[jira] [Commented] (CASSANDRA-15153) Caffeine cache return stale entries

["Per Otterström (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-15153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17067783#comment-17067783 ] 

Per Otterström commented on CASSANDRA-15153:
--------------------------------------------

I've created a [unit test|https://github.com/apache/cassandra/compare/trunk...eperott:15153-trunk] to reproduce this [issue|https://circleci.com/gh/eperott/cassandra/215#tests/containers/1].

In short, a {{LoadingCache}} may return a stale entry if its load function at some point start to throw exceptions for a key.

The bug seem to be fixed in Caffeine version 2.5.0 and later.

I guess there are a couple of questions that we need to take a stance on here.
# Should we risk upgrading the Caffeine version because of this? Caffeine is used in 12 different classes in trunk.
# And if so, should we make the minimal change and move to 2.5.0, or something later?

FWIW, I'm not able to create a scenario where I can exploit this. A potential one would've been to login as a user after it was deleted in the database (causing the load function to throw {{AuthenticationException}}). However, other permission checks prevent the login attempt from completing. Then again, this doesn't prove there isn't a way to exploit this!

> Caffeine cache return stale entries
> -----------------------------------
>
>                 Key: CASSANDRA-15153
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15153
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Per Otterström
>            Priority: Normal
>
> Version 2.3.5 of the Caffeine cache that we're using in various places can hand out stale entries in some cases. This seem to happen when an update fails repeatedly, in which case Caffeine may return a previously loaded value. For instance, the AuthCache may hand out permissions even though the reload operation is failing, see CASSANDRA-15041.



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