Tornado AsyncHTTPClient性能下降

Question

设置：Python 2.7.15，Tornado 5.1

我有一台网络服务器机器，每秒处理约40个/recommend请求。平均响应时间为25毫秒，但存在很大差异（一些请求可能需要超过500毫秒）。

每个请求在内部生成1-8个Elasticsearch查询（HTTP请求）。每个Elasticsearch查询可能需要1-150毫秒。

Elasticsearch请求通过elasticsearch-dsl库同步处理。

目标是减少I / O等待时间（查询到Elasticsearch）并每秒处理更多请求，这样我就可以减少机器数量。有一件事是不可接受的 - 我不想增加平均处理时间（25毫秒）。

我在网上发现了一些龙卷风弹性搜索实现，但由于我只需要使用一个端点到Elasticsearch（/_search），我试图单独做到这一点。

下面是我的网络服务器的退化实现。使用相同的负载（每秒约40个请求），平均请求响应时间增加到200ms！

深入研究，我发现内部异步处理时间（对Elasticsearch的查询）不稳定，每个fetch调用所花费的时间可能不同，并且总平均值（在ab负载测试中）很高。

我正在使用ab来模拟负载并通过打印当前的fetch处理时间，平均fetch处理时间和最大处理时间来内部测量它。当一次做一个请求（并发1）时：ab -p es-query-rcom.txt -T application/json -n 1000 -c 1 -k 'http://localhost:5002/recommend'

我的版画看起来像：[avg req_time: 3, dur: 3] [current req_time: 2, dur: 3] [max req_time: 125, dur: 125] reqs: 8000

但是当我尝试增加并发性（最多8个）时：ab -p es-query-rcom.txt -T application/json -n 1000 -c 8 -k 'http://localhost:5002/recommend'

现在我的版画看起来像：[avg req_time: 6, dur: 13] [current req_time: 4, dur: 4] [max req_time: 73, dur: 84] reqs: 8000

平均req现在慢了x2（或者我测量的x4）！我在这里想念什么？为什么我看到这种退化？

Web_server.朋友:

import tornado
from tornado.httpclient import AsyncHTTPClient
from tornado.options import define, options
from tornado.httpserver import HTTPServer
from web_handler import WebHandler

SERVICE_NAME = 'web_server'
NUM_OF_PROCESSES = 1


class Statistics(object):
    def __init__(self):
        self.total_requests = 0
        self.total_requests_time = 0
        self.total_duration = 0
        self.max_time = 0
        self.max_duration = 0


class RcomService(object):
    def __init__(self):
        print 'initializing RcomService...'
        AsyncHTTPClient.configure("tornado.curl_httpclient.CurlAsyncHTTPClient", max_clients=3)
        self.stats = Statistics()

    def start(self, port):
        define("port", default=port, type=int)
        db = self.get_db(self.stats)
        routes = self.generate_routes(db)
        app = tornado.web.Application(routes)
        http_server = HTTPServer(app, xheaders=True)
        http_server.bind(options.port)
        http_server.start(NUM_OF_PROCESSES)
        tornado.ioloop.IOLoop.current().start()

    @staticmethod
    def generate_routes(db):
        return [
            (r"/recommend", WebHandler, dict(db=db))
        ]

    @staticmethod
    def get_db(stats):
        return {
            'stats': stats
        }


def main():
    port = 5002
    print('starting %s on port %s', SERVICE_NAME, port)

    rcom_service = RcomService()
    rcom_service.start(port)


if __name__ == '__main__':
    main()

Web_handler.朋友:

import time
import ujson
from tornado import gen
from tornado.gen import coroutine
from tornado.httpclient import AsyncHTTPClient
from tornado.web import RequestHandler


class WebHandler(RequestHandler):
    def initialize(self, db):
        self.stats = db['stats']

    @coroutine
    def post(self, *args, **kwargs):
        result = yield self.wrapper_innear_loop([{}, {}, {}, {}, {}, {}, {}, {}])  # dummy queries (empty)
        self.write({
            'res': result
        })

    @coroutine
    def wrapper_innear_loop(self, queries):
        result = []
        for q in queries:  # queries are performed serially 
            res = yield self.async_fetch_gen(q)
            result.append(res)
        raise gen.Return(result)

    @coroutine
    def async_fetch_gen(self, query):
        url = 'http://localhost:9200/my_index/_search'

        headers = {
                'Content-Type': 'application/json',
                'Connection': 'keep-alive'
        }

        http_client = AsyncHTTPClient()
        start_time = int(round(time.time() * 1000))
        response = yield http_client.fetch(url, method='POST', body=ujson.dumps(query), headers=headers)
        end_time = int(round(time.time() * 1000))
        duration = end_time - start_time
        body = ujson.loads(response.body)
        request_time = int(round(response.request_time * 1000))
        self.stats.total_requests += 1
        self.stats.total_requests_time += request_time
        self.stats.total_duration += duration
        if self.stats.max_time < request_time:
            self.stats.max_time = request_time
        if self.stats.max_duration < duration:
            self.stats.max_duration = duration
        duration_avg = self.stats.total_duration / self.stats.total_requests
        time_avg = self.stats.total_requests_time / self.stats.total_requests
        print "[avg req_time: " + str(time_avg) + ", dur: " + str(duration_avg) + 
              "] [current req_time: " + str(request_time) + ", dur: " + str(duration) + "] [max req_time: " + 
              str(self.stats.max_time) + ", dur: " + str(self.stats.max_duration) + "] reqs: " + 
              str(self.stats.total_requests)
        raise gen.Return(body)

我尝试使用异步类（Simple vs curl），max_clients大小，但我不明白在我的情况下什么是最好的调整。但