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MapReduce提供了许多默认的输出格式,如TextOutputFormat、KeyValueOutputFormat等。MapReduce中输出文件的个数与Reduce的个数一致,默认情况下有一个Reduce,输出只有一个文件,文件名为part-r-00000,文件内容的行数与map输出中不同key的个数一致。如果有两个Reduce,输出的结果就有两个文件,第一个为part-r-00000,第二个为part-r-00001,依次类推。
MapReduce中默认实现输出功能的类是TextOutputFormat,它主要用来将文本数据输出到HDFS上。
public class TextOutputFormatextends FileOutputFormat { public static String SEPERATOR = "mapreduce.output.textoutputformat.separator"; // 定义了内部类用来实现输出,换行符为\n,分隔符为\t(可以通过参数修改) protected static class LineRecordWriter extends RecordWriter { public LineRecordWriter(DataOutputStream out) { // 实际为FSDataOutputStream this(out, "\t"); } /** 主要的结构就是两个方法:write和close **/ public synchronized void write(K key, V value)throws IOException { boolean nullKey = key == null || key instanceof NullWritable; boolean nullValue = value == null || value instanceof NullWritable; if (nullKey && nullValue) { return; } if (!nullKey) { writeObject(key); // 将Text类型数据处理成字节数组 } if (!(nullKey || nullValue)) { out.write(keyValueSeparator); } if (!nullValue) { writeObject(value); } out.write(newline); // 换行(newline = "\n".getBytes(utf8);) } public synchronized void close(TaskAttemptContext context) throws IOException { out.close(); } } // 内部类定义结束,下面为TextOutputFormat唯一的关键方法 public RecordWriter getRecordWriter(TaskAttemptContext job) throws IOException, InterruptedException { // 1、根据Configuration判定是否需要压缩,若需要压缩获取压缩格式及后缀; // 2. 获取需要生成的文件路径,getDefaultWorkFile(job, extension) // 3. 根据文件生成FSDataOutputStream对象,并return new LineRecordWriter。 Configuration conf = job.getConfiguration(); boolean isCompressed = getCompressOutput(job); String keyValueSeparator= conf.get(SEPERATOR, "\t"); CompressionCodec codec = null; String extension = ""; if (isCompressed) { // 如果是压缩,则根据压缩获取扩展名 Class extends CompressionCodec> codecClass = getOutputCompressorClass(job, GzipCodec.class); codec = (CompressionCodec) ReflectionUtils.newInstance(codecClass, conf); extension = codec.getDefaultExtension(); } // getDefaultWorkFile用来获取保存输出数据的文件名,由FileOutputFormat类实现 Path file = getDefaultWorkFile(job, extension); FileSystem fs = file.getFileSystem(conf); // 获取writer对象 if (!isCompressed) { FSDataOutputStream fileOut = fs.create(file, false); return new LineRecordWriter (fileOut, keyValueSeparator); } else { FSDataOutputStream fileOut = fs.create(file, false); DataOutputStream dataOut = new DataOutputStream(codec.createOutputStream(fileOut)); return new LineRecordWriter (dataOut, keyValueSeparator); } } }
通过TextFileOutput类分析出具体需要将数据保存到HDFS的什么位置上,是通过FileOutputFormat类的getDefaultWorkFile方法来获取的。实际上对于MapReduce中所有的输出都需要继承OutputFormat,先看一下OutputFormat的类定义。
/** * OutputFormat定义了Map-Reduce作业的输出规范,如: * 1、校验,如指定的输出目录是否存在,输出的空间是否足够大; * 2、指定RecordWriter来将MapReduce的输出写入到FileSystem(一般为HDFS); */ public abstract class OutputFormat{ // 获取与当前task相关联的RecordWriter对象 public abstract RecordWriter getRecordWriter(TaskAttemptContext context) throws IOException, InterruptedException; // 当提交job时检查当前job的输出规范是否有效,如输出目录是否已存在等 public abstract void checkOutputSpecs(JobContext context) throws IOException, InterruptedException; // Get the output committer for this output format. // This is responsible for ensuring the output is committed correctly. public abstract OutputCommitter getOutputCommitter(TaskAttemptContext context) throws IOException, InterruptedException; }
在TextOutputFormat中实现了getRecordWriter,而TextOutputFormat的是FileOutputFormat的子类,而FileOutputFormat是的子类。
