上篇博客介绍了 PostgreSQL-XC 基本原理，对 PostgreSQL-XC 体系结构和组件有了初步认识，今天计划在虚拟机上安装 PostgreSQL-XC, 以做进一步学习分析，下面是 PostgreSQL-XC 安装的整个过程。

安装准备

1.1 requiremetns
硬件需求：官方建议使用 64 位的系统，内存至少 4GB
系统需求：64bit CentOS 5.4 或者其它其它 LINUX 系统
软件需求：GNU make version: 3.80 or newer
Flex: 2.5.31 or later
Perl: 5.8 or later
GCC: Recent versions of GCC are recommendable

软件需求，具体可参考 http://postgres-xc.sourceforge.net/docs/1_0/install-requirements.html

1.2 实际安装环境
两台笔记本虚拟机 RHEL 6.2 ，内存 512 M
IP 192.168.1.35 ；192.168.1.36

1.3 安装规划
一个GTM节点，两个协调(Coordinator)节点，二个数据节点；这是第一次安装，为了操作简便，没有安装GTM-Standby,节点和 GTM-Proxy，这两个节点可以后期测试。
192.168.1.35
GTM节点: gtm 6666
协调节点一: coord1 1921
协调节点二: coord1 1925

192.168.1.36
数据节点一: db_1 15431
数据节点二: db_2 15432

1.4 安装规划图
PostgreSQL-XC : Installation

系统配置

两台主机上都操作。
2.1 创建 pgxc 系统用户并赋权

[root@redhatB bin]# groupadd pgxc  
[root@redhatB bin]# useradd pgxc -g pgxc  
[root@redhatB bin]# passwd pgxc  
Changing password for user pgxc.  
New password:  
BAD PASSWORD: it is based on a dictionary word  
Retype new password:  
passwd: all authentication tokens updated successfully.
[root@redhatB pgxc]# chown -R pgxc:pgxc /pgdata_xc

2.2系统层面其它配置
根据需要配置其它系统层参数，由于是在虚拟机上运行，其它系统参数暂不修改。

安装 Postgres-XC

两台主机上都安装 Postgres-XC 软件

3.1 pgxc_v1.0beta2 下载
https://sourceforge.net/projects/postgres-xc/files/
下载 pgxc_v1.0beta2.tar.gz

3.2 将安装包解压 ( 两台 )

1 2	cd /opt/soft_bak tar zxvf pgxc_v1.0beta2.tar.gz

备注：解压后，产生目录 pgxc

3.3 编译配置

./configure --prefix=/opt/pgsql_xc --with-segsize=8 --with-wal-segsize=64 --with-wal-blocksize=64 --with-perl --with-python --with-openssl --with-pam --with-ldap --with-libxml --with-libxslt --enable-thread-safety

备注：conifugre 过程中如有提示缺少相关包，yum 安装即可。

3.4 编译
gmake
备注：编译后，如果出现”All of PostgreSQL successfully made. Ready to install.”，说明编译成功。

3.5 安装 PostgreSQL XC

1	gmake install

备注：安装后如果提示 “PostgreSQL installation complete.” 说明安装成功。

配置数据节点

192.168.1.36 配置以下：
4.1 修改环境变量( .bash_profile )

export PGPORT=15431  
export PGDATA=/pgdata_xc/db_1/pg_root  
export LANG=en_US.utf8
export PGHOME=/opt/pgsql_xc  
export LD_LIBRARY_PATH=$PGHOME/lib:/lib64:/usr/lib64:/usr/local/lib64:/lib:/usr/lib:/usr/local/lib  
export DATE=`date +"%Y%m%d%H%M"`  
export PATH=$PGHOME/bin:$PATH:.  
export MANPATH=$PGHOME/share/man:$MANPATH  
alias rm='rm -i'  
alias ll='ls -lh'

4.2 创建数据目录

1 2	pgxc@redhatB pgdata_xc]$ mkdir -p /pgdata_xc/db_1/pg_root [pgxc@redhatB pgdata_xc]$ mkdir -p /pgdata_xc/db_2/pg_root

