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https://issues.apache.org/jira/browse/KYLIN-1883?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15374829#comment-15374829
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Zhong Yanghong edited comment on KYLIN-1883 at 7/14/16 7:03 AM:
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By the way, we can reduce the time between creating the referenceSet and
deleting to reduce the occurrence chance of the consensus issue. However, it
still cannot fix the consensus problem completely. The best way is to add a
lock before creating the referenceSet.
was (Author: yaho):
By the way, we can reduce the time between creating the referenceSet and
deleting to reduce the occurrence chance of the consensus issue. However, it
still cannot fix the consensus problem completely. The best way is to add a tag
for each item to indicate whether it is referenced or not.
> Consensus Problem when running the tool, MetadataCleanupJob
> -----------------------------------------------------------
>
> Key: KYLIN-1883
> URL: https://issues.apache.org/jira/browse/KYLIN-1883
> Project: Kylin
> Issue Type: Bug
> Reporter: Zhong Yanghong
> Assignee: Zhong Yanghong
> Attachments:
> better_solution_for_consensus_issue_of_MetadataCleanupJob.patch
>
>
> When do the cleanup, current strategy is as follows:
> 1. firstly create an referenceSet
> 2. then add items not belonging to the referenceSet to the toDeleteSet
> 3. finally delete those items in the toDeleteSet
> Consensus issue will occur since we cannot make sure that all of the items in
> toDeleteSet are not referenced in case that referenceSet changes during the
> process.
> For example, before the cleanup, SEGMENT_A is deleted and leave a DICT_A
> created at the building step. Then the referenceSet will not include DICT_A.
> After creating the reference set, SEGMENT_B is starting to build. Since
> DICT_A still exists, it can still be referenced by SEGMENT_B. Then DICT_A
> will still be included in the toDeleteSet and will be deleted later. Finally
> SEGMENT_B only owns a reference with no data.
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