Slony-I是一个“一主多备”的复制系统，支持级联复制(ascading)和失效转移failover.
官方文档：
slony-I的系统分析：https://wiki.postgresql.org/wiki/Slony
slony-I安装配置使用
系统要求：http://slony.info/documentation/requirements.html
使用限制：http://slony.info/documentation/2.2/limitations.html
配置与安装：http://slony.info/documentation/administration.html#INSTALLATION
使用配置：http://slony.info/documentation/tutorial.html#FIRSTDB
环境：
主库：centos linux 32bit虚拟机，ip为192.168.100.240
PostgreSQL9.2.13
Slony-I 2.2
备库： centos linux 32bit虚拟机， ip为192.168.100.241
PostgreSQL9.2.13
Slony-I 2.2
1.源码编译安装PostgreSQL
在主库和备库都，进行源码编译、安装、配置PostgreSQL数据库如下：
源码编译安装PostgbreSQL9.2。
安装目录：/opt/pgsql2
编译安装过程请参考：PostgreSQL在Linux下的源码编译安装
源码安装完毕后，要配置pg_hba.conf和postgresql.conf确保主、备库可以远程访问。
注意：PG版本要必须是Slony支持的版本，详见 http://slony.info/documentation/requirements.html 。
2.准备slony-I复制的主、备库
=====================
2.1声明环境变量
在主库和备库都，执行：
su - postgres
export CLUSTERNAME=lyy_cluster1
export MASTERDBNAME=masterdb
export SLAVEDBNAME=slavedb
export MASTERHOST=192.168.13.128
export SLAVEHOST=192.168.100.236
export REPLICATIONUSER=postgres
注意：
1.REPLICATIONUSER通常是PostgreSQL数据库的超级用户。
2.修改MASTERHOST和SLAVEHOST时，尽量不要使用localhost，因为可能会导致错误：ERROR remoteListenThread_1: db_getLocalNodeId() returned 2 - wrong database?。
2.2根据环境变量准备数据库
在主库和备库都，根据环境变量来创建相应对象：
--在主服务器中
cd /opt/pgsql2/bin
./createuser -p 5432 -U postgres -SRD -P $PGBENCHUSER --若已创建则无需再创建
input password for new user :（此处输入新用户的密码即可）
input password again:（此处输入新用户的密码即可）
password:（此处输入超级用户postgres的密码即可）
./createdb -p 5432 -U postgres -O $PGBENCHUSER -h $MASTERHOST $MASTERDBNAME
password:（此处输入超级用户postgres的密码即可）
--在备用服务器中
cd /opt/pgsql2/bin
./createuser -p 5432 -U postgres -SRD -P $PGBENCHUSER --若已创建则无需再创建
input password for new user :（此处输入新用户的密码即可）
input password again:（此处输入新用户的密码即可）
password:（此处输入超级用户postgres的密码即可）
./createdb -p 5432 -U postgres -O $PGBENCHUSER -h $SLAVEHOST $SLAVEDBNAME
password:（此处输入超级用户postgres的密码即可）
--在主服务器，创建要同步的数据表（数据表必须有主键或者唯一键，才能通过slony-i实现数据同步）
[postgres@localhost bin]$ ./psql -U $PGBENCHUSER -h $MASTERHOST -d $MASTERDBNAME
psql (9.2.13)
Type "help" for help..
