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From "Marshall McMullen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-965) Need a multi-update command to allow multiple znodes to be updated safely
Date Wed, 25 May 2011 06:56:49 GMT

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

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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