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https://issues.apache.org/jira/browse/HDFS-11926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16039281#comment-16039281
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Anu Engineer commented on HDFS-11926:
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[~cheersyang] Thanks for the update, it looks much better. Three questions /
Comments.
# if count is 0 or less than zero, I think we should just throw an
IllegalArgumentException. If there is a magic semantics of translating a -1 to
max int, it should be done in the caller function, not in a generic helper. My
point is that, this semantics might not be applicable to all listing operations
and we should just keep what is truly generic in this function.
# We do a DbIter.seekToFirst -- shouldn't we do that if and only if the
startKey == null ? It looks like it is a frivolous operation if startKey
argument is not null.
# Even though I did suggest that we should throw if cannot find the startKey,
We also need a plan to handle the situation where someone is iterating a bucket
with concurrent deletes going on, if we always throw then user will not be able
to make any forward progress(For this patch, I am good with this, we should
file a tracking JIRA if we are committing this). So we should tell user how to
back-off, that is take the last listing output and try the previous key, or
restart from the last successful startKey or retry the operations. In other
words, we need to cleanly define the semantics and usage of what the user needs
to do if and when they encounter this error.
> Ozone: Implement a common helper to return a range of KVs in levelDB
> --------------------------------------------------------------------
>
> Key: HDFS-11926
> URL: https://issues.apache.org/jira/browse/HDFS-11926
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ozone
> Reporter: Weiwei Yang
> Assignee: Weiwei Yang
> Priority: Blocker
> Attachments: HDFS-11926-HDFS-7240.001.patch,
> HDFS-11926-HDFS-7240.002.patch, HDFS-11926-HDFS-7240.003.patch
>
>
> There are quite some *LIST* operations need to get a range of keys or values
> from levelDB, and filter entries with key prefix.
> # HDFS-11782 listKeys
> # HDFS-11779 listBuckets
> # HDFS-11773 listVolumes
> # HDFS-11679 listContainers
> we need to implement a common utility for them.
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