masterdb=# CREATE TABLE lyy(id int primary key, name varchar);
CREATE TABLE
2.3创建pl/pgsql过程语言
Slony-I 需要数据库有 pl/pgSQL 过程语言，如果模板数据 template1已经安装了pl/pgSQL，那么新建的$MASTERDBNAME也就也有了pl/pgSQL，如果已经存在了，则不需要执行以下语句：
在主库和备库都执行：
--在bin目录下
./createlang -h $MASTERHOST plpgsql $MASTERDBNAME
2.4手动从主库将表定义导入备库
当备库Slony-I 订阅主库之后，Slony-I不能自动从主库拷贝表定义到备库，所以我们需要把表定义从主库导入备库，我们通过 pg_dump来实现表定义的主、备同步：
--在主服务器中执行pg_dump，将表定义备份到备库中
--在bin目录下
[postgres@localhost bin]$ ./pg_dump -s -U postgres -h 192.168.100.240 masterdb | ./psql -U postgres -h 192.168.100.241 slavedb
3.源码编译安装Slony-I
在主库和备库都，按照以下步骤安装slony-i。
slony下载地址：http://slony.info/downloads/2.2/source/
下载并解压slony-2.2，然后进行编译配置安装，要确保每一步安装正确后再进行下一步。
cd ../slony-2.2
./configure --with-pgconfigdir=/opt/pgsql944/bin --with-perltools
gmake all
gamke install
注意：如果slony-I后面的配置过程使用altperl脚本，则configure时必须指定--with-perltools。
4. 配置slony并启动同步复制
4.0配置并启用slony同步复制的理论基础（仅供理解）：
Configuring the Database For Replication.
Creating the configuration tables, stored procedures, triggers and configuration is all done through the slonik tool. It is a specialized scripting aid that mostly calls stored procedures in the master/slave (node) databases.
The example that follows uses slonik directly (or embedded directly into scripts). This is not necessarily the most pleasant way to get started; there exist tools for building slonik scripts under the tools directory, including:
Section 6.1.1 - a set of Perl scripts that build slonik scripts based on a single slon_tools.conf file.
Section 6.1.2 - a shell script (e.g. - works with Bash) which, based either on self-contained configuration or on shell environment variables, generates a set of slonik scripts to configure a whole cluster.
以下两种方法省略详细介绍，详见文档http://slony.info/documentation/tutorial.html#FIRSTDB。
方法一：Using slonik Command Directly
方法二：Using the altperl Scripts
扩展至：http://file:///C:/Users/Yuanyuan/Desktop/slony1-2.2.4/doc/adminguide/additionalutils.html#ALTPERL
4.1直接使用slonik命令(以上方法一)
在主库配置slony cluster
在主库，创建并执行slony_setup.sh文件，实现slony cluster的配置：
[postgres@localhost data]$ vi slony_setup.sh
CLUSTERNAME=lyy_cluster1
MASTERDBNAME=masterdb
SLAVEDBNAME=slavedb
MASTERHOST=192.168.100.240
SLAVEHOST=192.168.100.241
REPLICATIONUSER=postgres
/opt/pgsql92/bin/slonik <<_EOF_
#--
# define the namespace the replication system
# uses in our example it is slony_example
#--
cluster name = $CLUSTERNAME;
#--
# admin conninfo's are used by slonik to connect to
# the nodes one for eachnode on each side of the cluster,
# the syntax is that of PQconnectdb in
# the C-API
# --
node 1 admin conninfo = 'dbname=$MASTERDBNAME \
host=$MASTERHOST user=$REPLICATIONUSER';
node 2 admin conninfo = 'dbname=$SLAVEDBNAME \
host=$SLAVEHOST user=$REPLICATIONUSER';
#--
# init the first node. Its id MUST be 1. This creates
# the schema _$CLUSTERNAME containing all replication
# system specific database objects.
#--
init cluster ( id=1, comment = 'Master Node');
#--
# Slony-I organizes tables into sets. The smallest unit
# a node can subscribe is a set. The master or origin of
# the set is node 1.
#--
create set (id=1, origin=1, comment='All masterdb tables');
set add table (set id=1, origin=1, id=1,
fully qualified name = 'public.lyy',
comment='lyy table');
