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https://issues.apache.org/jira/browse/KYLIN-4153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16925702#comment-16925702
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ASF GitHub Bot commented on KYLIN-4153:
---------------------------------------
nichunen commented on pull request #818: KYLIN-4153 Delete marker if real file
not exists
URL: https://github.com/apache/kylin/pull/818
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> Failed to read big resource /dict/xxxx at "Build Dimension Dictionary" Step
> ----------------------------------------------------------------------------
>
> Key: KYLIN-4153
> URL: https://issues.apache.org/jira/browse/KYLIN-4153
> Project: Kylin
> Issue Type: Bug
> Components: Metadata
> Affects Versions: v2.6.0
> Reporter: Xiaoxiang Yu
> Assignee: Xiaoxiang Yu
> Priority: Major
>
> At the version of *Kylin 2.6.0*, kylin team has introduce an important
> refactor of Kylin's Metadata Store, which add a lot of enhancement such as
> upload/download metadata concurrently, store metadata with JDBC etc. Please
> refer to https://issues.apache.org/jira/browse/KYLIN-3671 for detail.
>
> When kylin want to save a *big resource*(such as dict or snapshot) into
> metadata store, it won't store it into metadata store(HBase or RDBMS)
> directly. Instead, kylin will first {color:red}save it into HDFS(Step
> 1){color}, and then {color:red}write a empty byte array as marker into
> metadata store(Step 2) {color}. If first action succeed and second action
> failed, a rollback method will be called to revert modification for HDFS
> files. We could regard it as a complete and atomic transaction.
>
> {color:#0747A6}Here is part of the source code added in KYLIN-3671.{color}
> Check it at
> https://github.com/apache/kylin/blob/8737bc1f555a2789a67462c8f8420b6ab3be97ce/core-common/src/main/java/org/apache/kylin/common/persistence/PushdownResourceStore.java#L58
> .
> {code:java}
> final void putBigResource(String resPath, ContentWriter content, long newTS)
> throws IOException {
> // pushdown the big resource to DFS file
> RollbackablePushdown pushdown = writePushdown(resPath, content); // Step
> 1: write big resource into HDFS
> try {
> // write a marker in resource store, to indicate the resource is now
> available
> logger.debug("Writing marker for big resource {}", resPath);
> putResourceWithRetry(resPath,
> ContentWriter.create(BytesUtil.EMPTY_BYTE_ARRAY), newTS); // Step 2: write
> marker into HBase/RDBMS
> } catch (Throwable ex) {
> pushdown.rollback();
> throw ex;
> } finally {
> pushdown.close();
> }
> }
> {code}
>
>
>
> But in some case, both step 1 and step 2 succeed but an exception still
> throwed in step 2,{color:red} the rollback won't clear marker written in Step
> 2{color}, which break the atomicity of this put action, thus cause the
> FileNotFoundException when Kylin want to read that dict later.
