客户端用java api 远程操作HDFS以及远程提交MR任务(源码和异常处理
http://blog.csdn.net/liuxingjiaofu/article/category/925559（转载地址，已经关注，可以看其hbase的相关文章）
两个类，一个HDFS文件操作类，一个是wordcount 词数统计类，都是从网上看来的。上代码：
- package mapreduce;
- import java.io.IOException;
- import java.util.ArrayList;
- import java.util.List;
- import org.apache.hadoop.conf.Configuration;
- import org.apache.hadoop.fs.BlockLocation;
- import org.apache.hadoop.fs.FSDataInputStream;
- import org.apache.hadoop.fs.FSDataOutputStream;
- import org.apache.hadoop.fs.FileStatus;
- import org.apache.hadoop.fs.FileSystem;
- import org.apache.hadoop.fs.Path;
- import org.apache.hadoop.hdfs.DistributedFileSystem;
- import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
- import org.apache.hadoop.io.IOUtils;
- /**
- * file operation on HDFS
- * @author liuxingjiaofu
- *
- */
- public class HDFS_File {
- //read the file from HDFS
- public void ReadFile(Configuration conf, String FileName){
- try{
- FileSystem hdfs = FileSystem.get(conf);
- FSDataInputStream dis = hdfs.open(new Path(FileName));
- IOUtils.copyBytes(dis, System.out, 4096, false);
- dis.close();
- }catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- }
- //copy the file from HDFS to local
- public void GetFile(Configuration conf, String srcFile, String dstFile){
- try {
- FileSystem hdfs = FileSystem.get(conf);
- Path srcPath = new Path(srcFile);
- Path dstPath = new Path(dstFile);
- hdfs.copyToLocalFile(true,srcPath, dstPath);
- }catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- }
- //copy the local file to HDFS
- public void PutFile(Configuration conf, String srcFile, String dstFile){
- try {
- FileSystem hdfs = FileSystem.get(conf);
- Path srcPath = new Path(srcFile);
- Path dstPath = new Path(dstFile);
- hdfs.copyFromLocalFile(srcPath, dstPath);
- } catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- }
- //create the new file
- public FSDataOutputStream CreateFile(Configuration conf, String FileName){
- try {
- FileSystem hdfs = FileSystem.get(conf);
- Path path = new Path(FileName);
- FSDataOutputStream outputStream = hdfs.create(path);
- return outputStream;
- } catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- return null;
- }
- //rename the file name
- public boolean ReNameFile(Configuration conf, String srcName, String dstName){
- try {
- Configuration config = new Configuration();
- FileSystem hdfs = FileSystem.get(config);
- Path fromPath = new Path(srcName);
- Path toPath = new Path(dstName);
- boolean isRenamed = hdfs.rename(fromPath, toPath);
- return isRenamed;
- }catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- return false;
- }
- //delete the file
- // tyep = true, delete the directory
- // type = false, delete the file
- public boolean DelFile(Configuration conf, String FileName, boolean type){
- try {
- FileSystem hdfs = FileSystem.get(conf);
- Path path = new Path(FileName);
- boolean isDeleted = hdfs.delete(path, type);
- return isDeleted;
- }catch (IOException e) {
- // TODO Auto-generated catch block
- e.printStackTrace();
- }
- return false;
- }
- //Get HDFS file last modification time
- public long GetFileModTime(Configuration conf, String FileName){
- try{
- FileSystem hdfs = FileSystem.get(conf);
- Path path = new Path(FileName);
- FileStatus fileStatus = hdfs.getFileStatus(path);
- long modificationTime = fileStatus.getModificationTime();
- return modificationTime;
- }catch(IOException e){
- e.printStackTrace();
- }
- return 0;
- }
- //check if a file exists in HDFS
- public boolean CheckFileExist(Configuration conf, String FileName){
- try{
- FileSystem hdfs = FileSystem.get(conf);
- Path path = new Path(FileName);
- boolean isExists = hdfs.exists(path);
- return isExists;
- }catch(IOException e){
- e.printStackTrace();
- }
- return false;
- }
- //Get the locations of a file in the HDFS cluster
- public List<String []> GetFileBolckHost(Configuration conf, String FileName){
- try{
- List<String []> list = new ArrayList<String []>();
- FileSystem hdfs = FileSystem.get(conf);
- Path path = new Path(FileName);
- FileStatus fileStatus = hdfs.getFileStatus(path);
- BlockLocation[] blkLocations = hdfs.getFileBlockLocations(fileStatus, 0, fileStatus.getLen());
- int blkCount = blkLocations.length;
- for (int i=0; i < blkCount; i++) {
- String[] hosts = blkLocations[i].getHosts();
- list.add(hosts);
- }
- return list;
- }catch(IOException e){
- e.printStackTrace();
- }
- return null;
- }
- //Get a list of all the nodes host names in the HDFS cluster
