insert into cassandra db with python multiprocessing

Question

i am newbie in python and cassandra. i tried to use python multiproccessing in cassandra and i got it in this site https://github.com/aholmberg/driver-multiprocessing/blob/py3/multiprocess_execute.py how can i fix the error, please tell me if any change i must apply. and this is my code:

from multiprocessing import Pool
import sys
import time
from cassandra.cluster import Cluster
from cassandra.query import tuple_factory

def query_gen(n):
    for _ in range(n):
        yield ('local', )


class QueryManager(object):

    batch_size = 10

    def __init__( self , cluster , process_count = None ):
        self.pool = Pool(processes=process_count, initializer=self._setup,          initargs=(cluster,))

    @classmethod
    def _setup(cls, cluster):
        cls.session = cluster.connect()
        cls.session = cluster.connect('new')


        cls.session.row_factory = tuple_factory
        cls.prepared = cls.session.prepare('SELECT * FROM new.mytbl')

    def close_pool( self ):
        self.pool.close()
        self.pool.join()

    def get_results(self, params):
        results = self.pool.map(_get_multiproc, params, self.batch_size)
        return results

    @classmethod
    def _execute_request(cls, params):
        return cls.session.execute(cls.prepared, params)

def _get_multiproc(params):
    return QueryManager._execute_request(params)


if __name__ == '__main__':
    try:
        iterations = 1
        processes = 2
    except (IndexError, ValueError):
        print("Usage: %s <num iterations> [<num processes>]" % 1)
        sys.exit(1)

    cluster = Cluster()
    cluster = Cluster(['127.0.0.1'])
    qm = QueryManager(cluster, processes)

    start = time.time()
    rows = qm.get_results(query_gen(iterations))
    delta = time.time() - start
#print("%d queries in %s seconds (%s/s)" % (iterations, delta, iterations / delta))

and this is error log:

File "multi.py", line 64, in rows = m.get_results(query_gen(iterations))

File "multi.py", line 40, in get_results results = self.pool.map(_get_multiproc, params, self.batch_size)

File "/usr/lib/python2.7/multiprocessing/pool.py", line 251, in map return self.map_async(func, iterable, chunksize).get()

File "/usr/lib/python2.7/multiprocessing/pool.py", line 567, in get raise self._value

ValueError: Too many arguments provided to bind() (got 1, expected 0)

Yash Sheth Yash Sheth · Accepted Answer · 2018-05-24T07:51:36

I am not sure whether what you are trying to accomplish but after taking a look at your code i think the problem lies here:

    @classmethod
    def _execute_request(cls, params):
    return cls.session.execute(cls.prepared, params)

session.execute(prepared_query)

As you query is just a select statement without any parameters and you are passing params into the execute statement its is showing you an error that too many params (got 1 expected 0 )

Try changing it to

return cls.session.execute(cls.prepared)

and see if that works!! Read More : here

insert into cassandra db with python multiprocessing

1 Answers

session.execute(prepared_query)

Try changing it to