[
https://issues.apache.org/jira/browse/HADOOP-941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12475597
]
David Bowen commented on HADOOP-941:
------------------------------------
Doug, I think that you may be missing a point here. From the point of view of
people who want to use this package outside of Hadoop, there is a significant
drawback to your suggestion of just including the two interfaces Writable and
WritableComparable in the stand-alone jar file. Namely, the generated code is
much larger, and results in more class files, because of the WritableComparator
subclasses that are generated. These classes don't provide any value to
non-Hadoop-users.
The difference between the generated code in the two cases, with and without
the -hadoop option, is pretty simple. There is just a bunch of stuff left out
when -hadoop is not specified. Therefore, I don't think that there is a strong
case to be made that this is adding excessive complexity to the rcc.
I don't buy your argument about the danger of using the wrong command-line
option and getting the wrong generated code. The command-line option will
generally be in a build.xml file, and if someone gets it wrong the compiler
will immediately point out the problem.
So I think this patch offers a clear benefit to a (currently) small number of
people, with essentially no downside. So I vote to commit it.
> Make Hadoop Record I/O Easier to use outside Hadoop
> ---------------------------------------------------
>
> Key: HADOOP-941
> URL: https://issues.apache.org/jira/browse/HADOOP-941
> Project: Hadoop
> Issue Type: Improvement
> Components: record
> Affects Versions: 0.10.1
> Environment: All
> Reporter: Milind Bhandarkar
> Assigned To: Milind Bhandarkar
> Attachments: jute-patch.txt
>
>
> Hadoop record I/O can be used effectively outside of Hadoop. It would
> increase its utility if developers can use it without having to import hadoop
> classes, or having to depend on Hadoop jars. Following changes to the current
> translator and runtime are proposed.
> Proposed Changes:
> 1. Use java.lang.String as a native type for ustring (instead of Text.)
> 2. Provide a Buffer class as a native Java type for buffer (instead of
> BytesWritable), so that later BytesWritable could be implemented as following
> DDL:
> module org.apache.hadoop.io {
> record BytesWritable {
> buffer value;
> }
> }
> 3. Member names in generated classes should not have prefixes 'm' before
> their names. In the above example, the private member name would be 'value'
> not 'mvalue' as it is done now.
> 4. Convert getters and setters to have CamelCase. e.g. in the above example
> the getter will be:
> public Buffer getValue();
> 5. Provide a 'swiggable' C binding, so that processing the generated C code
> with swig allows it to be used in scripting languages such as Python and Perl.
> 6. The default --language="java" target would generate class code for records
> that would not have Hadoop dependency on WritableComparable interface, but
> instead would have "implements Record, Comparable". (i.e. It will not have
> write() and readFields() methods.) An additional option "--writable" will
> need to be specified on rcc commandline to generate classes that "implements
> Record, WritableComparable".
> 7. Optimize generated write() and readFields() methods, so that they do not
> have to create BinaryOutputArchive or BinaryInputArchive every time these
> methods are called on a record.
> 8. Implement ByteInStream and ByteOutStream for C++ runtime, as they will be
> needed for using Hadoop Record I/O with forthcoming C++ MapReduce framework
> (currently, only FileStreams are provided.)
> 9. Generate clone() methods for records in Java i.e. the generated classes
> should implement Cloneable.
> 10. As part of Hadoop build process, produce a tar bundle for Record I/O
> alone. This tar bundle will contain the translator classes and ant task
> (lib/rcc.jar), translator script (bin/rcc), Java runtime (recordio.jar) that
> includes org.apache.hadoop.record.*, sources for the java runtime (src/java),
> and c/c++ runtime sources with Makefiles (src/c++, src/c).
> 11. Make generated Java codes for maps and vectors use Java generics.
> These are the proposed user-visible changes. Internally, the translator will
> be restructured so that it is easier to plug-in translators for different
> targets.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
