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https://issues.apache.org/jira/browse/CASSANDRA-18042?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17637373#comment-17637373
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Andres de la Peña commented on CASSANDRA-18042:
-----------------------------------------------
I was thinking on {{_warned}} instead of {{{}_warn{}}}, so it's more similar to
the existing {{{}_enabled{}}}:
{code:java}
zero_default_ttl_on_twcs_warned: true
zero_default_ttl_on_twcs_enabled: true
{code}
Or it could also be:
{code:java}
zero_default_ttl_on_twcs_discouraged: true
zero_default_ttl_on_twcs_enabled: true
{code}
It's a bit odd however that the two boolean properties have different
behaviours, where {{_enabled}} triggers the guardrails when it's {{{}false{}}},
whereas and {{_warned}} triggers it when it's {{{}true{}}}.
That would be solved by:
{code:java}
zero_default_ttl_on_twcs_fail: false
zero_default_ttl_on_twcs_warn: true
{code}
However, we already have multiple guardrails using {{_enabled}} in 4.1, and we
have to preserve them.
So using {{_fail}} for this guardrail would mean that {{EnableFlag}} sometimes
would receive {{_enabled}} properties, and sometimes would receive {{_fail}}
properties. That's not ideal and it might be problematic if at some point we
want to automatically generate property names from guardrail names.
Maybe [~jmckenzie], who has added a bunch of enable flags, has an opinion on
this.
As for how we manage the true/false properties, we could easily reverse the
predicates that we pass to the constructor.
> 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: 40m
> 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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