Hi, Most of the queries to that table are just getting a range of values for a metric: SELECT val FROM metrics_5min WHERE uid = ? AND metric = ? AND ts >= ? AND ts <= ?
I'm not sure from the logs what kind of compactions they are. This is what I see in system.log (grepping for that specific table): ... INFO [CompactionExecutor:742] 2014-04-06 13:30:11,223 CompactionTask.java (line 105) Compacting [SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14991-Data.db'), SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14990-Data.db')] INFO [CompactionExecutor:753] 2014-04-06 13:35:22,495 CompactionTask.java (line 105) Compacting [SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14992-Data.db'), SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14993-Data.db')] INFO [CompactionExecutor:770] 2014-04-06 13:41:09,146 CompactionTask.java (line 105) Compacting [SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14995-Data.db'), SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14994-Data.db')] INFO [CompactionExecutor:783] 2014-04-06 13:46:21,250 CompactionTask.java (line 105) Compacting [SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14996-Data.db'), SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14997-Data.db')] INFO [CompactionExecutor:798] 2014-04-06 13:51:28,369 CompactionTask.java (line 105) Compacting [SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14998-Data.db'), SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-14999-Data.db')] INFO [CompactionExecutor:816] 2014-04-06 13:57:17,585 CompactionTask.java (line 105) Compacting [SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-15000-Data.db'), SSTableReader(path='/mnt/disk1/cassandra/data/keyspace/metrics_5min/keyspace-metrics_5min-ic-15001-Data.db')] ... As you can see every ~5 minutes there's a compaction going on. On Sun, Apr 6, 2014 at 4:33 PM, Sergey Murylev <sergeymury...@gmail.com>wrote: > Hi Vincent, > > > Is that a good pattern for Cassandra? Is there some compaction tunings I > should take into account? > > Actually it depends on how you use Cassandra :). If you use it as > key-value storage TTL works fine. But if you would use rather complex CQL > queries to this table I not sure that it would be good. > > > With this structure is obvious that after one week inserting data, from > that moment there's gonna be new expired columns every 5 minutes in that > table. Because of that I've noticed that this table is being compacted > every 5 minutes. > > Compaction doesn't triggered when some column expired. It triggered on > gc_grace_seconds timeout and according compaction strategy. You can see > more detailed description of LeveledCompactionStrategy in following > article: Leveled compaction in > Cassandra<http://www.datastax.com/dev/blog/leveled-compaction-in-apache-cassandra>. > > > There are 2 types of compaction: minor and major, which kind of compaction > do you see and how come to conclusion that compaction triggered every 5 > minutes? If you see major compaction that situation is very bad otherwise > it is normal case. > > -- > Thanks, > Sergey > > > > On 06/04/14 15:48, Vicent Llongo wrote: > > Hi there, > > I have this table where I'm inserting timeseries values with a TTL of > 86400*7 (1week): > > CREATE TABLE metrics_5min ( > object_id varchar, > metric varchar, > ts timestamp, > val double, > PRIMARY KEY ((object_id, metric), ts) > ) > WITH gc_grace_seconds = 86400 > AND compaction = {'class': 'LeveledCompactionStrategy', > 'sstable_size_in_mb' : 100}; > > > With this structure is obvious that after one week inserting data, from > that moment there's gonna be new expired columns every 5 minutes in that > table. Because of that I've noticed that this table is being compacted > every 5 minutes. > > Is that a good pattern for Cassandra? Is there some compaction tunings I > should take into account? > > Thanks! > > > >