- // have no authorization to do this operation
- public String[] GetAllNodeName(Configuration conf){
- try{
- FileSystem fs = FileSystem.get(conf);
- DistributedFileSystem hdfs = (DistributedFileSystem) fs;
- DatanodeInfo[] dataNodeStats = hdfs.getDataNodeStats();
- String[] names = new String[dataNodeStats.length];
- for (int i = 0; i < dataNodeStats.length; i++) {
- names[i] = dataNodeStats[i].getHostName();
- }
- return names;
- }catch(IOException e){
- System.out.println("error!!!!");
- e.printStackTrace();
- }
- return null;
- }
- }
wordcount
- package mapreduce;
- import java.io.IOException;
- import java.util.StringTokenizer;
- import org.apache.hadoop.conf.Configuration;
- import org.apache.hadoop.fs.Path;
- import org.apache.hadoop.io.IntWritable;
- import org.apache.hadoop.io.LongWritable;
- import org.apache.hadoop.io.Text;
- import org.apache.hadoop.mapreduce.Job;
- import org.apache.hadoop.mapreduce.Mapper;
- import org.apache.hadoop.mapreduce.Reducer;
- import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
- import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
- import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
- public class mywordcount {
- public static class wordcountMapper extends
- Mapper<LongWritable, Text, Text, IntWritable>{
- private final static IntWritable one = new IntWritable(1);
- private Text word = new Text();
- public void map(LongWritable key, Text value, Context context)throws IOException, InterruptedException{
- String line = value.toString();
- StringTokenizer itr = new StringTokenizer(line);
- while(itr.hasMoreElements()){
- word.set(itr.nextToken());
- context.write(word, one);
- }
- }
- }
- public static class wordcountReducer extends
- Reducer<Text, IntWritable, Text, IntWritable>{
- public void reduce(Text key, Iterable<IntWritable>values, Context context)throws IOException, InterruptedException{
- int sum = 0;
- for (IntWritable str : values){
- sum += str.get();
- }
- context.write(key, new IntWritable(sum));
- }
- }
- /**
- * 2 args, the file you want to count words from and the directory you want to save the result
- * @param args /home/hadooper/testmp/testtext /home/hadooper/testmp/testresult
- * @throws Exception
- */
- public static void main(String args[])throws Exception{
- //首先定义两个临时文件夹，这里可以使用随机函数+文件名，这样重名的几率就很小。
- String dstFile = "temp_src";
- String srcFile = "temp_dst";
- //这里生成文件操作对象。
- HDFS_File file = new HDFS_File();
- Configuration conf = new Configuration();
- // must!!! config the fs.default.name be the same to the value in core-site.xml
- conf.set("fs.default.name","hdfs://node1");
- conf.set("mapred.job.tracker","node1:54311");
- //从本地上传文件到HDFS,可以是文件也可以是目录
- file.PutFile(conf, args[0], dstFile);
- System.out.println("up ok");
- Job job = new Job(conf, "mywordcount");
- job.setJarByClass(mywordcount.class);
- job.setInputFormatClass(TextInputFormat.class);
- job.setOutputKeyClass(Text.class);
- job.setOutputValueClass(IntWritable.class);
- job.setMapperClass(wordcountMapper.class);
- job.setReducerClass(wordcountReducer.class);
- job.setCombinerClass(wordcountReducer.class);
- //注意这里的输入输出都应该是在HDFS下的文件或目录
- FileInputFormat.setInputPaths(job, new Path(dstFile));
- FileOutputFormat.setOutputPath(job, new Path(srcFile));
- //开始运行
- job.waitForCompletion(true);
- //从HDFS取回文件保存至本地
- file.GetFile(conf, srcFile, args[1]);
- System.out.println("down the result ok!");
- //删除临时文件或目录
- file.DelFile(conf, dstFile, true);
- file.DelFile(conf, srcFile, true);
- System.out.println("delete file on hdfs ok!");
- }
- }
期间，遇到几个错误：
1.HDFS版本问题--Call to node1/172.*.*.*:8020 failed on local exception: java.io.EOFException
main() {……
Configuration conf = new Configuration();
conf.set("fs.default.name","hdfs://node1");//与conf/core-site里的值对应，必须
HDFS_File file = new HDFS_File();
//print all the node name
String[] host_name = file.GetAllNodeName(conf);
……}
public String[] GetAllNodeName(Configuration conf){
try{
// Configuration config = new Configuration();
FileSystem fs = FileSystem.get(conf);
DistributedFileSystem hdfs = (DistributedFileSystem) fs;
DatanodeInfo[] dataNodeStats = hdfs.getDataNodeStats();
String[] names = new String[dataNodeStats.length];
for (int i = 0; i < dataNodeStats.length; i++) {
names[i] = dataNodeStats[i].getHostName();
}
return names;
}catch(IOException e){
System.out.println("eeeeeeeeeeeeeeeeeeeerror!!!!");
e.printStackTrace();
}
return null;
}
异常：
eeeeeeeeeeeeeeeeeeeerror!!!!
