为什么我在mongodb中获得了读写性能？

Question

I use python to test the performance of tornado async performance asending. my code as below. then I use ab tool (apache benchmark) to test the performance. I get the performance of insert op is better than the read one. why ?

insert operation: Requests per second: 1323.44 [#/sec] (mean)

Read operation: Requests per second: 352.08 [#/sec] (mean)

=======code==========

import asyncmongo

client = asyncmongo.Client("pool1",host = '127.0.0.1', port = 27017, dbname='testdb')

import tornado.web
import tornado.httpserver
import tornado.ioloop

class InsertHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    def get(self):
    friends = client.connection('friends')
    friends.insert( {"AsyncInsert":1},callback=self.on_writen)

    def on_writen(self,response,error):
    self.write("Async insert ~ !")
    self.finish()


class ReadHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    def get(self):
    friends = client.connection('friends')
    friends.find_one( {'AsyncInsert':1}, callback=self.on_read)

    def on_read(self,response,error):
    self.write("Async read ~ !")
    self.finish()




if __name__ == "__main__":
    app = tornado.web.Application([(r'/insert/',InsertHandler),(r'/',ReadHandler)])
    server = tornado.httpserver.HTTPServer(app)
    server.listen(9005)
    tornado.ioloop.IOLoop.instance().start()

Answer 1

MongoDB write operation performance depends on many factors such as the amount of indexes used or document growth on updates.

It is important to note that the duration of the insert call of your MongoDB driver significantly depends on the write concern ( Errors Ignored, Unacknowledged, Acknowledged, Journaled, Replica Acknowledged ) chosen. If you use Errors Ignored or Unacknowledged the driver sends the write operation without any acknowledgment. Those writes are significantly faster than acknowledged writes, at least in terms of method duration of your driver. Note that there was a default write concern change in all official drivers.

In your particular case I would guess that you are using Unacknowledged write concerns. Running similar code i get the following results:

Insert with unacknowledged writes: Requests per second: 1373.51 [#/sec] (mean)
Insert with acknowledged writes: Requests per second: 619.33 [#/sec] (mean)
Reads: Requests per second: 740.99 [#/sec] (mean)