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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Resolved] (CASSANDRA-5552) Cassandra doesn't preload key caches from disk on start
Date Thu, 09 May 2013 13:49:15 GMT


Jonathan Ellis resolved CASSANDRA-5552.

    Resolution: Duplicate
> Cassandra doesn't preload key caches from disk on start
> -------------------------------------------------------
>                 Key: CASSANDRA-5552
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.1.9
>         Environment: CentOS 6.2, Datastax Cassandra Commutnity Edition package
>            Reporter: Alexey Plotnik
>              Labels: performance
> My cache related settings is default:
> {quote}
> key_cache_size_in_mb: # no value here
> key_cache_save_period: 14400
> row_cache_size_in_mb: 0
> row_cache_save_period: 0
> row_cache_provider: SerializingCacheProvider
> saved_caches_directory: /var/opt/cassandra/data/saved_caches
> {quote}
> Every time I restart Cassandra node with *service cassandra stop; service cassandra start*
commands I see with Zabbix or JMX or *nodetool info* the key cache has been nulled. It happens
every time I restart the node. This situation is stable on all the nodes of the cluster. I
guessed since the key cache is flushed to disk every 4 hours I should never see the situation
with cold caches.
> The output of *nodetool info* after 30 minutes from node has been started:
> bq.Key Cache        : size 2105664 (bytes), capacity 104857584 (bytes), 3812 hits, 47610
requests, 0.371 recent hit rate, 14400 save period in seconds
> Before restarting it looked as follows:
> bq.Key Cache        : size 104857584 (bytes), capacity 104857584 (bytes), 79777150 hits,
502884072 requests, 0.847 recent hit rate, 14400 save period in seconds
> All the nodes have the cache capacity auto-calculated to 104857584 (100 Mb) according
to settings I put above.
> The capacity of saved_caches directory on all the nodes is strange: with command
> bq.ansible cassandra -i hosts -m raw -a 'du -s /var/opt/cassandra/data/saved_caches'
| grep caches
> I see values from 50 to 100 Kb only, against the values of 100Mb the `nodetool info`
> After node restart in 1 week the key cache is filled up to ~2,2 million of keys, but
when I perform node restart (after running for few days) it is nulled again.
> I've never changed the default configuration of cassandra caches. What's going wrong?

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