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https://issues.apache.org/jira/browse/HAMA-499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13228902#comment-13228902
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Edward J. Yoon commented on HAMA-499:
-------------------------------------
Even though the Zookeeper servers went shut-down or restarted, Zookeeper's old
nodes are remained in memory for a while.
The goal is clearing all sub nodes of bspRoot when Hama cluster is started.
> Refactor clearZKNodes() in BSPMaster
> ------------------------------------
>
> Key: HAMA-499
> URL: https://issues.apache.org/jira/browse/HAMA-499
> Project: Hama
> Issue Type: Improvement
> Components: bsp
> Affects Versions: 0.4.0
> Reporter: Edward J. Yoon
> Labels: newbie
> Fix For: 0.5.0
>
> Attachments: HAMA-499.patch, HAMA-499_2.patch, move.sh
>
>
> As you know, Hama uses ZooKeepr for a barrier synchronization. User can use
> Hama ZK, or their own existing ZK cluster. To avoid some potential problems,
> BSPMaster calls clearZKNodes() to delete all remained sub-nodes of 'bspRoot'
> at initialization stage. That code is here and very ugly:
> {code}
> public void clearZKNodes() {
> try {
> for (String node : zk.getChildren(bspRoot, this)) {
> for (String subnode : zk.getChildren(bspRoot + "/" + node, this)) {
> for (String subnode2 : zk.getChildren(bspRoot + "/" + node, this)) {
> for (String subnode3 : zk.getChildren(bspRoot + "/" + node + "/"
> + subnode2, this)) {
> zk.delete(bspRoot + "/" + node + "/" + subnode + "/" + subnode2
> + "/" + subnode3, 0);
> }
> zk.delete(bspRoot + "/" + node + "/" + subnode + "/" + subnode2,
> 0);
> }
> zk.delete(bspRoot + "/" + node + "/" + subnode, 0);
> }
> zk.delete(bspRoot + "/" + node, 0);
> }
> } catch (KeeperException e) {
> } catch (InterruptedException e) {
> }
> }
> {code}
> In this issue, we'll refactor this method. For example, you can delete
> recursively.
> P.S., must use '-1' to delete all version of each node like this:
> {code}
> zk.delete(node, -1);
> {code}
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