threading

Wed Apr 9 10:46:50 EDT 2014

"Marko Rauhamaa" <marko at pacujo.net> wrote in message 
news:87lhveobeq.fsf at elektro.pacujo.net...
> "Frank Millman" <frank at chagford.com>:
>>> I understand that, if one uses threading, each thread *can* block
>> without affecting other threads, whereas if one uses the async
>> approach, a request handler must *not* block, otherwise it will hold
>> up the entire process and not allow other requests to be handled.
>> Yes.
>>> How does one distinguish betwen 'blocking' and 'non-blocking'? Is it
>> either/or, or is it some arbitrary timeout - if a handler returns within
>> that time it is non-blocking, but if it exceeds it it is blocking?
>> Old-school I/O primitives are blocking by default. Nonblocking I/O is
> enabled with the setblocking() method.
>> In the new asyncio package, I/O is nonblocking by default (I'm sure, but
> didn't verify).
>>> In my environment, most requests involve a database lookup. I
>> endeavour to ensure that a response is returned quickly (however one
>> defines quickly) but I cannot guarantee it if the database server is
>> under stress. Is this a good candidate for async, or not?
>> Database libraries are notoriously bad for nonblocking I/O. It's nothing
> fundamental; it's only that the library writers couldn't appreciate the
> worth of async communication. For that, asyncio provides special
> support:
>> <URL: https://docs.python.org/3.4/library/asyncio-dev.html#
> handle-blocking-functions-correctly>
>
Thanks for the reply, Marko.
I did have a look at the link you provided, but at the moment my brain is 
'blocking' on this, so I will need to read it a few times to get back into 
'async' mode.
As I asked Chris, (so you don't have to respond if he already has), I am 
finding difficulty in understanding the benefit of going async in my case. 
If most requests require a blocking handler, it seems that I might as well 
stick with each request being handled by a thread, independent of all other 
threads.
Frank