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https://issues.apache.org/jira/browse/PHOENIX-6092?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xinyi Yan updated PHOENIX-6092:
-------------------------------
    Fix Version/s:     (was: 4.16.0)
                   4.17.0
                   4.16.1

> Optionally queue DDL requests issued while metadata upgrade is in progress 
> and replay on upgrade failure
> --------------------------------------------------------------------------------------------------------
>
>                 Key: PHOENIX-6092
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-6092
>             Project: Phoenix
>          Issue Type: Improvement
>    Affects Versions: 5.0.0, 4.15.0
>            Reporter: Chinmay Kulkarni
>            Assignee: Chinmay Kulkarni
>            Priority: Critical
>             Fix For: 5.1.0, 4.16.1, 4.17.0
>
>
> Currently, if a metadata upgrade is in progress (either triggered by an 
> explicit "EXECUTE UPGRADE" command or by a new client with autoUpgrade 
> enabled), in-flight DDLs will generally go through and work as expected. 
> However, if the upgrade happens to fail, we restore the snapshot of 
> SYSTEM.CATALOG (and with 
> [PHOENIX-6086|https://issues.apache.org/jira/browse/PHOENIX-6086] even other 
> SYSTEM tables) to represent its state before the upgrade started. Due to 
> this, any DDLs issued after the upgrade began are lost.
> There are upgrade steps that need to iterate over each table/index/view in 
> the cluster and multiple steps that need full table scans on SYSTEM.CATALOG 
> and so this time window where we could potentially lose client DDLs is not 
> negligible (could be to the order of minutes).
> This Jira is to discuss ways to tackle this problem. Perhaps we can introduce 
> a configuration which when enabled could use some sort of write-ahead log to 
> store DDLs issued while the upgrade is in progress and replay those DDLs in 
> case we need to restore SYSTEM tables from their snapshot.



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