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https://issues.apache.org/jira/browse/HADOOP-6109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12724340#action_12724340
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thushara wijeratna commented on HADOOP-6109:
--------------------------------------------
debugging steps taken:
==================
i included LOG statements to get an idea of the latencies thus - inside
LineReader.readLine():
if (length >= 0) {
str.append(buffer, startPosn, length);
LOG.info("str.length= " + str.getLength() + " just wrote from " +
startPosn + " to " + length + " bytes");
}
and this is the kind of output i get:
at the beginning:
2009-06-03 09:35:56,863 INFO org.apache.hadoop.util.LineReader: str.length=
4096 just wrote from 0 to 4096 bytes
2009-06-03 09:35:56,864 INFO org.apache.hadoop.util.LineReader: str.length=
8192 just wrote from 0 to 4096 bytes
2009-06-03 09:35:56,865 INFO org.apache.hadoop.util.LineReader: str.length=
12288 just wrote from 0 to 4096 bytes
2009-06-03 09:35:56,866 INFO org.apache.hadoop.util.LineReader: str.length=
16384 just wrote from 0 to 4096 bytes
2009-06-03 09:35:56,866 INFO org.apache.hadoop.util.LineReader: str.length=
20480 just wrote from 0 to 4096 bytes
2009-06-03 09:35:56,867 INFO org.apache.hadoop.util.LineReader: str.length=
24576 just wrote from 0 to 4096 bytes
2009-06-03 09:35:56,867 INFO org.apache.hadoop.util.LineReader: str.length=
28672 just wrote from 0 to 4096 bytes
2009-06-03 09:35:56,868 INFO org.apache.hadoop.util.LineReader: str.length=
32768 just wrote from 0 to 4096 bytes
2009-06-03 09:35:56,869 INFO org.apache.hadoop.util.LineReader: str.length=
36864 just wrote from 0 to 4096 bytes
in the end:
2009-06-03 09:46:02,918 INFO org.apache.hadoop.util.LineReader: str.length=
60141568 just wrote from 0 to 4096 bytes
2009-06-03 09:46:03,048 INFO org.apache.hadoop.util.LineReader: str.length=
60145664 just wrote from 0 to 4096 bytes
2009-06-03 09:46:03,118 INFO org.apache.hadoop.util.LineReader: str.length=
60149760 just wrote from 0 to 4096 bytes
2009-06-03 09:46:03,183 INFO org.apache.hadoop.util.LineReader: str.length=
60153856 just wrote from 0 to 4096 bytes
2009-06-03 09:46:03,252 INFO org.apache.hadoop.util.LineReader: str.length=
60157952 just wrote from 0 to 4096 bytes
2009-06-03 09:46:03,317 INFO org.apache.hadoop.util.LineReader: str.length=
60162048 just wrote from 0 to 4096 bytes
2009-06-03 09:46:03,456 INFO org.apache.hadoop.util.LineReader: str.length=
60166144 just wrote from 0 to 4096 bytes
notice the times are degrading in the end - this is the pattern, there is about
1 millisecond between the 1st consecutive reads, and in the end there is more
than 50ms between 2 consecutive reads.
Text.append has a potential perf issue.
as you can see, about 60M of the input line is being read in 10 minutes.
> Handle large (several MB) text input lines in a reasonable amount of time
> -------------------------------------------------------------------------
>
> Key: HADOOP-6109
> URL: https://issues.apache.org/jira/browse/HADOOP-6109
> Project: Hadoop Common
> Issue Type: Improvement
> Components: util
> Affects Versions: 0.19.0
> Environment: Linux 2.6 kernel, java 1.6 AMD Dual-Core Opteron 2.6GHz
> with 1M L1/L2 cache 1.8G RAM
> Reporter: thushara wijeratna
> Attachments: HADOOP-1234.patch
>
>
> problem:
> =======
> hadoop was timing out on a simple pass-through job (with the default 10 min
> timeout)
> cause:
> =====
> i hunted this down to how Text lines are being processed inside
> org.apache.hadoop.util.LineReader.
> i have a fix, a task that took more than 20 minutes and still failed to
> complete, completes with this fix in under 30 s.
> i attach the patch (for trunk)
> the problem traces:
> ================
> hadoop version: 0.19.0
> userlogs on slave node:
> 2009-05-29 13:57:33,551 WARN org.apache.hadoop.mapred.TaskRunner: Parent
> died. Exiting attempt_200905281652_0013_m_000006_1
> [r...@domu-12-31-38-01-7c-92 attempt_200905281652_0013_m_000006_1]#
> tellingly, the last input line processed right before this WARN is 19K. (i
> log the full input line in the map function for debugging)
> output on map-reduce task:
> Task attempt_200905281652_0013_m_000006_2 failed to report status for 600
> seconds. Killing!
> 09/05/29 14:08:01 INFO mapred.JobClient: map 99% reduce 32%
> 09/05/29 14:18:05 INFO mapred.JobClient: map 98% reduce 32%
> java.io.IOException: Job failed!
> at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:1217)
> at
> com.adxpose.data.mr.DailyHeatmapAggregator.run(DailyHeatmapAggregator.java:547)
> at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
> at
> com.adxpose.data.mr.DailyHeatmapAggregator.main(DailyHeatmapAggregator.java:553)
> 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:165)
> at org.apache.hadoop.mapred.JobShell.run(JobShell.java:54)
> at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:65)
> at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:79)
> at org.apache.hadoop.mapred.JobShell.main(JobShell.java:68)
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