4.3 初始化数据节点1

1	initdb -D /pgdata_xc/db_1/pg_root --nodename db_1 -E UTF8 --locale=C -U postgres -W

4.4 修改数据节点一配置文件 postgresql.conf 参数

# - Connection Settings -  
port = 15431
# - Where to Log -  
log_destination = 'csvlog'  
logging_collector = on  
log_directory = 'pg_log'  
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'  
log_truncate_on_rotation = on  
log_rotation_age = 1d  
log_rotation_size = 10MB  
gtm_host = 'localhost'
# GTM CONNECTION  
gtm_host = '192.168.1.35'  
gtm_port = 6666  
pgxc_node_name = 'db_1'
# DATA NODES AND CONNECTION POOLING  
pooler_port = 6667  
max_pool_size = 100

4.5修改数据节点一 pg_hba.conf ，增加以下

1 2	host all all 192.168.1.35/32 trust host all all 0.0.0.0/0 md5

4.6 初始化数据节点2

1	initdb -D /pgdata_xc/db_2/pg_root --nodename db_2 -E UTF8 --locale=C -U postgres -W

4.7 修改数据节点二配置文件 postgresql.conf 参数

# - Connection Settings -  
port = 15432
# - Where to Log -  
log_destination = 'csvlog'  
logging_collector = on  
log_directory = 'pg_log'  
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'  
log_truncate_on_rotation = on  
log_rotation_age = 1d  
log_rotation_size = 10MB  
gtm_host = 'localhost'
# GTM CONNECTION  
gtm_host = '192.168.1.35'  
gtm_port = 6666  
pgxc_node_name = 'db_2'
# DATA NODES AND CONNECTION POOLING  
pooler_port = 6667  
max_pool_size = 100

4.8 修改数据节点一 pg_hba.conf ，增加以下

1 2	host all all 192.168.1.35/32 trust host all all 0.0.0.0/0 md5

配置 GTM 节点

192.168.1.35 配置以下
5.1 修改 .bash_profile

export PGPORT=1921  
export PGDATA=/database/1922/pgdata1/pgdata_xc/coord1  
export LANG=en_US.utf8
export PGHOME=/opt/pgsql_xc
export LD_LIBRARY_PATH=$PGHOME/lib:/lib64:/usr/lib64:/usr/local/lib64:/lib:/usr/lib:/usr/local/lib  
export DATE=`date +"%Y%m%d%H%M"`  
export PATH=$PGHOME/bin:$PATH:.  
export MANPATH=$PGHOME/share/man:$MANPATH  
alias rm='rm -i'  
alias ll='ls -lh'

5.2 创建 gtm 数据目录

1	[pgxc@redhat6 pgdata_xc]$ mkdir -p /database/1922/pgdata1/pgdata_xc/gtm

5.3 install gtm

[pgxc@redhat6 bin]$ initgtm -Z gtm -D /database/1922/pgdata1/pgdata_xc/gtm  
The files belonging to this GTM system will be owned by user "pgxc".  
This user must also own the server process.
fixing permissions on existing directory /database/1922/pgdata1/pgdata_xc/gtm ... ok  
creating configuration files ... ok
Success. You can now start the GTM server using:
 gtm -D /database/1922/pgdata1/pgdata_xc/gtm  
or  
 gtm_ctl -Z gtm -D /database/1922/pgdata1/pgdata_xc/gtm -l logfile start

配置 Coordinator 节点

192.168.1.35 配置以下

6.1 创建 coordinator 数据目录

1 2	[pgxc@redhat6 pgdata_xc]$ mkdir -p /database/1922/pgdata1/pgdata_xc/coord1 [pgxc@redhat6 pgdata_xc]$ mkdir -p /database/1922/pgdata1/pgdata_xc/coord2

6.2 install coord1

1	initdb -D /database/1922/pgdata1/pgdata_xc/coord1 --nodename coord1 -E UTF8 --locale=C -U postgres -W

