[jira] [Updated] (HUDI-5407) Rollbacks in MDT is not effective

["sivabalan narayanan (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HUDI-5407?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

sivabalan narayanan updated HUDI-5407:
--------------------------------------
    Reviewers: Ethan Guo

> Rollbacks in MDT is not effective
> ---------------------------------
>
>                 Key: HUDI-5407
>                 URL: https://issues.apache.org/jira/browse/HUDI-5407
>             Project: Apache Hudi
>          Issue Type: Bug
>          Components: metadata
>            Reporter: sivabalan narayanan
>            Assignee: sivabalan narayanan
>            Priority: Critical
>              Labels: pull-request-available
>             Fix For: 0.13.0
>
>
> On rare conditions, rollbacks in MDT is not effective. Apparenlty, we have set cleaning policy to be lazy. hence rollbacks happens only when cleaner kicks in and not when we start a new commit. Given MDT is a single writer table, rollback blocks are effective only when the commit to rollback is just prior to the rollback block. 
>  
> Scenarios where this could fail w/ inline compaction. 
>  
> {code:java}
> Data table timeline
> t1.dc   t2.comp.req.     |Crash  t3.dc     t2.comp.inflight    t2.commit
> MDT timeline
> t1.dc.  t2.comp.inflight |Crash  t3.dc  t4.rb(t2)           t2.dc
> {code}
>  
> The first attempt of t2 in MDT should be rolled back since it crashed mid-way. in other words, if there are any log blocks written by t2 in MDT, it should be deemed invalid. 
>  
> But what happens is, here is how the log blocks are laid out. 
> log1(t1).  log2(t2 first attempt) crash.... log3 (t3) log4(t4.rb rolling back t2) ... log5 (t2)
>  
> So, when we read the log blocks via AbstractLogRecordReader, ideally we want to ignore log2. but when we encounter log4 for a rollback block, we only check the previous log block for matching commit to rollback. since it does not match w/ t2, we assume log4 is a duplicate rollback and hence still deem log2 as a valid log block. 
> hence MDT could serve more data files which are not valid from a FS based listing standpoint. 
>  
> Impact:
> log blocks to be ignored are considered valid if not for this fix. 
>  
>  
>  



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