sql-server - 在 Hadoop 中访问 SQL Server

Question

我想做的: 该程序旨在从 SQL Server 2008 加载区域销售数据，并在 MapReduce 上运行简单的统计计算以获得每个区域的总销售额。我得到的错误说程序找不到 sqljdbc4.jar 文件，但是，该文件确实已复制到代码中指定的位置。

1. 所以代码如下:

   //fileName: MRExp.java
   public class MRExp {
       public static void main(String[] args) throws IOException {
           JobConf conf = new JobConf(MRExp.class);
           DistributedCache.addFileToClassPath(new Path("/userX/sqljdbc4.jar"), conf);
   
           conf.setMapperClass(MRMapper.class);
           conf.setReducerClass(MRReducer.class);
   
           conf.setMapOutputKeyClass(Text.class);
           conf.setMapOutputValueClass(LongWritable.class);
   
           conf.setOutputKeyClass(LongWritable.class);
           conf.setOutputValueClass(Text.class);
   
           conf.setInputFormat(DBInputFormat.class);
           FileOutputFormat.setOutputPath(conf, new Path(args[0]));
   
           DBConfiguration
                   .configureDB(
                           conf,
                           "com.microsoft.sqlserver.jdbc.SQLServerDriver",
                           "jdbc:sqlserver://MyDbServerAddr:1433;databaseName=ThisDb;integratedSecurity=true;",
                           "db_userName", "db_Pws");
   
           DBInputFormat
                   .setInput(conf, InfoUnit.class,
                           "SELECT R_NAME,L_ORDERKEY from dbo.United10MB ;"/* inputQuery */
                           , "SELECT COUNT(L_ORDERKEY) from dbo.United10MB"/* inputCountQuery */);
   
           try {
               JobClient.runJob(conf);
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   }
   

   //后面是MRMapper和MRReducer以及InfoUnit的定义。 InfoUnit 实现了 Writable、DBWritable。

2. 文件位置:

   [root@test MRExp]#密码
   /root/MRExp
   [root@test MRExp]# ls
   类 hadoop-0.20.2-core.jar MRExp.java sqljdbc4.jar

3. 然后，为了编译 MRExp.java:

   [root@test MRExp]# javac -classpath hadoop-0.20.2-core.jar -d classes/MRExp.java
   [root@test MRExp]# jar -cvf MRExp.jar -C classes/.

同时将 sqljdbc4.jar 复制到 HDFS:

[root@test MRExp]#  hadoop dfs -copyFromLocal sqljdbc4.jar /userX  

所以我们得到:

[root@test MRExp]# ls  
classes  hadoop-0.20.2-core.jar  MRExp.jar  MRExp.java  sqljdbc4.jar  

1. 完成上述操作后，启动 MapR 进程:

   [root@test MRExp]# hadoop jar MRExp.jar mrexp.MRExp/userX/output

但是程序说:

17:02:50 WARN mapreduce.JobSubmitter: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
12/10/28 17:02:50 INFO mapreduce.JobSubmitter: Cleaning up the staging area /tmp/hadoop-yarn/staging/root/.staging/job_1350984913454_0009
java.lang.RuntimeException: java.lang.RuntimeException: java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver
        at org.apache.hadoop.mapreduce.lib.db.DBInputFormat.setConf(DBInputFormat.java:165)
        at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:70)
        at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:130)
        at org.apache.hadoop.mapred.JobConf.getInputFormat(JobConf.java:607)
        at org.apache.hadoop.mapreduce.JobSubmitter.writeOldSplits(JobSubmitter.java:476)
        at org.apache.hadoop.mapreduce.JobSubmitter.writeSplits(JobSubmitter.java:468)
        at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:359)
        at org.apache.hadoop.mapreduce.Job$11.run(Job.java:1226)
        at org.apache.hadoop.mapreduce.Job$11.run(Job.java:1223)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:396)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1232)
        at org.apache.hadoop.mapreduce.Job.submit(Job.java:1223)
        at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:609)
        at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:604)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:396)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1232)
        at org.apache.hadoop.mapred.JobClient.submitJob(JobClient.java:604)
        at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:880)
        at mrexp.MRExp.main(MRExp.java:70)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.util.RunJar.main(RunJar.java:208)
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver
        at org.apache.hadoop.mapreduce.lib.db.DBInputFormat.getConnection(DBInputFormat.java:191)
        at org.apache.hadoop.mapreduce.lib.db.DBInputFormat.setConf(DBInputFormat.java:159)
        ... 25 more
Caused by: java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver
        at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:169)
        at org.apache.hadoop.mapreduce.lib.db.DBConfiguration.getConnection(DBConfiguration.java:148)
        at org.apache.hadoop.mapreduce.lib.db.DBInputFormat.getConnection(DBInputFormat.java:185)
        ... 26 more

Answer 1

在 hadoop jar ... 命令的“-libjars”命令行选项中包含 sqljdbc4.jar JAR。

请阅读this从 Cloudera 发布以获取更多信息。

更新:

执行以下操作

[root@test MRExp]#  hadoop dfs -ls /userX

将绝对路径复制到文件系统中的 sqljdbc4.jar 并放入以下行

DistributedCache.addFileToClassPath(new Path("<Absolute Path>/sqljdbc4.jar"), conf);

这将解决问题。