Questions about GIL and web services from a n00b

[Chris H]

So I'm in a startup where we are considering using python as our primary
development language for all the wonderful reasons you would expect.
However, I've had a couple of things come up from mentors and other
developers that is causing me to rethink whether python is the right
choice. I hope this is the right list for this type of discussion
(please forgive me if not and point me in the right direction).

We are looking to build an e-commerce integration product so the
majority of our work will be linking external SOAP and REST based web
service API's to our own REST based API and backend database. I have
had the following comments/questions come to me:

1. Are you sure you want to use python because threading is not good due
to the Global Lock (GIL)? Is this really an issue for multi-threaded
web services as seems to be indicated by the articles from a Google
search? If not, how do you avoid this issue in a multi-threaded process
to take advantage of all the CPU cores available?

2. Are there good web services frameworks available for building a REST
based service? I admit I have looked at web2py, Django, pyramid/pylons,
and a few others. SOAP seems to be pretty well supported but I'm not
finding the same for quick development of REST based services for
exchanging JSON or XML formatted data. This is probably just my n00b
status, but what tools are best for building a simple REST data exchange
API?

Thanks,
Chris

 

[sturlamolden]

1. Are you sure you want to use python because threading is not good due
to the Global Lock (GIL)?  Is this really an issue for multi-threaded
web services as seems to be indicated by the articles from a Google
search?  If not, how do you avoid this issue in a multi-threaded process
to take advantage of all the CPU cores available?

First, if you are stupid enough to to compute-bound work in Python,
without using a library, you have worse problems than the GIL. How
incompetent would you need to be to write multi-threaded matrix
multiplication or FFTs in pure Python, and blame the GIL for
lack for performance?

Second, if you think "advantage of all the CPU cores available"
will make difference for an I/O bound webservice, you're living
in cloud cookoo land. How on earth will multiple CPU cores
give you or your clients a faster network connection? The network
connection is likely to saturate long before you're burning the
CPU.

Sturla

 

[sturlamolden]

1. Are you sure you want to use python because threading is not good due
to the Global Lock (GIL)?  Is this really an issue for multi-threaded
web services as seems to be indicated by the articles from a Google
search?  If not, how do you avoid this issue in a multi-threaded process
to take advantage of all the CPU cores available?

By the way:

The main issue with the GIL is all the FUD written by
people who don't properly understand the issue. It's
not easy to discern the real information from the
unqualified FUD. I whish people who think in Java
would just shut up about things they don't understand.
The problem is they think they understand more than
they do.

Also, people that write multi-threaded programs which
fails to scale from false-sharing issues, really should
not pollute the web with FUD about Python's GIL. Java's
"free threading" model is not better when all you use it
for is to create dirty cache lines that must be reloaded
everywhere.


Sturla

 

[Lamont Nelson]

1. Are you sure you want to use python because threading is not
good due

to the Global Lock (GIL)?  Is this really an issue for multi-threaded
web services as seems to be indicated by the articles from a Google
search?  If not, how do you avoid this issue in a multi-threaded process
to take advantage of all the CPU cores available?

To take advantage of the cores on your server you'll want to consider
a multi-process design instead of multi-threading. You can achieve
this with something like http://projects.unbit.it/uwsgi/, which will
allow you to manage the processes. I've used this behind apache
successfully.

2. Are there good web services frameworks available for building a REST
based service?  I admit I have looked at web2py, Django, pyramid/pylons,
and a few others.  SOAP seems to be pretty well supported but I'm not
finding the same for quick development of REST based services for
exchanging JSON or XML formatted data.  This is probably just my n00b
status, but what tools are best for building a simple REST data exchange
API?

I've personally used Pyramid to implement REST web services with
multiple data transport formats (json, xml) for the same endpoints
with minimal fuss. It's basically as simple as returning an object
from your view and defining a renderer that knows how to translate
this object to the desired format. Look at
http://docs.pylonsproject.org/projects/pyramid/1.0/narr/renderers.html#views-which-use-a-renderer
and http://docs.pylonsproject.org/projects/pyramid/1.0/narr/viewconfig.html#view-config-chapter
for more information.

Lamont

 

[Chris H]

To take advantage of the cores on your server you'll want to consider
a multi-process design instead of multi-threading. You can achieve
this with something like http://projects.unbit.it/uwsgi/, which will
allow you to manage the processes. I've used this behind apache
successfully.

I've personally used Pyramid to implement REST web services with
multiple data transport formats (json, xml) for the same endpoints
with minimal fuss. It's basically as simple as returning an object
from your view and defining a renderer that knows how to translate
this object to the desired format. Look at
http://docs.pylonsproject.org/projects/pyramid/1.0/narr/renderers.html#views-which-use-a-renderer
and http://docs.pylonsproject.org/projects/pyramid/1.0/narr/viewconfig.html#view-config-chapter
for more information.

Lamont

Thanks to everyone who has replied. I have a better understanding of
the limitations around the GIL as well as the relatively architectures
for avoiding the issue. Now to find the right framework for a simple
web service. So far I've heard pyramid the most, but others we are
looking into include rest.ish.io, web2py, and flask. Anyone with
experience across these as to what is best for someone starting from
scratch now?

Chris