On Fri, Mar 11, 2016 at 9:22 AM, haosdent <[email protected]> wrote:
> I saw we use Seconds(-1) represent infinity in current code.
>
> ```
> ./3rdparty/libprocess/include/process/future.hpp: bool await(const
> Duration& duration = Seconds(-1)) const;
> ./3rdparty/libprocess/include/process/latch.hpp: bool await(const
> Duration& duration = Seconds(-1));
> ./3rdparty/libprocess/include/process/process.hpp:bool wait(const UPID&
> pid, const Duration& duration = Seconds(-1));
> ./3rdparty/libprocess/include/process/process.hpp:bool wait(const
> ProcessBase& process, const Duration& duration = Seconds(-1));
> ./3rdparty/libprocess/include/process/process.hpp:bool wait(const
> ProcessBase* process, const Duration& duration = Seconds(-1));
> ./3rdparty/libprocess/src/process.cpp: if (duration == Seconds(-1)) {
> ```
>
Those examples have unfortunate style, we would use Option<Duration> and
default to None() if we were to update these.
>
> On Fri, Mar 11, 2016 at 12:14 AM, Joris Van Remoortere <
> [email protected]>
> wrote:
>
> > Duration and TimePoint were introduced to map to the types in C++ (
> > http://en.cppreference.com/w/cpp/chrono).
> >
> > Duration is negative so as not to surprise users when they do TimePoints
> A
> > - B and end up with a positive duration when B > A. You could imagine a
> > user of these writing code to check if their maintenance window is in the
> > past:
> >
> > Duration remaining = Now - Scheduled;
> > if (remaining < 0) {
> > // Don't use offer.
> > } else {
> > // Still `remaining` time to use offer.
> > }
> >
> > This logic would compile correctly and likely pass review because it is
> > intuitive; however, if duration was an absolute value, then it would be a
> > bug.
> >
> > To represent infinity we currently wrap the Duration with an Option. The
> > None state represents infinity. You can find this in the protobufs.
> >
> > —
> > *Joris Van Remoortere*
> > Mesosphere
> >
> > On Wed, Mar 9, 2016 at 11:29 PM, Alexander Rojas <
> [email protected]>
> > wrote:
> >
> > > IMO durations should not be negative. The problem with having them
> define
> > > an infinite period is the following:
> > >
> > > Lets say you want to compute the duration between two durations A and
> B:
> > > C = A-B;
> > > if A < B, C is negative and it will be infinite.
> > >
> > > I one want’s to check for the case mentioned in [1] about sleeping 0
> > > marked with a negative duration, I think adding an explicit `if` is
> > better
> > > since it reflects the intention.
> > >
> > > So in to conclude:
> > >
> > > 1. Duration operations should always be positive so A-B is effectively
> > > |A.underlying_type - B.underlying_type|.
> > > 2. We do need a constant or an specific trait to represent an infinite
> > > duration.
> > >
> > > > On 09 Mar 2016, at 17:20, Klaus Ma <[email protected]> wrote:
> > > >
> > > > One case I can image is to use negative value for forever duration?
> > > >
> > > > ----
> > > > Da (Klaus), Ma (马达) | PMP® | Advisory Software Engineer
> > > > Platform OpenSource Technology, STG, IBM GCG
> > > > +86-10-8245 4084 | [email protected] | http://k82.me
> > > >
> > > > On Wed, Mar 9, 2016 at 8:21 PM, Alex Rukletsov <[email protected]>
> > > wrote:
> > > >
> > > >> Folks,
> > > >>
> > > >> I've recently realized that durations we use in mesos (stout's
> > > `Duration`
> > > >> and `DurationInfo` protobuf) are based on signed integers. Negative
> > > >> duration concept is a bit strange to me, so I googled around a bit
> and
> > > >> found an interesting thread [1].
> > > >>
> > > >> Was it an explicit intention to allow `Duration`s to be negative? Do
> > we
> > > use
> > > >> this feature? If yes, maybe we can introduce a class representing
> time
> > > >> delta (can be negative) and base `Duration` on top of it
> guaranteeing
> > > it is
> > > >> always non-negative?
> > > >>
> > > >> My ultimate intention is to avoid boilerplate code that validates
> > every
> > > >> single instance of `Duration` in the codebase. I'd rather have a
> class
> > > with
> > > >> guarantees certain invariants.
> > > >>
> > > >> [1]
> > > https://internals.rust-lang.org/t/unsigned-version-of-duration/893/2
> > > >>
> > >
> > >
> >
>
>
>
> --
> Best Regards,
> Haosdent Huang
>