# set add sequence (set id=1, origin = 1, id = 1,
# fully qualified name = 'public.t1_id_seq',
# comment = 't1 id sequence');
#--
# Create the second node (the slave) tell the 2 nodes how
# to connect to each other and how they should listen for events.
#--
store node (id=2, comment = 'Slave Node', event node=1);
store path (server = 1, client = 2, conninfo='dbname=$MASTERDBNAME \
host=$MASTERHOST user=$REPLICATIONUSER');
store path (server = 2, client = 1, conninfo='dbname=$SLAVEDBNAME \
host=$SLAVEHOST user=$REPLICATIONUSER');
_EOF_
[postgres@localhost data]$sh slony_setup.sh
注释：本步执行完毕后，初始化完毕一个名为lyy_cluster1的slony集群。
并相应的产生一个名为_lyy_cluster1的模式，里面含有slony运行所需的配置表、序列、函数、触发器等(主要是通过slony-i安装过程中在/opt/pgsql92/share下生成的slony1_base.2.2.4.sql和slony1_funcs.2.2.4.sql)。
还会在同步表lyy下创建相应的触发器。
在主库：
masterdb=# \d lyy
Table "public.lyy"
Column | Type | Modifiers
--------+-------------------+-----------
id | integer | not null
name | character varying |
Indexes:
"lyy_pkey" PRIMARY KEY, btree (id)
Triggers:
_lyy_cluster1_logtrigger AFTER INSERT OR DELETE OR UPDATE ON lyy FOR EACH ROW EXECUTE PROCEDURE _lyy_cluster1.logtrigger('_lyy_cluster1', '1', 'k')
_lyy_cluster1_truncatetrigger BEFORE TRUNCATE ON lyy FOR EACH STATEMENT EXECUTE PROCEDURE _lyy_cluster1.log_truncate('1')
_lyy_cluster_logtrigger AFTER INSERT OR DELETE OR UPDATE ON lyy FOR EACH ROW EXECUTE PROCEDURE _lyy_cluster.logtrigger('_lyy_cluster', '1', 'k')
_lyy_cluster_truncatetrigger BEFORE TRUNCATE ON lyy FOR EACH STATEMENT EXECUTE PROCEDURE _lyy_cluster.log_truncate('1')
Disabled triggers:
_lyy_cluster1_denyaccess BEFORE INSERT OR DELETE OR UPDATE ON lyy FOR EACH ROW EXECUTE PROCEDURE _lyy_cluster1.denyaccess('_lyy_cluster1')
_lyy_cluster1_truncatedeny BEFORE TRUNCATE ON lyy FOR EACH STATEMENT EXECUTE PROCEDURE _lyy_cluster1.deny_truncate()
_lyy_cluster_denyaccess BEFORE INSERT OR DELETE OR UPDATE ON lyy FOR EACH ROW EXECUTE PROCEDURE _lyy_cluster.denyaccess('_lyy_cluster')
_lyy_cluster_truncatedeny BEFORE TRUNCATE ON lyy FOR EACH STATEMENT EXECUTE PROCEDURE _lyy_cluster.deny_truncate()
在备库：
slavedb=# \d lyy
Table "public.lyy"
Column | Type | Modifiers
--------+-------------------+-----------
id | integer | not null
name | character varying |
Indexes:
"lyy_pkey" PRIMARY KEY, btree (id)
Triggers:
_lyy_cluster1_denyaccess BEFORE INSERT OR DELETE OR UPDATE ON lyy FOR EACH ROW EXECUTE PROCEDURE _lyy_cluster1.denyaccess('_lyy_cluster1')
_lyy_cluster1_truncatedeny BEFORE TRUNCATE ON lyy FOR EACH STATEMENT EXECUTE PROCEDURE _lyy_cluster1.deny_truncate()
Disabled triggers:
_lyy_cluster1_logtrigger AFTER INSERT OR DELETE OR UPDATE ON lyy FOR EACH ROW EXECUTE PROCEDURE _lyy_cluster1.logtrigger('_lyy_cluster1', '1', 'k')
_lyy_cluster1_truncatetrigger BEFORE TRUNCATE ON lyy FOR EACH STATEMENT EXECUTE PROCEDURE _lyy_cluster1.log_truncate('1')
在主库启动主库节点及监视器
在主库，执行以下命令启动slon daemon：
[postgres@localhost bin]$./slon lyy_cluster1 "dbname=masterdb user=postgres host=192.168.100.240"&
执行当前命令的终端会不断地返回检测信息，所以该终端不要关闭也不要再执行其他操作。
在备库启动备库节点及监视器
在备库。执行以下命令启动slon deamon：
[postgres@localhost bin]$./slon slony_example "dbname=slavedb user=postgres host=192.168.100.241" &
执行当前命令的终端会不断地返回检测信息，所以该终端不要关闭也不要再执行其他操作。
在主库执行备库订阅主库
在主库，执行订阅过程, 通过脚本文件subscribe_set.sh来执行订阅过程：
[postgres@localhost data]$ vi subscribe_set.sh
CLUSTERNAME=lyy_cluster1
MASTERDBNAME=masterdb
SLAVEDBNAME=slavedb
MASTERHOST=192.168.100.240
SLAVEHOST=192.168.100.241
REPLICATIONUSER=postgres
/opt/pgsql92/bin/slonik <<_EOF_
# ----
# This defines which namespace the replication system uses
# ----
cluster name = $CLUSTERNAME;
