Observers would be awesome especially with a couple enhancements / extensions:
An option for the observers to enter a special state if the WAN link goes down to the "master" cluster. A read-only option would be great. However, allowing certain types of writes to continue on a limited basis would be highly valuable as well. An observer could "own" a special node and its subnodes. Only these subnodes would be writable by the observer when there was a session break to the master cluster, and the master cluster would take all the changes when the link is reestablished. Essentially, it is a portion of the hierarchy that is writable only by a specitfic observer, and read-only for others. The purpose of this would be for when the WAN link goes down to the "master" ZKs for certain types of use cases - status updates or other changes local to the observer that are strictly read-only outside the Observer's 'realm'. On 7/19/09 12:16 PM, "Henry Robinson" <[email protected]> wrote: You can. See ZOOKEEPER-368 - at first glance it sounds like observers will be a good fit for your requirements. Do bear in mind that the patch on the jira is only for discussion purposes; I would not consider it currently fit for production use. I hope to put up a much better patch this week. Henry On Sat, Jul 18, 2009 at 7:38 PM, Ted Dunning <[email protected]> wrote: > Can you submit updates via an observer? > > On Sat, Jul 18, 2009 at 6:38 AM, Flavio Junqueira <[email protected]> > wrote: > > > 2- Observers: you could have one computing center containing an ensemble > > and observers around the edge just learning committed values. > > > > > -- > Ted Dunning, CTO > DeepDyve >
