我是python和cassandra的新手 . 我试图在cassandra中使用python multiproccessing,我在这个网站上得到它https://github.com/aholmberg/driver-multiprocessing/blob/py3/multiprocess_execute.py如何修复错误,请告诉我是否必须应用任何更改 . 这是我的代码:
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))
这是错误日志:
文件“multi.py”,第64行,行= m.get_results(query_gen(iterations))
文件“multi.py”,第40行,在get_results结果中= self.pool.map(_get_multiproc,params,self.batch_size)
文件“/usr/lib/python2.7/multiprocessing/pool.py”,第251行,在map中返回self.map_async(func,iterable,chunksize).get()
文件“/usr/lib/python2.7/multiprocessing/pool.py”,第567行,在get raise self._value中
ValueError:提供给bind()的参数太多(得1,预期0)
1 回答
我不确定你要完成的是什么,但在看了你的代码之后,我认为问题出在这里:
session.execute(prepared_query)
当你查询只是一个没有任何参数的select语句而你将params传递给execute语句时它会向你显示一个错误,即太多的params(得到1预期的0)
尝试将其更改为
return cls.session.execute(cls.prepared)
看看是否有效!!阅读更多:here