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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4707) Improvements to Hadoop Thrift bindings
Date Wed, 11 Feb 2009 21:49:59 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4707?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12672796#action_12672796

dhruba borthakur commented on HADOOP-4707:

> Would it make sense to open a new JIRA issue to implement the plugin functionality? 

Yes, please open a new JIRA to implement "export namenode/datanode functionality through a
pluggable RPC layer". The component for this jira will be "dfs". You can submit the code for
this new JIRA, get it vetted by the HDFS community and then commit to svn. After that is done,
then we can work on getting this one (HADOOP-4707) commiited. You might need a separate unit
test associated with this new JIRA.

> Reading is by far more important to me than writing, and I could just do the writes using
I like this staged approach. I know that many would like to write to HDFS using Thrift, but
with an eye to gettting this committed sooner, I would rather that we take it in steps.

> was very helpful during development. Will it be possible to do a similar thing when the
Thrift code moves back

Yes, If you move the TestThriftServer code to src/contrib/thriftfs/test/org/apache/hadoop/thriftfs,
that should be all that is required.

> Improvements to Hadoop Thrift bindings
> --------------------------------------
>                 Key: HADOOP-4707
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4707
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: contrib/thiftfs
>    Affects Versions: 0.20.0
>         Environment: Tested under Linux x86-64
>            Reporter: Carlos Valiente
>            Priority: Minor
>         Attachments: all.diff, BlockManager.java, build_xml.diff, DefaultBlockManager.java,
DFSBlockManager.java, gen.diff, HADOOP-4707.diff, hadoopfs_thrift.diff, hadoopthriftapi.jar,
HadoopThriftServer.java, HadoopThriftServer_java.diff, hdfs.py, hdfs_py_venky.diff, libthrift.jar,
> I have made the following changes to hadoopfs.thrift:
> #  Added namespaces for Python, Perl and C++.
> # Renamed parameters and struct members to camelCase versions to keep them consistent
(in particular FileStatus{blockReplication,blockSize} vs FileStatus.{block_replication,blocksize}).
> # Renamed ThriftHadoopFileSystem to FileSystem. From the perspective of a Perl/Python/C++
user, 1) it is already clear that we're using Thrift, and 2) the fact that we're dealing with
Hadoop is already explicit in the namespace.  The usage of generated code is more compact
and (in my opinion) clearer:
> {quote}
>         *Perl*:
>         use HadoopFS;
>         my $client = HadoopFS::FileSystemClient->new(..);
>          _instead of:_
>         my $client = HadoopFS::ThriftHadoopFileSystemClient->new(..);
>         *Python*:
>         from hadoopfs import FileSystem
>         client = FileSystem.Client(..)
>         _instead of_
>         from hadoopfs import ThriftHadoopFileSystem
>         client = ThriftHadoopFileSystem.Client(..)
>         (See also the attached diff [^scripts_hdfs_py.diff] for the
>          new version of 'scripts/hdfs.py').
>         *C++*:
>         hadoopfs::FileSystemClient client(..);
>          _instead of_:
>         hadoopfs::ThriftHadoopFileSystemClient client(..);
> {quote}
> # Renamed ThriftHandle to FileHandle: As in 3, it is clear that we're dealing with a
Thrift object, and its purpose (to act as a handle for file operations) is clearer.
> # Renamed ThriftIOException to IOException, to keep it simpler, and consistent with MalformedInputException.
> # Added explicit version tags to fields of ThriftHandle/FileHandle, Pathname, MalformedInputException
and ThriftIOException/IOException, to improve compatibility of existing clients with future
versions of the interface which might add new fields to those objects (like stack traces for
the exception types, for instance).
> Those changes are reflected in the attachment [^hadoopfs_thrift.diff].
> Changes in generated Java, Python, Perl and C++ code are also attached in [^gen.diff].
They were generated by a Thrift checkout from trunk
> ([http://svn.apache.org/repos/asf/incubator/thrift/trunk/]) as of revision
> 719697, plus the following Perl-related patches:
> * [https://issues.apache.org/jira/browse/THRIFT-190]
> * [https://issues.apache.org/jira/browse/THRIFT-193]
> * [https://issues.apache.org/jira/browse/THRIFT-199]
> The Thrift jar file [^libthrift.jar] built from that Thrift checkout is also attached,
since it's needed to run the Java Thrift server.
> I have also added a new target to src/contrib/thriftfs/build.xml to build the Java bindings
needed for org.apache.hadoop.thriftfs.HadoopThriftServer.java (see attachment [^build_xml.diff]
and modified HadoopThriftServer.java to make use of the new bindings (see attachment [^HadoopThriftServer_java.diff]).
> The jar file [^lib/hadoopthriftapi.jar] is also included, although it can be regenerated
from the stuff under 'gen-java' and the new 'compile-gen' Ant target.
> The whole changeset is also included as [^all.diff].

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