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HDFS-4852. Merging change r1619967 from trunk to branch-2. 

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1619968 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Chris Nauroth 2014-08-23 05:30:59 +00:00
parent 33229c1299
commit b2d86ebf78
2 changed files with 20 additions and 11 deletions
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2
hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
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@ -285,6 +285,8 @@ Release 2.6.0 - UNRELEASED
HDFS-6829. DFSAdmin refreshSuperUserGroupsConfiguration failed in
security cluster (zhaoyunjiong via Arpit Agarwal)
HDFS-4852. libhdfs documentation is out of date. (cnauroth)
Release 2.5.0 - 2014-08-11
INCOMPATIBLE CHANGES

29
hadoop-hdfs-project/hadoop-hdfs/src/site/apt/LibHdfs.apt.vm
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@ -26,14 +26,17 @@ C API libhdfs
(HDFS). It provides C APIs to a subset of the HDFS APIs to manipulate
HDFS files and the filesystem. libhdfs is part of the Hadoop
distribution and comes pre-compiled in
<<<${HADOOP_PREFIX}/libhdfs/libhdfs.so>>> .
<<<${HADOOP_HDFS_HOME}/lib/native/libhdfs.so>>> . libhdfs is compatible with
Windows and can be built on Windows by running <<<mvn compile>>> within the
<<<hadoop-hdfs-project/hadoop-hdfs>>> directory of the source tree.
* The APIs
The libhdfs APIs are a subset of: {{{hadoop fs APIs}}}.
The libhdfs APIs are a subset of the
{{{../../api/org/apache/hadoop/fs/FileSystem.html}Hadoop FileSystem APIs}}.
The header file for libhdfs describes each API in detail and is
available in <<<${HADOOP_PREFIX}/src/c++/libhdfs/hdfs.h>>>
available in <<<${HADOOP_HDFS_HOME}/include/hdfs.h>>>.
* A Sample Program
@ -55,24 +58,28 @@ C API libhdfs
fprintf(stderr, "Failed to 'flush' %s\n", writePath);
exit(-1);
}
hdfsCloseFile(fs, writeFile);
hdfsCloseFile(fs, writeFile);
}
----
* How To Link With The Library
See the Makefile for <<<hdfs_test.c>>> in the libhdfs source directory
(<<<${HADOOP_PREFIX}/src/c++/libhdfs/Makefile>>>) or something like:
<<<gcc above_sample.c -I${HADOOP_PREFIX}/src/c++/libhdfs -L${HADOOP_PREFIX}/libhdfs -lhdfs -o above_sample>>>
See the CMake file for <<<test_libhdfs_ops.c>>> in the libhdfs source
directory (<<<hadoop-hdfs-project/hadoop-hdfs/src/CMakeLists.txt>>>) or
something like:
<<<gcc above_sample.c -I${HADOOP_HDFS_HOME}/include -L${HADOOP_HDFS_HOME}/lib/native -lhdfs -o above_sample>>>
* Common Problems
The most common problem is the <<<CLASSPATH>>> is not set properly when
calling a program that uses libhdfs. Make sure you set it to all the
Hadoop jars needed to run Hadoop itself. Currently, there is no way to
programmatically generate the classpath, but a good bet is to include
all the jar files in <<<${HADOOP_PREFIX}>>> and <<<${HADOOP_PREFIX}/lib>>> as well
as the right configuration directory containing <<<hdfs-site.xml>>>
Hadoop jars needed to run Hadoop itself as well as the right configuration
directory containing <<<hdfs-site.xml>>>. It is not valid to use wildcard
syntax for specifying multiple jars. It may be useful to run
<<<hadoop classpath --glob>>> or <<<hadoop classpath --jar <path>>>> to
generate the correct classpath for your deployment. See
{{{../hadoop-common/CommandsManual.html#classpath}Hadoop Commands Reference}}
for more information on this command.
* Thread Safe