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Ekaterina Dimitrova commented on CASSANDRA-16063:
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Thanks for the review [~adelapena] and [~slebresne]
[~adelapena]'s point is correct. I was checking yesterday for a way to collect
the global information but I didn't find an implemented already way. Also,
additional test was added to handle this topic.
>From what we talked with [~adelapena] and other engineers, probably our best
>bet will be to use Gossip?
Before I start any implementation, I decided first to update the ticket and
confirm the approach.
[~adelapena] , [~slebresne] , [~marcuse], [~ifesdjeen], any thoughts here? Or
anyone else?
Maybe [~brandon.williams] or [~jwest] had some idea as they raised the upgrade
of SSTables topic as part of this ticket :)
To summarize, in order to enforce users to upgrade their SSTables before using
ALTER DROP COMPACT STORAGE, we need to be able to check globally which nodes we
need to update. It seems there is no current implementation to collect this
knowledge. So Gossip?
> Fix user experience when upgrading to 4.0 with compact tables
> -------------------------------------------------------------
>
> Key: CASSANDRA-16063
> URL: https://issues.apache.org/jira/browse/CASSANDRA-16063
> Project: Cassandra
> Issue Type: Bug
> Components: Legacy/CQL
> Reporter: Sylvain Lebresne
> Assignee: Ekaterina Dimitrova
> Priority: Normal
> Fix For: 4.0-beta
>
> Attachments: Compact_storage_upgrade_tests.txt
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> The code to handle compact tables has been removed from 4.0, and the intended
> upgrade path to 4.0 for users having compact tables on 3.x is that they must
> execute {{ALTER ... DROP COMPACT STORAGE}} on all of their compact tables
> *before* attempting the upgrade.
> Obviously, some users won't read the upgrade instructions (or miss a table)
> and may try upgrading despite still having compact tables. If they do so, the
> intent is that the node will _not_ start, with a message clearly indicating
> the pre-upgrade step the user has missed. The user will then downgrade back
> the node(s) to 3.x, run the proper {{ALTER ... DROP COMPACT STORAGE}}, and
> then upgrade again.
> But while 4.0 does currently fail startup when finding any compact tables
> with a decent message, I believe the check is done too late during startup.
> Namely, that check is done as we read the tables schema, so within
> [{{Schema.instance.loadFromDisk()}}|https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/service/CassandraDaemon.java#L241].
> But by then, we've _at least_ called
> {{SystemKeyspace.persistLocalMetadata()}}} and
> {{SystemKeyspaceMigrator40.migrate()}}, which will get into the commit log,
> and even possibly flush new {{na}} format sstables. As a results, a user
> might not be able to seemlessly restart the node on 3.x (to drop compact
> storage on the appropriate tables).
> Basically, we should make sure the check for compact tables done at 4.0
> startup is done as a {{StartupCheck}}, before the node does anything.
> We should also add a test for this (checking that if you try upgrading to 4.0
> with compact storage, you can downgrade back with no intervention whatsoever).
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