[jira] [Created] (HDFS-12594) SnapshotDiff - snapshotDiff fails if the snapshotDiff . report exceeds the RPC response limit

["Shashikant Banerjee (JIRA)" <ji...@apache.org>]

Shashikant Banerjee created HDFS-12594:
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             Summary: 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


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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