Each sstable has one or more random access readers (one per segment for example) and FileCacheService is a cache for such readers. When an sstable is closed, the cache is invalidated. If no single reader of an sstable is used for at least 512 milliseconds, all readers are evicted. If the sstable is opened again, new reader(s) will be created and added to the cache again.
FileCacheService was removed in cassandra 3.0 in favour of a pool of page-aligned buffers, and sharing the NIO file channels amongst the readers of an sstable, refer to CASSANDRA-8897 <https://issues.apache.org/jira/browse/CASSANDRA-8897> and CASSANDRA-8893 <https://issues.apache.org/jira/browse/CASSANDRA-8893> for more details. On Wed, Mar 16, 2016 at 3:30 PM, satoshi hikida <sahik...@gmail.com> wrote: > Hi, > > I have been working on some experiments for Cassandra and found some log > messages as follows in debug.log. > I am not sure what it exactly is, so I would appreciate if someone gives > me some explanations about it. > > In my verification, a Cassandra node runs as a stand-alone server on > Amazon EC2 instance(t2.medium). And I insert 1 Billion records (about 100GB > data size) to a table from a client application (which runs on another > instance separated from Cassandra node). After insertion, Cassandra > continues it's I/O activities for (probably) compaction and keep logging > the messages as follows: > > --- > ... > DEBUG [NonPeriodicTasks:1] 2016-03-16 09:59:25,170 > FileCacheService.java:102 - Evicting cold readers for > /var/lib/cassandra/data/system/local-7ad54392bcdd35a684174e047860b377/la-6-big-Data.db > DEBUG [NonPeriodicTasks:1] 2016-03-16 09:59:31,780 > FileCacheService.java:177 - Invalidating cache for > /var/lib/cassandra/data/test/user-3d988520e9e011e59d830f00df8833fa/tmplink-la-8348-big-Data.db > DEBUG [NonPeriodicTasks:1] 2016-03-16 09:59:36,899 > FileCacheService.java:177 - Invalidating cache for > /var/lib/cassandra/data/test/user-3d988520e9e011e59d830f00df8833fa/tmplink-la-8348-big-Data.db > DEBUG [NonPeriodicTasks:1] 2016-03-16 09:59:42,187 > FileCacheService.java:177 - Invalidating cache for > /var/lib/cassandra/data/test/user-3d988520e9e011e59d830f00df8833fa/tmplink-la-8348-big-Data.db > DEBUG [NonPeriodicTasks:1] 2016-03-16 09:59:47,308 > FileCacheService.java:177 - Invalidating cache for > /var/lib/cassandra/data/test/user-3d988520e9e011e59d830f00df8833fa/tmplink-la-8348-big-Data.db > ... > --- > > I guess these messages are related to the compaction process and > FileCacheService was invalidating cache which associated with a SSTable > file. But I'm not sure what it does actually mean. When the cache is > invalidated? And What happens is after cache invalidation? > > > Regards, > Satoshi > -- [image: datastax_logo.png] <http://www.datastax.com/> Stefania Alborghetti Apache Cassandra Software Engineer |+852 6114 9265| stefania.alborghe...@datastax.com