6.3 修改 coord1 配置文件 postgresql.conf

# - Connection Settings -  
listen_addresses = '*'  
port = 1921
# - Where to Log -  
log_destination = 'csvlog'  
logging_collector = on  
log_directory = 'pg_log'  
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'  
log_truncate_on_rotation = on  
log_rotation_age = 1d  
log_rotation_size = 10MB  
gtm_host = 'localhost'
# GTM CONNECTION  
gtm_host = 'localhost'  
gtm_port = 6666  
pgxc_node_name = 'coord1'
# DATA NODES AND CONNECTION POOLING  
pooler_port = 6667  
max_pool_size = 100

6.4 配置 coord1 pg_hba.conf

1 2	host all all 192.168.1.36/32 trust host all all 0.0.0.0/0 md5

6.5 install coord2

1	initdb -D /database/1922/pgdata1/pgdata_xc/coord2 --nodename coord2 -E UTF8 --locale=C -U postgres -W

6.6 配置 coord2 配置文件 postgresql.conf

# - Connection Settings -  
listen_addresses = '*'  
port = 1925
# - Where to Log -  
log_destination = 'csvlog'  
logging_collector = on  
log_directory = 'pg_log'  
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log'  
log_truncate_on_rotation = on  
log_rotation_age = 1d  
log_rotation_size = 10MB  
gtm_host = 'localhost'
# GTM CONNECTION  
gtm_host = 'localhost'  
gtm_port = 6666  
pgxc_node_name = 'coord2'
# DATA NODES AND CONNECTION POOLING  
pooler_port = 6668  
max_pool_size = 100

6.7 配置 coord1 pg_hba.conf

1 2	host all all 192.168.1.36/32 trust host all all 0.0.0.0/0 md5

6.8 修改防火墙，打开相应端口（两台）
为了测试简便，先暂时关闭防火墙和 seliniux。

启动 PostgreSQL-XC

7.1 start gtm

1 2	[pgxc@redhat6 bin]$ gtm -D /database/1922/pgdata1/pgdata_xc/gtm & [1] 6185

查看 gtm 是否启动

[pgxc@redhat6 bin]$ gtm_ctl status -S gtm -D /database/1922/pgdata1/pgdata_xc/gtm  
pid: 6185  
data: /database/1922/pgdata1/pgdata_xc/gtm  
active: 1
[pgxc@redhat6 bin]$ ps -ef | grep gtm  
pgxc 6185 6135 0 20:50 pts/4 00:00:00 gtm -D /database/1922/pgdata1/pgdata_xc/gtm
 备注： gtm 进程已经正常启动。

7.2 启动数据节点（ 192.168.1.36 ）

1 2	postgres -X -D /pgdata_xc/db_1/pg_root -p 15431 -i & postgres -X -D /pgdata_xc/db_2/pg_root -p 15432 -i &

备注：-X 表示datanode 节点。
查看数据节点是否启动

[pgxc@redhatB pg_log]$ ps -ef | grep pgxc  
root 371 351 0 09:16 pts/0 00:00:00 su - pgxc  
pgxc 372 371 0 09:16 pts/0 00:00:00 -bash  
root 420 398 0 09:16 pts/1 00:00:00 su - pgxc  
pgxc 421 420 0 09:16 pts/1 00:00:00 -bash  
pgxc 588 421 0 09:28 pts/1 00:00:00 postgres -X -D /pgdata_xc/db_1/pg_root -p 15431 -i  
pgxc 589 588 0 09:28 ? 00:00:00 postgres: logger process  
pgxc 591 588 0 09:28 ? 00:00:00 postgres: writer process  
pgxc 592 588 0 09:28 ? 00:00:00 postgres: wal writer process  
pgxc 593 588 0 09:28 ? 00:00:00 postgres: autovacuum launcher process  
pgxc 594 588 0 09:28 ? 00:00:00 postgres: stats collector process  
pgxc 595 421 0 09:28 pts/1 00:00:00 postgres -X -D /pgdata_xc/db_2/pg_root -p 15432 -i  
pgxc 596 595 0 09:28 ? 00:00:00 postgres: logger process  
pgxc 598 595 0 09:28 ? 00:00:00 postgres: writer process  
pgxc 599 595 0 09:28 ? 00:00:00 postgres: wal writer process  
pgxc 600 595 0 09:28 ? 00:00:00 postgres: autovacuum launcher process  
pgxc 601 595 0 09:28 ? 00:00:00 postgres: stats collector process

