Cassandra low performance?

Question

I have to choose Cassandra or MongoDB(or another nosql database, I accept suggestions) for a project with a lot of inserts(1M/day). So I create a small test to measure the write performance. Here's the code to insert in Cassandra:

import time
import os
import random
import string
import pycassa

def get_random_string(string_length):
    return ''.join(random.choice(string.letters) for i in xrange(string_length))

def connect():
    """Connect to a test database"""
    connection = pycassa.connect('test_keyspace', ['localhost:9160'])
    db = pycassa.ColumnFamily(connection,'foo')
    return db

def random_insert(db):
    """Insert a record into the database. The record has the following format
    ID timestamp
    4 random strings
    3 random integers"""
    record = {}
    record['id'] = str(time.time())
    record['str1'] = get_random_string(64)
    record['str2'] = get_random_string(64)
    record['str3'] = get_random_string(64)
    record['str4'] = get_random_string(64)
    record['num1'] = str(random.randint(0, 100))
    record['num2'] = str(random.randint(0, 1000))
    record['num3'] = str(random.randint(0, 10000))
    db.insert(str(time.time()), record)

if __name__ == "__main__":
    db = connect()
    start_time = time.time()
    for i in range(1000000):
        random_insert(db)
    end_time = time.time()
    print "Insert time: %lf " %(end_time - start_time)

And the code to insert in Mongo it's the same changing the connection function:

def connect():
    """Connect to a test database"""
    connection = pymongo.Connection('localhost', 27017)
    db = connection.test_insert
    return db.foo2

The results are ~1046 seconds to insert in Cassandra, and ~437 to finish in Mongo. It's supposed that Cassandra it's much faster than Mongo inserting data. So , What i'm doing wrong?

Answer 1

There is no equivalent to Mongo's unsafe mode in Cassandra. (We used to have one, but we took it out, because it's just a Bad Idea.)

The other main problem is that you're doing single-threaded inserts. Cassandra is designed for high concurrency; you need to use a multithreaded test. See the graph at the bottom of http://spyced.blogspot.com/2010/01/cassandra-05.html (actual numbers are over a year out of date but the principle is still true).

The Cassandra source distribution has such a test included in contrib/stress.