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From Nick Allen <n...@nickallen.org>
Subject Re: [DISCUSS] Expansion of the capabilities of PROFILE_GET
Date Tue, 31 Jan 2017 19:21:57 GMT
Yes, agreed.  However we specify the schedule, it would be decoupled from
the Profiler client functions.

timestamps := CRON("* * * ? * foo bar")
profiles := PROFILE_GET("profile1", "entity1", timestamps)


Or

timestamps := STELLAR_DSL("on every other Tuesday")
profiles := PROFILE_GET("profile1", "entity1", timestamps)




On Tue, Jan 31, 2017 at 2:01 PM, Casey Stella <cestella@gmail.com> wrote:

> One more point, one of the reasons for decoupling the PROFILE_GET from
> PROFILE_LOOKUP means that we could ahve alternative implementations of
> PROFILE_LOOKUP.  We could have a PROFILE_LOOKUP_CRON as well.
>
> On Tue, Jan 31, 2017 at 1:43 PM, Casey Stella <cestella@gmail.com> wrote:
>
> > Regarding the "?" syntax:
> > Wouldn't that be forking cron syntax so now we have a metron cron?  If
> > we're constructing our own syntax, then why not do it so that it reads
> like
> > natural language?
> >
> > Regarding the holiday problem:
> > Agreed, it's a smaller problem than constructing a DSL, but that's not
> > really the point, I think. The concern is that it would be unable to be
> > expressed using cron syntax in a natural way without modifying cron
> syntax,
> > which would be constructing a new DSL.  If quartz has a clever way of
> doing
> > that, then I'd like to see it.  From a quick search, I haven't seen a
> > scheduling example with a compact syntax that shows skipping holidays
> with
> > cron syntax.
> >
> >
> > On Tue, Jan 31, 2017 at 1:29 PM, Nick Allen <nick@nickallen.org> wrote:
> >
> >> >
> >> >    - Cron syntax allows you to construct only absolute lookbacks (i.e.
> >> >    "every tuesday at 3PM" not "every tuesday at the current hour")
> >>
> >>
> >> I think Cron would work for this.  I am no expert on cron expressions,
> but
> >> I think the following examples would work.
> >>
> >>    - If you want "every Tuesday at 3 PM"
> >>       - 0 0 15 ? * TUE *
> >>    - If you want "every Tuesday at current hour" then use something like
> >>    the "?" placeholder maybe.
> >>       - 0 0 ? ? * TUE *
> >>
> >> - Cron syntax allows you to specify a point in time, not a duration.  We
> >> >    could, of course, specify a duration as another argument
> >>
> >>
> >> Yes, a separate argument would be necessary.  We would have to allow the
> >> user to specify either a "start from date/time" or the "number of
> >> intervals
> >> to look back".
> >>
> >> Cron syntax does not allow you to skip things like holidays, etc.
> >>
> >>
> >> I agree, out-of-the-box Cron does not solve holiday calendars.  But this
> >> would be a smaller problem to solve then creating our own DSL.
> >>
> >> There is a tradition of creating shortcuts that look something like
> @Daily
> >> or @Weekdays or @Tuesdays that we could also use to make things easier
> for
> >> users.
> >>
> >> I have used Quartz with cron expressions in the past and there was some
> >> way
> >> to handle holidays with that.  I think you could create a custom
> calendar
> >> for the holidays and call it something; aka @USHolidays.  And then you
> >> would say "every Tuesday" except @USHolidays or something like that.
> I'd
> >> have to look into this some more.
> >>
> >> And there are also nice online Cron expression "translators" that we
> could
> >> mimic in a Metron user interface.  For example, https://crontab.guru.