7.3 启动 coordinator 节点

1 2	postgres -C -D /database/1922/pgdata1/pgdata_xc/coord1 -p 1921 -i & postgres -C -D /database/1922/pgdata1/pgdata_xc/coord2 -p 1925 -i &

备注：-C 表示 coordinator 节点。

查看 coordinator 节点是否启来

pgxc 11633 8961 0 10:25 pts/3 00:00:00 postgres -C -D /database/1922/pgdata1/pgdata_xc/coord1 -p 1921 -i  
pgxc 11634 11633 0 10:25 ? 00:00:00 postgres: logger process  
pgxc 11637 11633 0 10:25 ? 00:00:00 postgres: pooler process  
pgxc 11638 11633 0 10:25 ? 00:00:00 postgres: writer process  
pgxc 11639 11633 0 10:25 ? 00:00:00 postgres: wal writer process  
pgxc 11640 11633 0 10:25 ? 00:00:00 postgres: autovacuum launcher process  
pgxc 11641 11633 0 10:25 ? 00:00:00 postgres: stats collector process  
pgxc 11643 8961 0 10:25 pts/3 00:00:00 postgres -C -D /database/1922/pgdata1/pgdata_xc/coord2 -p 1925 -i  
pgxc 11644 11643 0 10:26 ? 00:00:00 postgres: logger process  
pgxc 11647 11643 0 10:26 ? 00:00:00 postgres: pooler process  
pgxc 11648 11643 0 10:26 ? 00:00:00 postgres: writer process  
pgxc 11649 11643 0 10:26 ? 00:00:00 postgres: wal writer process  
pgxc 11650 11643 0 10:26 ? 00:00:00 postgres: autovacuum launcher process  
pgxc 11651 11643 0 10:26 ? 00:00:00 postgres: stats collector process  
pgxc 12203 11633 0 10:53 ? 00:00:00 postgres: postgres postgres ::1(13531) idle  
pgxc 12372 11643 0 11:01 ? 00:00:00 postgres: postgres postgres ::1(14789) idle  
pgxc 12661 11643 0 11:16 ? 00:00:00 postgres: francs francs ::1(14825) idle

备注：coord1,coord2 节点分别多了个pooler process 进程，pooler process 用来与数据节点进行通信的。

7.4 查看GTM，POOL连接

[root@redhat6 ~]# netstat -anp | grep gtm  
tcp 0 0 0.0.0.0:6666 0.0.0.0:* LISTEN 11620/gtm  
tcp 0 0 :::6666 :::* LISTEN 11620/gtm  
tcp 0 0 ::1:6666 ::1:52228 ESTABLISHED 11620/gtm  
  
[root@redhat6 ~]# ps -ef | grep pool  
pgxc 11637 11633 0 10:25 ? 00:00:00 postgres: pooler process  
pgxc 11647 11643 0 10:26 ? 00:00:00 postgres: pooler process  
root 13375 11658 0 11:53 pts/2 00:00:00 grep pool

备注：如果到了这步，没有看到 pooler process ，或者没有 gtm 相关连接，说明配置有问题。

注册节点

8.4 在 coord1,cord2 上注册数据节点

CREATE NODE db_1 WITH (TYPE='datanode',HOST = '192.168.1.36', PORT=15431);  
CREATE NODE db_2 WITH (TYPE='datanode',HOST = '192.168.1.36', PORT=15432);  
CREATE NODE coord2 WITH (TYPE='coordinator',HOST = 'localhost', PORT=1925);  
CREATE NODE coord1 WITH (TYPE='coordinator',HOST = 'localhost', PORT=1921);
[pgxc@redhat6 gtm]$ psql -p 1921 -U postgres  
psql (PGXC 1.0beta2, based on PG 9.1.3)  
Type "help" for help.

