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https://issues.apache.org/jira/browse/HDFS-17509?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17844944#comment-17844944
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ASF GitHub Bot commented on HDFS-17509:
---------------------------------------
LiuGuH commented on code in PR #6784:
URL: https://github.com/apache/hadoop/pull/6784#discussion_r1595269674
##########
hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java:
##########
@@ -667,39 +667,28 @@ public void rename2(final String src, final String dst,
public void concat(String trg, String[] src) throws IOException {
rpcServer.checkOperation(NameNode.OperationCategory.WRITE);
- // See if the src and target files are all in the same namespace
- LocatedBlocks targetBlocks = getBlockLocations(trg, 0, 1);
- if (targetBlocks == null) {
- throw new IOException("Cannot locate blocks for target file - " + trg);
- }
- LocatedBlock lastLocatedBlock = targetBlocks.getLastLocatedBlock();
- String targetBlockPoolId = lastLocatedBlock.getBlock().getBlockPoolId();
- for (String source : src) {
- LocatedBlocks sourceBlocks = getBlockLocations(source, 0, 1);
- if (sourceBlocks == null) {
- throw new IOException(
- "Cannot located blocks for source file " + source);
- }
- String sourceBlockPoolId =
- sourceBlocks.getLastLocatedBlock().getBlock().getBlockPoolId();
- if (!sourceBlockPoolId.equals(targetBlockPoolId)) {
- throw new IOException("Cannot concatenate source file " + source
- + " because it is located in a different namespace"
- + " with block pool id " + sourceBlockPoolId
- + " from the target file with block pool id "
- + targetBlockPoolId);
- }
- }
+ // Concat only effects when all files in same namespace.
+ // And in router view, a file only exists in one RemoteLocation.
Review Comment:
Thanks for review.
> you can refer to this case:
>
> * /path mounts to NS1, NS2 and NS3
> * NS2 and NS3 contains /path
> * `OrderedResolver` returns NS1, NS2 and NS3
>
> for this case, we should proxy this `concat` to NS2 instead of NS1, right?
This only happens when /path is a directory. And for a file ,it must only be
from one exactly nameservice via dfsrouter.
> RBF: Fix ClientProtocol.concat will throw NPE if tgr is a empty file.
> ----------------------------------------------------------------------
>
> Key: HDFS-17509
> URL: https://issues.apache.org/jira/browse/HDFS-17509
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: liuguanghua
> Priority: Minor
> Labels: pull-request-available
>
> hdfs dfs -concat /tmp/merge /tmp/t1 /tmp/t2
> When /tmp/merge is a empty file, this command will throw NPE via DFSRouter.
>
>
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