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https://issues.apache.org/jira/browse/HDFS-12820?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16890872#comment-16890872
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Chen Zhang commented on HDFS-12820:
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Thanks [~hexiaoqiao] for your comments, my bad, ignored the order of subtract
operation and status change.
So I think we can resolve this issue as "not an issue"?
> Decommissioned datanode is counted in service cause datanode allcating failure
> ------------------------------------------------------------------------------
>
> Key: HDFS-12820
> URL: https://issues.apache.org/jira/browse/HDFS-12820
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: block placement
> Affects Versions: 2.4.0
> Reporter: Gang Xie
> Priority: Major
>
> When allocate a datanode when dfsclient write with considering the load, it
> checks if the datanode is overloaded by calculating the average xceivers of
> all the in service datanode. But if the datanode is decommissioned and become
> dead, it's still treated as in service, which make the average load much more
> than the real one especially when the number of the decommissioned datanode
> is great. In our cluster, 180 datanode, and 100 of them decommissioned, and
> the average load is 17. This failed all the datanode allocation.
> private void subtract(final DatanodeDescriptor node) {
> capacityUsed -= node.getDfsUsed();
> blockPoolUsed -= node.getBlockPoolUsed();
> xceiverCount -= node.getXceiverCount();
> {color:red} if (!(node.isDecommissionInProgress() ||
> node.isDecommissioned())) {{color}
> nodesInService--;
> nodesInServiceXceiverCount -= node.getXceiverCount();
> capacityTotal -= node.getCapacity();
> capacityRemaining -= node.getRemaining();
> } else {
> capacityTotal -= node.getDfsUsed();
> }
> cacheCapacity -= node.getCacheCapacity();
> cacheUsed -= node.getCacheUsed();
> }
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