[Flask] uWSGI and Flask - Slow and varying response times

[Tim van der Linden]

On Wed, 06 Jul 2016 18:28:15 +0800
Unai Rodriguez <unai at sysbible.org> wrote:

> Hi Tim,

Hi Unai

> For uwsgi/Python you could do the same, build a simple page and a more
> complicated one and compare (no database queries to isolate).

First a simple page on uWSGI using Flask and Jinja. The template only consists out of the bare minimals for a HTML page and a single string variable to be printed and the whole application is a single Python file with only one view. The timings are done using the Werkzeug profiler:

Local: 7 ms for initial request, 0.5ms for all following requests
Server: 160 ms for initial request, 1ms for all following requests

I will count that as identical. The Snakeviz graphs also look identical for both.

Then I added a few range(1, 1000) loops to be printed in Jinja2 and a load of simple text:

Local: 9 ms for initial request, 3 ms for all following requests
Server: 24 ms for initial request, 10 ms for all following requests

Slowly a difference between the two start to form.

I added some more elements to the view and template such as a WTF form, but the timings did not went up much. The difference stayed however: server being three times slower then local.

I also added a couple of (fast) database queries in the mix, opening and closing both cursors and connections per query:

Local: 16 ms for initial request, 11 ms for all following requests
Server: 51 ms for initial request, 33 ms for all following requests

> The server/os will have to be looked at some point as well. 

This was interesting but maybe less important since this is testing pure CPU throughput:, I yanked a primes Python script of the interwebs to test the raw processing speed and ran it on both machines.

Local: 3.3879199028 s
Server: 9.26460504532 s

This is a script without any extras, one Python function tested with Timeit and ran directly via the Python CLI. My local machine is three times faster than the server.

Installing Sysbench and doing a primers test (20000) outside of Python:

Local: 18.1605 seconds
Server: 42.1942 seconds

CPU info:

Local: 1 x i74790K (4 Ghz)
Server: 8 x Xeon E7-4820 v2 (2 Ghz)

> -- unai

Cheers,
Tim