[
https://issues.apache.org/jira/browse/KAFKA-4212?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16910650#comment-16910650
]
James Ritt commented on KAFKA-4212:
-----------------------------------
Hi [~guozhang] thanks for input! In the comments above, most of us clamoring
for this feature seem to have usages where there is a need to enable the TTL
just for RocksDB in order to prevent unbounded growth, and that strict
coherency with the topic isn't required. And given the feedback from Sophie &
Matthias, it definitely seemed like we were heading the KIP direction as I
couldn't come up with a good way to signal usage of the TTL RocksDB in the APIs
available now: `RocksDBConfigSetter` can't be repurposed as it currently
exists, we don't want to modify the `Stores` API, and `StreamsConfig`seemed too
high-level. So if anyone has an idea as to how to properly surface this as an
option it would help inform a KPI.
> Add a key-value store that is a TTL persistent cache
> ----------------------------------------------------
>
> Key: KAFKA-4212
> URL: https://issues.apache.org/jira/browse/KAFKA-4212
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Affects Versions: 0.10.0.1
> Reporter: Elias Levy
> Priority: Major
> Labels: api
>
> Some jobs needs to maintain as state a large set of key-values for some
> period of time. I.e. they need to maintain a TTL cache of values potentially
> larger than memory.
> Currently Kafka Streams provides non-windowed and windowed key-value stores.
> Neither is an exact fit to this use case.
> The {{RocksDBStore}}, a {{KeyValueStore}}, stores one value per key as
> required, but does not support expiration. The TTL option of RocksDB is
> explicitly not used.
> The {{RocksDBWindowsStore}}, a {{WindowsStore}}, can expire items via segment
> dropping, but it stores multiple items per key, based on their timestamp.
> But this store can be repurposed as a cache by fetching the items in reverse
> chronological order and returning the first item found.
> KAFKA-2594 introduced a fixed-capacity in-memory LRU caching store, but here
> we desire a variable-capacity memory-overflowing TTL caching store.
> Although {{RocksDBWindowsStore}} can be repurposed as a cache, it would be
> useful to have an official and proper TTL cache API and implementation.
--
This message was sent by Atlassian Jira
(v8.3.2#803003)