/** 用来实现写数据到HDFS的OutputFormat的基类 **/ public abstract class FileOutputFormatextends OutputFormat { /** 当有多个分区时,会有多个输出文件,通过NUMBER_FORMAT定义输出文件编号,如part-r-00000,00001等。 **/ private static final NumberFormat NUMBER_FORMAT = NumberFormat.getInstance(); /** 默认的输出文件为part开头的,可以通过该参数给指定一个输出的文件名 **/ protected static final String BASE_OUTPUT_NAME = "mapreduce.output.basename"; protected static final String PART = "part"; static { NUMBER_FORMAT.setMinimumIntegerDigits(5); NUMBER_FORMAT.setGroupingUsed(false); } // 对MapReduce的输出可以指定是否压缩及压缩形式,通过配置文件mapred-site.xml进行配置 // 默认为false public static final String COMPRESS ="mapreduce.output.fileoutputformat.compress"; // 默认为org.apache.hadoop.io.compress.DefaultCodec public static final String COMPRESS_CODEC = "mapreduce.output.fileoutputformat.compress.codec"; // 默认为RECORD,针对每行记录进行压缩。如果设置为BLOCK,针对一组记录进行压缩。 public static final String COMPRESS_TYPE = "mapreduce.output.fileoutputformat.compress.type"; // 设置map-reduce job的输出目录 public static void setOutputPath(Job job, Path outputDir) { try { outputDir = outputDir.getFileSystem(job.getConfiguration()).makeQualified(outputDir); } catch (IOException e) { // Throw the IOException as a RuntimeException to be compatible with MR1 throw new RuntimeException(e); } job.getConfiguration().set(FileOutputFormat.OUTDIR, outputDir.toString()); } // 进行check检查 public void checkOutputSpecs(JobContext job) throws FileAlreadyExistsException, IOException{ // 1. 判定是否设定了输出目录(FileOutputFormat.setOutputPath); // 2. 判定输出目录是否存在(需指定空目录)。 } // 获取输出的committer对象,MRv2引入的,以允许用户自己定制合适的OutputCommitter实现 public synchronized OutputCommitter getOutputCommitter(TaskAttemptContext context) throws IOException { if (committer == null) { Path output = getOutputPath(context); committer = new FileOutputCommitter(output, context); } return committer; } // 获取当前output format对应的默认输出路径和文件名 public Path getDefaultWorkFile(TaskAttemptContext context, String extension) throws IOException{ FileOutputCommitter committer = (FileOutputCommitter) getOutputCommitter(context); return new Path(committer.getWorkPath(), getUniqueFile(context, getOutputName(context), extension)); } /** * Generate a unique filename, based on the task id, name, and extension * 获取文件名,如part-r-00000,00001等 * @param context the task that is calling this * @param name the base filename * @param extension the filename extension * @return a string like $name-[mrsct]-$id$extension */ public synchronized static String getUniqueFile(TaskAttemptContext context, String name, String extension) { TaskID taskId = context.getTaskAttemptID().getTaskID(); int partition = taskId.getId(); StringBuilder result = new StringBuilder(); result.append(name); result.append('-'); result.append(TaskID.getRepresentingCharacter(taskId.getTaskType())); result.append('-'); result.append(NUMBER_FORMAT.format(partition)); result.append(extension); return result.toString(); } }
任务的类型是通过类org.apache.hadoop.mapreduce.TaskID$CharTaskTypeMaps获取
static String allTaskTypes = "(m|r|s|c|t)"; static { setupTaskTypeToCharMapping(); setupCharToTaskTypeMapping(); } private static void setupTaskTypeToCharMapping() { typeToCharMap.put(TaskType.MAP, 'm'); typeToCharMap.put(TaskType.REDUCE, 'r'); typeToCharMap.put(TaskType.JOB_SETUP, 's'); typeToCharMap.put(TaskType.JOB_CLEANUP, 'c'); typeToCharMap.put(TaskType.TASK_CLEANUP, 't'); } private static void setupCharToTaskTypeMapping() { charToTypeMap.put('m', TaskType.MAP); charToTypeMap.put('r', TaskType.REDUCE); charToTypeMap.put('s', TaskType.JOB_SETUP); charToTypeMap.put('c', TaskType.JOB_CLEANUP); charToTypeMap.put('t', TaskType.TASK_CLEANUP); } // 获取part-r-00000中间的那个r static char getRepresentingCharacter(TaskType type) { return typeToCharMap.get(type); }
应用示例:把首字母相同的单词放到一个文件里面
输入文件内容:
[hadoop@nnode code]$ [hadoop@nnode code]$ hdfs dfs -ls /data Found 2 items -rw-r--r-- 1 hadoop hadoop 47 2015-06-09 17:59 /data/file1.txt -rw-r--r-- 2 hadoop hadoop 36 2015-06-09 17:59 /data/file2.txt [hadoop@nnode code]$ hdfs dfs -text /data/file1.txt hello world hello markhuang hello hadoop [hadoop@nnode code]$ hdfs dfs -text /data/file2.txt hadoop ok hadoop fail hadoop 2.3 [hadoop@nnode code]$
自定义OutputFormat:
package com.lucl.hadoop.mapreduce.multiple; import java.io.IOException; import java.util.HashMap; import java.util.Iterator; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FSDataOutputStream; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.Writable; import org.apache.hadoop.io.WritableComparable; import org.apache.hadoop.io.compress.CompressionCodec; import org.apache.hadoop.io.compress.GzipCodec; import org.apache.hadoop.mapreduce.OutputCommitter; import org.apache.hadoop.mapreduce.RecordWriter; import org.apache.hadoop.mapreduce.TaskAttemptContext; import org.apache.hadoop.mapreduce.lib.output.FileOutputCommitter; import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat; import org.apache.hadoop.util.ReflectionUtils; /** * @author luchunli * @description 自定义OutputFormat,这里继承TextOutputFormat,避免了自己实现OutputCommitter,
* MapReduce中key要求为WritableComparable类型的,value要求为Writable类型的. */ public class MultipleOutputFormat, V extends Writable> extends TextOutputFormat { /** * OutputFormat通过获取Writer对象,将数据输出到指定目录特定名称的文件中。 */ private MultipleRecordWriter writer = null; // 在TextOutputFormat实现的时候对于每一个map或task任务都有一个唯一的标识,通过TaskID来控制, // 其在输出时文件名是固定的,每一个输出文件对应一个LineRecordWriter,取其输出流对象(FSDataOutputStream), // 在输出时通过输出流对象实现数据输出。 // // 但是在这里实现的时候,实际上是要求对于一个task任务,将它需要输出的数据写入多个文件,文件是不固定的; // 因此在每次输出的时候判定对应的文件是否已经有Writer对象,若有则通过该对象继续输出,否则创建新的。 @Override public RecordWriter getRecordWriter(TaskAttemptContext context) throws IOException, InterruptedException { if (null == writer) { writer = new MultipleRecordWriter(context, this.getTaskOutputPath(context)); } return writer; } // 获取任务的输出路径,仍然采用从committer中获取,TaskAttemptContext封装了task的上下文,后续分析。 // 在TextOutputFormat中是通过调用父类(FileOutputFormat)的getDefaultWorkFile来实现的, // 而getDefaultWorkFile中获取MapReduce定义的默认的文件名,如需要自定义文件名,需自己实现 private Path getTaskOutputPath(TaskAttemptContext context) throws IOException { Path workPath = null; OutputCommitter committer = super.getOutputCommitter(context); if (committer instanceof FileOutputCommitter) { // Get the directory that the task should write results into. workPath = ((FileOutputCommitter) committer).getWorkPath(); } else { // Get the {@link Path} to the output directory for the map-reduce job. // context.getConfiguration().get(FileOutputFormat.OUTDIR); Path outputPath = super.getOutputPath(context); if (null == outputPath) { throw new IOException("Undefined job output-path."); } workPath = outputPath; } return workPath; } /** * @author luchunli * @description 自定义RecordWriter, MapReduce的TextOutputFormat的LineRecordWriter也是内部类,这里参照其实现方式 */ public class MultipleRecordWriter extends RecordWriter { /** RecordWriter的缓存 **/ private HashMap > recordWriters = null; private TaskAttemptContext context; /** 输出目录 **/ private Path workPath = null; public MultipleRecordWriter () {} public MultipleRecordWriter(TaskAttemptContext context, Path path) { super(); this.context = context; this.workPath = path; this.recordWriters = new HashMap >(); } @Override public void write(K key, V value) throws IOException, InterruptedException { String baseName = generateFileNameForKeyValue (key, value, this.context.getConfiguration()); RecordWriter rw = this.recordWriters.get(baseName); if (null == rw) { rw = this.getBaseRecordWriter(context, baseName); this.recordWriters.put(baseName, rw); } // 这里实际仍然为通过LineRecordWriter来实现的 rw.write(key, value); } // 通过MultipleRecordWriter对LineRecordWriter进行了封装,对于同一个task在输出的时候进行了拆分 // 在MapReduce实现中,默认情况下只有一个reduce(Reduce的数量分区部分分析),根据之前的示例所有的输出都将写入到part-r-00000的文件中, // 这里所做的工作就是屏蔽了到part-r-00000的输出,而是将同一个reduce的数据拆分为多个文件。 