I am just curious but are you using Writable? If so there is a
WritableComparator...
If you are going to interpret every bytes (you create a String, so you
do), there no clear reason for choosing such a low level API.
Regards
Bertrand
On Thu, Aug 9, 2012 at 4:47 PM, Björn-Elmar Macek
<[email protected] <mailto:[email protected]>> wrote:
Hi again,
this is an direct response to my previous posting with the title
"Logs cannot be created", where logs could not be created (Spill
failed). I got the hint, that i gotta check privileges, but that
was not the problem, because i own the folders that were used for
this.
I finally found an important hint in a log saying:
12/08/09 15:30:49 WARN mapred.JobClient: Error reading task
outputhttp://its-cs229.its.uni-kassel.de:50060/tasklog?plaintext=true&attemptid=attempt_201208091516_0001_m_000048_0&filter=stdout
<http://its-cs229.its.uni-kassel.de:50060/tasklog?plaintext=true&attemptid=attempt_201208091516_0001_m_000048_0&filter=stdout>
12/08/09 15:30:49 WARN mapred.JobClient: Error reading task
outputhttp://its-cs229.its.uni-kassel.de:50060/tasklog?plaintext=true&attemptid=attempt_201208091516_0001_m_000048_0&filter=stderr
<http://its-cs229.its.uni-kassel.de:50060/tasklog?plaintext=true&attemptid=attempt_201208091516_0001_m_000048_0&filter=stderr>
12/08/09 15:34:34 INFO mapred.JobClient: Task Id :
attempt_201208091516_0001_m_000055_0, Status : FAILED
java.io.IOException: Spill failed
at
org.apache.hadoop.mapred.MapTask$MapOutputBuffer.collect(MapTask.java:1029)
at
org.apache.hadoop.mapred.MapTask$OldOutputCollector.collect(MapTask.java:592)
at
uni.kassel.macek.rtprep.RetweetMapper.map(RetweetMapper.java:26)
at
uni.kassel.macek.rtprep.RetweetMapper.map(RetweetMapper.java:12)
at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
at
org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:436)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:372)
at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at
org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1093)
at org.apache.hadoop.mapred.Child.main(Child.java:249)
Caused by: java.lang.NumberFormatException: For input string: ""
at
java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:468)
at java.lang.Integer.parseInt(Integer.java:497)
at uni.kassel.macek.rtprep.Tweet.getRT(Tweet.java:126)
at
uni.kassel.macek.rtprep.TwitterValueGroupingComparator.compare(TwitterValueGroupingComparator.java:47)
at
org.apache.hadoop.mapred.MapTask$MapOutputBuffer.compare(MapTask.java:1111)
at
org.apache.hadoop.util.QuickSort.sortInternal(QuickSort.java:95)
at org.apache.hadoop.util.QuickSort.sort(QuickSort.java:59)
at
org.apache.hadoop.mapred.MapTask$MapOutputBuffer.sortAndSpill(MapTask.java:1399)
at
org.apache.hadoop.mapred.MapTask$MapOutputBuffer.access$1800(MapTask.java:853)
at
org.apache.hadoop.mapred.MapTask$MapOutputBuffer$SpillThread.run(MapTask.java:1344)
corresponding to the following lines of code within the class
TwitterValueGroupingComparator:
public class TwitterValueGroupingComparator implements
RawComparator<Text> {
...
public int compare(byte[] text1, int start1, int length1,
byte[] text2,
int start2, int length2) {
byte[] tweet1 = new byte[length1];// length1-1 (???)
byte[] tweet2 = new byte[length2];// length1-1 (???)
System.arraycopy(text1, start1, tweet1, 0, length1);//
start1+1 (???)
System.arraycopy(text2, start2, tweet2, 0, length2);//
start2+1 (???)
Tweet atweet1 = new Tweet(new String(tweet1));
Tweet atweet2 = new Tweet(new String(tweet2));
String key1 = atweet1.getAuthor();
String key2 = atweet2.getAuthor();
////////////////////////////////////////////////////////////////
//THE FOLLOWING LINE IS THE ONE MENTIONED IN THE LOG (47)
/////////////////////////////////////////////////////////////////
if (atweet1.getRT() > 0 && !atweet1.getMention().equals(""))
key1 = atweet1.getMention();
if (atweet2.getRT() > 0 && !atweet2.getMention().equals(""))
key2 = atweet2.getMention();
int realKeyCompare = key1.compareTo(key2);
return realKeyCompare;
}
}
As i am taking the incoming bytes and interpret them as Tweets by
recreating the appropriate CSV-Strings and Tokenizing it, i was
kind of sure, that the problem somehow are the leading bytes, that
Hadoop puts in front of the data being compared. Since i never
really understood what hadoop is doing to the strings when they
are sent to the KeyComparator i simply appended all strings to a
file in order to see myself.
You can see the results here:
??2009-06-12 07:32:47, davedilbeck, tampabaycom, , ,
http://tinyurl.com/nookw7, 1, 1, Lots of vivid imagery here but
it's mostly bullshit Alex Sink June Cleaver or Joan Crawford, null
??2009-06-12 07:32:47, davedilbeck, tampabaycom, , ,
http://tinyurl.com/nookw7, 1, 1, Lots of vivid imagery here but
it's mostly bullshit Alex Sink June Cleaver or Joan Crawford, null
I2009-06-12 04:33:19, ntmp, tsukunep, , , , 1, 0,
??????????????????, null
??2009-06-12 07:32:47, davedilbeck, tampabaycom, , ,
http://tinyurl.com/nookw7, 1, 1, Lots of vivid imagery here but
it's mostly bullshit Alex Sink June Cleaver or Joan Crawford, null
^2009-06-12 04:33:20, aclouatre, , , , , 0, 0, Bored out of my
mind Watching food network, null
b2009-06-12 04:33:20, djnewera, adoremii369, , , , 1, 0, LOL
WORDUP ANT NOTHING LIKE THE HOOD, null
As you can see there are different leading characters: sometimes
its "??", other times its "b" or "^", etc.
My question is now:
How many bits do i have to cut off, so i get the original Text as
a String that i put into the key-position of my mapper output?
What are the concepts behind this?
Thanks for your help in advance!
Best regards,
Elmar Macek
--
Bertrand Dechoux
