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From Neeraja Rentachintala <nrentachint...@maprtech.com>
Subject Re: Dynamic UDFs support
Date Tue, 21 Jun 2016 16:46:00 GMT
While trying to figure out the design of where to load the jars from and
how to distribute across Drillbits, we need to keep one thing mind.
The primary goal of the Dynamic UDFs feature is that Central IT has
deployed a Drill cluster and users of the environment that are working with
the data on the cluster need to be able write their own UDFs and deploy
them onto the cluster without having to work with the IT/deployments teams
to restart Drill cluster.

To this extent, one question I have is who is responsible to place the UDF
jar on the specific locations on Drillbits Are we expecting end users to
keep the jars accessible for Drill to load. Or does the user simply supply
a local directory of the jar which is taken by Drill and deployed on all
the Drillbits in the cluster either with YARN or without YARN.



On Tue, Jun 21, 2016 at 9:34 AM, Arina Yelchiyeva <
arina.yelchiyeva@gmail.com> wrote:

> 1. DELETE command - I missed to indicate it document but had it in my mind.
> When user issues DELETE command, all UDF associated with indicated jar is
> removed from DrillFunctionRegistry. And then binary and source files are
> also deleted from UDF classpath.
>
> 2. Distribution race condition described by Paul
> User issues CREATE command and gets confirmation that UDFs is registered
> only if all drilllbits have confirmed that registration was successful.
> I don't expect user to start using UDFs in queries prior to CREATE command
> success / failure result, which is possible but strange.
>
> 3. DoY
> @Paul
> If instead of using $DRILL_HOME/jars/3rdparty/udf directly we use
> $DRILL_UDF environment variable which will be set during drillbit start
> (like $DRILL_LOG_DIR). Location stored in this variable will be added to
> Drill classpath during start.
> Will it ease DoY integration somehow?
>
> Kind regards
> Arina
>
> On Tue, Jun 21, 2016 at 7:15 PM yuliya Feldman <yufeldman@yahoo.com.invalid
> >
> wrote:
>
> > Just thoughts:
> > You can try to reuse distributed cache Let Drill AM do the needful in
> > terms of orchestrating UDF jars distribution.
> > But
> > I would be inclined to have a common path that is independent of the fact
> > that it is Drill on YARN or not, as maintaining two separate ways of
> > dealing with loading/unloading UDFs will be painful and error prone.
> > One more note (I left a comment in the doc) - not sure about
> authorization
> > model here - we need to have some.
> > Just my 2cThanks
> >
> >       From: Paul Rogers <progers@maprtech.com>
> >  To: "dev@drill.apache.org" <dev@drill.apache.org>
> >  Sent: Monday, June 20, 2016 7:32 PM
> >  Subject: Re: Dynamic UDFs support
> >
> > Hi Neeraja,
> >
> > The proposal calls for the user to copy the jar file to each Drillbit
> > node. The jar would go into a new $DRILL_HOME/jars/3rdparty/udf
> directory.
> >
> > In Drill-on-YARN (DoY), YARN is responsible for copying Drill code to
> each
> > node (which is good.) YARN puts that code in a location known only to
> YARN.
> > Since the location is private to YARN, the user can’t easily hunt down
> the
> > location in order to add the udf jar. Even if the user did find the
> > location, the next Drillbit to start would create a new copy of the Drill
> > software, without the udf jar.
> >
> > Second, in DoY we have separated user files from Drill software. This
> > makes it much easier to distribute the software to each node: we give the
> > Drill distribution tar archive to YARN, and YARN copies it to each node
> and
> > untars the Drill files. We make a separate copy of the (far smaller) set
> of
> > user config files.
> >
> > If the udf jar goes into a Drill folder ($DRILL_HOME/jars/3rdparty/udf),
> > then the user would have to rebuild the Drill tar file each time they
> add a
> > udf jar. When I tried this myself when building DoY, I found it to be
> slow
> > and error-prone.
> >
> > So, the solution is to place the udf code in the new “site” directory:
> > $DRILL_SITE/jars. That’s what that is for. Then, let DoY automatically
> > distribute the code to every node. Perfect! Except that it does not work
> to
> > dynamically distribute code after Drill starts.
