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From Adam P Fuchs <adam.p.fu...@ugov.gov>
Subject Re: [PROPOSAL] Accumulo for the Apache Incubator
Date Sat, 03 Sep 2011 15:35:53 GMT
Hi Bernd,

The latest stable release of Accumulo contains roughly 200,000 lines of code, of which about
85,000 are machine generated thrift code. Of the remaining code, about 15,000 lines are derived
from other Apache projects, and about 1,500 of those are derived from HBase code. The code
derived from HBase comprises a query caching layer (block cache, index cache, multi-level
LRU logic, etc.).

More broadly, there are aspects of both systems that share common design elements, while many
of the advanced features of the two systems are complementary. For example, the iterator framework
in Accumulo and the coprocessor framework in HBase are distinct mechanisms for server-side
execution of user-defined functions that can be used to encode different types of applications.
The iterator framework provides a unique capability to encode functions (e.g. filtering and
aggregation) within the compaction steps that happen in the background of the tablet server/region
server, but they cannot be as easily used for inter-process communication as coprocessors
without introducing the possibility of deadlock.

In addition to the complementary features, many of the low-level designs of the two projects,
while supporting similar functionality, differ in various dimensions of performance. Some
examples of this are the way we implement column family partitioning/locality groups, our
file selection algorithms for compactions, tablet/region metadata handling, RPC libraries,
user-level security, testing suites (which could also be considered complementary), administrative
tools, methods of dealing with the java garbage collector, server-side threading models, client
code threading models, file compression, Key classes, and write-ahead logs.

Going forward, both projects are going to be able to adapt complementary aspects of the other
(we're already doing this with the query cache, and we are investigating adapting coprocessors
from HBase). We look at having two systems that are so similar in core functionality but differ
in implementation as a great opportunity for empirical exploration of the design space that
will benefit both projects. I think that having both projects hosted in Apache gives us more
incentive and opportunity to improve API compatibility between the two. If/when we find that
the design space exploration has settled I expect that this will also be the best avenue towards
merging the two projects if that becomes the desired goal.

Cheers,
Adam



----- Original Message -----
From: Bernd Fondermann <bernd.fondermann@googlemail.com>
To: general@incubator.apache.org
Sent: Sat, 03 Sep 2011 11:17:10 -0000
Subject: Re: [PROPOSAL] Accumulo for the Apache Incubator

On Friday, September 2, 2011, Billie J Rinaldi <billie.j.rinaldi@ugov.gov>
wrote:
> Greetings,
>
> I would like to propose Accumulo to be an Apache Incubator project.
 Accumulo is a distributed key/value store that provides expressive
cell-level access labels and a server-side programming mechanism that can
modify key/value pairs at various points in the data management process.  It
is based on Google's BigTable design and runs over Apache Hadoop and
Zookeeper.

How is the project's relation to HBase? Especially, how much code - if any -
in the Accumolo code base is directly taken from HBase?

