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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, 04 May 2011 04:17:03 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13028580#comment-13028580
] 

Marshall McMullen commented on ZOOKEEPER-965:
---------------------------------------------

Additional debugging... Note that as zk server is coming up it's reading in a snapshot:

2011-05-03 22:14:16,872 [myid:] - INFO  [main:Environment@98] - Server environment:java.io.tmpdir=/tmp
2011-05-03 22:14:16,872 [myid:] - INFO  [main:Environment@98] - Server environment:java.compiler=<NA>
2011-05-03 22:14:16,872 [myid:] - INFO  [main:Environment@98] - Server environment:os.name=Linux
2011-05-03 22:14:16,873 [myid:] - INFO  [main:Environment@98] - Server environment:os.arch=amd64
2011-05-03 22:14:16,873 [myid:] - INFO  [main:Environment@98] - Server environment:os.version=2.6.37-gentoo-r4
2011-05-03 22:14:16,874 [myid:] - INFO  [main:Environment@98] - Server environment:user.name=marshall
2011-05-03 22:14:16,874 [myid:] - INFO  [main:Environment@98] - Server environment:user.home=/home/marshall
2011-05-03 22:14:16,875 [myid:] - INFO  [main:Environment@98] - Server environment:user.dir=/home/marshall/zookeeper-multi/src/c
2011-05-03 22:14:16,880 [myid:] - INFO  [main:ZooKeeperServer@713] - tickTime set to 3000
2011-05-03 22:14:16,881 [myid:] - INFO  [main:ZooKeeperServer@722] - minSessionTimeout set
to -1
2011-05-03 22:14:16,881 [myid:] - INFO  [main:ZooKeeperServer@731] - maxSessionTimeout set
to -1
2011-05-03 22:14:16,899 [myid:] - INFO  [main:NIOServerCnxnFactory@94] - binding to port 0.0.0.0/0.0.0.0:22181
2011-05-03 22:14:16,916 [myid:] - INFO  [main:FileSnap@83] - Reading snapshot /tmp/zkdata/version-2/snapshot.0
2011-05-03 22:14:16,927 [myid:] - INFO  [main:FileTxnSnapLog@186] - >> PROCESSING HDR=85490560384172033,1304482428,3,1304482430503,14
TXN=null

This ends up triggering the null pointer exception b/c the TXN (which is of type MultiTxn)
is NULL due to a failed multi-op. I'll try to track down better what the error handling is
around a multi txn that fails and see why the Txn in the snapshot is null...


> 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
>
>
> 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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