[libvirt] [PATCH v2 6/6] libvirtaio: add .drain() coroutine

[Wojtek Porczyk]

On Mon, Sep 25, 2017 at 02:53:01PM +0100, Daniel P. Berrange wrote:
> On Thu, Sep 14, 2017 at 02:41:12AM +0200, Wojtek Porczyk wrote:
> > The intended use is to ensure that the implementation is empty, which is
> > one way to ensure that all connections were properly closed and file
> > descriptors reclaimed.
> > 
> > Signed-off-by: Wojtek Porczyk <woju at invisiblethingslab.com>
> > ---
(snip)
> > +    @asyncio.coroutine
> > +    def drain(self):
> > +        '''Wait for the implementation to become idle.
> > +
> > +        This is a coroutine.
> > +        '''
> > +        self.log.debug('drain()')
> > +        if self._pending:
> > +            yield from self._finished.wait()
> > +        self.log.debug('drain ended')
> 
> What is responsible for calling 'drain'  ?

Users of the library, and they do it at their pleasure. This is to allow the
loop to actually run the scheduled tasks. After calling virConnect.close() the
handles/timeouts aren't actually closed until the loop run the scheduled
callbacks. In practice a simple `yield` in a coroutine would be also
sufficient since respective Tasks are in the _ready queue and all run during
next loop cycle, but that's not guaranteed in asyncio specification.


-- 
pozdrawiam / best regards       _.-._
Wojtek Porczyk               .-^'   '^-.
Invisible Things Lab         |'-.-^-.-'|
                             |  |   |  |
 I do not fear computers,    |  '-.-'  |
 I fear lack of them.        '-._ :  ,-'
    -- Isaac Asimov             `^-^-_>
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