java.io.IOException: Call to node1/172.10.39.250:8020 failed on local exception: java.io.EOFException
at org.apache.hadoop.ipc.Client.wrapException(Client.java:775)
at org.apache.hadoop.ipc.Client.call(Client.java:743)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:220)
at $Proxy0.getProtocolVersion(Unknown Source)
at org.apache.hadoop.ipc.RPC.getProxy(RPC.java:359)
at org.apache.hadoop.hdfs.DFSClient.createRPCNamenode(DFSClient.java:112)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:213)
at org.apache.hadoop.hdfs.DFSClient.<init>(DFSClient.java:176)
at org.apache.hadoop.hdfs.DistributedFileSystem.initialize(DistributedFileSystem.java:82)
at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:1378)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:66)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:1390)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:196)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:95)
at mapreduce.HDFS_File.GetAllNodeName(HDFS_File.java:151)
at mapreduce.File_Operation.main(File_Operation.java:15)
Caused by: java.io.EOFException
at java.io.DataInputStream.readInt(DataInputStream.java:392)
at org.apache.hadoop.ipc.Client$Connection.receiveResponse(Client.java:501)
at org.apache.hadoop.ipc.Client$Connection.run(Client.java:446)
Exception in thread "main" java.lang.NullPointerException
at mapreduce.File_Operation.main(File_Operation.java:16)
原因：版本问题，确保java中的jar包跟hadoop集群的jar包是相同版本的
2.HDFS权限问题
org.apache.hadoop.security.AccessControlException: org.apache.hadoop.security.AccessControlException: Permission denied: user=hadooper, access=WRITE, inode="/user":root:supergroup:drwxr-xr-x
解决方案之
（1 added this entry to conf/hdfs-site.xml
<property>
<name>dfs.permissions</name>
<value>false</value>
</property>
（2.放开 要写入目录 hadoop 目录的权限 ， 命令如下 ：$ hadoop fs -chmod 777 /user/
我用的是第2种方案
3.HDFS 2011-12-20 17:00:32 org.apache.hadoop.util.NativeCodeLoader <clinit>
警告: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
在Hadoop的配置文件core-site.xml中可以设置是否使用本地库：
<property>
<name>hadoop.native.lib</name>
<value>true</value>
<description>Should native hadoop libraries, if present, be used.</description>
</property>
Hadoop默认的配置为启用本地库。
另外，可以在环境变量中设置使用本地库的位置：
export JAVA_LIBRARY_PATH=/path/to/hadoop-native-libs
有的时候也会发现Hadoop自带的本地库无法使用，这种情况下就需要自己去编译本地库了。在$HADOOP_HOME目录下，使用如下命令即可：
ant compile-native
编译完成后，可以在$HADOOP_HOME/build/native目录下找到相应的文件，然后指定文件的路径或者移动编译好的文件到默认目录下即可
我试了下，那个是64位的，我电脑是32位的，没有源代码，编译不了，那只好一段段程序的试，找出哪段代码出了这个警告，我的是
try {
FileSystem hdfs = FileSystem.get(conf);
Path srcPath = new Path(srcFile);
Path dstPath = new Path(dstFile);
hdfs.copyToLocalFile(true,srcPath, dstPath);//定位到此句
}catch (IOException e) {
到了此步，便只能如此了，为什么呢，java不是跨平台的吗
4.MR-jar包缺失
ClassNotFoundException: org.codehaus.jackson.map.JsonMappingException
NoClassDefFoundError: org/apache/commons/httpclient/HttpMethod
添加jar包到java工程中
jackson-core-asl-1.5.2.jar
jackson-mapper-asl-1.5.2.jar
commons-httpclient-3.0.1.jar
我是不习惯将所有Jar包都加到工程里，觉得这样很容易便加多了，浪费时空。
完成第一次mapreduce，不错！
5.远程的JOB挂掉了，居然还能运行成功，发现是mapred.job.tracker属性没设，默认在local下运行，其值在namenode的mapred-site.xml中看
conf.set("mapred.job.tracker","node1:54311");
配置完了，运行可以初始化，但是找不到mapper类：
信息: Task Id : attempt_201112221123_0010_m_000000_0, Status : FAILED
java.lang.RuntimeException: java.lang.ClassNotFoundException: mapreduce.mywordcount$wordcountMapper
at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:996)
at org.apache.hadoop.mapreduce.JobContext.getMapperClass(JobContext.java:212)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:611)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:325)
at org.apache.hadoop.mapred.Child$4.run(Child.java:270)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1127)
at org.apache.hadoop.mapred.Child.main(Child.java:264)
将程序打成jar包放到hadoop集群的jobtracker上可用，正常，结果也正确，但是在客户端运行却报上述错误，暂时还没解决。
总结
1.远程操作HDFS文件以及远程提交MR任务，必须配置的两项（其他暂时还没发现）：
conf.set("fs.default.name","hdfs://node1");//与conf/core-site.xml里的值对应，必须
conf.set("mapred.job.tracker","node1:54311");//mapred-site.xml