Thanks,

 Bernd


>
> Here is a link to the proposal in the Incubator wiki:
> http://wiki.apache.org/incubator/AccumuloProposal
>
> I've also pasted the initial contents below.
>
> Thanks,
> Billie Rinaldi
>
>
> = Accumulo Proposal =
>
> == Abstract ==
> Accumulo is a distributed key/value store that provides expressive,
cell-level access labels.
>
> == Proposal ==
> Accumulo is a sorted, distributed key/value store based on Google's
BigTable design.  It is built on top of Apache Hadoop, Zookeeper, and
Thrift.  It features a few novel improvements on the BigTable design in the
form of cell-level access labels and a server-side programming mechanism
that can modify key/value pairs at various points in the data management
process.
>
> == Background ==
> Google published the design of BigTable in 2006.  Several other open
source projects have implemented aspects of this design including HBase,
CloudStore, and Cassandra.  Accumulo began its development in 2008.
>
> == Rationale ==
> There is a need for a flexible, high performance distributed key/value
store that provides expressive, fine-grained access labels.  The communities
we expect to be most interested in such a project are government, health
care, and other industries where privacy is a concern.  We have made much
progress in developing this project over the past 3 years and believe both
the project and the interested communities would benefit from this work
being openly available and having open development.
>
> == Current Status ==
>
> === Meritocracy ===
> We intend to strongly encourage the community to help with and contribute
to the code.  We will actively seek potential committers and help them
become familiar with the codebase.
>
> === Community ===
> A strong government community has developed around Accumulo and training
classes have been ongoing for about a year.  Hundreds of developers use
Accumulo.
>
> === Core Developers ===
> The developers are mainly employed by the National Security Agency, but we
anticipate interest developing among other companies.
>
> === Alignment ===
> Accumulo is built on top of Hadoop, Zookeeper, and Thrift.  It builds with
Maven.  Due to the strong relationship with these Apache projects, the
incubator is a good match for Accumulo.
>
> == Known Risks ==
> === Orphaned Products ===
> There is only a small risk of being orphaned.  The community is committed
to improving the codebase of the project due to its fulfilling needs not
addressed by any other software.
>
> === Inexperience with Open Source ===
> The codebase has been treated internally as an open source project since
its beginning, and the initial Apache committers have been involved with the
code for multiple years.  While our experience with public open source is
limited, we do not anticipate difficulty in operating under Apache's
development process.
>
> === Homogeneous Developers ===
> The committers have multiple employers and it is expected that committers
from different companies will be recruited.
>
> === Reliance on Salaried Developers ===
> The initial committers are all paid by their employers to work on Accumulo
and we expect such employment to continue.  Some of the initial committers
would continue as volunteers even if no longer employed to do so.
>
> === Relationships with Other Apache Products ===
> Accumulo uses Hadoop, Zookeeper, Thrift, Maven, log4j, commons-lang, -net,
-io, -jci, -collections, -configuration, -logging, and -codec.
>
> === Relationship to HBase ===
> Accumulo and HBase are both based on the design of Google's BigTable, so
there is a danger that potential users will have difficulty distinguishing
the two or that they will not see an incentive in adopting Accumulo.  There
are a few key areas in which Accumulo differs from HBase.  Some of the
desired features of Accumulo could be incorporated into HBase, however the
most important of these may be unlikely to be adopted (see cell-level access
labels and iterators below).  It is a possibility that the codebases will
ultimately converge, but the number of differences at the current time
warrants a separate project for Accumulo.
>
> ==== Access Labels ====
> Accumulo has an additional portion of its key that sorts after the column
qualifier and before the timestamp.  It is called column visibility and
enables expressive cell-level access control.  Authorizations are passed
with each query to control what data is returned to the user.  The column
visibilities are boolean AND and OR combinations of arbitrary strings (such
as "(A&B)|C") and authorizations are sets of strings (such as {C,D}).
>
> ==== Iterators ====
> Accumulo has a novel server-side programming mechanism that can modify the
data written to disk or returned to the user.  This mechanism can be
configured for any of the scopes where data is read from or written to disk.
 It can be used to perform joins on data within a single tablet.
>
> ==== Flexibility ====
> HBase requires the user to specify the set of column families to be used
up front.  Accumulo places no restrictions on the column families.  Also,
each column family in HBase is stored separately on disk.  Accumulo allows
column families to be grouped together on disk, as does BigTable.  This
enables users to configure how their data is stored, potentially providing
improvements in compression and lookup speeds.  It gives Accumulo a
row/column hybrid nature, while HBase is currently column-oriented.
>
> ==== Testing ====
> Accumulo has testing frameworks that have resulted in its achieving a high
