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From "Liang Geng (Jira)" <j...@apache.org>
Subject [jira] [Created] (KYLIN-4291) Parallel segment building may causes WriteConflictException
Date Tue, 10 Dec 2019 12:42:00 GMT
Liang Geng created KYLIN-4291:
---------------------------------

             Summary: Parallel segment building may causes WriteConflictException
                 Key: KYLIN-4291
                 URL: https://issues.apache.org/jira/browse/KYLIN-4291
             Project: Kylin
          Issue Type: Bug
          Components: Job Engine
    Affects Versions: v2.6.4
            Reporter: Liang Geng


We noticed a segment refresh job at ERROR status at "*2019-12-10 02:27:15*". After a deep
dive into kylin.log, we found that the WriteConflictException was raised when trying to update
the last modified time for the dict.

 

(Sensitive content are consered)
{code:java}
2019-12-10 02:27:15,576 ERROR [Scheduler 1186524190 Job f76fb12e-477f-b404-e021-adaf520d04bb-321]
common.HadoopShellExecutable:65 : error execute HadoopShellExecutable{id=f76fb12e-477f-b404-e021-adaf520d04bb-03,
name=Build Dimension Dictionary, state=RUNNING}
org.apache.kylin.common.persistence.WriteConflictException: Overwriting conflict /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict,
expect old TS 1575916011421, but it is 1575916035573
at org.apache.kylin.storage.hbase.HBaseResourceStore.updateTimestampImpl(HBaseResourceStore.java:372)
at org.apache.kylin.common.persistence.ResourceStore.lambda$updateTimestampWithRetry$4(ResourceStore.java:443)
at org.apache.kylin.common.persistence.ExponentialBackoffRetry.doWithRetry(ExponentialBackoffRetry.java:52)
at org.apache.kylin.common.persistence.ResourceStore.updateTimestampWithRetry(ResourceStore.java:442)
at org.apache.kylin.common.persistence.ResourceStore.updateTimestampCheckPoint(ResourceStore.java:437)
at org.apache.kylin.common.persistence.ResourceStore.updateTimestamp(ResourceStore.java:432)
at org.apache.kylin.dict.DictionaryManager.updateExistingDictLastModifiedTime(DictionaryManager.java:197)
at org.apache.kylin.dict.DictionaryManager.trySaveNewDict(DictionaryManager.java:157)
at org.apache.kylin.dict.DictionaryManager.saveDictionary(DictionaryManager.java:339)
at org.apache.kylin.cube.CubeManager$DictionaryAssist.saveDictionary(CubeManager.java:1145)
at org.apache.kylin.cube.CubeManager.saveDictionary(CubeManager.java:1107)
at org.apache.kylin.cube.cli.DictionaryGeneratorCLI.processSegment(DictionaryGeneratorCLI.java:100)
at org.apache.kylin.cube.cli.DictionaryGeneratorCLI.processSegment(DictionaryGeneratorCLI.java:69)
at org.apache.kylin.engine.mr.steps.CreateDictionaryJob.run(CreateDictionaryJob.java:73)
at org.apache.kylin.engine.mr.MRUtil.runMRJob(MRUtil.java:93)
at org.apache.kylin.engine.mr.common.HadoopShellExecutable.doWork(HadoopShellExecutable.java:63)
at org.apache.kylin.job.execution.AbstractExecutable.execute(AbstractExecutable.java:167)
at org.apache.kylin.job.execution.DefaultChainedExecutable.doWork(DefaultChainedExecutable.java:71)
at org.apache.kylin.job.execution.AbstractExecutable.execute(AbstractExecutable.java:167)
at org.apache.kylin.job.impl.threadpool.DefaultScheduler$JobRunner.run(DefaultScheduler.java:114)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
{code}
We have a glance at the codebase (Kylin-2.6.4), we found the last modified time of the dict
(which has been built) will be updated at the step "Build Dimension Dictionary". The log blow
shows the same dict is processed many times.
{code:java}
Liangs-MacBook-Pro:~ pwrliang$ cat 12-10.log |grep "has already been built, save it"|grep
"THIS_IS_COLUMN_NAME"
2019-12-10 02:07:10,103 DEBUG [Scheduler 1186524190 Job 5c4b2ee9-c8aa-9a69-ffb0-3a6811ad22a9-372]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:07:11,036 DEBUG [Scheduler 1186524190 Job 593979b8-e80b-590f-335b-526c2fc49080-295]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:07:20,455 DEBUG [Scheduler 1186524190 Job 160952f3-fef2-4fdf-c08a-77d49f830805-246]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:07:20,888 DEBUG [Scheduler 1186524190 Job 69304c1c-cc02-3bbe-67d4-efdd3858e88a-234]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:07:21,634 DEBUG [Scheduler 1186524190 Job 345b688c-7992-f2cf-ae06-835675f545ea-117]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:07:23,040 DEBUG [Scheduler 1186524190 Job 0ea711ed-71b5-ae47-a34a-f0a27fd9d7cc-303]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:07:36,358 DEBUG [Scheduler 1186524190 Job 6daf351f-5073-128f-8754-f499e345db54-308]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:26:43,716 DEBUG [Scheduler 1186524190 Job c90a765c-976f-49c2-38d8-e6812d091cfb-295]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:26:44,944 DEBUG [Scheduler 1186524190 Job cd108004-12c6-078f-8646-f29841de9e40-205]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:26:51,306 DEBUG [Scheduler 1186524190 Job d808dadf-8eea-34db-1b1f-d50e923b4e3a-372]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:27:15,523 DEBUG [Scheduler 1186524190 Job ea07ef8f-b2b7-b3f8-c481-df615025217d-117]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:27:15,535 DEBUG [Scheduler 1186524190 Job f76fb12e-477f-b404-e021-adaf520d04bb-321]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it
2019-12-10 02:29:42,504 DEBUG [Scheduler 1186524190 Job f894f427-b170-19b6-76fb-e1b671659771-321]
cli.DictionaryGeneratorCLI:99 : Dict for 'THIS_IS_COLUMN_NAME' has already been built, save
it