postgres=# select * from pgxc_node;  
node_name | node_type | node_port | node_host | nodeis_primary | nodeis_preferred | node_id  
-----------+-----------+-----------+-----------+----------------+------------------+------------  
coord1 | C | 5432 | localhost | f | f | 1885696643  
(1 row)
postgres=# CREATE NODE db_1 WITH (TYPE='datanode',HOST = '192.168.1.36', PORT=15431,PRIMARY, PREFERRED);  
CREATE NODE  
postgres=# CREATE NODE db_2 WITH (TYPE='datanode',HOST = '192.168.1.36', PORT=15432);  
CREATE NODE  
postgres=# CREATE NODE coord2 WITH (TYPE='coordinator',HOST = '192.168.1.35', PORT=1925);  
CREATE NODE  

postgres=# select * from pgxc_node;  
node_name | node_type | node_port | node_host | nodeis_primary | nodeis_preferred | node_id  
-----------+-----------+-----------+--------------+----------------+------------------+-------------  
coord1 | C | 5432 | localhost | f | f | 1885696643  
db_1 | D | 15431 | 192.168.1.36 | f | f | 1356996994  
db_2 | D | 15432 | 192.168.1.36 | f | f | -822936791  
coord2 | C | 1925 | localhost | f | f | -1197102633

postgres=# select pgxc_pool_reload();  
pgxc_pool_reload  
------------------  
t  
(1 row)

备注：到了这里， PostgreSQL-XC 安装完成，接下来验证下。

测试

9.1 coord1 创建测试库和表

[pgxc@redhat6 coord2]$ psql -p 1921 -U postgres  
psql (PGXC 1.0beta2, based on PG 9.1.3)  
Type "help" for help.
postgres=# /l  
 List of databases  
 Name | Owner | Encoding | Collate | Ctype | Access privileges  
-----------+----------+----------+---------+-------+------------------------  
francs | postgres | UTF8 | C | C | =Tc/postgres +  
 | | | | | postgres=CTc/postgres +  
 | | | | | francs=C*T*c*/postgres  
postgres | postgres | UTF8 | C | C |  
template0 | postgres | UTF8 | C | C | =c/postgres +  
 | | | | | postgres=CTc/postgres  
template1 | postgres | UTF8 | C | C | =c/postgres +  
 | | | | | postgres=CTc/postgres  
(4 rows)

postgres=# create database test_xc;  
CREATE DATABASE

postgres=# /l  
 List of databases  
 Name | Owner | Encoding | Collate | Ctype | Access privileges  
-----------+----------+----------+---------+-------+------------------------  
postgres | postgres | UTF8 | C | C |  
template0 | postgres | UTF8 | C | C | =c/postgres +  
 | | | | | postgres=CTc/postgres  
template1 | postgres | UTF8 | C | C | =c/postgres +  
 | | | | | postgres=CTc/postgres  
test_xc | postgres | UTF8 | C | C |  
(5 rows)

postgres=# /c test_xc  
You are now connected to database "test_xc" as user "postgres".  
test_xc=# create table test_1 (id integer,name varchar(32));  
CREATE TABLE  
test_xc=# insert into test_1 select generate_series(1,100),'test_xc';  
INSERT 0 100

