自己编写接口用于获取Hadoop Job conf 信息
Hadoop Job完成后可以设置回调接口，一个自定义的URL，比如我的：
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public static RunningJob getJobById(String jobId) {Configuration conf = new Configuration();conf.set("mapred.job.tracker", Constants.MAP_REDUCE_URL);JobClient client;try {client = new JobClient(new JobConf(conf));return client.getJob(jobId);} catch (IOException e) {throw new RuntimeException(e);}}?关键是这个RunningJob对象只可以获取jobname信息，但是无法获取我们设置的conf信息。为了解决这个问题，我写了一个jsp，放到namenode上，用于读取本地log文件，并将结果反馈给调用者。代码如下，希望对大家有帮助：
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<%@ page contentType="text/xml; charset=UTF-8" import="javax.servlet.*" import="javax.servlet.http.*" import="java.io.*" import="java.net.URL" import="org.apache.hadoop.util.*" import="javax.servlet.jsp.JspWriter"%><%!private static final long serialVersionUID = 1L; public File getHistoryFile(final String jobId) { File dir = new File("/opt/hadoop/logs/history/done/"); File[] files = dir.listFiles(new FilenameFilter() { public boolean accept(File dir, String name) {if (name.indexOf(jobId) >= 0 && name.endsWith(".xml")) {return true;} return false; } }); if (files != null && files.length > 0) { return files[0]; } return null; }public void printXML(JspWriter out, String jobId) throws IOException {FileInputStream jobFile = null;String[] outputKeys = { "db_id", "channel_id", "channel_name", "user_id", "user_name", "job_day", "pub_format_type", "mapred.output.dir" };String line = "";try {jobFile = new FileInputStream(getLogFilePath(jobId));BufferedReader reader = new BufferedReader(new InputStreamReader(jobFile));while ((line = reader.readLine()) != null) {for (String key : outputKeys) {if (!line.startsWith("<property>") || line.indexOf("<name>" + key + "</name>") >= 0) {out.println(line);break;}}}} catch (Exception e) {out.println("Failed to retreive job configuration for job '" + jobId + "!");out.println(e);} finally {if (jobFile != null) {try {jobFile.close();} catch (IOException e) {}}}}private File getLogFilePath(String jobId) {String logDir = System.getProperty("hadoop.log.dir");if (logDir == null || logDir.length() == 0) {logDir = "/opt/hadoop/logs/";}File logFile = new File(logDir + File.separator + jobId + "_conf.xml");return logFile.exists() ? logFile : getHistoryFile(jobId);}%><% response.setContentType("text/xml"); final String jobId = request.getParameter("jobid"); if (jobId == null) { out.println("<h2>Missing 'jobid' for fetching job configuration!</h2>"); return; } printXML(out, jobId);%>?? ? 这里有个要点，运行中和刚完成的job xml文件放到了"/opt/hadoop/logs"下，归档的job xml放到了“/opt/hadoop/logs/history/done/”，所以要判断第一个地方找不到文件，去第二个地方找。
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? ? 功能很简单，但是很有用。
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--heipark
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