我已经使用新的2.x版本设置了一个Hadoop集群。我根据本指南安装了 snappy 和 hadoop snappy，以便在地图输出中启用 snappy 压缩。
运行示例字数统计时，发生错误：
[dm@node1 ~]$ hadoop jar /opt/hadoop-2.0.5-alpha/share/hadoop/mapreduce/hadoop-mapreduce-examples-2.0.5-alpha.jar wordcount /in /out
13/09/06 05:09:52 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
13/09/06 05:09:53 INFO service.AbstractService: Service:org.apache.hadoop.yarn.client.YarnClientImpl is inited.
13/09/06 05:09:53 INFO service.AbstractService: Service:org.apache.hadoop.yarn.client.YarnClientImpl is started.
13/09/06 05:10:04 INFO input.FileInputFormat: Total input paths to process : 1
13/09/06 05:10:04 INFO snappy.LoadSnappy: Snappy native library loaded
13/09/06 05:10:04 INFO lzo.GPLNativeCodeLoader: Loaded native gpl library
13/09/06 05:10:04 INFO lzo.LzoCodec: Successfully loaded & initialized native-lzo library [hadoop-lzo rev d0f5a10f99f1b2af4f6610447052c5a67b8b1cc7]
13/09/06 05:10:04 INFO mapreduce.JobSubmitter: number of splits:1
13/09/06 05:10:04 WARN conf.Configuration: mapred.jar is deprecated. Instead, use mapreduce.job.jar
13/09/06 05:10:04 WARN conf.Configuration: mapred.output.value.class is deprecated. Instead, use mapreduce.job.output.value.class
13/09/06 05:10:04 WARN conf.Configuration: mapreduce.combine.class is deprecated. Instead, use mapreduce.job.combine.class
13/09/06 05:10:04 WARN conf.Configuration: mapreduce.map.class is deprecated. Instead, use mapreduce.job.map.class
13/09/06 05:10:04 WARN conf.Configuration: mapred.job.name is deprecated. Instead, use mapreduce.job.name
13/09/06 05:10:04 WARN conf.Configuration: mapreduce.reduce.class is deprecated. Instead, use mapreduce.job.reduce.class
13/09/06 05:10:04 WARN conf.Configuration: mapred.input.dir is deprecated. Instead, use mapreduce.input.fileinputformat.inputdir
13/09/06 05:10:04 WARN conf.Configuration: mapred.output.dir is deprecated. Instead, use mapreduce.output.fileoutputformat.outputdir
13/09/06 05:10:04 WARN conf.Configuration: mapred.map.tasks is deprecated. Instead, use mapreduce.job.maps
13/09/06 05:10:04 WARN conf.Configuration: mapred.output.key.class is deprecated. Instead, use mapreduce.job.output.key.class
13/09/06 05:10:04 WARN conf.Configuration: mapred.working.dir is deprecated. Instead, use mapreduce.job.working.dir
13/09/06 05:10:05 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_1378415309099_0001
13/09/06 05:10:06 INFO client.YarnClientImpl: Submitted application application_1378415309099_0001 to ResourceManager at node1/192.168.56.101:60832
13/09/06 05:10:06 INFO mapreduce.Job: The url to track the job: http://node1:60888/proxy/application_1378415309099_0001/
13/09/06 05:10:06 INFO mapreduce.Job: Running job: job_1378415309099_0001
13/09/06 05:10:32 INFO mapreduce.Job: Job job_1378415309099_0001 running in uber mode : false
13/09/06 05:10:32 INFO mapreduce.Job: map 0% reduce 0%
13/09/06 05:10:53 INFO mapreduce.Job: map 100% reduce 0%
13/09/06 05:11:02 INFO mapreduce.Job: Task Id : attempt_1378415309099_0001_m_000000_0, Status : FAILED
Error: org.apache.hadoop.util.NativeCodeLoader.buildSupportsSnappy()Z
Container killed by the ApplicationMaster.
13/09/06 05:11:03 INFO mapreduce.Job: map 0% reduce 0%
13/09/06 05:11:07 INFO mapreduce.Job: Task Id : attempt_1378415309099_0001_m_000000_1, Status : FAILED
Error: org.apache.hadoop.util.NativeCodeLoader.buildSupportsSnappy()Z
13/09/06 05:11:13 INFO mapreduce.Job: Task Id : attempt_1378415309099_0001_m_000000_2, Status : FAILED
Error: org.apache.hadoop.util.NativeCodeLoader.buildSupportsSnappy()Z
13/09/06 05:11:19 INFO mapreduce.Job: map 100% reduce 0%
13/09/06 05:11:19 INFO mapreduce.Job: Job job_1378415309099_0001 failed with state FAILED due to: Task failed task_1378415309099_0001_m_000000
Job failed as tasks failed. failedMaps:1 failedReduces:0
13/09/06 05:11:19 INFO mapreduce.Job: Counters: 6
Job Counters
Failed map tasks=4
Launched map tasks=4
Other local map tasks=3
Data-local map tasks=1
Total time spent by all maps in occupied slots (ms)=42989
Total time spent by all reduces in occupied slots (ms)=0
我在谷歌上搜索了错误消息"错误：org.apache.hadoop.util.NativeCodeLoader.buildSupportsSnappy（）Z"，但没有找到这个问题的解决方案。所以我想知道如何在Hadoop 2.x中启用快速压缩？谢谢。
好的服务器：
$ hadoop checknative -a | grep snappy
15/06/18 14:51:05 INFO bzip2.Bzip2Factory: Successfully loaded & initialized native-bzip2 library system-native
15/06/18 14:51:05 INFO zlib.ZlibFactory: Successfully loaded & initialized native-zlib library
snappy: true /opt/cloudera/parcels/CDH-5.4.2-1.cdh5.4.2.p0.2/lib/hadoop/lib/native/libsnappy.so.1
不好的服务器：
$ hadoop checknative -a | grep snappy
15/06/18 14:50:31 INFO bzip2.Bzip2Factory: Successfully loaded & initialized native-bzip2 library system-native
15/06/18 14:50:31 INFO zlib.ZlibFactory: Successfully loaded & initialized native-zlib library
snappy: true /usr/lib64/libsnappy.so.1
请注意，在一种情况下，"hadoop checknative"命令返回系统的libsnappy，在另一种情况下 - 一个来自Hadoop发行版。如果你在某些主机上有hadoop，报告他们使用系统的libsnappy，像".hadoop.mapred.YarnChild：运行子级时出错：java.lang.UnsatisfiedLinkError：org.apache.hadoop.util.NativeCodeLoader.buildSupportsSnappy（）Z at org.apache.hadoop.util.NativeCodeLoader.buildSupportsSnappy（Native Method）"是很有可能的。
从您提供的输出（WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform...等）来看，您的本机库似乎没有加载。 我认为值得尝试构建和安装本机库，然后在 <HADOOP_HOME>/lib/native/ 中添加 Snappy 库。 我认为这可能会解决问题。希望对您有所帮助！
看起来您的代码无法加载活泼的本机库。对此可能有两种可能的解释。要么您使用的是与您安装的Hadoop版本不兼容的snappy版本。或者 您尚未在类路径中添加库。
该指南上的第二个参数是错误的。
请改用mapreduce.map.output.compress.codec。