Hadoop通过C的API访问HDFS
2012-02-24 13:57
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在HADOOP_HOM下通过ant compile-c++-libhdfs -Dislibhdfs=true(ant是类似于make的工具,主要应该与java,利用build.xml问价),产生libhdfs.so
或者在HADOOP_HOME/src/c++/libhdfs执行:①./configure --enable-shared JVM_ARCH=tune=k8 --prefix=`pwd`/nativelib
②make install
在通过Hadoop的C的API 访问HDFS的时候,编译和运行出现了不少问题,在这边,做个总结吧:
系统:Ubuntu11.04,Hadoop-0.20.203.0
样例代码就是参考官方文档中提供到:
[cpp] view
plaincopy
#include "hdfs.h"
int main(int argc, char **argv) {
hdfsFS fs = hdfsConnect("default", 0);
const char* writePath = "/tmp/testfile.txt";
hdfsFile writeFile = hdfsOpenFile(fs, writePath, O_WRONLY|O_CREAT, 0, 0, 0);
if(!writeFile) {
fprintf(stderr, "Failed to open %s for writing!\n", writePath);
exit(-1);
}
char* buffer = "Hello, World!";
tSize num_written_bytes = hdfsWrite(fs, writeFile, (void*)buffer, strlen(buffer)+1);
if (hdfsFlush(fs, writeFile)) {
fprintf(stderr, "Failed to 'flush' %s\n", writePath);
exit(-1);
}
hdfsCloseFile(fs, writeFile);
}
编译:官网这样描述
See the Makefile for hdfs_test.c in the libhdfs source directory (${HADOOP_HOME}/src/c++/libhdfs/Makefile) or something like:
gcc above_sample.c -I${HADOOP_HOME}/src/c++/libhdfs -L${HADOOP_HOME}/libhdfs -lhdfs -o above_sample
但是我两个方法都试了,不行,后面发现原来是要少了:
[plain] view
plaincopy
LIB = -L$(HADOOP_INSTALL)/c++/Linux-i386-32/lib/
libjvm=/usr/lib/jvm/java-6-openjdk/jre/lib/i386/client/libjvm.so
所以完整到makefile就是:
[plain] view
plaincopy
HADOOP_INSTALL=/home/fzuir/hadoop-0.20.203.0
PLATFORM=Linux-i386-32
JAVA_HOME=/usr/lib/jvm/java-6-openjdk/
CPPFLAGS= -I$(HADOOP_INSTALL)/src/c++/libhdfs
LIB = -L$(HADOOP_INSTALL)/c++/Linux-i386-32/lib/
libjvm=/usr/lib/jvm/java-6-openjdk/jre/lib/i386/client/libjvm.so
LDFLAGS += -lhdfs
testHdfs: testHdfs.c
gcc testHdfs.c $(CPPFLAGS) $(LIB) $(LDFLAGS) $(libjvm) -o testHdfs
clean:
rm testHdfs
好了,编译通过,但是运行的时候出现以下错误信息:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/configuration/Configuration
...
Call to org.apache.hadoop.fs.Filesystem::get(URI, Configuration) failed!
Exception in thread "main" java.lang.NullPointerException
Call to get configuration object from filesystem failed!
解决方法:将HADOOP_HOME和HADOOP_HOME/lib下所有到jar包加入/usr/lib/jvm/java-6-openjdk/jre/lib/ext/(其实只要需要到加入,但是不知道哪些是需要的)
最后,恭喜你,问题解决了。
或者在HADOOP_HOME/src/c++/libhdfs执行:①./configure --enable-shared JVM_ARCH=tune=k8 --prefix=`pwd`/nativelib
②make install
在通过Hadoop的C的API 访问HDFS的时候,编译和运行出现了不少问题,在这边,做个总结吧:
系统:Ubuntu11.04,Hadoop-0.20.203.0
样例代码就是参考官方文档中提供到:
[cpp] view
plaincopy
#include "hdfs.h"
int main(int argc, char **argv) {
hdfsFS fs = hdfsConnect("default", 0);
const char* writePath = "/tmp/testfile.txt";
hdfsFile writeFile = hdfsOpenFile(fs, writePath, O_WRONLY|O_CREAT, 0, 0, 0);
if(!writeFile) {
fprintf(stderr, "Failed to open %s for writing!\n", writePath);
exit(-1);
}
char* buffer = "Hello, World!";
tSize num_written_bytes = hdfsWrite(fs, writeFile, (void*)buffer, strlen(buffer)+1);
if (hdfsFlush(fs, writeFile)) {
fprintf(stderr, "Failed to 'flush' %s\n", writePath);
exit(-1);
}
hdfsCloseFile(fs, writeFile);
}
编译:官网这样描述
See the Makefile for hdfs_test.c in the libhdfs source directory (${HADOOP_HOME}/src/c++/libhdfs/Makefile) or something like:
gcc above_sample.c -I${HADOOP_HOME}/src/c++/libhdfs -L${HADOOP_HOME}/libhdfs -lhdfs -o above_sample
但是我两个方法都试了,不行,后面发现原来是要少了:
[plain] view
plaincopy
LIB = -L$(HADOOP_INSTALL)/c++/Linux-i386-32/lib/
libjvm=/usr/lib/jvm/java-6-openjdk/jre/lib/i386/client/libjvm.so
所以完整到makefile就是:
[plain] view
plaincopy
HADOOP_INSTALL=/home/fzuir/hadoop-0.20.203.0
PLATFORM=Linux-i386-32
JAVA_HOME=/usr/lib/jvm/java-6-openjdk/
CPPFLAGS= -I$(HADOOP_INSTALL)/src/c++/libhdfs
LIB = -L$(HADOOP_INSTALL)/c++/Linux-i386-32/lib/
libjvm=/usr/lib/jvm/java-6-openjdk/jre/lib/i386/client/libjvm.so
LDFLAGS += -lhdfs
testHdfs: testHdfs.c
gcc testHdfs.c $(CPPFLAGS) $(LIB) $(LDFLAGS) $(libjvm) -o testHdfs
clean:
rm testHdfs
好了,编译通过,但是运行的时候出现以下错误信息:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/configuration/Configuration
...
Call to org.apache.hadoop.fs.Filesystem::get(URI, Configuration) failed!
Exception in thread "main" java.lang.NullPointerException
Call to get configuration object from filesystem failed!
解决方法:将HADOOP_HOME和HADOOP_HOME/lib下所有到jar包加入/usr/lib/jvm/java-6-openjdk/jre/lib/ext/(其实只要需要到加入,但是不知道哪些是需要的)
最后,恭喜你,问题解决了。
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