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https://issues.apache.org/jira/browse/CASSANDRA-16063?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17193913#comment-17193913
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Ekaterina Dimitrova edited comment on CASSANDRA-16063 at 9/28/20, 1:28 AM:
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So the reason for the [CommitLog.instance.start()|#L214] being set before the
startup checks are
{code:java}
checkSystemKeyspaceState,
checkDatacenter,
checkRack,
checkLegacyAuthTables{code}
and the following dependency:
* In order to read from the table, we have to first create a
{{ColumnFamilyStore.}}
* {{ColumnFamilyStore}}, in order to function "normally", has to create a
memtable.
* In order to create Memtable, we have to get a current position from commit
log.
was (Author: e.dimitrova):
So the reason for the [CommitLog.instance.start()|#L214] being set before the
startup checks are
{code:java}
checkSystemKeyspaceState,
checkDatacenter,
checkRack,
checkLegacyAuthTables{code}
and the following dependency:
* In order to read from the table, we have to first create a
{{ColumnFamilyStore.}}
* {{ColumnFamilyStore}}, in order to function "normally", has to create a
memtable.
* In order to create Memtable, we have to get a current position from commit
log.
I'll have to think in detail about how we can workaround this but at first
glance it doesn't look trivial to me(?) and I am not sure whether it will
qualify for beta(?). I will get back to this again tomorrow.
> 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
>
>
> 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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