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https://issues.apache.org/jira/browse/HDFS-12594?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16218301#comment-16218301
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Shashikant Banerjee commented on HDFS-12594:
--------------------------------------------
[~ehiggs], Thanks for the review comments. I will upload a patch with review
comments soon.
[~szetszwo], thanks for the review comments.
Implementing RemoteIterator class so that rpc calls are made on demand while
consuming the diff may not be possible here. We need the entire diff which is
collection of modify list ,createList and DeleteList generated at the namenode
with each RPC, so as to exactly figure out the Renames across directories
within the Snapshottable Root Directory at the client itself. All the Renames
within the Snapshottable directory can be figured out after the complete diff
processing of the snapshottable directory tree.
> SnapshotDiff - snapshotDiff fails if the snapshotDiff report exceeds the RPC
> response limit
> -------------------------------------------------------------------------------------------
>
> Key: HDFS-12594
> URL: https://issues.apache.org/jira/browse/HDFS-12594
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs
> Reporter: Shashikant Banerjee
> Assignee: Shashikant Banerjee
> Attachments: HDFS-12594.001.patch, HDFS-12594.002.patch,
> HDFS-12594.003.patch, SnapshotDiff_Improvemnets .pdf
>
>
> The snapshotDiff command fails if the snapshotDiff report size is larger than
> the configuration value of ipc.maximum.response.length which is by default
> 128 MB.
> Worst case, with all Renames ops in sanpshots each with source and target
> name equal to MAX_PATH_LEN which is 8k characters, this would result in at
> 8192 renames.
>
> SnapshotDiff is currently used by distcp to optimize copy operations and in
> case of the the diff report exceeding the limit , it fails with the below
> exception:
> Test set:
> org.apache.hadoop.hdfs.server.namenode.snapshot.TestSnapshotDiffReport
> -------------------------------------------------------------------------------
> Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 112.095 sec
> <<< FAILURE! - in
> org.apache.hadoop.hdfs.server.namenode.snapshot.TestSnapshotDiffReport
> testDiffReportWithMillionFiles(org.apache.hadoop.hdfs.server.namenode.snapshot.TestSnapshotDiffReport)
> Time elapsed: 111.906 sec <<< ERROR!
> java.io.IOException: Failed on local exception:
> org.apache.hadoop.ipc.RpcException: RPC response exceeds maximum data length;
> Host Details : local host is: "hw15685.local/10.200.5.230"; destination host
> is: "localhost":59808;
> Attached is the proposal for the changes required.
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