asyncio event loop or IOLoop ?

[aliane abdelouahab]

Hi,

Since now Tornado plays perfectly with async/await, which means we can directly use Async/Await libraries for databases, right ?

for example this one for Posgresql https://magicstack.github.io/asyncpg/current/ (since momoko dont support Tornado 5.0),

So, will the Tornado's IOLoop plays perfectly with those libraries or do we have to add a bridge ?

Which one will take the global event loop ?

asyncio.get_event_loop().run_until_complete(some_function)

or

tornado.ioloop.IOLoop.instance().start()

[Ben Darnell]

On Fri, Jun 1, 2018 at 6:05 PM aliane abdelouahab <alabde...@gmail.com> wrote:

Hi,

Since now Tornado plays perfectly with async/await, which means we can directly use Async/Await libraries for databases, right ?

for example this one for Posgresql https://magicstack.github.io/asyncpg/current/ (since momoko dont support Tornado 5.0),

So, will the Tornado's IOLoop plays perfectly with those libraries or do we have to add a bridge ?

Yes, with Tornado 5.0 you can use asyncio-based libraries like asyncpg without doing anything special. 

 

Which one will take the global event loop ?

asyncio.get_event_loop().run_until_complete(some_function)

or

tornado.ioloop.IOLoop.instance().start()

You can do either one; they both start the asyncio event loop (run_forever() is the asyncio equivalent of tornado's start(). run_until_complete() is the equivalent of tornado's run_sync()). Python 3.7 introduces a function asyncio.run() which I'm personally going to start using instead of run_sync() because it's less to type. 

-Ben

 

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[aliane abdelouahab]

Ah, Thank you very much for this explaination,

I have another question, what is the best way to deal with databases connection in this case ? in the past the connection was done once, to avoid opening/closing which costs time, so what is the best way to initialize the connection with database and Tornado while using Async/Await ?

[Ben Darnell]

Using a single connection was a bit of a hack, because the fact that the database api was synchronous meant that there would be no sharing. With an asynchronous database driver, you should use a connection pool (for example, with asyncpg.create_pool), just like you would with a multi-threaded application. 

-Ben

[aliane abdelouahab]

Got it, Thank you again