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https://issues.apache.org/jira/browse/HDFS-12357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16151290#comment-16151290
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Yongjun Zhang commented on HDFS-12357:
--------------------------------------
{quote}
As in the v001 version, this is avoided.
{quote}
Not really. In the following code,
we get HDFS attributes first by {{INodeAttributes nodeAttrs =
node.getSnapshotINode(snapshot);}}. Then we get the external provider attribute
if needed.
In v001, for special user, it's not needed to get external provider attribute,
thus we don't call {{nodeAttrs = attributeProvider.getAttributes(components,
nodeAttrs);}};
However, in the wrapper solution, we will go into the {{if (attributeProvider
!= null) {}} block and call it. If the {{attributeProvider.getAttributes}}
decides to bypass external provider, it's going to do the same thing as
{{INodeAttributes nodeAttrs = node.getSnapshotINode(snapshot);}} to get the
HDFS version attribute. So we get the HDFS attribute twice.In v001, we only get
it once.
{code}
INodeAttributes getAttributes(INodesInPath iip)
throws FileNotFoundException {
INode node = FSDirectory.resolveLastINode(iip);
int snapshot = iip.getPathSnapshotId();
INodeAttributes nodeAttrs = node.getSnapshotINode(snapshot);
if (attributeProvider != null) {
// permission checking sends the full components array including the
// first empty component for the root. however file status
// related calls are expected to strip out the root component according
// to TestINodeAttributeProvider.
byte[][] components = iip.getPathComponents();
components = Arrays.copyOfRange(components, 1, components.length);
nodeAttrs = attributeProvider.getAttributes(components, nodeAttrs);
}
return nodeAttrs;
}
{code}
> Let NameNode to bypass external attribute provider for special user
> -------------------------------------------------------------------
>
> Key: HDFS-12357
> URL: https://issues.apache.org/jira/browse/HDFS-12357
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Yongjun Zhang
> Assignee: Yongjun Zhang
> Attachments: HDFS-12357.001.patch, HDFS-12357.002.patch,
> HDFS-12357.003.patch, HDFS-12357.004.patch
>
>
> This is a third proposal to solve the problem described in HDFS-12202.
> The problem is, when we do distcp from one cluster to another (or within the
> same cluster), in addition to copying file data, we copy the metadata from
> source to target. If external attribute provider is enabled, the metadata may
> be read from the provider, thus provider data read from source may be saved
> to target HDFS.
> We want to avoid saving metadata from external provider to HDFS, so we want
> to bypass external provider when doing the distcp (or hadoop fs -cp)
> operation.
> Two alternative approaches were proposed earlier, one in HDFS-12202, the
> other in HDFS-12294. The proposal here is the third one.
> The idea is, we introduce a new config, that specifies a special user (or a
> list of users), and let NN bypass external provider when the current user is
> a special user.
> If we run applications as the special user that need data from external
> attribute provider, then it won't work. So the constraint on this approach
> is, the special users here should not run applications that need data from
> external provider.
> Thanks [~asuresh] for proposing this idea and [~chris.douglas], [~daryn],
> [~manojg] for the discussions in the other jiras.
> I'm creating this one to discuss further.
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