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https://issues.apache.org/jira/browse/HDFS-8643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14659892#comment-14659892
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Rakesh R commented on HDFS-8643:
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bq. Instead of directly adding name list to SnapshottableDirectoryStatus, I
think it may be better to directly enhance the lsSnapshottableDir cmd by making
multiple RPC calls (i.e., do "ls xxx/.snapshot" for each snapshottable dir).
Note that we have RPC packet limitation and a large number of snapshot list or
some long snapshot names can cause issue.
[~jingzhao], I agree with you. *lsSnapshottableDir* cmd is using the
{{DistributedFileSystem#getSnapshottableDirListing()}} API which is returning
{{SnapshottableDirectoryStatus[]}} array, the entire snapshot list. I'm
thinking to improve DistributedFileSystem API, that would be helpful to the
users also. How about exposing {{BatchedRemoteIterator<Long,
SnapshottableDirectoryStatus>}} to return batch of snapshots. Also, the same
can be used in lsSnapshottableDir cmd implementation.
Following are the initial thoughts to support the batch operation,
# Expose new API in {{DistributedFileSystem#listSnapshottableDirs()}}
# Add new API in {{ClientProtocol#listSnapshottableDirs(prevId)}}
# Expose configuration for batch size
{{dfs.namenode.list.snapshottable.dirs.num.responses}}, defaulting to 100
# Modify {{SnapshotManager#snapshottables}} datastructure to
{{java.util.TreeMap}}, this will help to make the navigation easy through
{{TreeMap.tailMap(prevId, false)}} function.
> Add snapshot names list to SnapshottableDirectoryStatus
> -------------------------------------------------------
>
> Key: HDFS-8643
> URL: https://issues.apache.org/jira/browse/HDFS-8643
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Rakesh R
> Assignee: Rakesh R
> Attachments: HDFS-8643-00.patch, HDFS-8643-01.patch
>
>
> The idea of this jira to enhance {{SnapshottableDirectoryStatus}} by adding
> {{snapshotNames}} attribute into it, presently it has the {{snapshotNumber}}.
> IMHO this would help the users to get the list of snapshot names created.
> Also, the snapshot names can be used while renaming or deleting the snapshots.
> {code}
> org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus.java
> /**
> * @return Snapshot names for the directory.
> */
> public List <String> getSnapshotNames() {
> return snapshotNames;
> }
> {code}
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