> >>
> >>
> >>
> >>
> >> On Tue, Jan 31, 2017 at 12:00 PM, Casey Stella <cestella@gmail.com>
> >> wrote:
> >>
> >> > I actually did consider cron initially but dismissed it for the
> >> following
> >> > reasons:
> >> >
> >> >    - Cron syntax allows you to construct only absolute lookbacks (i.e.
> >> >    "every tuesday at 3PM" not "every tuesday at the current hour")
> >> >    - Cron syntax allows you to specify a point in time, not a
> >> duration.  We
> >> >    could, of course, specify a duration as another argument
> >> >    - Cron syntax does not allow you to skip things like holidays, etc.
> >> >
> >> > You could use Cron syntax as part of a broader API to specify the days
> >> to
> >> > look back and have other arguments handle the aspects that cron
> doesn't
> >> > support out of the box.  I share your concern at making another DSL,
> but
> >> > cron seemed to not be a complete solution and it's syntax, despite
> being
> >> > well known by admins, may not be well known to analysts.  Also, and
> >> this is
> >> > just a personal bias, I find it inscrutable without a fair amount of
> >> > wikipedia and man page reading.
> >> >
> >> > On Tue, Jan 31, 2017 at 11:47 AM, Nick Allen <nick@nickallen.org>
> >> wrote:
> >> >
> >> > > I do prefer the flexibility of the DSL, but would prefer not to
> create
> >> > yet
> >> > > another DSL for our users to learn.  Couldn't we somehow use cron
> >> > > expressions for this functionality?
> >> > >
> >> > > On Mon, Jan 23, 2017 at 3:01 PM, Casey Stella <cestella@gmail.com>
> >> > wrote:
> >> > >
> >> > > > Hi All,
> >> > > >
> >> > > > I'm planning to expand the capabilities of PROFILE_GET and wanted
> to
> >> > pass
> >> > > > an idea past the community.
> >> > > >
> >> > > > *Current State*
> >> > > >
> >> > > > Currently, the functionality of PROFILE_GET is fairly
> >> straightforward:
> >> > > >
> >> > > >    - profile - The name of the profile.
> >> > > >    - entity - The name of the entity.
> >> > > >    - durationAgo - How long ago should values be retrieved from?
> >> > > >    - units - The units of 'durationAgo'.
> >> > > >    - groups_list - Optional, must correspond to the 'groupBy'
list
> >> used
> >> > > in
> >> > > >    profile creation - List (in square brackets) of groupBy values
> >> used
> >> > to
> >> > > >    filter the profile. Default is the empty list, meaning groupBy
> >> was
> >> > not
> >> > > > used
> >> > > >    when creating the profile.
> >> > > >    - config_overrides - Optional - Map (in curly braces) of
> >> name:value
> >> > > >    pairs, each overriding the global config parameter of the
same
> >> name.
> >> > > >    Default is the empty Map, meaning no overrides.
> >> > > >
> >> > > > This has the advantage of providing a relatively simple mechanism
> to
> >> > > > support the dominant use-case, gathering the profiles for a
> trailing
> >> > > > window.  The issues, however, are a couple:
> >> > > >
> >> > > >    - We may need more complex semantics for specifying the window
> >> > > >    (motivated below)
> >> > > >    - As such, this couples the gathering of the profiles with
the
> >> > > >    specification of the window.
> >> > > >
> >> > > > I propose to decouple these two concepts. I propose that we
> extract
> >> the
> >> > > > notion of the lookback into a separate, more featureful function
> >> called
> >> > > > PROFILE_LOOKBACK() which could be composed with an adjusted
> >> > PROFILE_GET,
> >> > > > whose arguments look like:
> >> > > >
> >> > > >
