我在Scrapy中有一个Web抓取器,可以获取数据项.我想异步地将它们插入到数据库中.
例如,我有一个事务,使用sqlAlchemy Core将一些项目插入到我的数据库中:
def process_item(self,item,spider):
with self.connection.begin() as conn:
conn.execute(insert(table1).values(item['part1'])
conn.execute(insert(table2).values(item['part2'])
我知道可以与Twisted with alchimia
异步使用sqlAlchemy Core.alchimia的文档代码示例如下.
我不明白的是如何在alchimia框架中使用我的上述代码.如何设置process_item以使用反应器?
我可以这样做吗?
@inlineCallbacks
def process_item(self,spider):
with self.connection.begin() as conn:
yield conn.execute(insert(table1).values(item['part1'])
yield conn.execute(insert(table2).values(item['part2'])
我怎么写反应堆部分?
或者是否有更简单的方法在Scrapy管道中进行非阻塞数据库插入?
供参考,以下是alchimia文档中的代码示例:
from alchimia import TWISTED_STRATEGY
from sqlalchemy import (
create_engine,MetaData,Table,Column,Integer,String
)
from sqlalchemy.schema import CreateTable
from twisted.internet.defer import inlineCallbacks
from twisted.internet.task import react
@inlineCallbacks
def main(reactor):
engine = create_engine(
"sqlite://",reactor=reactor,strategy=TWISTED_STRATEGY
)
Metadata = MetaData()
users = Table("users",Metadata,Column("id",Integer(),primary_key=True),Column("name",String()),)
# Create the table
yield engine.execute(CreateTable(users))
# Insert some users
yield engine.execute(users.insert().values(name="Jeremy Goodwin"))
yield engine.execute(users.insert().values(name="Natalie Hurley"))
yield engine.execute(users.insert().values(name="Dan Rydell"))
yield engine.execute(users.insert().values(name="Casey McCall"))
yield engine.execute(users.insert().values(name="Dana Whitaker"))
result = yield engine.execute(users.select(users.c.name.startswith("D")))
d_users = yield result.fetchall()
# Print out the users
for user in d_users:
print "Username: %s" % user[users.c.name]
if __name__ == "__main__":
react(main,[])
最佳答案
How can I set up process_item to use a reactor?
您无需在管道中管理另一个反应堆.
相反,您可以通过从管道返回延迟来在项目管道中执行异步数据库交互.
另见Scrapy’s doc和sample code doing asynchronous operations within an item pipeline by returning a deferred.