{code}
 

Since we issue the refresh segments request concurrently (with REST APIs), the dict has a
chance to be modified concurrently. Kylin uses checkAndPut to update HBase to prevent race-condition,
so the WriteConflictException may be raised when updating the same resource. 
 
{code:java}
Liangs-MacBook-Pro:~ pwrliang$ cat 12-10.log |grep /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict|grep
"Update dictionary "
2019-12-10 02:07:10,223 INFO  [Scheduler 1186524190 Job 5c4b2ee9-c8aa-9a69-ffb0-3a6811ad22a9-372]
dict.DictionaryManager:198 : Update dictionary /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict
lastModifiedTime to 1575914830203
2019-12-10 02:07:11,109 INFO  [Scheduler 1186524190 Job 593979b8-e80b-590f-335b-526c2fc49080-295]
dict.DictionaryManager:198 : Update dictionary /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict
lastModifiedTime to 1575914831090
2019-12-10 02:07:20,554 INFO  [Scheduler 1186524190 Job 160952f3-fef2-4fdf-c08a-77d49f830805-246]
dict.DictionaryManager:198 : Update dictionary /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict
lastModifiedTime to 1575914840528
2019-12-10 02:07:21,762 INFO  [Scheduler 1186524190 Job 345b688c-7992-f2cf-ae06-835675f545ea-117]
dict.DictionaryManager:198 : Update dictionary /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict
lastModifiedTime to 1575914841727
2019-12-10 02:07:23,253 INFO  [Scheduler 1186524190 Job 0ea711ed-71b5-ae47-a34a-f0a27fd9d7cc-303]
dict.DictionaryManager:198 : Update dictionary /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict
lastModifiedTime to 1575914843095
2019-12-10 02:26:43,843 INFO  [Scheduler 1186524190 Job c90a765c-976f-49c2-38d8-e6812d091cfb-295]
dict.DictionaryManager:198 : Update dictionary /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict
lastModifiedTime to 1575916003771
2019-12-10 02:26:51,436 INFO  [Scheduler 1186524190 Job d808dadf-8eea-34db-1b1f-d50e923b4e3a-372]
dict.DictionaryManager:198 : Update dictionary /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict
lastModifiedTime to 1575916011421
2019-12-10 02:27:15,593 INFO  [Scheduler 1186524190 Job ea07ef8f-b2b7-b3f8-c481-df615025217d-117]
dict.DictionaryManager:198 : Update dictionary /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict
lastModifiedTime to 1575916035573
2019-12-10 02:29:42,564 INFO  [Scheduler 1186524190 Job f894f427-b170-19b6-76fb-e1b671659771-321]
dict.DictionaryManager:198 : Update dictionary /dict/THIS_IS_CUBE_NAME/THIS_IS_COLUMN_NAME/010dbf72-52a9-e759-08a7-ed7cde0c6e0d.dict
lastModifiedTime to 1575916182549
{code}
{color:#000000}The log above shown that the job "f76fb12e-477f-b404-e021-adaf520d04bb" has
not been print out the log - "Update dictionary blablabla...." because of the WriteConflictException.{color}
 
[After contacted with community|[https://lists.apache.org/thread.html/c75e96857da1eecb74b8e9ef18e6ed242b2933cf87e43c023d8b54da%40%3Cuser.kylin.apache.org%3E]],
[~shaofengshi] has been confirmed that seems to be a bug introduced in [KYLIN-3977|https://issues.apache.org/jira/browse/KYLIN-3977]
in Kylin 2.6.3.
 

 

 



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