Hadoop lzo 正确安装及问题解决

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     之前有篇文章http://guoyunsky.iteye.com/blog/1237327介绍解hadoop-lzo相关问题,同时也介绍到了如何安装.但发现这种安装方法会出现一些问题.

      同时这种安装方法也是网上流传的安装方法,我这里予以纠正.先说下大概原因:hadoop-lzo-xxx的前身是hadoop-gpl-compression-xxx,之前是放在google code下管理,地址:http://code.google.com/p/hadoop-gpl-compression/ .但由于协议问题后来移植到github上,也就是现在的hadoop-lzo-xxx,github,链接地址:https://github.com/kevinweil/hadoop-lzo.网上介绍hadoop lzo压缩都是基于hadoop-gpl-compression的介绍.而hadoop-gpl-compression还是09年开发的,跟现在hadoop版本已经无法再完全兼容,会发生一些问题.而按照网上的方法,为了兼容hadoop,使用hadoop-lzo-xxx,但安装hadoop-gpl-compression会报错.具体报错如下:

11/12/02 14:28:41 INFO lzo.GPLNativeCodeLoader: Loaded native gpl library
11/12/02 14:28:41 WARN lzo.LzoCompressor: java.lang.NoSuchFieldError: workingMemoryBuf
11/12/02 14:28:41 ERROR lzo.LzoCodec: Failed to load/initialize native-lzo library
11/12/02 14:28:41 WARN mapred.LocalJobRunner: job_local_0001
java.lang.RuntimeException: native-lzo library not available
	at com.hadoop.compression.lzo.LzoCodec.createCompressor(LzoCodec.java:165)
	at com.hadoop.compression.lzo.LzopCodec.createOutputStream(LzopCodec.java:50)
	at org.apache.hadoop.mapreduce.lib.output.TextOutputFormat.getRecordWriter(TextOutputFormat.java:132)
	at org.apache.hadoop.mapred.MapTask$NewDirectOutputCollector.<init>(MapTask.java:520)
	at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:635)
	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:322)
	at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:210)

   我调试源码才发现原因,因为hadoop lzo实际上得依赖C/C++开发的lzo去压缩,而他们通过JNI去调用.如果使用hadoop-gpl-compression下的Native,但使用hadoop-lzo-xxx的话,会导致版本不一致问题.所以正确的做法是,将hadoop-lzo-xxx下的Native放入到/usr/local/lib下.而你每升级一个hadoop-lzo-xxx版本,或许就得重复将新lzo版本下的native目录放入/usr/local/lib下.具体需要测试.

   同时这里说下,hadoop-lzo-xxx的验证原理,让我们更系统的了解为什么使用hadoop-lzo会报的一系列错误.

   1)首先Hadoop-lzo会通过JNI调用gplcompression,如果调取不到会报Could not load native gpl library异常.具体代码如下:

   static {

    try {
      //try to load the lib
      System.loadLibrary("gplcompression");
      nativeLibraryLoaded = true;
      LOG.info("Loaded native gpl library");
    } catch (Throwable t) {
      LOG.error("Could not load native gpl library", t);
      nativeLibraryLoaded = false;
    }
}

   2)获取了gplcompression后需要初始化加载以便可以调用,如果加载不成功,如我刚才说的版本冲突等也会报一系列错误.

    同时这里的加载和初始化分成两步,一步是压缩,对应Java的类是LzoCompressor.另一步解压缩,对应Java的类是LzoDecompressor.先看下LzoCompressor是如何加载初始化的,代码如下:

static {
  if (GPLNativeCodeLoader.isNativeCodeLoaded()) {
    // Initialize the native library
    try {
      initIDs();
      nativeLzoLoaded = true;
    } catch (Throwable t) {
      // Ignore failure to load/initialize native-lzo
      LOG.warn(t.toString());
      nativeLzoLoaded = false;
    }
    LZO_LIBRARY_VERSION = (nativeLzoLoaded) ? 0xFFFF & getLzoLibraryVersion()
        : -1;
  } else {
    LOG.error("Cannot load " + LzoCompressor.class.getName() + 
    " without native-hadoop library!");
    nativeLzoLoaded = false;
    LZO_LIBRARY_VERSION = -1;
  }
}

   如我这里所报的警告WARN lzo.LzoCompressor: java.lang.NoSuchFieldError: workingMemoryBuf

就是由这里的LOG.warn(t.toString());所抛出.同时这里也会先加载gplcompression,加载不成功同样会报without native-hadoop library!错误.

 

  再看看解压缩LzoDecompressor,原理差不多,不再阐述,代码如下:

static {
  if (GPLNativeCodeLoader.isNativeCodeLoaded()) {
    // Initialize the native library
    try {
      initIDs();
      nativeLzoLoaded = true;
    } catch (Throwable t) {
      // Ignore failure to load/initialize native-lzo
      LOG.warn(t.toString());
      nativeLzoLoaded = false;
    }
    LZO_LIBRARY_VERSION = (nativeLzoLoaded) ? 0xFFFF & getLzoLibraryVersion()
        : -1;
  } else {
    LOG.error("Cannot load " + LzoDecompressor.class.getName() + 
    " without native-hadoop library!");
    nativeLzoLoaded = false;
    LZO_LIBRARY_VERSION = -1;
  }
}

    

   以上基本包含了hadoop-lzo安装使用所遇到的问题.最后回到本文的主题,正确安装hadoop-lzo.

   1)首先下载https://github.com/kevinweil/hadoop-lzo/,我这里下载到/home/guoyun/Downloads//home/guoyun/hadoop/kevinweil-hadoop-lzo-2dd49ec

  2)通过ant生成native和jar,命令如下:

      ant tar

        在build目录下生成对应的tar包,解压缩后,进入该目录可以看到对应的jar包hadoop-lzo-0.4.14.jar.同时将lib/native/Linux-amd64-64/目录下所有文件拷贝到$HADOOP_HOME/lib和/usr/local/lib两个目录下.

        注明:拷贝到/usr/local/lib是便于调试,如是生产环境则无需拷贝.

   

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