Open Stack

Eoghan, thanks for you comments. I will change it to openstack-common.

--jyh

> -----Original Message-----
> From: Eoghan Glynn [mailto:eglynn at redhat.com]
> Sent: Monday, September 10, 2012 10:33 PM
> To: Jiang, Yunhong
> Cc: openstack at lists.launchpad.net; Robert Collins
> Subject: Re: [Openstack] One potential issue on the normalize_time() in
> timeutils
> 
> 
> Thanks Yunhong for pointing this issue out and submitting a patch in quick
> order.
> 
> Your reasoning for switching from if offset to if offset is None, in order to avoid
> including the offset==0 case, makes perfect sense.
> 
> You'll just have to propose the change first to openstack-common, from where
> it will be copied to the nova, glance etc. codebases.
> 
> Cheers,
> Eoghan
> 
> 
> ----- Original Message -----
> > I create a patch for it https://review.openstack.org/#/c/12705/ and
> > please help to review.
> >
> > Thanks
> > --jyh
> >
> > > -----Original Message-----
> > > From: openstack-bounces+yunhong.jiang=intel.com at lists.launchpad.net
> > > [mailto:openstack-bounces+yunhong.jiang=intel.com at lists.launchpad.ne
> > > t]
> > > On
> > > Behalf Of Jiang, Yunhong
> > > Sent: Monday, September 10, 2012 8:17 AM
> > > To: Robert Collins
> > > Cc: openstack at lists.launchpad.net
> > > Subject: Re: [Openstack] One potential issue on the
> > > normalize_time() in
> > > timeutils
> > >
> > > Rob, thanks for comments.
> > > I totally agree with you that aware datetime object is better than
> > > naive one.
> > > The key thing is, utcnow() will return naive object, that means in
> > > some time, we have to use naive object to compare with utcnow(), and
> > > we need a conversion function to convert from aware to naive. The
> > > normalize_time() is the best candidate for this purpose, but it will
> > > fail to convert to naive datetime object in some situation. That's
> > > why I send the mail. I just want to change the
> > > normalize_time() to make sure it will always return naive object.
> > >
> > > Thanks
> > > --jyh
> > >
> > > > -----Original Message-----
> > > > From: Robert Collins [mailto:robertc at robertcollins.net]
> > > > Sent: Monday, September 10, 2012 3:25 AM
> > > > To: Jiang, Yunhong
> > > > Cc: eglynn at redhat.com; openstack at lists.launchpad.net
> > > > Subject: Re: [Openstack] One potential issue on the
> > > > normalize_time()
> > > > in timeutils
> > > >
> > > > On Mon, Sep 10, 2012 at 3:09 AM, Jiang, Yunhong
> > > > <yunhong.jiang at intel.com>
> > > > wrote:
> > > > > Hi, Eoghan and all,
> > > > >
> > > > >         When I implement an enhancement to trusted_filter, I
> > > > >         need
> > > > > utilize
> > > > timeutils() to parse ISO time. However, I suspect there is one
> > > > potential issue in
> > > > normalize_time() and want to get some input from your side.
> > > > >
> > > > >         In normalize_time(), if the parameter "timestamp" is an
> > > > > aware
> > > > object (http://docs.python.org/library/datetime.html) , it's
> > > > output will vary depends on the input. If the timestamp is UTC
> > > > time, it will be return as is without convention, i.e still an
> > > > aware object.
> > > > However, if it's not an UTC time, it will be converted to be a
> > > > naive object.
> > > > >         This mean that the function will return different type
> > > > > depends on
> > > > input, that's not so good IMHO.
> > > > >
> > > > >         The worse is, any compare/substract between naïve
> > > > >         object and
> > > > > aware object will fail. Because the timeutils.utcnow() and
> > > > > datetime.datetime.now() returns naive object, so
> > > > > compare/substract between the uctnow() and normalize_time() may
> > > > > fail, or not, depends on input from the API user. I'm a bit
> > > > > surprised that changes-since works on such situation :)
> > > > >
> > > > >         I suspect this is caused by the "if offset". When
> > > > >         timestamp
> > > > > is
> > > > naïve object, the offset is None. Thus check "if offset" will
> > > > avoid operation type exception. However, if the timestamp is UTC
> > > > time, the offset will be date.timeslot(0), which will return false
> > > > also for "if offset".
> > > > >
> > > > >         Are there any special reason that we need keep aware
> > > > >         object
> > > > > if
> > > > input is at UTC time already? Can I changes the function to always
> > > > return naive object? If yes, I can create a patch for it.
> > > >
> > > > You are probably better off creating an aware datetime object, and
> > > > using them pervasively across the codebase, than using naive
> > > > objects.
> > > > As you note, they are not interoperable, and I've seen countless
> > > > bugs where folk try to mix and match. If we want to show local
> > > > date time to users *anywhere*, we'll need TZ aware objects, which
> > > > is why that variation is the one to standardise on. Otherwise, you
> > > > end up with multiple conversion points, and you can guarantee that
> > > > at least one will get it
> > > wrong.
> > > >
> > > > -Rob
> > >
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