On 01:24 am, johann.bo...@densedata.com wrote: >Alec Matusis wrote: >>In desperation of not finding the real memory leak on the production >>server, >> >>I wrote a test server that I can push to arbitrary high RSS memory. I >>am far >>from sure if this the same leak that I observe in production, but I >>would >>like to understand what this one is. >>This is the server code: >> >>Server.py: >> >>import twisted.protocols.basic >>from twisted.internet.protocol import Factory >>from twisted.internet import reactor >> >>class HiRate(twisted.protocols.basic.LineOnlyReceiver): >> MAX_LENGTH = 20000 >> >> def lineReceived(self, line): >> if line == 'get': >> out = 'a'*4000+'\r\r' >> self.transport.write(out) >> >> >> >>factory = Factory() >>factory.protocol = HiRate >> >>reactor.listenTCP(8007, factory, backlog=50, interface='10.18.0.2') >>reactor.run() >>[...] >>To reproduce the memory leak, I either need two machines with fast LAN >>between them (since the client program takes 100% CPU), or possibly >>one >>machine with a dual core CPU (I have not tried that). It is important >>that >>client.py is given a separate CPU to run. >>When the length of the response from the server is sufficient, (out = >>'a'*4000+'\r\r' , 4000 is enough in my case), the RSS of the server >>process >>starts to leak without a bound. >>If you introduce a small delay in the client (#time.sleep(.001)), the >>leak >>does not occur. >Hi Alec, >I wouldn't call that a memory leak. In your example ( SC/s = (n* CS) / >s ; n > 1, SC: bytes sent to the client, CS: bytes sent to the server >) >there is some CS that satifies the condition SC/s > [available >bandwidth]. For all CS that exceed that limit, the data will be first >queued in the Send-Q of the socket and then inside twisted, because the >Send-Q is full. That's the reason why you see increasing memory usage, >but it's not a leak, it is a server that can not cope with this kind of >DOS attack. Twisted can not handle this situation for you because that >would mean it had to decide which packets, connections, etc. to drop. >Such decisions have to be made by your application.
You can get notifications about when your send buffers are full by registering a producer with the transport. http://twistedmatrix.com/documents/current/core/howto/producers.html describes the APIs involved. This will help you make these decisions in your application. Jean-Paul _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