> >
> > For DoY, the solution requirements are:
> >
> > 1. Distribute code using Drill itself, rather than manually copying jars
> > to (unknown) Drill directories.
> > 2. Ensure the solution works even if another Drillbit is spun up later,
> > and uses the original Drill tar file.
> >
> > I’m thinking we want to leverage DFS: place udf files into a well-known
> > DFS directory. Register the udf into, say, ZK. When a new Drillbit
> starts,
> > it looks for new udf jars in ZK, copies the file to a temporary location,
> > and launches. An existing Drill is notified of the change and does the
> same
> > download process. Clean-up is needed at some point to remove ZK entries
> if
> > the udf jar becomes statically available on the next launch. That needs
> > more thought.
> >
> > We’d still need the phases mentioned earlier to ensure consistency.
> >
> > Suggestions anyone as to how to do this super simply & still get it to
> > work with DoY?
> >
> > Thanks,
> >
> > - Paul
> >
> > > On Jun 20, 2016, at 7:18 PM, Neeraja Rentachintala <
> > nrentachintala@maprtech.com> wrote:
> > >
> > > This will need to work with YARN (Once Drill is YARN enabled, I would
> > > expect a lot of users using it in conjunction with YARN).
> > > Paul, I am not clear why this wouldn't work with YARN. Can you
> elaborate.
> > >
> > > -Neeraja
> > >
> > > On Mon, Jun 20, 2016 at 7:01 PM, Paul Rogers <progers@maprtech.com>
> > wrote:
> > >
> > >> Good enough, as long as we document the limitation that this feature
> > can’t
> > >> work with YARN deployment as users generally do not have access to the
> > >> temporary “localization” directories where the Drill code is placed
by
> > YARN.
> > >>
> > >> Note that the jar distribution race condition issue occurs with the
> > >> proposed design: I believe I sketched out a scenario in one of the
> > earlier
> > >> comments. Drillbit A receives the CREATE FUNCTION command. It tells
> > >> Drillbit B. While informing the other Drillbits, Drillbit B plans and
> > >> launches a query that uses the function. Drillbit Z starts execution
> of
> > the
> > >> query before it learns from A about the new function. This will be
> rare
> > —
> > >> just rare enough to create very hard to reproduce bugs.
> > >>
> > >> The only reliable solution is to do the work in multiple passes:
> > >>
> > >> Pass 1: Ask each node to load the function, but not make it available
> to
> > >> the planner. (it would be available to the execution engine.)
> > >> Pass 2: Await confirmation from each node that this is done.
> > >> Pass 3: Alert every node that it is now free to plan queries with the
> > >> function.
> > >>
> > >> Finally, I wonder if we should design the SQL syntax based on a
> > long-term
> > >> design, even if the feature itself is a short-term work-around.
> Changing
> > >> the syntax later might break scripts that users might write.
> > >>
> > >> So, the question for the group is this: is the value of semi-complete
> > >> feature sufficient to justify the potential problems?
> > >>
> > >> - Paul
> > >>
> > >>> On Jun 20, 2016, at 6:15 PM, Parth Chandra <pchandra@maprtech.com>
> > >> wrote:
> > >>>
> > >>> Moving discussion to dev.
> > >>>
> > >>> I believe the aim is to do a simple implementation without the
> > complexity
> > >>> of distributing the UDF. I think the document should make this
> > limitation
> > >>> clear.
> > >>>
> > >>> Per Paul's point on there being a simpler solution of just having
> each
> > >>> drillbit detect the if a UDF is present, I think the problem is if
a
> > UDF
> > >>> get's deployed to some but not all drillbits. A query can then start
> > >>> executing but not run successfully. The intent of the create commands
> > >> would
> > >>> be to ensure that all drillbits have the UDF or none would.
> > >>>
> > >>> I think Jacques' point about ownership conflicts is not addressed
> > >> clearly.
> > >>> Also, the unloading is not clear. The delete command should probably
> > >> remove
> > >>> the UDF and unload it.
