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https://issues.apache.org/jira/browse/ZOOKEEPER-723?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13049831#comment-13049831
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Benjamin Reed commented on ZOOKEEPER-723:
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yeah i don't like the floating out there indefinitely with no children part
either.
one use case for allowing different session is the barrier like case in which
you want to find out when everyone is done using a resource: you create a
parent znode, /myresource, with a child called available. processes that use
the resource will create children under /myresource. when the resource manager
wants to stop providing the resource, it removes /myresource/available and then
watches for /myresource to disappear.
> ephemeral parent znodes
> -----------------------
>
> Key: ZOOKEEPER-723
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-723
> Project: ZooKeeper
> Issue Type: New Feature
> Components: server
> Reporter: Benjamin Reed
> Assignee: Daniel Gómez Ferro
> Attachments: ZOOKEEPER-723.patch
>
>
> ephemeral znodes have the nice property of automatically cleaning up after
> themselves when the creator goes away, but since they can't have children it
> is hard to build subtrees that will cleanup after the clients that are using
> them are gone.
> rather than changing the semantics of ephemeral nodes, i propose ephemeral
> parents: znodes that disappear when they have no more children. this cleanup
> would happen automatically when the last child is removed. an ephemeral
> parent is not tied to any particular session, so even if the creator goes
> away, the ephemeral parent will remain as long as there are children.
> the when an ephemeral parent is created it will have an initial child, so
> that it doesn't get immediately removed. i think this child should be an
> ephemeral znode with a predefined name, "firstChild".
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