> >> > > >    - profile - The name of the profile.
> >> > > >    - entity - The name of the entity.
> >> > > >    - timestamps - The list of timestamps to retrieve
> >> > > >    - groups_list - Optional, must correspond to the 'groupBy'
list
> >> used
> >> > > in
> >> > > >    profile creation - List (in square brackets) of groupBy values
> >> used
> >> > to
> >> > > >    filter the profile. Default is the empty list, meaning groupBy
> >> was
> >> > not
> >> > > > used
> >> > > >    when creating the profile.
> >> > > >    - config_overrides - Optional - Map (in curly braces) of
> >> name:value
> >> > > >    pairs, each overriding the global config parameter of the
same
> >> name.
> >> > > >    Default is the empty Map, meaning no overrides.
> >> > > >
> >> > > > So, PROFILE_GET would have the output of PROFILE_LOOKBACK passed
> to
> >> it
> >> > as
> >> > > > its 3rd argument (e.g. PROFILE_GET( 'my_profile', 'my_entity',
> >> > > > PROFILE_LOOKBACK(...)) ).
> >> > > >
> >> > > > *Motivation for Change*
> >> > > >
> >> > > > The justification for this is that sometimes you want to compare
> >> time
> >> > > bins
> >> > > > for a long duration back, but you don't want to skew the data
by
> >> > > including
> >> > > > periods that aren't distributionally similar (due to seasonal
> data,
> >> for
> >> > > > instance).  You might want to compare a value to statistically
> >> baseline
> >> > > of
> >> > > > the median of the values for the same time window on the same
day
> >> for
> >> > the
> >> > > > last month (e.g. every tuesday at this time).
> >> > > >
> >> > > > Also, we might want a trailing window that does not start at
the
> >> > current
> >> > > > time (in wall-clock), but rather starts an hour back or from
the
> >> time
> >> > > that
> >> > > > the data was originally ingested.
> >> > > >
> >> > > >
> >> > > > *PROFILE_LOOKBACK*
> >> > > >
> >> > > > I propose that we support the following features:
> >> > > >
> >> > > >    - A starting point that is not current time
> >> > > >    - Sparse bins (i.e. the last hour for every tuesday for the
> last
> >> > > month)
> >> > > >    - The ability to skip events (e.g. weekends, holidays)
> >> > > >
> >> > > >
> >> > > > This would result in a new function with the following arguments:
> >> > > >
> >> > > >    -
> >> > > >
> >> > > >    from - The lookback starting point (default to now)
> >> > > >    -
> >> > > >
> >> > > >    fromUnits - The units for the lookback starting point
> >> > > >    -
> >> > > >
> >> > > >    to - The ending point for the lookback window (default to
from
> +
> >> > > > binSize)
> >> > > >    -
> >> > > >
> >> > > >    toUnits - The units for the lookback ending point
> >> > > >    -
> >> > > >
> >> > > >    including - A list of conditions which we would skip.
> >> > > >    - weekend
> >> > > >       - holiday
> >> > > >       - sunday through saturday
> >> > > >    -
> >> > > >
> >> > > >    excluding - A list of conditions which we would skip.
> >> > > >    - weekend
> >> > > >       - holiday
> >> > > >       - sunday through saturday
> >> > > >    -
> >> > > >
> >> > > >    binSize - The size of the lookback bin
> >> > > >    -
> >> > > >
> >> > > >    binUnits - The units of the lookback bin
> >> > > >
> >> > > > Given the number of arguments and their complexity and the fact
> that
> >> > > many,
> >> > > > many are optional, I propose that either
> >> > > >
> >> > > >    - PROFILE_LOOKBACK take a Map so that we can get essentially
> >> named
> >> > > >    params in stellar.
