Manoj Govindassamy created HDFS-12203:
-----------------------------------------
Summary: INodeAttributesProvider#getAttributes() support for
default/passthrough mode
Key: HDFS-12203
URL: https://issues.apache.org/jira/browse/HDFS-12203
Project: Hadoop HDFS
Issue Type: Improvement
Reporter: Manoj Govindassamy
Assignee: Manoj Govindassamy
{{INodeAttributeProvider}}
{noformat}
..
public abstract INodeAttributes getAttributes(String[] pathElements,
INodeAttributes inode);
public INodeAttributes getAttributes(byte[][] components, INodeAttributes
inode) {
String[] elements = new String[components.length];
for (int i = 0; i < elements.length; i++) {
elements[i] = DFSUtil.bytes2String(components[i]);
}
return getAttributes(elements, inode);
}
{noformat}
The abstract method {{INodeAttributesProvider#getAttributes()}} currently takes
in INode path elements and the INode. Many a times, the provider falls back to
the local INode attributes. But, there isn't a way for the caller to tell the
provider to fall back to local attribute on demand. Below is one such usecase,
where the caller of getAttributes() wants to use the local attributes instead
of the one coming from the external provider.
Assume the external attributes provider takes care of providing custom
ACLFeature for some specific directories and all its descendants (like Sentry)
and fallsback to the default INode ACLFeature for all other files/directories.
And lets assume that the external provider also has its meta data properly
replicated to another site.
An operation like snapshot diff iterates over the children of given snapshot
pair and generates the diff list. In order to generate the diff list, files are
compared which involves their metadata comparisons. Once HDFS-12201 is fixed,
metadata comparisons will compare the attributes from external providers as
well. Given that external attributes can be ignored as they are taken care by
other means, Snapshot diff wants the meta data comparison to ignore the
features coming from external attribute provider and fall back to the local
INode features. This on-demand fall-back or passthrough mode for
INodeAttributesProvider will help to avoid the huge performance, or memory over
consumption problems arising out of the external provider plugins.
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