We have talked about this in the past. There are several clear advantages.
Do you have an appropriate immutable DataTree? What did you use to implement this? On Tue, Nov 1, 2011 at 9:40 AM, Thomas Koch <tho...@koch.ro> wrote: > Hi, > > I'm like two days away from having a version of ZooKeeper with an immutable > DataTree on the server. This means that for any modification of the > DataTree, > all Nodes from the modified one up to the root are replaced by new nodes. > > Advantages: > > - No synchronisation needed when accessing the DataTree. > - The snapshotter thread gets an immutable datatree and will write a > consistent DataTree to the disk. > - No headaches whether multi transactions could lead to issues with > (de)serialization. > - Much better testability. > - No concurrency - No headaches. > - I hope for considerable speed improvements. Maybe also some memory > savings, > at least from refactorings possible after this step. > > Possible further improvements: > > Read requests actually don't need to enter the processor pipeline. Instead > each server connection could get a reference to a (zxid, tree) tuple. > Updates > are delivered as (zxid, newTree, triggerWatchesCallback) to the server > connections. > The watches could be managed at each server connection instead of centraly > at > the DataTree. > > I'm pre-announcing this now to give an explanaition of my intends with ZK. > > I've created a couple of patches that refactor ZK in small incrementally > and > individually tested steps as far as possible towards the immutable data > tree. > The Branch is here: > https://github.com/thkoch2001/zookeeper/tree/proposed_patches > > I'm working on the final step now, that really makes DataNode immutable and > which is the only larger change. I don't see yet how I can split this in > smaller steps. > > Of course it's totaly up to you, whether you'd like to take this road. > > Once I've got there, I'd like to do performance comparissions between old > and > new. However I don't have accesses to hardware for such a test. So this > would > only be possible, if somebody would like to sponsor me with access to a > cluster or some machine hours at amazon. > > Best regards, > > Thomas Koch, http://www.koch.ro >