level of correctness and performance.  We have observed that under some
configurations and conditions Accumulo will outperform HBase and provide
greater data integrity.
>
> ==== Logging ====
> HBase uses a write-ahead log on the Hadoop Distributed File System.
 Accumulo has its own logging service that does not depend on communication
with the HDFS NameNode.
>
> ==== Storage ====
> Accumulo has a relative key file format that improves compression.
>
> ==== Areas in which HBase features improvements over Accumulo ====
> in memory tables, upserts, coprocessors, connections to other projects
such as Cascading and Pig
>
> === Expectations ===
> There is a risk that Accumulo will be criticized for not providing
adequate security.  The access labels in Accumulo do not in themselves
provide a complete security solution, but are a mechanism for labeling each
piece of data with the authorizations that are necessary to see it.
>
> === Apache Brand ===
> Our interest in releasing this code as an Apache incubator project is due
to its strong relationship with other Apache projects, i.e. Hadoop,
Zookeeper, and HBase.
>
> == Documentation ==
> There is not currently documentation about Accumulo on the web, but a fair
amount of documentation and training materials exists and will be provided
on the Accumulo wiki at apache.org.  Also, a paper discussing YCSB results
for Accumulo will be presented at the 2011 Symposium on Cloud Computing.
>
> == Initial Source ==
> Accumulo has been in development since spring 2008.  There are hundreds of
developers using it and tens of developers have contributed to it.  The core
codebase consists of 200,000 lines of code (mainly Java) and 100s of pages
of documentation.  There are also a few projects built on top of Accumulo
that may be added to its contrib in the future.  These include support for
Hive, Matlab, YCSB, and graph processing.
>
> == Source and Intellectual Property Submission Plan ==
> Accumulo core code, examples, documention, and training materials will be
submitted by the National Security Agency.
>
> We will also be soliciting contributions of further plugins from MIT
Lincoln Labs, Carnegie Mellon University, and others.
>
> Accumulo has been developed by a mix of government employees and private
companies under government contract.  Material developed by government
employees is in the public domain and no U.S. copyright exists in works of
the federal government.  For the contractor developed material in the
initial submission, the U.S. Government has sufficient authority per the
ICLA from the copyright owner to contribute the Accumulo code to the
incubator.
>
> There has been some discussion regarding accepting contributions from US
Government sources on
[https://issues.apache.org/jira/browse/LEGAL-93LEGAL-93]. We propose
that the NSA will sign an ICLA/CCLA if that document
could be slightly modified to explicitly address copyright in works of
government employees. Specifically, we propose that the definition of “You”
be modified to include “the copyright owner, the owner of a Contribution not
subject to copyright, or legal entity authorized by the copyright owner that
is making this Agreement.” In addition, section 2, the copyright license
grant be modified after “You hereby grant” that either states “to the extent
authorized by law” or “to the extent copyright exists in the Contribution.”
 These changes will permit US Government employee developed work to be
included.
>
> One proposed solution is to form a Collaborative Research and Development
Agreement (CRADA) between the Apache Software Foundation and the US
Government, but this will not solve the underlying problem that U.S. law
does not grant copyright to works of government employees.  At this time a
CRADA is not necessary but should it be determined that a CRADA is
necessary, we would like to work through that process during the incubation
phase of Accumulo rather than before acceptance as this may take time to
enter into an agreement.
>
> == External Dependencies ==
> jetty (Apache and EPL), jline (BSD), jfreechart (LGPL), jcommon (LGPL),
slf4j (MIT), junit (CPL)
>
> == Cryptography ==
> none
>
> == Required Resources ==
>  * Mailing Lists
>   * accumulo-private
>   * accumulo-dev
>   * accumulo-commits
>   * accumulo-user
>
>  * Subversion Directory
>   * https://svn.apache.org/repos/asf/incubator/accumulo
>
>  * Issue Tracking
>   * JIRA Accumulo (ACCUMULO)
>
>  * Continuous Integration
>   * Jenkins builds on https://builds.apache.org/
>
>  * Web
>   * http://incubator.apache.org/accumulo/
>   * wiki at http://wiki.apache.org or http://cwiki.apache.org
>
> == Initial Committers ==
>  * Aaron Cordova (aaron at cordovas dot org)
>  * Adam Fuchs (adam.p.fuchs at ugov dot gov)
>  * Eric Newton (ecn at swcomplete dot com)
>  * Billie Rinaldi (billie.j.rinaldi at ugov dot gov)
>  * Keith Turner (keith.turner at ptech-llc dot com)
>  * John Vines (john.w.vines at ugov dot gov)
>  * Chris Waring (christopher.a.waring at ugov dot gov)
>
> == Affiliations ==
>  * Aaron Cordova, The Interllective
>  * Adam Fuchs, National Security Agency
>  * Eric Newton, SW Complete Incorporated
>  * Billie Rinaldi, National Security Agency
>  * Keith Turner, Peterson Technology LLC
>  * John Vines, National Security Agency
>  * Chris Waring, National Security Agency
>
> == Sponsors ==
>  * Champion: Doug Cutting
>  * Nominated Mentors: Benson Margulies, ?, ?
>  * Sponsoring Entity: Apache Incubator
>
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