Aravindan Vijayan created HDFS-14989:
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Summary: Add a 'swapBlockList' operation to Namenode.
Key: HDFS-14989
URL: https://issues.apache.org/jira/browse/HDFS-14989
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: Aravindan Vijayan
Assignee: Aravindan Vijayan
Borrowing from the design doc.
bq.
The swapBlockList takes two parameters, a source file and a destination file.
This operation swaps the blocks belonging to the source and the destination
atomically.
The namespace metadata of interest is the INodeFile class. A file (INodeFile)
contains a header composed of PREFERRED_BLOCK_SIZE, BLOCK_LAYOUT_AND_REDUNDANCY
and STORAGE_POLICY_ID. In addition, an INodeFile contains a list of blocks
(BlockInfo[]). The operation will swap BLOCK_LAYOUT_AND_REDUNDANCY header bits
and the block lists. But it will not touch other fields. To avoid complication,
this operation will abort if either file is open (isUnderConstruction() == true)
Additionally, this operation introduces a new opcode OP_SWAP_BLOCK_LIST to
record the change persistently.
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