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https://issues.apache.org/jira/browse/ZOOKEEPER-965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13038987#comment-13038987
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Marshall McMullen commented on ZOOKEEPER-965:
---------------------------------------------

I've just pushed a change to github with the changes requested by Benjamin in 
his review on review board. It addresses these core issues:

(1) Tighten up C API to use a union of structs for each op type instead of one 
mismashed set of fields. Removed macros to init zoo_op_t and created more 
explicit init functions for each type of op.

(2) Removed zoo_check and zoo_acheck as there's no need to expose the check 
operation outside the context of a multi op. It was only added for completeness 
but it's totally unnecessaryR and needless adds clutter.

(3) Removed superfluous logging in PrepRequestProcessor indicating ops were 
being skipped after a failing op in a multi op. There's already logging when 
the op fails, and a very clear log statement indicating all subsequent ops in 
the multi op will be skipped.

(4) Converted all tabs to spaces (in my day job we use tabs and I forgot to 
adjust my editor's settings)

(5) Removed TxnHeader from Txn since all we really need is the type. Replaced 
it with one int for the type.


> 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
>    Affects Versions: 3.3.3
>            Reporter: Ted Dunning
>            Assignee: Ted Dunning
>             Fix For: 3.4.0
>
>         Attachments: ZOOKEEPER-965.patch, ZOOKEEPER-965.patch, 
> ZOOKEEPER-965.patch, ZOOKEEPER-965.patch, ZOOKEEPER-965.patch, 
> ZOOKEEPER-965.patch, ZOOKEEPER-965.patch, ZOOKEEPER-965.patch, 
> ZOOKEEPER-965.patch, ZOOKEEPER-965.patch, ZOOKEEPER-965.patch, 
> ZOOKEEPER-965.patch, ZOOKEEPER-965.patch, ZOOKEEPER-965.patch
>
>
> 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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