备注：在 coord1 节点上创建了测试库 test_xc，并在里面创建了一张表，接下来看看 coord2, db_1,db_2 节点情况。

9.2 coord2 上验证

[pgxc@redhat6 pg_log]$ psql -p 1925 -U postgres  
psql (PGXC 1.0beta2, based on PG 9.1.3)  
Type "help" for help.
postgres=# /l  
 List of databases  
 Name | Owner | Encoding | Collate | Ctype | Access privileges  
-----------+----------+----------+---------+-------+------------------------  
postgres | postgres | UTF8 | C | C |  
template0 | postgres | UTF8 | C | C | =c/postgres +  
 | | | | | postgres=CTc/postgres  
template1 | postgres | UTF8 | C | C | =c/postgres +  
 | | | | | postgres=CTc/postgres  
test_xc | postgres | UTF8 | C | C |  
(5 rows)

postgres=# /c test_xc  
You are now connected to database "test_xc" as user "postgres".  
test_xc=# /d  
 List of relations  
Schema | Name | Type | Owner  
--------+--------+-------+----------  
public | test_1 | table | postgres  
(1 row)
test_xc=# select count(*) from test_1;  
count  
-------  
 100  
(1 row)

9.3 数据节点 db_1 上验证

[pgxc@redhatB pg_log]$ psql -p 15431 -U postgres -d test_xc  
psql (PGXC 1.0beta2, based on PG 9.1.3)  
Type "help" for help.
test_xc=# /d  
WARNING: Do not have a GTM snapshot available  
WARNING: Do not have a GTM snapshot available  
 List of relations  
Schema | Name | Type | Owner  
--------+--------+-------+----------  
public | test_1 | table | postgres  
(1 row)
test_xc=# select count(*) from test_1;  
WARNING: Do not have a GTM snapshot available  
WARNING: Do not have a GTM snapshot available  
count  
-------  
 42  
(1 row)

9.4 数据节点 db_2 上验证

[pgxc@redhatB pg_log]$ psql -p 15432 -U postgres -d test_xc  
psql (PGXC 1.0beta2, based on PG 9.1.3)  
Type "help" for help.
test_xc=# select count(*) from test_1;  
WARNING: Do not have a GTM snapshot available  
WARNING: Do not have a GTM snapshot available  
count  
-------  
 58  
(1 row)

备注：表共有100条记录，数据节点一分布了 42 条，数据节点二分布了 58 条，可见数据已经分片到数据节点上。
当然在创建表时，也可以设置 replication 模式，这样数据就会完全复制到每个节点。

常见错误

1
2
3

[pgxc@redhat6 coord1]$ psql -p 1921 -U postgres  
postgres=# create database test;  
ERROR: Failed to get pooled connections

备注：如果在 coord1 节点上操作时，报 “ERROR: Failed to get pooled connections”，可能的原因很多，可能是节点没有注册好，这时要查看 pgxc_node 视图；也有可能是 pg_hba.conf，防火墙，selinux 等问题，总之逐一排查。

总结

本次测试只是简单将 PostgreSQL-XC 搭建起来了，其中 gmt_standby，GTM-Proxy 没有配置，这个以后可以测试下；
由于在 PostgreSQL-XC 体系中，coordinator 并不存储数据，数据被分片在数据节点中，这种机制与Greenplum有点类似；而 coordinator 节点新增了 pooler process 进程，个人觉得 coordinator 很像一个连接池。
PostgreSQL-XC 所谓的多主节点( muti-master) 同时对外服务，实际上对应用服务的是 coordinator 节点，而不是数据节点本身；原来俺的理解是数据节点同时读写(多份数据，mater 同时读写)，而在 PostgreSQL-XC 中并不是这样。
由于每个数据节点存储一部分数据，那么如果数据节点 down 掉，整个 PostgreSQL-XC 将不可用，不知是否有
更好的方案，例如给每个数据节点配置个 standby 节点？
由于在 PostgreSQL-XC 体系中数据分片在多个数据节点中，IO 性能会提升，同时对网络压力会提升；具体性能目前还没有测试。
6.尽管疑问重多，但还是要感谢来自日本的 PostgreSQL-XC 开发团队，他们为 PostgreSQL 带来了 muti-master的集群方案。

参考

http://postgres-xc.sourceforge.net/
http://postgres-xc.sourceforge.net/docs/1_0/index.html
http://blog.163.com/digoal@126/blog/static/16387704020121952051174/
http://michael.otacoo.com/tag/postgres-xc/

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PostgreSQL-XC : Installation