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From Casey Stella <ceste...@gmail.com>
Subject Re: [DISCUSS] Expansion of the capabilities of PROFILE_GET
Date Tue, 31 Jan 2017 19:01:57 GMT
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>
>>
>
>

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