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https://issues.apache.org/jira/browse/CASSANDRA-18042?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17642075#comment-17642075
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Josh McKenzie commented on CASSANDRA-18042:
-------------------------------------------
Had time to sleep on it. I'm almost with you now Andres, and we should follow
up ticket to break out the warn vs. enable on existing guardrails just so we
don't forget it.
So we're looking at something like:
{code:java}
# feature can be enabled or disabled via guardrail, and operators can optionally
# have it warn the user of edge cases and provide a contact email to reach out
to
# in the event they have questions about usage
feature_enabled: false
feature_warned: true
feature_attribute_a: 100MiB
feature_attribute_b: false
feature_attribute_b_warned: true
feature_attribute_c: LZ4
{code}
My only outstanding minor uncertainty is whether we go with _warned or
something slightly different:
{code:java}
feature_warned: true
feature_warning: true
feature_warn_on_use: true
{code}
"feature_warned" seems ambiguous as to whether we warn on feature use or are
warning the feature of something. I tend to try to achieve clarity at the
expense of verbosity (... clearly), so I'm partial to the "warn_on_use" form.
> Implement a guardrail for not having zero default ttl on tables with TWCS
> -------------------------------------------------------------------------
>
> Key: CASSANDRA-18042
> URL: https://issues.apache.org/jira/browse/CASSANDRA-18042
> Project: Cassandra
> Issue Type: Improvement
> Components: Feature/Guardrails, Legacy/Core
> Reporter: Stefan Miklosovic
> Assignee: Stefan Miklosovic
> Priority: Normal
> Fix For: 4.x
>
> Time Spent: 3h
> Remaining Estimate: 0h
>
> A user was surprised that his data have not started to expire after 90 days
> on his TWCS, he noticed that default_time_to_live on the table was set to 0
> (by accident from his side) and inserts were using TTL = 0 too.
> It is questionable why it it possible to create a table with TWCS and enable
> a user to specify default_time_to_live to be zero.
> On the other hand, I would argue that having default_time_to_live set to 0 on
> TWCS does not necessarily mean that such combination is illegal. It is about
> people just using that with advantage very often so tables are compacted away
> nicely. However, that does not have to mean that they could not use it with
> 0. But I yet have to see a use-case where TWCS was used and default ttl was
> set to 0 on purpose. Merely looking into Cassandra codebase, there are only
> cases when this parameter is not 0.
> There are three approaches:
> 1) just reject such statements (for CreateTable and AlterTable statements)
> where default_time_to_live = 0
> 2) Implement a guardrail for 1) so it can be enabled / disabled on demand
> 3) Leave possibility to set default_time_to_live to 0 on a table but make a
> guardrail for UpdateStatement so it might reject queries for tables with
> default_time_to_live is zero and for which its TTL (on that update statement)
> is set to 0 too.
> I would be careful about making the current configuration illegal because of
> backward compatibility. For that reason 2) makes the most sense to me.
> Maybe implementing 3) would make sense as well. There might be a table which
> has default ttl set to 0 as it expects a user to supply TTL every time.
> However, as it is not currently enforced anywhere, a client might still
> insert TTLs to be set to 0 even by accident.
> POC for 2) is here
> https://github.com/instaclustr/cassandra/commit/0b4dcc3d3deeffa393c02a3b80e27482007f9579
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