[jira] [Commented] (KUDU-2690) Alter schema seems to be missing

["Andrew Wong (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KUDU-2690?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16763109#comment-16763109 ] 

Andrew Wong commented on KUDU-2690:
-----------------------------------

Another point to note is that this appears to be viral: whatever this is can lead to multiple failed replicas for a given tablet.

> Alter schema seems to be missing
> --------------------------------
>
>                 Key: KUDU-2690
>                 URL: https://issues.apache.org/jira/browse/KUDU-2690
>             Project: Kudu
>          Issue Type: Bug
>          Components: log, master, tablet
>    Affects Versions: 1.7.1
>            Reporter: Andrew Wong
>            Priority: Major
>
> I've seen an issue that looks as though an ADD_COLUMN is not fully applied before performing writes. This results in a failure to bootstrap with an error like:
> {{F0112 19:58:08.591284  8692 transaction_driver.cc:383] T 578f2c6e60d84cb18d704889ea323cda P dc0af5867d52468f8fd47abf13c08040 S R-NP Ts 6317323785408049152: Cannot cancel transactions that have already replicated: Invalid argument: Client provided column <COLUMN NAME>[double NULLABLE] not present in tablet transaction:R-NP WriteTransaction [type=REPLICA, start_time=2019-01-12 19:58:08, state=WriteTransactionState 0x5d52000 [op_id=(term: 2548 index: 160364490), ts=6317323785408049152, rows=[]]]}}
>  
> One clue is that in the WALs, the "client schema" (the schema in each write request) contains a column that is not in the "tablet schema" (the schema in the log segment), and so dumping the WALs will fail. This alone shouldn't prevent bootstrapping, but when replaying the WAL, we decode the write request against the schema in the tablet metadata. This failure seems to indicate that the tablet metadata's schema is missing a column that is being used by a committed write. I've been trying to piece together various ALTER SCHEMA bugs that we have (e.g. KUDU-860) to recreate this, but haven't had much luck.
>  
> It's worth noting that this cluster is misconfigured so its tablet servers point to duplicate master addresses, and is therefore susceptible to KUDU-2681 and KUDU-2684, meaning each tablet report will result in multiple concurrent tasks being scheduled in response.



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