private RecordWriter getBaseRecordWriter(TaskAttemptContext context, String baseName) throws IOException { Configuration conf = context.getConfiguration(); boolean isCompressed = getCompressOutput(context); // 在LineRecordWriter的实现中,分隔符是通过变量如下方式指定的: // public static String SEPERATOR = "mapreduce.output.textoutputformat.separator"; // String keyValueSeparator= conf.get(SEPERATOR, "\t"); // 这里给了个逗号作为分割 String keyValueSeparator = ","; RecordWriter rw = null; if (isCompressed) { Class extends CompressionCodec> codecClass = getOutputCompressorClass(context, GzipCodec.class); CompressionCodec codec = ReflectionUtils.newInstance(codecClass, conf); Path file = new Path(workPath, baseName + codec.getDefaultExtension()); FSDataOutputStream out = file.getFileSystem(conf).create(file, false); rw = new LineRecordWriter<>(out, keyValueSeparator); } else { Path file = new Path(workPath, baseName); FSDataOutputStream out = file.getFileSystem(conf).create(file, false); rw = new LineRecordWriter<>(out, keyValueSeparator); } return rw; } @Override public void close(TaskAttemptContext context) throws IOException, InterruptedException { Iterator > it = this.recordWriters.values().iterator(); while (it.hasNext()) { RecordWriter rw = it.next(); rw.close(context); } this.recordWriters.clear(); } /** 获取生成的文件的后缀名 **/ private String generateFileNameForKeyValue(K key, V value, Configuration configuration) { char c = key.toString().toLowerCase().charAt(0); if (c >= 'a' && c <= 'z') { return c + ".txt"; } return "other.txt"; } } }
实现Mapper
package com.lucl.hadoop.mapreduce.multiple; import java.io.IOException; import java.util.StringTokenizer; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Mapper; /** * @author luchunli * @description 自定义Mapper */ public class TokenizerMapper extends Mapper{ private static final IntWritable one = new IntWritable(1); private Text text = new Text(); @Override protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { StringTokenizer token = new StringTokenizer(value.toString()); while (token.hasMoreTokens()) { String word = token.nextToken(); text.set(word); context.write(text, one); } } }
实现Reducer
package com.lucl.hadoop.mapreduce.multiple; import java.io.IOException; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Reducer; /** * @author luchunli * @description 自定义Reducer */ public class TokenizerReducer extends Reducer{ @Override protected void reduce(Text key, Iterable value, Context context) throws IOException, InterruptedException { int sum = 0; for (IntWritable intWritable : value) { sum += intWritable.get(); } context.write(key, new IntWritable(sum)); } }
实现Driver
package com.lucl.hadoop.mapreduce.multiple; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.util.Tool; import org.apache.hadoop.util.ToolRunner; /** * @author luchunli * @description 驱动类 */ public class MultipleWorkCount extends Configured implements Tool { public static void main(String[] args) { try { ToolRunner.run(new MultipleWorkCount(), args); } catch (Exception e) { e.printStackTrace(); } } @Override public int run(String[] args) throws Exception { Job job = Job.getInstance(this.getConf(), this.getClass().getSimpleName()); job.setJarByClass(MultipleWorkCount.class); FileInputFormat.addInputPath(job, new Path(args[0])); job.setMapperClass(TokenizerMapper.class); job.setMapOutputKeyClass(Text.class); job.setMapOutputValueClass(IntWritable.class); job.setReducerClass(TokenizerReducer.class); job.setOutputKeyClass(Text.class); job.setOutputKeyClass(IntWritable.class); job.setOutputFormatClass(MultipleOutputFormat.class); FileOutputFormat.setOutputPath(job, new Path(args[1])); return job.waitForCompletion(true) ? 0 : 1; } }
调用执行
[hadoop@nnode code]$ hadoop jar MultipleMR.jar /data /2015120500010 15/12/05 16:45:54 INFO client.RMProxy: Connecting to ResourceManager at nnode/192.168.137.117:8032 15/12/05 16:45:55 INFO input.FileInputFormat: Total input paths to process : 2 15/12/05 16:45:55 INFO mapreduce.JobSubmitter: number of splits:2 15/12/05 16:45:55 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1449302623953_0004 15/12/05 16:45:56 INFO impl.YarnClientImpl: Submitted application application_1449302623953_0004 15/12/05 16:45:56 INFO mapreduce.Job: The url to track the job: http://nnode:8088/proxy/application_1449302623953_0004/ 