Plugable block id generation
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Key: HDFS-1245
URL: https://issues.apache.org/jira/browse/HDFS-1245
Project: Hadoop HDFS
Issue Type: New Feature
Components: name-node
Reporter: Dmytro Molkov
The idea is to have a way to easily create block id generation engines that may
fit a certain purpose. One of them could be HDFS-898 started by Konstantin, but
potentially others.
We chatted with Dhruba about this for a while and came up with the following
approach:
There should be a BlockIDGenerator interface that has following methods:
void blockAdded(Block)
void blockRemoved(Block)
Block nextBlock()
First two methods are needed for block generation engines that hold a certain
state. During the restart, when namenode reads the fsimage it will notify
generator about all the blocks it reads from the image and during runtime
namenode will notify the generator about block removals on file deletion.
The instance of the generator will also have a reference to the block registry,
the interface that BlockManager implements. The only method there is
__blockExists(Block)__, so that the current random block id generation can be
implemented, since it needs to check with the block manager if the id is
already present.
What does the community think about this proposal?
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