Jing Zhao created HDFS-10968:
--------------------------------
Summary: BlockManager#isNewRack should consider decommissioning
nodes
Key: HDFS-10968
URL: https://issues.apache.org/jira/browse/HDFS-10968
Project: Hadoop HDFS
Issue Type: Sub-task
Components: erasure-coding, namenode
Affects Versions: 3.0.0-alpha1
Reporter: Jing Zhao
Assignee: Jing Zhao
For an EC block, it is possible we have enough internal blocks but without
enough racks. The current reconstruction code calls {{BlockManager#isNewRack}}
to check if the target node can increase the total rack number for the case,
which compares the target node's rack with source node racks:
{code}
for (DatanodeDescriptor src : srcs) {
if (src.getNetworkLocation().equals(target.getNetworkLocation())) {
return false;
}
}
{code}
However here the {{srcs}} may include a decommissioning node, in which case we
should allow the target node to be in the same rack with it.
For e.g., suppose we have 11 nodes: h1 ~ h11, which are located in racks r1,
r1, r2, r2, r3, r3, r4, r4, r5, r5, r6, respectively. In case that an EC block
has 9 live internal blocks on (h1~h8 + h11), and one internal block on h9 which
is to be decommissioned. The current code will not choose h10 for
reconstruction because isNewRack thinks h10 is on the same rack with h9.
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