>
>
>
> {color:#0747A6}Here is part of reporter's kylin.log of incomplete rollback
> action.{color}
>
>
> {noformat}
> 2019-08-29 05:13:51,237 INFO [Scheduler 169045403 Job
> ca4a4a08-54e2-b922-70bb-2aa2bf58709f-492] dict.DictionaryManager:388 : Saving
> dictionary at
> /dict/KYLIN_VIEW.USER_SECRET_TABLE/COUNTRY/66292068-e8eb-975a-3e44-b56c933c14cc.dict
> 2019-08-29 05:13:51,238 DEBUG [Scheduler 169045403 Job
> ca4a4a08-54e2-b922-70bb-2aa2bf58709f-492] persistence.HDFSResourceStore:98 :
> Writing pushdown file
> /kylin/kylin_metadata/resources/dict/KYLIN_VIEW.USER_SECRET_TABLE/COUNTRY/66292068-e8eb-975a-3e44-b56c933c14cc.dict.temp.-1798610090
> 2019-08-29 05:13:51,256 DEBUG [Scheduler 169045403 Job
> ca4a4a08-54e2-b922-70bb-2aa2bf58709f-492] persistence.HDFSResourceStore:117 :
> Move
> /kylin/kylin_metadata/resources/dict/KYLIN_VIEW.USER_SECRET_TABLE/COUNTRY/66292068-e8eb-975a-3e44-b56c933c14cc.dict.temp.-1798610090
> to
> /kylin/kylin_metadata/resources/dict/KYLIN_VIEW.USER_SECRET_TABLE/COUNTRY/66292068-e8eb-975a-3e44-b56c933c14cc.dict
> 2019-08-29 05:13:51,258 DEBUG [Scheduler 169045403 Job
> ca4a4a08-54e2-b922-70bb-2aa2bf58709f-492] persistence.HDFSResourceStore:65 :
> Writing marker for big resource
> /dict/KYLIN_VIEW.USER_SECRET_TABLE/COUNTRY/66292068-e8eb-975a-3e44-b56c933c14cc.dict
> 2019-08-29 05:13:56,263 WARN
> [hconnection-0x56f3258e-shared--pool10944-t54867] client.AsyncProcess:1263 :
> #10545, table=kylin_metadata, attempt=1/1 failed=1ops, last exception:
> java.io.IOException: Call to tx-dn41.data/10.14.243.51:60020 failed on local
> exception: org.apache.hadoop.hbase.ipc.CallTimeoutException: Call id=2662317,
> waitTime=5001, operationTimeout=5000 expired. on
> tx-dn41.data,60020,1565943919204, tracking started Thu Aug 29 05:13:51
> GMT+08:00 2019; not retrying 1 - final failure
> 2019-08-29 05:13:56,266 ERROR [Scheduler 169045403 Job
> ca4a4a08-54e2-b922-70bb-2aa2bf58709f-492] persistence.HDFSResourceStore:134 :
> Rollback
> /kylin/kylin_metadata/resources/dict/KYLIN_VIEW.USER_SECRET_TABLE/COUNTRY/66292068-e8eb-975a-3e44-b56c933c14cc.dict
> from <empty>
> 2019-08-29 05:13:56,274 ERROR [Scheduler 169045403 Job
> ca4a4a08-54e2-b922-70bb-2aa2bf58709f-492] common.HadoopShellExecutable:65 :
> error execute
> HadoopShellExecutable{id=ca4a4a08-54e2-b922-70bb-2aa2bf58709f-03, name=Build
> Dimension Dictionary, state=RUNNING}
> 2019-08-29 05:13:56,274 INFO [Scheduler 169045403 Job
> ca4a4a08-54e2-b922-70bb-2aa2bf58709f-492] execution.AbstractExecutable:162 :
> Retry 1
> {noformat}
>
>
>
>
> {color:#0747A6}Here is part of reporter's kylin.log of reading a non-exist
> dict in HDFS in "Build Dimension Dictionary" Step.
> {color}
>
> {noformat}
> 2019-08-29 14:54:59,602 INFO [Scheduler 343338459 Job
> af4b847d-afa6-3729-4c19-03a5db08447b-498] steps.CreateDictionaryJob:110 :
> DictionaryProvider read dict from file:
> hdfs://CDH-cluster-main/kylin/kylin_metadata/kylin-af4b847d-afa6-3729-4c19-03a5db08447b/209_new_device/fact_distinct_columns/USER_SECRET_TABLE.COUNTRY/COUNTRY.rldict-r-00004
> 2019-08-29 14:54:59,602 DEBUG [Scheduler 343338459 Job
> af4b847d-afa6-3729-4c19-03a5db08447b-498] cli.DictionaryGeneratorCLI:73 :
> Dict for 'COUNTRY' has already been built, save it
> 2019-08-29 14:54:59,720 ERROR [Scheduler 343338459 Job
> af4b847d-afa6-3729-4c19-03a5db08447b-498] persistence.ResourceStore:233 :
> Error reading resource
