多线程和代理会增加 30 秒的延迟。我可以做什么来避免

Question

我使用 PyQt、QThreads 和 couchdb-python 与本地 LAN 上的 couchDB 实例进行通信。

为了测试多线程在网络速度慢的情况下是否可以工作，我在 GUI 和沙发之间放置了一个代理。

网络已记录。日志以 That 开头

13:52:46.303 (1) send: HEAD /cubic HTTP/1.1CRLFHost: localhost:5981CRLFContent-Length: 0CRLFAccept: application/jsonCRLFUser-Agent: CouchDB-Python/0.8CRLFCRLF

13:52:46.308 (1) recv: HTTP/1.1 200 OKCRLFServer: CouchDB/1.0.1 (Erlang OTP/R13B)CRLFDate: Mon, 21 Feb 2011 13:47:18 GMTCRLFContent-Type: application/jsonCRLFContent-Length: 219CRLFCache-Control: must-revalidateCRLFCRLF
13:53:16.312 (1) recv: link closed
13:53:16.319 (2) send: GET /cubic/_design/Company/_view/by_name HTTP/1.1CRLFHost: localhost:5981CRLFContent-Length: 0CRLFAccept: application/jsonCRLFUser-Agent: CouchDB-Python/0.8CRLFCRLF
13:53:16.330 (2) recv: HTTP/1.1 200 OKCRLFTransfer-Encoding: chunkedCRLFServer: CouchDB/1.0.1 (Erlang OTP/R13B)CRLFEtag: "243QGZGN1ETGA4VN9H1OMB86Z"CRLFDate: Mon, 21 Feb 2011 13:47:48 GMTCRLFContent-Type: application/jsonCRLFCache-Control: must-revalidateCRLFCRLF
13:53:16.331 (2) recv: a0CRLF{"total_rows":9,"offset":0,"rows":[CRLF{"id":"c182c1a2f71c3547ccee45556300770e","key":["A first Company","231","345 East of Eden" ,"Manchester",null],"value":null}CRLF
13:53:16.332 (2) recv: 77CRLF,CRLF{"id":"c182c1a2f71c3547ccee455563001254","key":["C-U-B","1","9-11 March Business Centre","March",null],"value":null}CRLF72CRLF,CRLF{"id":"421261e8a3311c356c4900185800d976","key":"Four","104","4 Fourth street","Four Score",null],"value":null}CRLF74CRLF,CRLF{"id":"c182c1a2f71c3547ccee455563003de8","key":["Fred Smith","431","30 High street","Somehow",null],"value":null}CRLF
13:53:16.334 (2) recv: 83CRLF,CRLF{"id":"7bc7f2014593d108b5b681fe03002ad6","key":["Ian Hobson","1002","31 Sheerwater Dr","Northampton, Nhants",null],"value":null}CRLF76CRLF,CRLF{"id":"c182c1a2f71c3547ccee455563003139","key":["Julie Bloggs","302","30 Back Lane","Somewhere",null],"value":null}CRLF7cCRLF,CRLF{"id":"c182c1a2f71c3547ccee455563002e87","key": "Kingfisher Group","323","33 Westmister Rd","Londonx",null],"value":null}CRLF
13:53:16.335 (2) recv: 7aCRLF,CRLF{"id":"c182c1a2f71c3547ccee455563005894","key":["New Company","212","34 Back Street","Another Town",null],"value":null}CRLF72CRLF,CRLF{"id":"421261e8a3311c356c4900185800d7e2","key":["Three","103","3 High Street","Liverpool 8",null],"value":null}CRLF4CRLFCRLF]}CRLF1CRLFLFCRLF0CRLFCRLF
13:53:46.337 (2) recv: link closed

，与预期完全一致，只是在 13:52:46.308 打开数据库后有 30 秒的延迟，同时 recv 链接超时。直到发生这种情况，代码才能打开在 13:53:16.319 发生的视图，

但是代理使用不同的线程{(2)而不是(1)}。应用程序部分在没有代理的情况下工作得很好，所以我怀疑代理。

代理代码基于microproxy，下面

import re, sys, datetime
import socket 
import threading 
PORT = 5981
class ConnectionThread(threading.Thread): 
    def __init__(self, (conn,addr),id): 
        self.conn = conn 
        self.addr = addr
        self.id = id
        threading.Thread.__init__(self)

    def report(self,data,dir):
        txt = data.replace("\n",'LF')
        txt = txt.replace("\r",'CR')
        now = datetime.datetime.now()
        print "%s (%s) %s: %s" % (now.isoformat()[11:23],self.id,dir,txt)      

    def run(self): 
        data = self.conn.recv(1024*1024) 
        request = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
        request.connect(('192.168.0.1',5984)) 
        self.report(data,'send')
        request.send(data) 
        while True: 
            temp = request.recv(1024) 
            if ('' == temp):
                self.report('link closed','recv')
                break 
            self.report(temp,'recv')
            self.conn.send(temp)
        self.conn.close()

class ProxyThread(threading.Thread): 
    def __init__(self, port): 
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
        self.sock.bind(('localhost', port))
        self.count = 1
        threading.Thread.__init__(self) 
    def run(self): 
        self.sock.listen(3) 
        while True:
            temp = ConnectionThread(self.sock.accept(),self.count)
            temp.start()   # each message handled in own thread
            self.count += 1
if __name__ == "__main__": 
    print "Starting a proxy on port", PORT
    proxy = ProxyThread(PORT) 
    proxy.run() 

打开数据库的请求和视图的请求都是在同一个（非GUI）中进行的 线。为什么会发生延迟？

我怎样才能改变事情而不是这样呢？

Answer 1

您的循环仅从被代理的连接的一端读取。这样，当回复从服务器转发到客户端并且客户端断开连接时，代码不会注意到客户端断开连接，并继续等待服务器回复或断开连接。

要解决这个问题，它需要从服务器（请求）和客户端（self.conn）套接字读取。使用非阻塞套接字最容易做到这一点。

Answer 2

HTTP 规范 规定（第 9.4 节）

HEAD 方法与 GET 相同，只是服务器不得在响应中返回消息正文。

这意味着 CRLFCRLF 后面没有任何内容，但您的代理正在等待数据而不是从传入连接中读取数据。我怀疑 couchdb 库正在尝试使用保持活动连接，但您正在查看错误的套接字。

您的基本问题是您声称可以与 HTTP 1.1 通信，但实际上却没有。您应该注意 CRLFCRLF 序列和内容大小标头。如果发现读取了这么多数据就跳出循环，如果没有就立即break。