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From Hyunsik Choi <>
Subject [VOTE] Accept S2Graph into Apache Incubation
Date Tue, 24 Nov 2015 00:53:31 GMT
Hello folks,

Thanks for all the feedback on the S2Graph Proposal.

I would like to call for a [VOTE] on S2Graph joining the ASF as an
incubation project.

The vote is open for at least 72 hours:

[ ] +1 accept S2Graph in the Incubator
[ ] ±0
[ ] -1 (please give reason)

S2Graph provides a scalable distributed graph database engine over a
key/value store such as HBase. S2Graph provides a fully asynchronous
API to manipulate data as a property graph model and fast
breadth-first-search queries over the graph. S2Graph is designed for
OLTP-like workloads on graph data sets instead of batch processing,
and it also provides INSERT/UPDATE operations on them.

The proposal is available on the wiki here:

Best regards,

<COPY of the proposal wiki>
= S2Graph Proposal =

== Abstract ==
S2Graph is a distributed and scalable OLTP graph database built on
Apache HBase to support fast traversal of extremely large graphs.

== Proposal ==
S2Graph provides a scalable distributed graph database engine over a
key/value store such as HBase. S2Graph provides a fully asynchronous
API to manipulate data as a property graph model and fast
breadth-first-search queries over the graph. S2Graph is designed for
OLTP-like workloads on graph data sets instead of batch processing.
Also, S2Graph provides INSERT/UPDATE operations. Its name 'S2Graph' is
an abbreviated word of '''S'''uper '''S'''imple '''Graph''' Database.

Here are additional materials to introduce S2Graph.
 * HBaseCon 2015 -
 * Apache: Big Data 2015 -

== Background ==
S2Graph initially started as an internal project at to
efficiently store user relations and user activities as one large
graph and to provide a unified query interface to traverse the graph.
It was open sourced on Github about a 3 months ago in June 2015.

Over time, S2Graph using HBase as the storage tier has begun by
adapted into various applications, such as messaging, social feeds,
and realtime recommendations at Kakao.

Users can benefit by using S2Graph`s generalized high level graph
abstraction API instead of querying via low-level key/value APIs, just
as Apache Phoenix provides a SQL layer over HBase.

== Rationale ==
Graph data (highly interconnected data) is very abundant and important
these days. When users have a multitude of relationships, each with
complex properties associated with them, a graph model is more
intuitive and efficient than tabular formats (RDBMS).

There are many ASF projects that provide SQL tiers, but there is no
ASF projects that provide a scalable graph layer on top of the
existing hadoop ecosystem. When graph data grows to the trillion edge
scale, the process of traversing takes a long time and can be costly.
However, with the benefit of HBase`s scalable architecture, S2Graph
can traverse large graphs in a breadth-first-search manner

S2Graph also interoperates with several existing Apache projects
(HBase, Apache Spark) to provide means of merging real time events and
batch processed data using the property graph data model.

Many developers run their own domain specific API servers to serve
their data products, but a graph model is general and the S2Graph API
fully supports traversal of the graph, so it can be used as a scalable
general purpose API serving layer for various domains. As long as data
can be modeled as graph, then users can avoid tedious work developing
customized API servers if they use S2Graph.

== Initial Goals ==
The initial goals will be to move the existing codebase to Apache and
integrate with the Apache development process. Once this is
accomplished, we plan for incremental development and releases that
follow the Apache guidelines.

== Current Status ==

=== Meritocracy ===
S2Graph operated on meritocratic principles from the get go.
Currently, all the discussions pertaining to S2Graph development are
public on Github. The current incubation proposal includes the major
code contributors to S2Graph. Several additional people have worked on
the S2graph codebase for industry use cases and would be interested in
becoming committers. We are starting with a small committer group and
we plan to add additional committers following an open merit-based
decision process during the incubation phase.

=== Community ===
We have already begun building a community but at this time the
community consists only of S2Graph developers – all Kakao employees –
and prospective users. S2Graph seeks to develop developer and user
communities during incubation.

=== Core Developers ===
S2Graph is currently being designed and developed by 2 engineers from
Kakao. - Doyung Yoon, Deawon Jeong.

=== Alignment ===
Our proposed S2Graph effort aligns closely with Apache HBase. The
HBase project perimeter is denoted by a simple byte-array based
Create, Read, Update, Delete and Scan API with no current plans to
extend beyond these bounds.

S2Graph complements this with a higher level API for a property graph model.

S2Graph was designed to offer a scalable distributed graph database
skin over HBase from the beginning in order to provide a property
graph model and breadth first search, and will continue to focus on
providing the graph model.