> > >>>
> > >>>
> > >>> On Fri, Jun 17, 2016 at 11:19 AM, Paul Rogers <progers@maprtech.com>
> > >> wrote:
> > >>>
> > >>>> Reviewed the spec; many comments posted. Three primary comments
for
> > the
> > >>>> community to consider.
> > >>>>
> > >>>> 1. The design conflicts with the Drill-on-YARN project. Is this
a
> > >> specific
> > >>>> fix for one unique problem, or is it worth expanding the solution
to
> > >> work
> > >>>> with Drill-on-YARN deployments? Might be hard to make the two work
> > >> together
> > >>>> later. See comments in docs for details.
> > >>>>
> > >>>> 2. Have we, by chance, looked at how other projects handle code
> > >>>> distribution? Spark, Storm and others automatically deploy code
> across
> > >> the
> > >>>> cluster; no manual distribution to each node. The key difference
> > between
> > >>>> Drill and others is that, for Storm, say, code is associated with
a
> > job
> > >>>> (“topology” in Storm terms.) But, in Drill, functions are global
and
> > >> have
> > >>>> no obvious life cycle that suggests when the code can be unloaded.
> > >>>>
> > >>>> 3. Have considered the class loader, dependency and name space
> > isolation
> > >>>> issues addressed by such products as Tomcat (web apps) or Eclipse
> > >>>> (plugins)? Putting user code in the same namespace as Drill code
 is
> > >> quick
> > >>>> & dirty. It turns out, however, that doing so leads to problems
that
> > >>>> require long, frustrating debugging sessions to resolve.
> > >>>>
> > >>>> Addressing item 1 might expand scope a bit. Addressing items 2
and 3
> > >> are a
> > >>>> big increase in scope, so I won’t be surprised if we leave those
> > issues
> > >> for
> > >>>> later. (Though, addressing item 2 might be the best way to address
> > item
> > >> 1.)
> > >>>>
> > >>>> If we want a very simple solution that requires minimal change,
> > perhaps
> > >> we
> > >>>> can use an even simpler solution. In the proposed design, the user
> > still
> > >>>> must distribute code to all the nodes. The primary change is to
tell
> > >> Drill
> > >>>> to load (or unload) that code. Can accomplish the same result easier
> > >> simply
> > >>>> by having Drill periodically scan certain directories looking for
> new
> > >> (or
> > >>>> removed) jars? Still won’t work with YARN, or solve the name
space
> > >> issues,
> > >>>> but will work for existing non-YARN Drill users without new SQL
> > syntax.
> > >>>>
> > >>>> Thanks,
> > >>>>
> > >>>> - Paul
> > >>>>
> > >>>>> On Jun 16, 2016, at 2:07 PM, Jacques Nadeau <jacques@dremio.com>
> > >> wrote:
> > >>>>>
> > >>>>> Two quick thoughts:
> > >>>>>
> > >>>>> - (user) In the design document I didn't see any discussion
of
> > >>>>> ownership/conflicts or unloading. Would be helpful to see the
> > thinking
> > >>>> there
> > >>>>> - (dev) There is a row oriented facade via the
> > >>>>> FieldReader/FieldWriter/ComplexWriter classes. That would be
a good
> > >> place
> > >>>>> to start when trying to implement an alternative interface.
> > >>>>>
> > >>>>>
> > >>>>> --
> > >>>>> Jacques Nadeau
> > >>>>> CTO and Co-Founder, Dremio
> > >>>>>
> > >>>>> On Thu, Jun 16, 2016 at 11:32 AM, John Omernik <john@omernik.com>
> > >> wrote:
> > >>>>>
> > >>>>>> Honestly, I don't see it as a priority issue. I think some
of the
> > >> ideas
> > >>>>>> around community java UDFs could be a better approach.
I'd hate to
> > >> take
> > >>>>>> away from other work to hack in something like this.
