Postgres-X2 is an open source project to provide horizontal scalability including write-scalability, synchronous multi-master, and transparent PostgreSQL interface. It is a collection of tightly coupled database components which can be installed in more than one hardware or virtual machines.

• About the name

This project used the name Postgres-XC originally, it is renamed to Postges-X2 from 2015 after it was moved to Github. In many of the documents and code, we still use Postgres-XC.

Please refer to the Charter for the project information

#License This project uses the same license as PostgreSQL, PostgreSQL license (like BSD).

#What is Postgres-X2

• Share nothing Cluster :Multiple collaborating PostgreSQL-like servers, No resources shared, Scaling by adding commodity hardware
• Write scalable PostgreSQL cluster : More than 3× scalability performance speedup with five servers, compared with pure PostgreSQL (DBT‐1). Result as of 1.0 release.
• Synchronous multi‐master configuration : Any update to any master is visible from other masters immediately.
• Table location transparent : Can continue to use the same applications. No change in transaction handling.
• Based upon PostgreSQL :Same API to Apps as PostgreSQL

• Latest release The latest release is Postgres-XC 1.2.1 based on PostgreSQL 9.3, you can download it from here Postgres-XC 1.2.1
• The stable development version The stable development version is here REL1_2_STABLE
• Next release Postgres-X2 1.2.2 is planned to be released at August 2015, please refer to the [1.2.2 milestone] (https://github.com/postgres-x2/postgres-x2/milestones/1.2.2)

Subscribing grougle groups, issueing pull request and creating issues are the way to begin with. For more information please refer to our development page

• MailList

Subscribe Postgres-X2-dev group(postgres-x2-dev@googlegroups.com) from google groups titled "postgres-x2-dev". You can post your issues and ideas here.

• Pull request and create issues

If you have codes for new feature or fix, you can issue pull request. This page contains Postgres-X2 development community information. Posgres-X2 repositories will be found at postgres-x2 developer page. You can also create issue to report bugs, to raise discussion, to post your ideas, etc.

• Report Bugs

[Report Issues] (https://github.com/postgres-x2/postgres-x2/issues)

For any project information please contact the project repensentive Koichi Suzuki or Galy Lee

• Download

you can download the stable release from here Postgres-XC 1.2.1

or you can download the stable development version, it is here REL1_2_STABLE

wget https://github.com/postgres-x2/postgres-x2/archive/REL1_2_STABLE.zip

• Installation

install depedency packages

yum -y install gcc* libtool* libxml2-devel readline-devel flex bison crypto* perl-ExtUtils-Embed zlib-devel pam-devel libxslt-devel openldap-devel python-devel openssl-devel cmake

Unzip

unzip REL1_2_STABLE.zip

Configure

cd /home/galy/pgxc/stable (your source code place)
./configure --prefix=/home/galy/pgxc/stable 

Please change the installation path to the location you want to install.

make

cd /home/galy/pgxc/stable (your source code place)
make install

• Before you start

Before you start to configure Postgres-XC cluster, you need to determine several things and make hardware/software ready.

Components

Postgres-XC database cluster consists of the following components:

gtm

gtm stands for "global transaction manager", which provides core of transaction management feature needed to run all the Postgres-XC component in a integrated way. Coordinators and datanodes connect to GTM to run transactions consisitently at different servers.

gtm_proxy

This is a proxy of a connection form coordinators/datanodes to GTM to reduce the amount of interaction and data.

coordinator This is a connection point to Postgres-XC applications. A coordinator accepts SQL statements from applications, analyze and determines where the data is stored and handles SQL statements to each datanode. You can configure as many coordinators in Postgres-XC.

datanode

This node stores user data Datanode reads its local SQL statements from coordinators and handle them.

How many servers you need?

If you are just testing Postgres-XC, you need only one server. This can even be a virtual machine. You can run sufficient component on this machine but it's not a good idea to run slave of each components. pgxc_ctl will provide configuration file template but it is not suitable for this purpose. You may have to rewrite many of the template to fit to your single-server configuration.

If you are deploying Postgres-XC for more serious use, you should consider how many servers you need to store your data. You may want to run GTM at a separate server mainly for availability purpose and you may want another server to run GTM slave for hight availability.It is highly advised to install gtm_proxy, coordinator and datanode at the rest of the servers. This simplifies the configuration and maintains worload of each servers nearly even.

• Quick Start

The following is a quick example to setup one coordinator, two data nodes and one GTM

 Init gtm, datanode, coordinator
  >initgtm -Z gtm -D gtm
  >initdb -D datanode1 --nodename dn1 #Initialize Datanode 1
  >initdb -D datanode2 --nodename dn2 #Initialize Datanode 2
  >initdb -D coord1 --nodename co1 # Initialize Coordinator 1

  Change configuration
  *Show and check gtm.conf and each postgresql.conf, change port values for Datanodes => 15432 for Dn1, 15433 for Dn2

  Node start-up
  >gtm -D gtm &
  >postgres -X -D datanode1 -i & # -X for a Datanode
  >postgres -X -D datanode2 -i & # -X for a Datanode
  >postgres -C -D coord1 -i & # -C for a Coordinator

  connect to coordinator
  >psql postgres

  launch that to set up cluster:
  >CREATE NODE dn1 WITH (TYPE='datanode', PORT=15432);
  >CREATE NODE dn2 WITH (TYPE='datanode', PORT=15433);
  >select * from pgxc_node;
  >select pgxc_pool_reload();

  Then you can connect to Coordinator 1 and test your newly-made cluster

Please refer to roadmap in our wiki page.

• online reference

Postgres-X2 online reference is here

• Configuration Overview

Pgxc_ctl primer gives overall description of postgres-x2 architecture, cluster design, configuration and operation using pgxc_ctl utility.

This is the presentation slide deck of postgres-x2 configuration and operation demo at PG-Open, 2013

• Talks

There are a lot of talks materials here

• Architecture design

The architecture design and implementation detail is in this [document] (http://postgres-x2.github.io/presentation_docs/2014-07-PGXC-Implementation/pgxc.pdf)

• Internal Overview

The offical document has an internal of Postgres-X2 [section] (http://postgres-x2.github.io/reference/1.2/html/xc-overview.html)