> >> > > >    - PROFILE_LOOKBACK accept a string backed by a DSL to express
> >> these
> >> > > >    criteria
> >> > > >
> >> > > >
> >> > > > Ok, so that's a lot to take in.  How about we look at some
> >> motivating
> >> > > > use-cases.
> >> > > >
> >> > > > *Base Case: A lookback of 1 hour ago*
> >> > > >
> >> > > > As a map, this would look like:
> >> > > >
> >> > > > PROFILE_LOOKBACK( { 'binSize' : 1, 'binUnits' : 'HOURS' } )
> >> > > >
> >> > > > As a DSL this would look like:
> >> > > > PROFILE_LOOKBACK( '1 hour bins from now')
> >> > > >
> >> > > >
> >> > > > *The same time window every tuesday for the last month starting
> one
> >> > hour
> >> > > > ago*
> >> > > >
> >> > > > Just to make this as clear as possible, if this is run at 3PM
on
> >> Monday
> >> > > > January 23rd, 2017, it would include the following bins:
> >> > > >
> >> > > >    - January 17th, 2PM - 3PM
> >> > > >    - January 10th, 2PM - 3PM
> >> > > >    - January 3rd, 2PM - 3PM
> >> > > >    - December 27th, 2PM - 3PM
> >> > > >
> >> > > > As a map, this would look like:
> >> > > >
> >> > > > PROFILE_LOOKBACK( { 'from' : 1, 'fromUnits' : 'HOURS', 'to' :
1,
> >> > > 'toUnits'
> >> > > > : 'MONTH', 'including' : [ 'tuesday' ], 'binSize' : 1, 'binUnits'
> :
> >> > > 'HOURS'
> >> > > > } )
> >> > > >
> >> > > > As a DSL this would look like:
> >> > > > PROFILE_LOOKBACK( '1 hour bins from 1 hour to 1 month including
> >> > > tuesdays')
> >> > > >
> >> > > > *The same time window every sunday for the last month starting
one
> >> hour
> >> > > ago
> >> > > > skipping holidays*
> >> > > >
> >> > > > Just to make this as clear as possible, if this is run at 3PM
on
> >> Monday
> >> > > > January 22rd, 2017, it would include the following bins:
> >> > > >
> >> > > >    - January 16th, 2PM - 3PM
> >> > > >    - January 9th, 2PM - 3PM
> >> > > >    - January 2rd, 2PM - 3PM
> >> > > >    - NOT December 25th
> >> > > >
> >> > > > As a map, this would look like:
> >> > > >
> >> > > > PROFILE_LOOKBACK( { 'from' : 1, 'fromUnits' : 'HOURS', 'to' :
1,
> >> > > 'toUnits'
> >> > > > : 'MONTH', 'including' : [ 'tuesday'], 'excluding' : [ 'holidays'
> ],
> >> > > > 'binSize' : 1, 'binUnits' : 'HOURS' } )
> >> > > >
> >> > > > As a DSL this would look like:
> >> > > > PROFILE_LOOKBACK( '1 hour bins from 1 hour to 1 month including
> >> > tuesdays
> >> > > > excluding holidays')
> >> > > >
> >> > > > *DSL vs API*
> >> > > >
> >> > > > So, here's my personal rundown of the two approaches:
> >> > > >
> >> > > > DSL:
> >> > > >
> >> > > >    - PRO
> >> > > >    - Clear.  As you can see, it reads like a sentence
> >> > > >       - Concise
> >> > > >    - CON:
> >> > > >       - More complex to implement
> >> > > >       - Another DSL to learn
> >> > > >
> >> > > > API:
> >> > > >
> >> > > >    - PRO
> >> > > >       - Simpler to implement (though marginally so, IMO)
> >> > > >    - CON
> >> > > >       - A bit more complex to understand (also, IMO)
> >> > > >
> >> > > > I'd like to solicit feedback from the community at this point:
> >> > > >
> >> > > >    - What do you think of this change?
> >> > > >    - Would you prefer the DSL, API or other approach?
> >> > > >
> >> > > > Thanks,
> >> > > >
> >> > > > Casey
> >> > > >
> >> > >
> >> > >
> >> > >
> >> > > --
> >> > > Nick Allen <nick@nickallen.org>
> >> > >
> >> >
> >>
> >>
> >>
> >> --
> >> Nick Allen <nick@nickallen.org>
> >>
> >
> >
>



-- 
Nick Allen <nick@nickallen.org>

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