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https://issues.apache.org/jira/browse/HDFS-14989?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aravindan Vijayan updated HDFS-14989:
-------------------------------------
    Description: 
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.

bq. 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)

bq. Additionally, this operation introduces a new opcode OP_SWAP_BLOCK_LIST to 
record the change persistently.


  was:
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.



> 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
>            Priority: Major
>
> 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.
> bq. 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)
> bq. Additionally, this operation introduces a new opcode OP_SWAP_BLOCK_LIST 
> to record the change persistently.



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