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https://issues.apache.org/jira/browse/CASSANDRA-19948?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17884690#comment-17884690
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Stefan Miklosovic edited comment on CASSANDRA-19948 at 9/25/24 5:38 PM:
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I plan to take a closer look in a few days. But even you were right, this
happens "only" when there is a mixed cluster, isn't it? The issue you have is
different, your cluster isn't mixed. However, by definition, if you have a way
how to configure memtables on 4.1 and you change the schema but it is not on
4.0, well then the schema indeed disagrees, no? Anyway we need to test this
properly but I think that I was looking into this already as I was coding the
auto snaphots thing and I do not remember that schemas would disgree. Let's
see. Maybe I am wrong.
I think that when you are upgrading the cluster one node at a time, you will
indeed hit the disagreement for a while, until all nodes are upgraded. This is
imho just normal, operationally-wise.
was (Author: smiklosovic):
I plan to take a closer look in a few days. But even you were right, this
happens "only" when there is a mixed cluster, isn't it? The issue you have is
different, your cluster isn't mixed. However, by definition, if you have a way
how to configure memtables on 4.1 and you change the schema but it is not on
4.0, well then the schema indeed disagrees, no? Anyway we need to test this
properly but I think that I was looking into this already as I was coding the
auto snaphots thing and I do not remember that schemas would disgree. Let's
see. Maybe I am wrong.
> 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
>
>
> 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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