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https://issues.apache.org/jira/browse/ZOOKEEPER-965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13027569#comment-13027569
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Marshall McMullen commented on ZOOKEEPER-965:
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I've committed an initial pass at the necessary work in the C client. I did
some refactoring to avoid some massive code duplication as well. Notes from my
checkin comments:
This adds new zoo_multi and zoo_amulti interfaces to the C client to
atomically commit (either synchronously or asynchronously) a set of
operations. The server side guarantees transactional consistency
in that *all* the ops either fail or succeed.
Limitations of this implementation:
- asynchronous interface (zoo_amulti) doesn't work yet.
- can't get back the index of the failing op from zoo_multi though
zoo_amulti is designed to support this. I have a plan for how
to implement this in zoo_multi too.
- Only limited testing done on C client. The one test I did write
only works in multithread mode. Looks to be a limitation of the
test case I modelled mine after.
Cleanup/refactoring needed:
- Deal with deeply nested errors in zoo_amulti better (free any
allocated memory, etc).
- Don't need the existing ErrorResponse (added on java side to
allow determining which op failed). On C side it was so much
easier to just add a field to MultiHeader to indicate if that
op failed or not. That will make the Java side a lot cleaner
> Need a multi-update command to allow multiple znodes to be updated safely
> -------------------------------------------------------------------------
>
> Key: ZOOKEEPER-965
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-965
> Project: ZooKeeper
> Issue Type: Bug
> Reporter: Ted Dunning
> Assignee: Ted Dunning
> Fix For: 3.4.0
>
>
> The basic idea is to have a single method called "multi" that will accept a
> list of create, delete, update or check objects each of which has a desired
> version or file state in the case of create. If all of the version and
> existence constraints can be satisfied, then all updates will be done
> atomically.
> Two API styles have been suggested. One has a list as above and the other
> style has a "Transaction" that allows builder-like methods to build a set of
> updates and a commit method to finalize the transaction. This can trivially
> be reduced to the first kind of API so the list based API style should be
> considered the primitive and the builder style should be implemented as
> syntactic sugar.
> The total size of all the data in all updates and creates in a single
> transaction should be limited to 1MB.
> Implementation-wise this capability can be done using standard ZK internals.
> The changes include:
> - update to ZK clients to all the new call
> - additional wire level request
> - on the server, in the code that converts transactions to idempotent form,
> the code should be slightly extended to convert a list of operations to
> idempotent form.
> - on the client, a down-rev server that rejects the multi-update should be
> detected gracefully and an informative exception should be thrown.
> To facilitate shared development, I have established a github repository at
> https://github.com/tdunning/zookeeper and am happy to extend committer
> status to anyone who agrees to donate their code back to Apache. The final
> patch will be attached to this bug as normal.
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