15/12/05 16:45:56 INFO mapreduce.Job: Running job: job_1449302623953_0004 15/12/05 16:46:27 INFO mapreduce.Job: Job job_1449302623953_0004 running in uber mode : false 15/12/05 16:46:27 INFO mapreduce.Job: map 0% reduce 0% 15/12/05 16:46:56 INFO mapreduce.Job: map 50% reduce 0% 15/12/05 16:46:58 INFO mapreduce.Job: map 100% reduce 0% 15/12/05 16:47:16 INFO mapreduce.Job: map 100% reduce 100% 15/12/05 16:47:18 INFO mapreduce.Job: Job job_1449302623953_0004 completed successfully 15/12/05 16:47:18 INFO mapreduce.Job: Counters: 49 File System Counters FILE: Number of bytes read=152 FILE: Number of bytes written=323517 FILE: Number of read operations=0 FILE: Number of large read operations=0 FILE: Number of write operations=0 HDFS: Number of bytes read=271 HDFS: Number of bytes written=55 HDFS: Number of read operations=9 HDFS: Number of large read operations=0 HDFS: Number of write operations=7 Job Counters Launched map tasks=2 Launched reduce tasks=1 Data-local map tasks=2 Total time spent by all maps in occupied slots (ms)=58249 Total time spent by all reduces in occupied slots (ms)=17197 Total time spent by all map tasks (ms)=58249 Total time spent by all reduce tasks (ms)=17197 Total vcore-seconds taken by all map tasks=58249 Total vcore-seconds taken by all reduce tasks=17197 Total megabyte-seconds taken by all map tasks=59646976 Total megabyte-seconds taken by all reduce tasks=17609728 Map-Reduce Framework Map input records=6 Map output records=12 Map output bytes=122 Map output materialized bytes=158 Input split bytes=188 Combine input records=0 Combine output records=0 Reduce input groups=7 Reduce shuffle bytes=158 Reduce input records=12 Reduce output records=7 Spilled Records=24 Shuffled Maps =2 Failed Shuffles=0 Merged Map outputs=2 GC time elapsed (ms)=313 CPU time spent (ms)=4770 Physical memory (bytes) snapshot=511684608 Virtual memory (bytes) snapshot=2545770496 Total committed heap usage (bytes)=257171456 Shuffle Errors BAD_ID=0 CONNECTION=0 IO_ERROR=0 WRONG_LENGTH=0 WRONG_MAP=0 WRONG_REDUCE=0 File Input Format Counters Bytes Read=83 File Output Format Counters Bytes Written=55 [hadoop@nnode code]$
查看输出结果:
[hadoop@nnode code]$ hdfs dfs -ls /2015120500010 Found 7 items -rw-r--r-- 2 hadoop hadoop 0 2015-12-05 16:47 /2015120500010/_SUCCESS -rw-r--r-- 2 hadoop hadoop 7 2015-12-05 16:47 /2015120500010/f.txt -rw-r--r-- 2 hadoop hadoop 17 2015-12-05 16:47 /2015120500010/h.txt -rw-r--r-- 2 hadoop hadoop 12 2015-12-05 16:47 /2015120500010/m.txt -rw-r--r-- 2 hadoop hadoop 5 2015-12-05 16:47 /2015120500010/o.txt -rw-r--r-- 2 hadoop hadoop 6 2015-12-05 16:47 /2015120500010/other.txt -rw-r--r-- 2 hadoop hadoop 8 2015-12-05 16:47 /2015120500010/w.txt [hadoop@nnode code]$ hdfs dfs -text /2015120500010/h.txt hadoop,4 hello,3 [hadoop@nnode code]$ hdfs dfs -text /2015120500010/o.txt ok,1 [hadoop@nnode code]$ hdfs dfs -text /2015120500010/other.txt 2.3,1 [hadoop@nnode code]$
错误记录:
1、java.lang.RuntimeException: java.lang.InstantiationException
[hadoop@nnode code]$ hadoop jar MultipleMR.jar /data /2015120500001 15/12/05 16:18:19 INFO client.RMProxy: Connecting to ResourceManager at nnode/192.168.137.117:8032 java.lang.RuntimeException: java.lang.InstantiationException at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:131) at org.apache.hadoop.mapreduce.JobSubmitter.checkSpecs(JobSubmitter.java:559) at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:432) at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1296) at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1293) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:415) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628) at org.apache.hadoop.mapreduce.Job.submit(Job.java:1293) at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1314) at