[
https://issues.apache.org/jira/browse/ZOOKEEPER-1665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13774473#comment-13774473
]
Rakesh R commented on ZOOKEEPER-1665:
-------------------------------------
Hi [~ted_yu], From the HBASE-7847 description, I've seen the usecase of HBase
is to delete recursively all the child znodes atomically. I could see the
multi-transaction api behavior is not actually executing the operations in an
atomic fashion.
If needed I would help in uploading a simple patch which uses multi-transaction
api, but I feel, it would not actually serving the usecase mentioned in the
HBASE-7847 jira.
I also had a similar usecase, where I need to atomically delete all the
childnodes. When I observed the behavior, in server 'multi-op' is iterating and
committing one by one operations orderly, if any of the operation fails, it
would mark all the subsequent operations as 'Code.RUNTIMEINCONSISTENCY' and
return without rollback the previously committed operations.
Following snippet in zk server code shows the behavior:
{code}
/* If we've already failed one of the ops, don't bother
* trying the rest as we know it's going to fail and it
* would be confusing in the logfiles.
*/
if (ke != null) {
type = OpCode.error;
txn = new
ErrorTxn(Code.RUNTIMEINCONSISTENCY.intValue());
}
{code}
For example, I've the following znodes created:
/parent/child1
/parent/child2
/parent/child3
/parent/child4
Given '/parent' node for the recursive deletion of its child. Say
zkclient#multi prepares Op#delete in the order child1, child2, child3, child4
and submits these to the server.
Now, assume after deleting child2, server fails to delete child3(one possible
case is NoNodeException occurs - child3 doesn't exists, due to a race condition
with some other delete operations). The multi call will immediately return with
return codes : child1 - OK, child2 - OK, child3 - RUNTIMEINCONSISTENCY, child4
- RUNTIMEINCONSISTENCY. Here its not trying for the child4 node at all.
Please correct me if I'm missing anything.
> Support recursive deletion in multi
> -----------------------------------
>
> Key: ZOOKEEPER-1665
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1665
> Project: ZooKeeper
> Issue Type: New Feature
> Reporter: Ted Yu
>
> Use case in HBase is that we need to recursively delete multiple subtrees:
> {code}
> ZKUtil.deleteChildrenRecursively(watcher, acquiredZnode);
> ZKUtil.deleteChildrenRecursively(watcher, reachedZnode);
> ZKUtil.deleteChildrenRecursively(watcher, abortZnode);
> {code}
> To achieve high consistency, it is desirable to use multi for the above
> operations.
> This JIRA adds support for recursive deletion in multi.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
