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From Aaron Kimball <aa...@cloudera.com>
Subject Re: Writing to a db with DBOutputFormat spits out IOException Error
Date Tue, 25 Aug 2009 00:42:12 GMT
As a more general note -- any jars needed by your mappers and reducers
either need to be in your job jar in the lib/ directory of the .jar file, or
in $HADOOP_HOME/lib/ on all tasktracker nodes where mappers and reducers get
run.

- Aaron


On Fri, Aug 21, 2009 at 10:47 AM, ishwar ramani <rvmishwar@gmail.com> wrote:

> For future reference.
>
> This is a class not found exception for the mysql driver.  The
> DBOuputFormat converts
> it into an IO exception grrrrr.
>
> I had the mysql-connector in both $HADOOP/lib and $HADOOP_CLASSPATH.
> That did not help.
>
> I had to pkg the mysql jar into my map reduce jar to fix this problem.
>
> Hope that saves a day for some one!
>
> On Thu, Aug 20, 2009 at 4:52 PM, ishwar ramani<rvmishwar@gmail.com> wrote:
> > Hi,
> >
> > I am trying to run a simple map reduce that writes the result from the
> > reducer to a mysql db.
> >
> > I Keep getting
> >
> > 09/08/20 15:44:59 INFO mapred.JobClient: Task Id :
> > attempt_200908201210_0013_r_000000_0, Status : FAILED
> > java.io.IOException: com.mysql.jdbc.Driver
> >        at
> org.apache.hadoop.mapred.lib.db.DBOutputFormat.getRecordWriter(DBOutputFormat.java:162)
> >        at
> org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:435)
> >        at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:413)
> >        at org.apache.hadoop.mapred.Child.main(Child.java:170)
> >
> > when the reducer is run.
> >
> > Here is my code. The user name and password are valid and works fine.
> > Is there any way get more info on this exception?
> >
> >
> >
> > static class MyWritable implements Writable, DBWritable {
> >  long id;
> >  String description;
> >
> >  MyWritable(long mid, String mdescription) {
> >    id = mid;
> >    description = mdescription;
> >  }
> >
> >  public void readFields(DataInput in) throws IOException {
> >    this.id = in.readLong();
> >    this.description = Text.readString(in);
> >  }
> >
> >  public void readFields(ResultSet resultSet)
> >      throws SQLException {
> >    this.id = resultSet.getLong(1);
> >    this.description = resultSet.getString(2);
> >  }
> >
> >  public void write(DataOutput out) throws IOException {
> >    out.writeLong(this.id);
> >    Text.writeString(out, this.description);
> >  }
> >
> >  public void write(PreparedStatement stmt) throws SQLException {
> >    stmt.setLong(1, this.id);
> >    stmt.setString(2, this.description);
> >  }
> > }
> >
> >
> >
> >
> >
> >
> > public static class Reduce extends MapReduceBase implements
> > Reducer<Text, IntWritable, MyWritable, IntWritable> {
> >  public void reduce(Text key, Iterator<IntWritable> values,
> > OutputCollector<MyWritable, IntWritable> output, Reporter reporter)
> > throws IOException {
> >    int sum = 0;
> >    while (values.hasNext()) {
> >      sum += values.next().get();
> >    }
> >
> >    output.collect(new MyWritable(sum, key.toString()), new
> IntWritable(sum));
> >  }
> > }
> >
> >
> >
> >
> >
> > public static void main(String[] args) throws Exception {
> >  JobConf conf = new JobConf(WordCount.class);
> >  conf.setJobName("wordcount");
> >
> >  conf.setMapperClass(Map.class);
> >
> >  conf.setReducerClass(Reduce.class);
> >
> >  DBConfiguration.configureDB(conf, "com.mysql.jdbc.Driver",
> > "jdbc:mysql://localhost:8100/testvmysqlsb", "dummy", "pass");
> >
> >
> >  String fields[] = {"id", "description"};
> >  DBOutputFormat.setOutput(conf, "funtable", fields);
> >
> >
> >
> >  conf.setNumMapTasks(1);
> >  conf.setNumReduceTasks(1);
> >
> >  conf.setMapOutputKeyClass(Text.class);
> >  conf.setMapOutputValueClass(IntWritable.class);
> >
> >
> >  conf.setOutputKeyClass(MyWritable.class);
> >  conf.setOutputValueClass(IntWritable.class);
> >
> >  conf.setInputFormat(TextInputFormat.class);
> >
> >
> >
> >
> >  FileInputFormat.setInputPaths(conf, new Path(args[0]));
> >
> >
> >  JobClient.runJob(conf);
> > }
> >
>

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