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Date: Tue, 31 May 2011 18:32:47 +0000 (UTC)
From: "Ted Dunning (JIRA)" <jira@apache.org>
To: dev@zookeeper.apache.org
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Subject: [jira] [Commented] (ZOOKEEPER-965) Need a multi-update command to
 allow multiple znodes to be updated safely
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    [ https://issues.apache.org/jira/browse/ZOOKEEPER-965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13041733#comment-13041733 ] 

Ted Dunning commented on ZOOKEEPER-965:
---------------------------------------

{quote}
 I don't see any corresponding changes in FileTxnSnapLog
{quote}

Of course, you are correct here.  The individual operations in a multi work exactly like the 
individual operations.  Unless we somehow inherit the right behavior, your change will need
to be replicated.


I won't get to this for a day or two.  Would it be possible for you to drop this change in on
the github version?

> 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, 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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