Re: [hibernate-dev] [OGM] Transaction-aware

Hi Sanne, All, On Mon, Mar 26, 2012 at 3:38 PM, Sanne Grinovero <sanne(a)hibernate.org&gt; wrote: Both actually. Just to give you more context I'm looking into OGM as a JPA interface for 2 NoSQL data stores: (1) Neo4j - from what I can see it should already support JTA transactions so not much problem here. BTW: is there any ongoing effort integrating Neo4j into OGM? If so I would be keen on helping out (or start looking into it if there are no such efforts). (2) Git (used as a versioned key-value store, based on jgit). I know it might sound a bit crazy but I'm using jgit as an embeded, versioned key value store. It works great in situations where: a) most of the content stored is text-like and strict versioning / history is needed b) a storage is mostly-read (I mean, there are far more reads as compared to writes) So it is really cool in situations like CMS / WIKI where content versioning / auditing is stricly needed. Combine it with OGM + hibernate search and you get a very interesting data storage. Now, for the jgit-backed storage there is no JTA support (althought people were thiniking about it: http://git.661346.n2.nabble.com/Any-plans-to-support-JTA-and-XA-in-jgit-t...) but from my knowledge of jgit it would be relativelly easy to implement (having concurent transactions would be next to impossible but this is not a use case I'm targetting here - sequential transactions would be fine for rare-write use case like CMS). So once again, given the above idea of intgrating git storage, the transactional behaviour would look like this: 1) on transaction's start I would rember a git's commit id and create an in-memory git index (easy with jgit); 2) any operation inside of a transaction would write objects to git's repo + update in-memory index; 3) on transaction's commit I would simply create a new commit in git and move rev pointer to this new commit (here is the place were it is very easy to detect any concurent modifications); 4) transaction's rollback is trivial - I would just drop the in-memory index (git object written to a git database would be removed during a standard cleanup / garbage collection of a git repository). Given the above it wonder if I should take a route of implementing an XAResource for jgit or maybe there is another place in OGM I could plug into to be notified on transaction's start/commit/rollback. Yes, I see. Digging more into the EHCache and Infinispan implementation at the moment to make sure that I understand all the details. Thnx for your input so far, it would be also interesting to know if other people would be interested in a such versioned key-value store. It works perfectly for my particular use case but I wonder if others would be interested as well. Cheers, Pawel