@boris https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/db/MeteredFlusher.java#L51
On Sun, Jul 8, 2012 at 8:44 AM, Boris Yen <yulin...@gmail.com> wrote: > I am not sure, but I think there should be only 6 memtables (max) based on > the example. 1 is active, 4 are in the queue, 1 is being flushed. > > Is this correct? > > > On Wed, Jun 6, 2012 at 9:08 PM, rohit bhatia <rohit2...@gmail.com> wrote: >> >> Also, Could someone please explain how the factor of 7 comes in the >> picture in this sentence >> >> "For example if memtable_total_space_in_mb is 100MB, and >> memtable_flush_writers is the default 1 (with one data directory), and >> memtable_flush_queue_size is the default 4, and a Column Family has no >> secondary indexes. The CF will not be allowed to get above one seventh >> of 100MB or 14MB, as if the CF filled the flush pipeline with 7 >> memtables of this size it would take 98MB. " >> >> On Wed, Jun 6, 2012 at 6:22 PM, rohit bhatia <rohit2...@gmail.com> wrote: >> > Hi.. >> > >> > the link http://thelastpickle.com/2011/05/04/How-are-Memtables-measured/ >> > mentions that "From version 0.7 onwards the worse case scenario is up >> > to CF Count + Secondary Index Count + memtable_flush_queue_size >> > (defaults to 4) + memtable_flush_writers (defaults to 1 per data >> > directory) memtables in memory the JVM at once.". >> > >> > So it implies that for flushing, Cassandra copies the memtables content. >> > So does this imply that writes to column families are not stopped even >> > when it is being flushed? >> > >> > Thanks >> > Rohit >> > >> > On Wed, Jun 6, 2012 at 9:42 AM, rohit bhatia <rohit2...@gmail.com> >> > wrote: >> >> Hi Aaron >> >> >> >> Thanks for the link, I have gone through it. But this doesn't justify >> >> nodes of exactly same config/specs differing in their flushing >> >> frequency. >> >> The traffic on all node is same as we are using RandomPartitioner >> >> >> >> Thanks >> >> Rohit >> >> >> >> On Wed, Jun 6, 2012 at 12:24 AM, aaron morton <aa...@thelastpickle.com> >> >> wrote: >> >>> See the section on memtable_total_space_in_mb here >> >>> http://thelastpickle.com/2011/05/04/How-are-Memtables-measured/ >> >>> >> >>> Cheers >> >>> ----------------- >> >>> Aaron Morton >> >>> Freelance Developer >> >>> @aaronmorton >> >>> http://www.thelastpickle.com >> >>> >> >>> On 6/06/2012, at 2:27 AM, rohit bhatia wrote: >> >>> >> >>> I am trying to understand the variance in flushes frequency in a 8 >> >>> node Cassandra cluster. >> >>> All the flushes are of the same type and initiated by >> >>> MeteredFlusher.java => >> >>> >> >>> "INFO [OptionalTasks:1] 2012-06-05 06:32:05,873 MeteredFlusher.java >> >>> (line 62) flushing high-traffic column family CFS(Keyspace='Stats', >> >>> ColumnFamily='Minutewise_Channel_Stats') (estimated 501695882 bytes)" >> >>> [taken from system.log] >> >>> >> >>> Number of flushes for 1 column family vary from 6 flushes per day to >> >>> 24 flushes per day among nodes of same configuration and same >> >>> hardware. >> >>> Could you please throw light on the what conditions does >> >>> MeteredFlusher use to trigger memtable flushes. >> >>> Also how accurate is the estimated size in the above logfile entry. >> >>> >> >>> Regards >> >>> Rohit Bhatia >> >>> Software Engineer, Media.net >> >>> >> >>> > >
