>From a quick glance at your code, it looks like you are preparing your insert statement multiple times. You only need to prepare it once. I would expect to see some improvement with that change.
On Wed, Feb 19, 2014 at 5:27 AM, Rüdiger Klaehn <rkla...@gmail.com> wrote: > Hi all, > > I am evaluating Cassandra for satellite telemetry storage and analysis. I > set up a little three node cluster on my local development machine and > wrote a few simple test programs. > > My use case requires storing incoming telemetry updates in the database at > the same rate as they are coming in. A telemetry update is a map of > name/value pairs that arrives at a certain time. > > The idea is that I want to store the data as quickly as possible, and then > later store it in an additional format that is more amenable to analysis. > > The format I have chosen for my test is the following: > > CREATE TABLE IF NOT EXISTS test.wide ( > time varchar, > name varchar, > value varchar, > PRIMARY KEY (time,name)) > WITH COMPACT STORAGE > > The layout I want to achieve with this is something like this: > > +-------+-------+-------+-------+-------+-------+ > | | name1 | name2 | name3 | ... | nameN | > | time +-------+-------+-------+-------+-------+ > | | val1 | val2 | val3 | ... | valN | > +-------+-------+-------+-------|-------+-------+ > > (Time will at some point be some kind of timestamp, and value will become > a blob. But this is just for initial testing) > > The problem is the following: I am getting very low performance for bulk > inserts into the above table. In my test program, each insert has a new, > unique time and creates a row with 10000 name/value pairs. This should map > into creating a new row in the underlying storage engine, correct? I do > that 1000 times and measure both time per insert and total time. > > I am getting about 0.5s for each insert of 10000 name/value pairs, which > is much lower than the rate at which the telemetry is coming in at my > system. I have read a few previous threads on this subject and am using > batch prepared statements for maximum performance ( > https://issues.apache.org/jira/browse/CASSANDRA-4693 ). But that does not > help. > > Here is the CQL benchmark: > https://gist.github.com/rklaehn/9089304#file-cassandratestminimized-scala > > I have written the exact same thing using the thrift API of astyanax, and > I am getting much better performance. Each insert of 10000 name/values > takes 0.04s using a ColumnListMutation. When I use async calls for both > programs, as suggested by somebody on Stackoverflow, the difference gets > even larger. The CQL insert remains at 0.5s per insert on average, whereas > the astyanax ColumnListMutation approach takes 0.01s per insert on > average, even on my test cluster. That's the kind of performance I need. > > Here is the thrift benchmark, modified from an ast example: > https://gist.github.com/rklaehn/9089304#file-astclient-java > > I realize that running on a test cluster on localhost is not a 100% > realistic test. But nevertheless you would expect both tests to have > roughly similar performance. > > I saw a few suggestions to create a table with CQL and fill it using the > thrift API. For example in this thread > http://mail-archives.apache.org/mod_mbox/cassandra-user/201309.mbox/%3c523334b8.8070...@gmail.com%3E. > But I would very much prefer to use pure CQL for this. It seems that the > thrift API is considered deprecated, so I would not feel comfortable > starting a new project using a legacy API. > > I already posted a question on SO about this, but did not get any > satisfactory answer. Just general performance tuning tips that do nothing > to explain the difference between the CQL and thrift approaches. > > http://stackoverflow.com/questions/21778671/cassandra-how-to-insert-a-new-wide-row-with-good-performance-using-cql > > Am I doing something wrong, or is this a fundamental limitation of CQL. If > the latter is the case, what's the plan to mitigate the issue? > > There is a JIRA issue about this ( > https://issues.apache.org/jira/browse/CASSANDRA-5959 ), but it is marked > as a duplicate of https://issues.apache.org/jira/browse/CASSANDRA-4693 . > But according to my benchmarks batch prepared statements do not solve this > issue! > > I would really appreciate any help on this issue. The telemetry data I > would like to import into C* for testing contains ~2*10^12 samples, where > each sample consists of time, value and status. If quick batch insertion is > not possible, I would not even be able to insert it in an acceptable time. > > best regards, > > Rüdiger > -- - John
