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From Jitendra Pandey <>
Subject [DISCUSS] Concur for Apache Incubator
Date Wed, 23 Nov 2016 08:29:28 GMT
Dear all,
    We would like to start a discussion on accepting Concur, a java implementation for RAFT
consensus protocol, into the Apache Incubator.

Here is the link to the proposal on the wiki

The text of the proposal is included below.



= Concur Proposal =

== Abstract ==
Concur is an open source java implementation for RAFT consensus protocol[1]. RAFT is being
used successfully as an alternative to Paxos to implement a consistently replicated log. RAFT
is proven to be safe and is designed to be simpler to understand.

== Proposal ==
Concur is implemented as an independent RAFT library that can be used by any application to
manage their replicated logs or replicated state machines. The implementation closely follows
the original design proposed in the RAFT paper.

== Background ==
Replicated log is a frequently used technique in distributed systems for reliability and parallelism.
The consistency of replicas is an important requirement to ensure the correctness of the applications
accessing the data in these replicas. Many algorithms have been proposed and used to maintain
consistency and correctness. RAFT paper was proposed in 2012 and has gained significant popularity
since then to manage the replicated logs and replicated state in many popular projects. Data
replication is a requirement for many projects in ASF ecosystem for example Apache Hadoop,
Apache HBase etc. We believe the Concur project can provide an implementation of RAFT that
can fulfill the needs similar to these systems and strengthen the ASF ecosystem.

== Rationale ==
There are a few RAFT implementations[2], but none are a part of ASF. Concur is significantly
different because one of the critical goals of the project is to use it as a library with
pluggability for different RPC, Raft log and state machine implementations. Another important
goal of Apache Concur is to provide high throughput for large ingest rates of data, with data
pipeline support. This will simplify the problem of data replication across the board. Apache
Kudu uses RAFT protocol, but it has its own C++ implementation. Apache DistributedLog project[3]
(in incubation) provides a replicated log service. However, Apache Concur is different as
it provides a java library that other projects can use to implement their own replicated state
machine, without deploying another service.

== Current Status ==
The source code is available with Apache v2 license at
Significant amount of code has been added and basic functionality of RAFT is available for
testing. The code is still in pre-alpha stage and is currently being tried out in POC mode.

== Meritocracy ==
We plan to invest in supporting meritocracy. We intend to invite additional developers to
participate. We will encourage and monitor community participation so that privileges can
be extended to those that contribute.

== Community ==
The developers on the initial committers list are experienced in the ASF ecosystem:
   * Jing Zhao  (jing9 at apache dot org)
   * Tsz Wo Nicholas Sze (szetetszwo at apache dot org)
   * Li Lu (llu at hortonworks dot com)
   * Enis Soztutar (enis at apache dot org)
   * Anu Engineer (anu at apache dot org)
   * Arpit Agarwal (arpitagarwal at apache dot org)
   * Chris Nauroth (cnauroth at apache dot org)
   * Jakob Homan (jghoman at apache dot org)
   * Mayank Bansal (mayank_bansal at apache dot org)
   * Xiaoyu Yao (xyao at apache dot org)
   * Chen Liang (cliang at hortonworks dot com)
   * Hanisha Koneru (hkoneru at hortonworks dot com)
   * Xiaobing Zhou (xiaobingo at gmail dot com)
   * Mingliang Liu (liuml07 at apache dot org)
   * Uma Maheswara Rao G (umamahesh at apache dot org)
   * Jitendra Pandey (jitendra at apache dot org)

== Affiliations ==
   * Jing Zhao, Tsz Wo Nicholas Sze, Li Lu, Enis Soztutar, Anu Engineer, Arpit Agarwal, Xiaoyu
Yao, Chen Liang, Hanisha Koneru, Mingliang Liu, Jitendra Pandey, Devaraj Das
      * Hortonworks
   * Uma Gangumalla,  Intel
   * Mayank Bansal, Uber
   * Jakob Homan, OfferUp
   * Chris Nauroth, Disney

== Alignment ==
We believe that Concur will address the requirements of several projects and communities in
the Apache ecosystem and will gain great adoption.

== Known Risks ==

=== Orphaned Products ===
The contributors are leading users and vendors in the Apache Hadoop ecosystem, with significant
open source experience, so the risk of being orphaned is relatively low. The project could
be at risk if vendors decided to change their strategies in the market. In such an event,
the current committers plan to continue working on the project on their own time, though the
progress will likely be slower. We plan to mitigate this risk by encouraging and recruiting
additional committers. Since replicated log is a very common technique useful for large number
of applications, we believe many developers would like to join and contribute to the project.

=== Inexperience with Open Source ===
The initial committers include veteran Apache Members (Committers, PMC Members and Apache
Members) and other developers who have varying degrees of experience with open source projects.
All have been involved with source code that has been released under an open source license,
and also have experience developing code with an open source development process.

=== Homogenous Developers ===
The initial list of committers include senior Apache developers from multiple different organizations
including Hortonworks, OfferUp, Intel, Uber etc. We believe this project will benefit many
different projects and therefore more and more diverse set of developers will join over time.

=== Reliance on Salaried Developers ===
It is expected that Concur development will occur on both salaried time and on volunteer time,
after hours. The majority of initial committers are paid by their employer to contribute to
this project. However, they are all passionate about the project, and we are confident that
the project will continue even if no salaried developers contribute to the project. We are
committed to recruiting additional committers including non-salaried developers.

=== Relationships with Other Apache Products ===
Most of the initial developers are active participants in Apache Hadoop community and we expect
adoption of Concur by Hadoop Community. However, Concur is a generic RAFT library and we will
strive to take it to more general adoption. This project depends on Apache Maven, Apache Commons
{collections,configuration,io} and Apache Hadoop.

== Initial Source ==

== External Dependencies ==
   * Apache Maven
   * Apache Commons {collections,configuration,io}
   * Apache Hadoop
   * Netty (Apache 2.0)
   * Guava (Apache 2.0)
   * Protobuf (Google 2014)
   * gRPC (Google 2015)
   * slf4j (MIT License)
   * Mockito (MIT)
   * junit (EPL 1.0)
   * FindBugs (LGPL)

== Required Resources ==

=== Mailing List ===
   * concur-private
   * concur-dev
   * concur-user
   * concur-issues

=== Git Repository ===
Git is the preferred source control system: git://

=== Issue Tracking ===
JIRA Concur (Concur)

== Sponsors ==

=== Champion ===
Jitendra Pandey (jitendra)

=== Nominated Mentors ===
 * Chris Nauroth (cnauroth)
 * Devaraj Das  (devaraj)
 * Jakob Homan (jghoman)
 * Uma Maheswara Rao G (umamahesh)

=== Sponsoring Entity ===
Incubator PMC

== Reference ==
  * [1] Diego Ongaro and John Ousterhout. 2014. In search of an understandable consensus algorithm.
In Proceedings of the 2014 USENIX conference on USENIX Annual Technical Conference (USENIX
ATC'14), Garth Gibson and Nickolai Zeldovich (Eds.). USENIX Association, Berkeley, CA, USA,
  * [2]
  * [3]  Apache DistributedLog (incubating)

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