Python Scalability TCP Server + Background Game

[Chris Angelico]

On Sat, Jan 18, 2014 at 6:44 PM,  <phiwer at gmail.com> wrote:
>> Quick smoke test. How big are your requests/responses? You mention
>>
>> REST, which implies they're going to be based on HTTP. I would expect
>>
>> you would have some idea of the rough size. Multiply that by 50,000,
>>
>> and see whether your connection can handle it. For instance, if you
>>
>> have a 100Mbit/s uplink, supporting 50K requests/sec means your
>>
>> requests and responses have to fit within about 256 bytes each,
>>
>> including all overhead. You'll need a gigabit uplink to be able to
>>
>> handle a 2KB request or response, and that's assuming perfect
>>
>> throughput. And is 2KB enough for you?
>>
>>
>>
>> ChrisA
>
> My assumption is that there will be mostly reads and some writes; maybe in the order of 80-20%. There is a time element in the game, which forces player's entity to update on-demand. This is part of the reason why I wanted the server to be able to handle so many reques, so that it could handle the read part without having any caching layer.
>

(You're using Google Groups, which means your replies are
double-spaced and your new text is extremely long lines. Please fix
this, either by the fairly manual job of fixing every post you make,
or the simple method of switching to a better client. Thanks.)

My point was just about the REST API, nothing else. You have to handle
a request and a response for every API call. Whether they're reads or
writes, you need to receive an HTTP request and send an HTTP response
for each one. In order to support the 50k requests per second you hope
for, you would have to handle 50k requests coming in and 50k responses
going out. To do that, you would need - at a very VERY rough estimate
- a maximum request size of 2KB and a gigabit internet connection
(which is expensive). No further calculations are worth pursuing if
you can't handle those requests and responses.

(And small requests tend to be more expensive than large ones. Since
you'll need a minimum of >SYN, <SYN/ACK, >ACK, >DATA, <DATA, >FIN,
<FIN/ACK, >ACK in order to transmit and receive one single packet's
worth of data each way, you're looking at roughly 8 packets minimum
for a one-byte message and one-byte response. But at a very very rough
estimate, 2KB each direction is the most you can sustain.)

ChrisA