> There are 86,400 seconds in a day. If you handle 1 request per second
> you are handling 86,400 requests per day. If you handle 10 requests
> per second you are handling 864,000 requests per day (or nearly 1
> million requests a day) and if you can handle 100 requests per second
> you are handling 8,640,000 (over 8 million), so 100 requests per
> second is usually a good starting point. Unfortunately, usage is not
> evenly distributed like this and you tend to get bursts of requests
> which can impact your server.

> In your case, another factor to consider is how much data you deliver
> (a 1k page, a 10k page, a 100k page, etc) and how long your sql
> requests take. I tend to use a service oriented architecture where the
> sql requests go over the wire to a farm of services which do the
> actual sql access. I use async call backs on the front end and using
> this approach I have noticed a communication overhead of about 2ms per
> request. The actual sql takes about 20ms and misc overhead contributes
> enough for us to say a typical request will take about 25ms.

> Assuming a single threaded approach where requests happen serially
> (which is not the case, but just for performance analysis) this means
> you can get about 40 requests per second (1,000 ms per second divided
> by 25ms per request) out of a single single threaded instance. Now in
> the case of tornado you can get more than one request going at a time,
> so you will get more than 40 requests per second out of a single
> tornado instance.

> Usually the limiting factor is the page payload and front-end
> bandwidth. Assuming you deliver 100k per page and you have a 10mbs
> link to your website, you can deliver about 10 pages a second
> (remember 100k is in bytes, mbs is in bits; there is about a 10:1
> ratio here) or put another way; you can support 10 simultaneous
> users.

> But lets forget about front-end bandwidth concerns (assume you are on
> a cloud with unlimited bandwidth) and concentrate on server
> performance. Now lets say each tornado instance as described above can
> deliver roughly 40-100 requests per second (which is what we see on
> our small cloud machine which is a 1Ghz Athelon with about 380Mb of
> memory) then you can easily increase this by using nginx to load
> balance several of the front-end (we call them MVCs or on-lines)
> machines in parallel. To keep this post brief I will summarize what we
> currently see ...

> Using 1 Front-ends and 1 service instance we get about 25 rps.
> Using 2 Front-ends and 2 service instances we get about 40 rps.
> Using 4 Front-ends and 16 service instances we get about 80 rps.
> Using 8 Front-ends and 32 service instances we get about 125 rps.

> Not what we were expecting but we are investigating what is wrong as I
> speak (for example, we also have couch db running on that box, a rails
> app and some other stuff). Now keep in mind when I say "Using 8 Front-
> ends and 32 service instances we get about 125 rps" what I really mean
> is on that single 1Ghz machine (with about 380Mb of memory) we start
> one instance of nginx (to load balance both the front and back ends)
> 32 instances of our back end service and 8 tornados (each on its on
> port obviously) so we are probably overloading our poor 1Ghz cloud
> machine but like I said, we are currently investigating. Still, we get
> about 100rps for a single very small machine. I know that when I did
> some tests at work (the small cloud machine is for a home start-up we
> are working on) on dedicated hardware I was seeing closer to
> 500-700rps which is about what I expected and is not bad for a single
> server.

> So to summarize; if you want to support about a million requests a day
> you need to be able to handle at least 10 requests per second
> sustained. This should only require one small server.

> Hope that helps a bit.

> On Dec 2, 6:29 am, Stanislav <vishnevs...@gmail.com> wrote:

> > We are developing a large site and we love Tornado, however we were
> > wondering how many requests per second is a good number for a single
> > Tornado instance? This instance is of course doing queries to SQL, and
> > rendering a template.

> > I would greatly appreciate a reply.