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https://issues.apache.org/jira/browse/PHOENIX-6092?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17181471#comment-17181471
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Geoffrey Jacoby commented on PHOENIX-6092:
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How long do the upgrades usually take? If it's fairly short, is just throwing
an exception back to the client saying that DDL is not supported during
upgrades sufficient?
The WAL would certainly work, just trying to quantify how big a problem this.
> 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, 4.16.0
>
>
> 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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