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From "Marc P." <marc.par...@gmail.com>
Subject Re: [DISCUSS] Would a visibility histogram on a table be harmful?
Date Wed, 12 Oct 2016 11:12:27 GMT
What prevents the owners of the system from doing this in their own table?
Keeping track of that information is a use case of Accumulo. I think this
may be an example of external code that the user must install. Placing the
onus on the consumer mitigates concern that Mike "Mike" Drob and others may
have .

A new role wouldn't be needed if permissions were placed on the
user/table/namespace that stored this information, correct?

On Wed, Oct 12, 2016 at 12:56 AM, Christopher <ctubbsii@apache.org> wrote:

> Keith, Russ, myself (and possible others) were discussing this at the
> hackathon after the Accumulo Summit, and I think our consensus were
> basically this:
>
> We need a generic pluggable mechanism for injecting arbitrary user counters
> into the RFiles. We can then use these counters in custom compaction
> strategies, or other analysis. We can aggregate these counters at the
> tablet, and table levels, and expose them in the API.
>
> These counters could store information about visibility frequencies, number
> of delete entries, etc.
>
> The interface might just be a Function<Entry<Key,Value>,Map<String,
> Long>>.
>
> In the discussion, there were lots of variations on the theme, though. So,
> the actual implementation could vary. But, having something like this could
> support a large number of use cases beyond just the histogram case.
>
> On Tue, Oct 11, 2016 at 10:06 PM Josh Elser <josh.elser@gmail.com> wrote:
>
> > Trivially. We could do something more intelligent like also cache it in
> > metadata (updating with compactions). Don't read too much into the
> > implementation at this point; it was just the first idea I had about how
> we
> > could do it :). I'm more concerned with the idea and its security
> > implications right now.
> >
> > In general, it seems like people are ok with it protected by a new
> > permission role. Do you have more to add, Mike? Was your comment based on
> > your interpretation of how Accumulo works or more a concern about
> > implementing such a feature?
> >
> > On Oct 11, 2016 21:29, <dlmarion@comcast.net> wrote:
> >
> > > So, to get the set of visibilities used in a table, we would have to
> open
> > > all of the rfiles?
> > >
> > > > -----Original Message-----
> > > > From: Dylan Hutchison [mailto:dhutchis@cs.washington.edu]
> > > > Sent: Tuesday, October 11, 2016 3:43 PM
> > > > To: Accumulo Dev List
> > > > Subject: Re: [DISCUSS] Would a visibility histogram on a table be
> > > harmful?
> > > >
> > > > Interesting idea.  It begs the question: should we allow any custom
> > > index at
> > > > the RFile level?  If RFile indexes were user-extensible, then a
> > > visibility index
> > > > would be something any developer could write.  That said, we can
> still
> > > > include such an index as an example, and if we did it could be used
> by
> > > the
> > > > Accumulo monitor.
> > > >
> > > > The RFile-level sampling followed this path.  I would support further
> > > work
> > > > similar to it, though I admit I don't know how difficult a job it
> > > entails.
> > > > Bonus points if the index information could be accessed from
> iterators
> > > the
> > > > same way that sampled data can.
> > > >
> > > > I can't speak to the appropriateness of visibility histograms on the
> > > monitor
> > > > *by default*, but it would be a strictly useful feature if it could
> be
> > > enabled via
> > > > a conf option.
> > > >
> > > >
> > > > On Tue, Oct 11, 2016 at 12:20 PM, Josh Elser <josh.elser@gmail.com>
> > > wrote:
> > > >
> > > > > Today at Accumulo Summit, our own Russ Weeks gave a talk. One topic
> > he
> > > > > mentioned was the lack of insight into the distribution of data
> > marked
> > > > > with certain visibilities in a table. He presented an example
> similar
> > > to this:
> > > > >
> > > > > Image a hypothetical system backed by Accumulo which stores medical
> > > > > information. There are three labels in the system: PRIVATE,
> > > > > ANONYMIZED, and PUBLIC. PRIVATE data is that which could reasonably
> > be
> > > > > considered to identify the individual. ANONYMIZED data is some
> > altered
> > > > > version of the attribute that retains some portion of the original
> > > > > value, but is missing enough context to not identify the individual
> > > > > (e.g. converting the name "Josh Elser" to "J E"). PUBLIC data is
> for
> > > > > attributes which are cannot identify the individual.
> > > > >
> > > > > Doctors would be able to read the PRIVATE data, while researchers
> > > > > could only read the ANONYMIZED and PUBLIC data. This leads to a
> > > > > question: how much of each kind of data is in the system? Without
> > > > > knowing how much data is in the system, how can some application
> > > > > developer (who does not have the ability to read all of the PRIVATE
> > > > > data) know that their application is returning an reasonably
> correct
> > > > > amount of data? (there are many examples of questions which could
> be
> > > > > answer on this data alone)
> > > > >
> > > > > Concretely, this histogram would look like (50 records with
> PRIVATE,
> > > > > 50 with ANONYMIZED, and 20 with PUBLIC; 120 records total):
> > > > >
> > > > > ```
> > > > > PRIVATE: 50
> > > > > ANONYMIZED: 50
> > > > > PUBLIC: 20
> > > > > ```
> > > > >
> > > > > Technically, I think this would actually be relatively simple to
> > > > > implement. Inside of each RFile, we could maintain some histogram
> of
> > > > > the visibilities observed in that file. This would allow us to very
> > > > > easily report how much data in each table has each visibility
> label.
> > > > >
> > > > > However, would this feature be harmful to one of the core tenants
> of
> > > > > Accumulo? Or, is acknowledging the existence of data in Accumulo
> with
> > > > > a certain visibility acceptable? Would a new permission to use such
> > an
> > > > > API to access this information be sufficient to protect the data?
> > > > >
> > > > > - Josh
> > > > >
> > >
> > >
> >
>

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