== Known Risks ==
=== Orphaned Products ===
The core developers of S2Graph team plan to work full time on this
project. There is very little risk of S2Graph getting orphaned since
at least one large company (Kakao) is extensively using it in their
production HBase clusters. For example, currently there are 20+ use
cases with more than 1+Trillion edges and 140 million breadth first
search query requests per minute using S2Graph in production. We plan
to extend and diversify this community further through Apache.

=== Inexperience with Open Source ===
The core developers are all active users and followers of open source.
They are already committers and contributors to the S2Graph Github
project. All have been involved with the source code that has been
released under an open source license. Though the core set of
Developers do not have Apache Open Source experience, there are plans
to onboard individuals with Apache open source experience to the

=== Homogenous Developers ===
Most committers in this proposal belong to the same institution
(Kakao). The engagement of these committers goes well beyond the
necessary development to support research, and all committers work on
S2Graph full time. Several people from other institutions are working
on and are familiar with the S2Graph codebase. We will work to attract
them as future committers during the incubation phase, following a
merit-based approach.

=== Reliance on Salaried Developers ===
Kakao invested in S2Graph as the distributed graph database solution
on top of HBase and some of its key engineers are working full time on
the project. We look forward to other Apache developers and
researchers contributing to the project. Also key to addressing the
risk associated with relying on Salaried developers from a single
entity is to increase the diversity of the contributors and actively
lobby for Domain experts in the graph database space to contribute.
Apache S2Graph intends to do this.

=== Relationships with Other Apache Products ===
S2Graph has a strong relationship and dependency with Apache HBase and
Apache Spark. Being part of Apache’s Incubation community, could help
with a closer collaboration among these two projects and as well as

In terms of graph processing frameworks, S2Graph and Apache Giraph
look similar. However, their goals are apparently different to each
other. Giraph aims at analytical batch processing on immutable graph
data sets. In contrast, S2Graph is designed for OLTP-like workloads on
graph data sets, and S2Graph provides INSERT/UPDATE operations too.

=== An Excessive Fascination with the Apache Brand ===
S2Graph is proposing to enter incubation at Apache in order to help
efforts to diversify the committer-base, not so much to capitalize on
the Apache brand. The S2Graph project is in production use already
inside Kakao, but is not expected to be a Kakao product for external
customers. As such, the S2Graph project is not seeking to use the
Apache brand as a marketing tool.

== Documentation ==
Information about S2Graph can be found at The following links provide more
information about S2Graph in open source:
 * S2Graph web site:
 * Codebase at Github:
 * Issue Tracking:
 * User community:!forum/s2graph

== Initial Source ==

The S2Graph codebase is currently hosted on Github:

=== Source and Intellectual Property Submission Plan ===

Currently, the S2Graph codebase is distributed under the Apache 2.0 License.

== External Dependencies ==

Beyond relying on Apache HBase, S2Graph has the following external dependencies:
 * Asynchbase (BSD)
 * Play Framework (Apache 2.0 license)
 * Scala (
 * Spark (Apache 2.0 license)
 * Kafka (Apache 2.0 license)

== Required Resources ==

=== Mailing list ===

We will migrate our mailing lists to the following:

=== Source control ===

The S2Graph team would like to use Git for source code control, due to
our current use of Git. We request a writeable Git repo for S2Graph,
and mirroring to be set up to Github through INFRA.

=== Issue Tracking ===

S2Graph currently uses the github issue tracking system associated
with its github repo ( We
will migrate to the Apache JIRA

=== Other Resources ===

 * Jenkins/Hudson for builds and test running.
 * Wiki for documentation purposes.
 * Blog to improve project dissemination.

== Initial Committers ==

 * Doyung Yoon <shom83 at gmail dot com>
 * Daewon Jeong <blueiur at gmail dot com>
 * Jaesang Kim <honeysleep at gmail dot com>
 * Hwansung Yu <deejayfwan at gmail dot com>
 * Min-Seok Kim < at gmail dot com>
 * Chul Kang <miralchul at gmail dot com>
 * Luke Han <lukehan at apache dot org>
 * Alexander Bezzubov <bzz at apache dot org>

== Affiliations ==

 * Doyung Yoon, Kakao
 * Daewon Jeong, Kakao
 * Jaesang Kim, Kakao
 * Hwansung Yu, Kakao
 * Min-Seok Kim, Kakao
 * Chul Kang, Kakao,
 * Luke Han, Ebay Inc.
 * Alexander Bezzubov, NFLabs

== Sponsors ==

=== Champion ===
Hyunsik Choi

=== Nominated Mentors ===
 * Andrew Purtell - Apache Member, Salesforce
 * Sergio Fernández - Apache Member, Redlink
 * Hyunsik Choi - Apache Member, Gruter Inc.
 * Seetharam Venkatesh - IPMC, Hortonworks Inc.

=== Sponsoring Entity ===

 * The Apache Incubator

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