问题导读:
1.建一个MapReduce Project,运行时发现出问题:Could not locate executable null,该如何解决?2.Could not locate executabl ....\hadoop-2.2.0\hadoop-2.2.0\bin\winutils.exe in the Hadoop binaries.该如何解决?
1.创建一个MapReduce Project,运行时发现出问题了。
java.io.IOException: Could not locate executable null\bin\winutils.exe in the Hadoop binaries.
跟代码就去发现是HADOOP_HOME的问题。如果HADOOP_HOME为空,必然fullExeName为null\bin\winutils.exe。解决方法很简单啦,乖乖的配置环境变量吧,不想重启电脑可以在MapReduce程序里加上System.setProperty("hadoop.home.dir", "...");暂时缓缓。org.apache.hadoop.util.Shell.java
public static final String getQualifiedBinPath(String executable)
throws IOException {
// construct hadoop bin path to the specified executable
String fullExeName = HADOOP_HOME_DIR + File.separator + "bin"
+ File.separator + executable;
File exeFile = new File(fullExeName);
if (!exeFile.exists()) {
throw new IOException("Could not locate executable " + fullExeName
+ " in the Hadoop binaries.");
}
return exeFile.getCanonicalPath();
}
private static String HADOOP_HOME_DIR = checkHadoopHome();
private static String checkHadoopHome() {
// first check the Dflag hadoop.home.dir with JVM scope
String home = System.getProperty("hadoop.home.dir");
// fall back to the system/user-global env variable
if (home == null) {
home = System.getenv("HADOOP_HOME");
}
...
}
2. 这个时候得到完整的地址fullExeName,我机器上是D:\Hadoop\tar\hadoop-2.2.0\hadoop-2.2.0\bin\winutils.exe。继续执行代码又发现了错误
Could not locate executable D:\Hadoop\tar\hadoop-2.2.0\hadoop-2.2.0\bin\winutils.exe in the Hadoop binaries.
3. 继续出问题
at org.apache.hadoop.util.Shell.execCommand(Shell.java:661)at org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:639)at org.apache.hadoop.fs.RawLocalFileSystem.mkdirs(RawLocalFileSystem.java:435)
继续跟代码org.apache.hadoop.util.Shell.java public static String[] getSetPermissionCommand(String perm, boolean recursive,
String file) {
String[] baseCmd = getSetPermissionCommand(perm, recursive);
String[] cmdWithFile = Arrays.copyOf(baseCmd, baseCmd.length + 1);
cmdWithFile[cmdWithFile.length - 1] = file;
return cmdWithFile;
}
/** Return a command to set permission */
public static String[] getSetPermissionCommand(String perm, boolean recursive) {
if (recursive) {
return (WINDOWS) ? new String[] { WINUTILS, "chmod", "-R", perm }
: new String[] { "chmod", "-R", perm };
} else {
return (WINDOWS) ? new String[] { WINUTILS, "chmod", perm }
: new String[] { "chmod", perm };
}
}
cmdWithFile数组的内容为{"D:\Hadoop\tar\hadoop-2.2.0\hadoop-2.2.0\bin\winutils.exe", "chmod", "755", "xxxfile"},我把这个单独在cmd里执行了一下,发现 无法启动此程序,因为计算机中丢失 MSVCR100.dll
应用程序无法正常启动(0xc000007b)
4. 到了这里,已经看到曙光了,但问题又来了
Exception in thread "main" java.lang.UnsatisfiedLinkError: org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Ljava/lang/String;I)Z
代码就去 /** Windows only method used to check if the current process has requested* access rights on the given path. */
private static native boolean access0(String path, int requestedAccess);
显然缺少dll文件,还记得 https://github.com/srccodes/hadoop-common-2.2.0-bin 下载的东西吧,里面就有hadoop.dll,最好的方法就是用hadoop-common-2.2.0-bin-master/bin目录替换本地hadoop的bin目录,并在环境变量里配置PATH=HADOOP_HOME/bin,重启电脑。
1.下载地址
hadoop家族、strom、spark、Linux、flume等jar包、安装包汇总下载(持续更新)
注意的问题:
环境变量一定配置正确,否则还是不能运行
PATH=HADOOP_HOME/bin,如果这个不行,可以换成绝对路径
5.终于看到了MapReduce的正确输出output99。
总结
- hadoop eclipse插件不是必须的,其作用在我看来就是如下三点(这个是一个错误的认识,具体请参考http://zy19982004.iteye.com/blog/2031172)。study-hadoop是一个普通project,直接运行(不通过Run on Hadoop这只大象),一样可以调试到MapReduce。
-
- 对hadoop中的文件可视化。
- 创建MapReduce Project时帮你引入依赖的jar。
- Configuration conf = new Configuration();时就已经包含了所有的配置信息。
-
- 还是自己下载hadoop2.2的源码编译好,应该是不会有任何问题的(没有亲测)。
六. 其它问题
还是
Exception in thread "main" java.lang.UnsatisfiedLinkError: org.apache.hadoop.io.nativeio.NativeIO$Windows.access0(Ljava/lang/String;I)Z
代码跟到org.apache.hadoop.util.NativeCodeLoader.java去看 static {
// Try to load native hadoop library and set fallback flag appropriately
if(LOG.isDebugEnabled()) {
LOG.debug("Trying to load the custom-built native-hadoop library...");
}
try {
System.loadLibrary("hadoop");
LOG.debug("Loaded the native-hadoop library");
nativeCodeLoaded = true;
} catch (Throwable t) {
// Ignore failure to load
if(LOG.isDebugEnabled()) {
LOG.debug("Failed to load native-hadoop with error: " + t);
LOG.debug("java.library.path=" +
System.getProperty("java.library.path"));
}
}
if (!nativeCodeLoaded) {
LOG.warn("Unable to load native-hadoop library for your platform... " +
"using builtin-java classes where applicable");
}
}
这里报错如下 DEBUG org.apache.hadoop.util.NativeCodeLoader - Failed to load native-hadoop with error: java.lang.UnsatisfiedLinkError: HADOOP_HOME\bin\hadoop.dll: Can't load AMD 64-bit .dll on a IA 32-bit platform
怀疑是32位jdk的问题,替换成64位后,没问题了
2014-03-11 19:43:08,805 DEBUG org.apache.hadoop.util.NativeCodeLoader - Trying to load the custom-built native-hadoop library...
2014-03-11 19:43:08,812 DEBUG org.apache.hadoop.util.NativeCodeLoader - Loaded the native-hadoop library
这里也解决了一个常见的警告 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable