issue of cache coherence or reuse for avro map reduce
-----------------------------------------------------
Key: AVRO-782
URL: https://issues.apache.org/jira/browse/AVRO-782
Project: Avro
Issue Type: Bug
Components: java
Affects Versions: 1.5.0
Environment: Mac with VMWare running Linux training-vm
2.6.28-19-server #61-Ubuntu
Reporter: ey-chih chow
Our map reduce jobs are using Avro map/reduce API. For one of the jobs, we got
the following trace for the reducer:
====================================================================================================
attempt_20110310145147365_0002_r_000000_0/syslog:2011-03-10 14:52:31,226 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000000000000000000000000000000000 whose rowKey is
0000000000000000000000000000000000000
attempt_20110310145315542_0002_r_000000_0/syslog:2011-03-10 14:53:59,010 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000000000000000000000000000000000 whose rowKey is
0000000000000000000000000000000000000
attempt_20110310145315542_0002_r_000000_0/syslog:2011-03-10 14:53:59,016 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000100000000000000000000000000001 whose rowKey is
0000000200000000000000000000000000002
attempt_20110310145315542_0002_r_000000_0/syslog:2011-03-10 14:53:59,017 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000200000000000000000000000000002 whose rowKey is
0000000300000000000000000000000000003
attempt_20110310145315542_0002_r_000000_0/syslog:2011-03-10 14:53:59,021 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000300000000000000000000000000003 whose rowKey is
0000000400000000000000000000000000004
attempt_20110310145315542_0002_r_000000_0/syslog:2011-03-10 14:53:59,023 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000400000000000000000000000000004 whose rowKey is
0000000500000000000000000000000000005
attempt_20110310145315542_0002_r_000000_0/syslog:2011-03-10 14:53:59,024 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000500000000000000000000000000005 whose rowKey is
0000000500000000000000000000000000005
====================================================================================================
If we add the following two lines to the reducer code:
====================================================================================================
boolean workAround =
getConf().getBoolean(NgActivityGatheringJob.NG_AVRO_BUG_WORKAROUND, true);
Utf8 dupKey = (workAround) ? new Utf8(key.toString()) : key; // use dupKey
instead of key passed to reducer
====================================================================================================
We got the following trace, which we consider as the right behavior:
====================================================================================================
2011-03-10 15:04:33,431 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000000000000000000000000000000000 whose rowKey is
0000000000000000000000000000000000000
attempt_20110310150517897_0002_r_000000_0/syslog:2011-03-10 15:06:01,374 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000000000000000000000000000000000 whose rowKey is
0000000000000000000000000000000000000
attempt_20110310150517897_0002_r_000000_0/syslog:2011-03-10 15:06:01,381 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000100000000000000000000000000001 whose rowKey is
0000000100000000000000000000000000001
attempt_20110310150517897_0002_r_000000_0/syslog:2011-03-10 15:06:01,383 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000200000000000000000000000000002 whose rowKey is
0000000200000000000000000000000000002
attempt_20110310150517897_0002_r_000000_0/syslog:2011-03-10 15:06:01,389 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000300000000000000000000000000003 whose rowKey is
0000000300000000000000000000000000003
attempt_20110310150517897_0002_r_000000_0/syslog:2011-03-10 15:06:01,391 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000400000000000000000000000000004 whose rowKey is
0000000400000000000000000000000000004
attempt_20110310150517897_0002_r_000000_0/syslog:2011-03-10 15:06:01,393 INFO
com.ngmoco.ngpipes.sourcing.NgActivityGatheringReducer: working on
0000000500000000000000000000000000005 whose rowKey is
0000000500000000000000000000000000005
====================================================================================================
According to Scott Carey, this might relate to object reuse. We have created
an Unit test case that will reproduce the problem. The test case will be
attached as a patch. Note that we run this test case under our Ngmoco dev
environment, which might need to make some adjustment to run on other
environment.
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