qinyuren created HDFS-16333:
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Summary: fix balancer bug when transfer an EC block
Key: HDFS-16333
URL: https://issues.apache.org/jira/browse/HDFS-16333
Project: Hadoop HDFS
Issue Type: Bug
Components: balancer & mover
Reporter: qinyuren
Attachments: image-2021-11-18-17-25-13-089.png,
image-2021-11-18-17-25-50-556.png, image-2021-11-18-17-28-03-155.png
We set the EC policy to (6+3) and we also have nodes that were decommissioning
when we executed balancer.
With the balancer running, we find many error logs as follow.
!image-2021-11-18-17-25-13-089.png!
Node A wants to transfer an EC block to node B, but we found that the block is
not on node A. The FSCK command to show the block status as follow
!image-2021-11-18-17-25-50-556.png!
Assume that the location of the an EC block look like this
indices:[0, 1, 2, 3, 4, 5, 6, 7, 8]
node:[a, b, c, d, e, f, g, h, i]
after decommission operation, the internal block on indices[1] were
decommission to another node.
indices:[0, 1, 2, 3, 4, 5, 6, 7, 8]
node:[a, j, c, d, e, f, g, h, i]
So the location of this block may as follow, the location of indices[1] change
from node b to node j.
In the dispatcher. getBlockList function
!image-2021-11-18-17-28-03-155.png!
If a node is not found in storageGroupMap, it will not be add to
block.locations.
But the indices is not updated.
finally, the block location may like this,
indices:[0, 1, 2, 3, 4, 5, 6, 7, 8]
block.location:[a, c, d, e, f, g, h, i]
the location of the nodes does not match their indices
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