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>> On Thu, Jun 16, 2016 at 1:19 PM, Paul Rogers <
> progers@maprtech.com>
> > >>>> wrote:
> > >>>>>>
> > >>>>>>> Ted refers to source code transformation. Drill gains
its speed
> > from
> > >>>>>> value
> > >>>>>>> vectors. However, VVs are a far cry from the row-based
interface
> > that
> > >>>>>> most
> > >>>>>>> mere mortals are accustomed to using. Since VVs are
very type
> > >> specific,
> > >>>>>>> code is typically generated to handle the specifics
of each type.
> > >>>>>> Accessing
> > >>>>>>> VVs in Jython may be a bit of a challenge because of
the
> "impedence
> > >>>>>>> mismatch" between how VVs work and the row-and-column
view
> expected
> > >> by
> > >>>>>> most
> > >>>>>>> (non-Drill) developers.
> > >>>>>>>
> > >>>>>>> I wonder if we've considered providing a row-oriented
"facade"
> that
> > >> can
> > >>>>>> be
> > >>>>>>> used by roll-your own data sources and user-defined
row
> transforms?
> > >>>> Might
> > >>>>>>> be a hiccup in the fast VV pipeline, but might be handy
for users
> > >>>> willing
> > >>>>>>> to trade a bit of speed for convenience. With such
a facade, the
> > >> Jython
> > >>>>>> row
> > >>>>>>> transforms that John mentions could be quite simple.
> > >>>>>>>
> > >>>>>>> On Thu, Jun 16, 2016 at 10:36 AM, Ted Dunning <
> > ted.dunning@gmail.com
> > >>>
> > >>>>>>> wrote:
> > >>>>>>>
> > >>>>>>>> Since UDF's use source code transformation, using
Jython would
> be
> > >>>>>>>> difficult.
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>> On Thu, Jun 16, 2016 at 9:42 AM, Arina Yelchiyeva
<
> > >>>>>>>> arina.yelchiyeva@gmail.com> wrote:
> > >>>>>>>>
> > >>>>>>>>> Hi Charles,
> > >>>>>>>>>
> > >>>>>>>>> not that I am aware of. Proposed solution doesn't
invent
> anything
> > >>>>>> new,
> > >>>>>>>> just
> > >>>>>>>>> adds possibility to add UDFs without drillbit
restart. But
> > >>>>>>> contributions
> > >>>>>>>>> are welcomed.
> > >>>>>>>>>
> > >>>>>>>>> On Thu, Jun 16, 2016 at 4:52 PM Charles Givre
<
> cgivre@gmail.com>
> > >>>>>>> wrote:
> > >>>>>>>>>
> > >>>>>>>>>> Arina,
> > >>>>>>>>>> Has there been any discussion about making
it possible via
> > Jython
> > >>>>>> or
> > >>>>>>>>>> something for users to write simple UDFs
in Python?
> > >>>>>>>>>> My ideal would be to have this capability
integrated in the
> web
> > >> GUI
> > >>>>>>>> such
> > >>>>>>>>>> that a user could write their UDF (in Python)
right there,
> > submit
> > >>>>>> it
> > >>>>>>>> and
> > >>>>>>>>> it
> > >>>>>>>>>> would be deployed to Drill if it passes
validation tests.
> > >>>>>>>>>> —C
> > >>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>>> On Jun 16, 2016, at 09:34, Arina Yelchiyeva
<
> > >>>>>>>>> arina.yelchiyeva@gmail.com>
> > >>>>>>>>>> wrote:
> > >>>>>>>>>>>
> > >>>>>>>>>>> Hi all!
> > >>>>>>>>>>>
> > >>>>>>>>>>> I have created Jira to allow dynamic
UDFs support in Drill (
> > >>>>>>>>>>> https://issues.apache.org/jira/browse/DRILL-4726).
There is
> a
> > >>>>>> link
> > >>>>>>>> to
> > >>>>>>>>>>> design document in Jira description.
> > >>>>>>>>>>> Comments or suggestions are welcomed.
> > >>>>>>>>>>>
> > >>>>>>>>>>> Kind regards
> > >>>>>>>>>>> Arina
> > >>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>>
> > >>>>>>>
> > >>>>>>
> > >>>>
> > >>>>
> > >>
> > >>
> >
> >
> >
>

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