > until it > > has completed syncing (i.e. reading pre-existing state from the > > checkpoint.) > > > > Dave > > _______________________________________________ Openais mailing list Openais@lists.linux-foundation.org https://lists.linux-foundation.org/mailman/listinfo/openais
