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From Kathleen Ting <kathl...@apache.org>
Subject Re: direct mode for mysql export vs. default jdbc
Date Thu, 20 Mar 2014 16:46:06 GMT
Hi Jason,

Rather than using the JDBC interface for transferring data, the direct
mode delegates the job of transferring data to the native utilities
provided by the database vendor. In the case of MySQL, the mysqldump
and mysqlimport will be used for retrieving data from the database
server or moving data back. Using native utilities will greatly
improve performance, as they are optimized to provide the best
possible transfer speed while putting less burden on the database
server. That said, there are several limitations that come with this
faster import. In the case of MySQL, each node hosting a TaskTracker
service needs to have both mysqldump and mysqlimport utilities
installed. Another limitation of the direct mode is that not all
parameters are supported. As the native utilities usually produce text
output, binary formats like SequenceFile or Avro won't work. Also,
parameters that customize the escape characters, type mapping, column
and row delimiters, or the NULL substitution string might not be
supported in all cases.

Can you share your entire Sqoop command and the contents of failed
task attempt attempt_201403180842_0202_m_000002_1?


On Thu, Mar 20, 2014 at 8:24 AM, Jason Rosenberg <jbr@squareup.com> wrote:
> Thoughts anyone?
> Thanks,
> Jason
> On Tue, Mar 18, 2014 at 2:23 PM, Jason Rosenberg <jbr@squareup.com> wrote:
>> Hi,
>> I'm wondering if there is expected performance increases with using the
>> --direct flag for exporting from hive to mysql.  If so, how much speedup?
>> Also, I've been getting lock contention errors during export, and I'm
>> wondering if these are less likely using --direct mode?  E.g. I'm getting
>> these sorts of exceptions on the sqoop console:
>> 14/03/18 14:44:15 INFO mapred.JobClient: Task Id :
>> attempt_201403180842_0202_m_000002_1, Status : FAILED
>> java.io.IOException: Can't export data, please check failed map task logs
>>         at
>> org.apache.sqoop.mapreduce.TextExportMapper.map(TextExportMapper.java:112)
>>         at
>> org.apache.sqoop.mapreduce.TextExportMapper.map(TextExportMapper.java:39)
>>         at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:140)
>>         at
>> org.apache.sqoop.mapreduce.AutoProgressMapper.run(AutoProgressMapper.java:64)
>>         at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:672)
>>         at org.apache.hadoop.mapred.MapTask.run(MapTask.java:330)
>>         at org.apache.hadoop.mapred.Child$4.run(Child.java:268)
>>         at java.security.AccessController.doPrivileged(Native Method)
>>         at javax.security.auth.Subject.doAs(Subject.java:415)
>>         at
>> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1408)
>>         at org.apache.hadoop.mapred.Child.main(Child.java:262)
>> Caused by: java.io.IOException: java.sql.BatchUpdateException: Deadlock
>> found when trying to get lock; try restarting transaction
>>         at
>> org.apache.sqoop.mapreduce.AsyncSqlRecordWriter.write(AsyncSqlRecordWr
>> Thanks,
>> Jason

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