com.lucl.hadoop.mapreduce.multiple.MultipleWorkCount.run(MultipleWorkCount.java:49) at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70) at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:84) at com.lucl.hadoop.mapreduce.multiple.MultipleWorkCount.main(MultipleWorkCount.java:22) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.apache.hadoop.util.RunJar.run(RunJar.java:221) at org.apache.hadoop.util.RunJar.main(RunJar.java:136) Caused by: java.lang.InstantiationException at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:48) at java.lang.reflect.Constructor.newInstance(Constructor.java:526) at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:129) ... 19 more [hadoop@nnode code]$
原因:
由于之前还有一个子类,在Driver中是通过子类定义输出,后来感觉子类没有必要,于是去掉了,但是MultipleOutputFormat类定义仍然为abstract MultipleOutputFormat,没有把abstract给注释掉。
2、Error: java.io.IOException: Unable to initialize any output collector
[hadoop@nnode code]$ hadoop jar MultipleMR.jar /data /2015120500005 15/12/05 16:26:06 INFO client.RMProxy: Connecting to ResourceManager at nnode/192.168.137.117:8032 15/12/05 16:26:07 INFO input.FileInputFormat: Total input paths to process : 2 15/12/05 16:26:07 INFO mapreduce.JobSubmitter: number of splits:2 15/12/05 16:26:08 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1449302623953_0003 15/12/05 16:26:08 INFO impl.YarnClientImpl: Submitted application application_1449302623953_0003 15/12/05 16:26:08 INFO mapreduce.Job: The url to track the job: http://nnode:8088/proxy/application_1449302623953_0003/ 15/12/05 16:26:08 INFO mapreduce.Job: Running job: job_1449302623953_0003 15/12/05 16:26:43 INFO mapreduce.Job: Job job_1449302623953_0003 running in uber mode : false 15/12/05 16:26:43 INFO mapreduce.Job: map 0% reduce 0% 15/12/05 16:27:13 INFO mapreduce.Job: Task Id : attempt_1449302623953_0003_m_000000_0, Status : FAILED Error: java.io.IOException: Unable to initialize any output collector at org.apache.hadoop.mapred.MapTask.createSortingCollector(MapTask.java:412) at org.apache.hadoop.mapred.MapTask.access$100(MapTask.java:81) at org.apache.hadoop.mapred.MapTask$NewOutputCollector.(MapTask.java:695) at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:767) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341) at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:163) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:415) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628) at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158) 15/12/05 16:27:13 INFO mapreduce.Job: Task Id : attempt_1449302623953_0003_m_000001_0, Status : FAILED Error: java.io.IOException: Unable to initialize any output collector at org.apache.hadoop.mapred.MapTask.createSortingCollector(MapTask.java:412) at org.apache.hadoop.mapred.MapTask.access$100(MapTask.java:81) at org.apache.hadoop.mapred.MapTask$NewOutputCollector. (MapTask.java:695) at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:767) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341) at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:163) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:415) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628) at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158) ^C[hadoop@nnode code]$
原因:
Text引用错了:com.sun.jersey.core.impl.provider.entity.XMLJAXBElementProvider.Text
正确的引用:org.apache.hadoop.io.Text
说明:
attempt_1449302623953_0003_m_000000_0
通过第二个错误信息能看到map task的命名规则:
// TaskAttemptID represents the immutable and unique identifier for a task attempt. // Each task attempt is one particular instance of a Map or Reduce Task identified by TaskID. // An example TaskAttemptID is : attempt_200707121733_0003_m_000005_0 // zeroth task attempt for the fifth map task in the third job running at the jobtracker started at 200707121733 public class TaskAttemptID extends org.apache.hadoop.mapred.ID { protected static final String ATTEMPT = "attempt"; private TaskID taskId; // ...... }