Benefits of asyncio

[Marko Rauhamaa]

Chris Angelico <rosuav at gmail.com>:

> Okay, but how do you handle two simultaneous requests going through
> the processing that you see above? You *MUST* separate them onto two
> transactions, otherwise one will commit half of the other's work. (Or
> are you forgetting Databasing 101 - a transaction should be a logical
> unit of work?) And since you can't, with most databases, have two
> transactions on one connection, that means you need a separate
> connection for each request. Given that the advantages of asyncio
> include the ability to scale to arbitrary numbers of connections, it's
> not really a good idea to then say "oh but you need that many
> concurrent database connections". Most systems can probably handle a
> few thousand threads without a problem, but a few million is going to
> cause major issues; but most databases start getting inefficient at a
> few thousand concurrent sessions.

I will do whatever I have to. Pooling transaction contexts
("connections") is probably necessary. Point is, no task should ever
block.

I deal with analogous situations all the time, in fact, I'm dealing with
one as we speak.

> Alright. I'm throwing down the gauntlet. Write me a purely nonblocking
> web site concept that can handle a million concurrent connections,
> where each one requires one query against the database, and one in a
> hundred of them require five queries which happen atomically. I can do
> it with a thread pool and blocking database queries, and by matching
> the thread pool size and the database concurrent connection limit, I
> can manage memory usage fairly easily; how do you do it efficiently
> with pure async I/O?

Sorry, I'm going to pass. That doesn't look like a 5-liner.


Marko