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https://issues.apache.org/jira/browse/ZOOKEEPER-2052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14162998#comment-14162998
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Yip Ng commented on ZOOKEEPER-2052:
-----------------------------------
Rakesh R, Hongchao Deng.
Yes, I think you guys are right. Since the list is empty after the revert in
rollbackPendingChanges(), this means possibly the FinalRequestProcessor thread
have processed ChangeRecord and have removed it from the outstandingChanges
list; hence, the logic in rollbackPendingChanges() should not apply any of the
prior saved changes back into outstandingChangesForPath map.
So in summary, it appears there are two bugs found so far:
1) getPendingChanges() saves ChangeRecord(s) for path that does not exist in
outstandingChangesForPath ( zxid = -1 )
2) rollbackPendingChanges() puts back prior saved changes back to
outstandingChangesForPath when the outstandingChange list is empty.
Working on another patch now and will resubmit it for review.
> Unable to delete a node when the node has no children
> -----------------------------------------------------
>
> Key: ZOOKEEPER-2052
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2052
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Affects Versions: 3.4.6, 3.5.0
> Environment: Red Hat Enterprise Linux 6.1 x86_64, standalone or 3
> node ensemble (v3.4.6), 2 Java clients (v3.4.6)
> Reporter: Yip Ng
> Attachments: ZOOKEEPER-2052.patch, ZOOKEEPER-2052.patch,
> ZOOKEEPER-2052.patch, zookeeper.log
>
>
> We stumbled upon a ZooKeeper bug where a node with no children cannot be
> removed on our 3 node ZooKeeper ensemble or standalone ZooKeeper on Red Hat
> Enterprise Linux x86_64 environment. Here is an example scenario/setup:
> o Standalone ZooKeeper or 3 node ensemble (v3.4.6)
> o 2 Java clients (v3.4.6)
> - Client A creates a persistent node (e.g.: /metadata/resources)
> - Client B creates ephemeral nodes under this persistent node
> o Client A attempts to remove the /metadata/resources node via multi op
> delete but fails since there are children
> o Client B's session expired, all the ephemeral nodes are removed
> o Client A attempts to recursively remove /metadata/resources node via
> multi op, this is expected to succeed but got the following exception:
> org.apache.zookeeper.KeeperException$NotEmptyException:
> KeeperErrorCode = Directory not empty
> (Note that Client B is the only client that creates these ephemeral nodes)
> o After this, we use zkCli.sh to inspect the problematic node but the
> zkCli.sh shows the /metadata/resources node indeed have no children but it
> will not allow /metadata/resources node to get deleted. (shown below)
> [zk: localhost:2181(CONNECTED) 0] ls /
> [zookeeper, metadata]
> [zk: localhost:2181(CONNECTED) 1] ls /metadata
> [resources]
> [zk: localhost:2181(CONNECTED) 2] get /metadata/resources
> null
> cZxid = 0x3
> ctime = Wed Oct 01 22:04:11 PDT 2014
> mZxid = 0x3
> mtime = Wed Oct 01 22:04:11 PDT 2014
> pZxid = 0x9
> cversion = 2
> dataVersion = 0
> aclVersion = 0
> ephemeralOwner = 0x0
> dataLength = 0
> numChildren = 0
> [zk: localhost:2181(CONNECTED) 3] delete /metadata/resources
> Node not empty: /metadata/resources
> [zk: localhost:2181(CONNECTED) 4] get /metadata/resources
> null
> cZxid = 0x3
> ctime = Wed Oct 01 22:04:11 PDT 2014
> mZxid = 0x3
> mtime = Wed Oct 01 22:04:11 PDT 2014
> pZxid = 0x9
> cversion = 2
> dataVersion = 0
> aclVersion = 0
> ephemeralOwner = 0x0
> dataLength = 0
> numChildren = 0
> o The only ways to remove this node is to either:
> a) Restart the ZooKeeper server
> b) set data to /metadata/resources then followed by a subsequent delete.
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