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https://issues.apache.org/jira/browse/CASSANDRA-19948?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17885072#comment-17885072
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Josh McKenzie commented on CASSANDRA-19948:
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I think I was wrong.
We need to have these protections in place _regardless_ of pre/post 8099
versions on both side of a connection since post 8099 we have no tolerance for
/ handling for columns that we don't know; it's treated as a schema mismatch
and the connection severed, hence all the handlers protecting.
See CASSANDRA-12236 for details: here
Basically, we live in a paradigm now where the expectation is "If a feature is
disabled, you don't send the data for it across the wire as that's our proxy
for if you're in a mixed version cluster where the other end might not know
that schema and will forcefully terminate if it's found to mismatch".
We need a solution that triggers off the perceived _version_ of the remote node
rather than whether the feature is enabled or disabled locally. This will still
lead to disconnects in edge cases where Gossip state is incorrect but should be
bulletproof in a post-TCM world.
> Changing cdc table property can cause schema disagreement
> ---------------------------------------------------------
>
> Key: CASSANDRA-19948
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19948
> Project: Cassandra
> Issue Type: Bug
> Components: Cluster/Schema
> Reporter: Bowen Song
> Priority: Normal
> Fix For: 4.1.x, 5.0.x, 5.x
>
> Attachments: 4.1.1.txt, 4.1.6.txt, 5.0.0-corrected.txt,
> cdc_schema_disagreement.sh
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> In the cassandra.yaml file, there is a parameter named "cdc_enabled" which
> allows CDC to be enabled or disabled on each individual nodes.
> It has been found that it can cause schema disagreement or discrepancy when
> an "ALTER TABLE ... WITH cdc=..." statement is ran against a node which has
> "cdc_enabled" set to "false" in a cluster in which nodes have mixed
> "true"/"false" values for the "cdc_enabled" settings.
> The exact behaviour of the above is version-dependant.
> On Cassandra 4.1.1, the cluster will end up in the schema disagreement state.
> A rolling restart will bring the schema back in sync, but the changes made to
> the `cdc` table property will be lost.
> On Cassandra 4.1.6, the cluster will not have visible schema disagreement in
> the "nodetool describecluster" command's output, but the "ALTER TABLE"
> statement only has cosmetic effect on the node it is run. The node with
> "cdc_enabled" set to "false" will show the "cdc" table property has changed,
> but this does not affect its behaviour in any way. At the same time, other
> nodes do not see that table property change at all. This is perhaps even
> worse than on 4.1.1, because the alter table statement is silently failing.
> On Casandra 5.0.0, the behaviour is the same as 4.1.6.
> A shell script for reproducing the above described behaviours in Docker, and
> the outputs of it on both 4.1.1 and 4.1.6 and 5.0.0 are attached.
>
> Edit on 25 Sep: added test result on 5.0.0
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