Just to check, are you concerned about minimizing that latency or maximizing throughput?
I'll that latency is what you're actually concerned about. A fair amount of that latency is probably happening in the python driver. Although it can easily execute ~8k operations per second (using cpython), in some scenarios it can be difficult to guarantee sub-ms latency for an individual query due to how some of the internals work. In particular, it uses python's Conditions for cross-thread signalling (from the event loop thread to the application thread). Unfortunately, python's Condition implementation includes a loop with a minimum sleep of 1ms if the Condition isn't already set when you start the wait() call. This is why, with a single application thread, you will typically see a minimum of 1ms latency. Another source of similar latencies for the python driver is the Asyncore event loop, which is used when libev isn't available. I would make sure that you can use the LibevConnection class with the driver to avoid this. On Fri, Mar 27, 2015 at 6:24 AM, Artur Siekielski <a...@vhex.net> wrote: > I'm running Cassandra locally and I see that the execution time for the > simplest queries is 1-2 milliseconds. By a simple query I mean either > INSERT or SELECT from a small table with short keys. > > While this number is not high, it's about 10-20 times slower than > Postgresql (even if INSERTs are wrapped in transactions). I know that the > nature of Cassandra compared to Postgresql is different, but for some > scenarios this difference can matter. > > The question is: is it normal for Cassandra to have a minimum latency of 1 > millisecond? > > I'm using Cassandra 2.1.2, python-driver. > > > -- Tyler Hobbs DataStax <http://datastax.com/>
