[jira] [Created] (PHOENIX-6092) Queue DDL requests issued while metadata upgrade is in progress and replay on upgrade failure

["Chinmay Kulkarni (Jira)" <ji...@apache.org>]

Chinmay Kulkarni created PHOENIX-6092:
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             Summary: 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: 4.15.0, 5.0.0
            Reporter: Chinmay Kulkarni
            Assignee: Chinmay Kulkarni
             Fix For: 5.1.0, 4.16.0


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.

This Jira is to discuss ways to tackle this problem. Perhaps we should 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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