> /dict/KYLIN_VIEW.USER_SECRET_TABLE/COUNTRY/66292068-e8eb-975a-3e44-b56c933c14cc.dict
> java.io.IOException: Failed to read big resource
> /dict/KYLIN_VIEW.USER_SECRET_TABLE/COUNTRY/66292068-e8eb-975a-3e44-b56c933c14cc.dict
> at
> org.apache.kylin.common.persistence.PushdownResourceStore.openPushdown(PushdownResourceStore.java:176)
> at
> org.apache.kylin.storage.hbase.HBaseResourceStore.getInputStream(HBaseResourceStore.java:256)
> at
> org.apache.kylin.storage.hbase.HBaseResourceStore.rawResource(HBaseResourceStore.java:226)
> at
> org.apache.kylin.storage.hbase.HBaseResourceStore.access$000(HBaseResourceStore.java:64)
> at
> org.apache.kylin.storage.hbase.HBaseResourceStore$1.visit(HBaseResourceStore.java:159)
> at
> org.apache.kylin.storage.hbase.HBaseResourceStore.visitFolder(HBaseResourceStore.java:204)
> at
> org.apache.kylin.storage.hbase.HBaseResourceStore.visitFolderImpl(HBaseResourceStore.java:152)
> at
> org.apache.kylin.common.persistence.ResourceStore.visitFolderInner(ResourceStore.java:689)
> at
> org.apache.kylin.common.persistence.ResourceStore.visitFolderAndContent(ResourceStore.java:675)
> at
> org.apache.kylin.common.persistence.ResourceStore$2.call(ResourceStore.java:224)
> at
> org.apache.kylin.common.persistence.ResourceStore$2.call(ResourceStore.java:220)
> at
> org.apache.kylin.common.persistence.ExponentialBackoffRetry.doWithRetry(ExponentialBackoffRetry.java:52)
> at
> org.apache.kylin.common.persistence.ResourceStore.getAllResources(ResourceStore.java:220)
> at
> org.apache.kylin.common.persistence.ResourceStore.getAllResources(ResourceStore.java:209)
> at
> org.apache.kylin.dict.DictionaryManager.checkDupByInfo(DictionaryManager.java:334)
> at
> org.apache.kylin.dict.DictionaryManager.saveDictionary(DictionaryManager.java:314)
> at
> org.apache.kylin.cube.CubeManager$DictionaryAssist.saveDictionary(CubeManager.java:1127)
> at
> org.apache.kylin.cube.CubeManager.saveDictionary(CubeManager.java:1089)
> at
> org.apache.kylin.cube.cli.DictionaryGeneratorCLI.processSegment(DictionaryGeneratorCLI.java:74)
> at
> org.apache.kylin.cube.cli.DictionaryGeneratorCLI.processSegment(DictionaryGeneratorCLI.java:55)
> 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)
> Caused by: java.io.FileNotFoundException:
> /kylin/kylin_metadata/resources/dict/KYLIN_VIEW.USER_SECRET_TABLE/COUNTRY/66292068-e8eb-975a-3e44-b56c933c14cc.dict
> (FS: DFS[DFSClient[clientName=DFSClient_NONMAPREDUCE_-784809092_27,
> ugi=kylin (auth:SIMPLE)]])
> at
> org.apache.kylin.common.persistence.PushdownResourceStore.openPushdown(PushdownResourceStore.java:173)
> ... 29 more
> {noformat}
>
> This often happen in Build Step 4: {color:#0747A6}Build Dimension
> Dictionary{color}. And this incomplete metadata entry will cause same
> failure(*_FileNotFoundException_*) of {color:#DE350B}*ALL*{color} following
> cube rebuild job.
>
> As far as I can see, my *{color:#0747A6}workaround{color}* should be delete
> that marker. Since this is a broken metadata entry, deletion won't make
> damage. After the deletion, following rebuilt job will succeed.
>
> This is some related report mail :
> 1.
> http://apache-kylin.74782.x6.nabble.com/How-to-repair-the-cube-that-it-lost-someone-dictionary-td12989.html
> 2.
> http://mail-archives.apache.org/mod_mbox/kylin-user/201908.mbox/%3c4bcca64e.4af8.16cdb473a62.coremail.itzhangqi...@163.com%3e
>
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