Thank you for your very useful advice!
Definitely, I'm using Cassandra V2.2.5 not 3.x. And basically I've understood what does these logs mean. But I have more a few questions. So I would very much appreciate If I get some explanations about these questions. * Q1. In my understand, when open a SSTable, a lot of RandomAccessReaders(RARs) are created. A number of RARs is equal to a number of segments of SSTable. Is a number of segments(=RARs) equal to follows? a number of segments = size of SSTable / size of segments * Q2. What is happen if the Cassandra open a SSTable file which bigger than JVM heap (or memory)? * Q3. In my case, there are a lot of invalidating messages for the same SSTable file (e.g. at least 11 records for tmplink-la-8348-big-Data.db in my previous post). In some cases, there are more than 600 invalidating messages for the same file and these messages logged for a few hours. Would that closing a big SSTable is the cause? * Q4. I saw "tmplink-xxx" or "tmp-xxx" files in the logs and also data directories. Are these files temporary in compaction process? Here is my experimental configurations. - Cassandra node: An aws EC2 instance(t2.medium. 4GBRAM, 2vCPU) - Cassandra version: 2.2.5 - inserted data size: about 100GB - cassandra-env.sh: default - cassandra.yaml - compaction_throughput_mb_per_sec: 8 (or default) - concurrent_compactors: 1 - sstable_preemptive_open_interval_in_mb: 25 (or default) - memtable_flush_writers: 1 Regards, Satoshi On Wed, Mar 16, 2016 at 5:47 PM, Stefania Alborghetti < stefania.alborghe...@datastax.com> wrote: > 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 > > > >
