Todd, Comments in line:
On 8/5/09 12:10 PM, "Todd Greenwood" <to...@audiencescience.com> wrote: > Flavio/Patrick/Mahadev - > > Thanks for your support to date. As I understand it, the sticky points > w/ respect to WAN deployments are: > > 1. Leader Election: > > Leader elections in the WAN config (pod zk server weight = 0) is a bit > troublesome (ZOOKEEPER-498) Yes, until ZOOKEEPER-498 is fixed, you wont be able to use it with groups and zero weight. > > 2. Network Connectivity Required: > > ZooKeeper clients cannot read/write to ZK Servers if the Server does not > have network connectivity to the quorum. In short, there is a hard > requirement to have network connectivity in order for the clients to > access the shared memory graph in ZK. Yes > > Alternative > ----------- > > I have seen some discussion about in the past re: multi-ensemble > solutions. Essentially, put one ensemble in each physical location > (POD), and another in your DC, and have a fairly simple process > coordinate synchronizing the various ensembles. If the POD writes can be > confined to a sub-tree in the master graph, then this should be fairly > simple. I'm imagining the following: > > DC (master) graph: > /root/pods/1/data/item1 > /root/pods/1/data/item2 > /root/pods/1/data/item3 > /root/pods/2 > /root/pods/3 > ...etc > /root/shared/allpods/readonly/data/item1 > /root/shared/allpods/readonly/data/item2 > ...etc > > This has the advantage of minimizing cross pod traffic, which could be a > real perf killer in an WAN. It also provides transacted writes in the > PODs, even in the disconnected state. Clearly, another portion of the > business logic has to reconcile the DC (master) graph such that each of > the pods data items are processed, etc. > > Does anyone have any experience with this (pitfalls, suggestions, etc.?) As far as I understand is that you mean that have a master Cluster with other in a different data center syncing with the master (just a subtree)? Is that correct? If yes, this is what one of our users in Yahoo! Search do. They have a master cluster and a smaller cluster in a different datacenter and a brdige that copies data from the master cluster (only a subtree) to the smaller one and keeps them in syncs. Thanks mahadev > > -Todd