# ----
# Admin conninfo's are used by the slonik program to connect
# to the node databases. So these are the PQconnectdb arguments
# that connect from the administrators workstation (where
# slonik is executed).
# ----
node 1 admin conninfo = 'dbname=$MASTERDBNAME host=$MASTERHOST \
user=$REPLICATIONUSER';
node 2 admin conninfo = 'dbname=$SLAVEDBNAME host=$SLAVEHOST \
user=$REPLICATIONUSER';
# ----
# Node 2 subscribes set 1
# ----
subscribe set ( id = 1, provider = 1, receiver = 2, forward = no);
_EOF_
[postgres@localhost data]$sh subscribe_set.sh
目前，本次数据库的slony的同步复制已经配置完毕。
验证slony-I同步复制生效
在主库，向表lyy插入数据：
[postgres@localhost bin]$ ./psql -U postgres -d masterdb
psql (9.2.13)
Type "help" for help.
masterdb=# insert into lyy values(1,'lyy');
INSERT 0 1
在备库，查询表lyy中的数据情况：
postgres@localhost bin]$ ./psql -U postgres -d slavedb
psql (9.2.13)
Type "help" for help.
slavedb=# select * from lyy;
id | name
----+------
(0 rows)
slavedb=# select * from lyy;
id | name
----+------
1 | lyy
(1 row)
可以在主库执行增删操作，然后在备库执行查询操作，进行比对。
注意：slony-I 同步复制的备库是不能对同步的表数据进行修改的：
slavedb=# insert into test values(4,'fff');
ERROR: Slony-I: Table test is replicated and cannot be modified on a subscriber node - role=0
4.2使用altperl脚本配置并启动（以上方法二）：
配置slony_tool.conf并初始化slony集群
默认情况下，slony的配置文件样本已默认安装至/usr/local/etc/slon_tools.conf-sample。
cd /usr/local/etc
--复制一个slon_tools.conf-sample，命名为slon_tools.conf
[root@localhost etc]#cp slon_tools.conf-sample /usr/local/etc/slon_tools.conf
--开始编辑slon_tools.conf
[root@localhost etc]#vi slon_tools.conf
配置详情：
#修改CLUSTER_NAME为前面我们设置的
# The name of the replication cluster. This will be used to
# create a schema named _$CLUSTER_NAME in the database which will
# contain Slony-related data.
$CLUSTER_NAME = 'lyy_cluster1';
#slony的pid文件目录。如果没有，则根据提示创建，并授予要求的权限。
# The directory where Slony store PID files. This
# directory will need to be writable by the user that invokes
# Slony.
$PIDFILE_DIR = '/var/run/slony1';
#日志文件存储目录，如果没有，则修改配置或者根据配置创建目录。
# The directory where Slony should record log messages. This
# directory will need to be writable by the user that invokes
# Slony.
$LOGDIR = '/var/log/slony1';
#修改节点信息为我们的主、备节点的信息，样本中提供的多出的节点可以注释或者删除掉。
# Include add_node lines for each node in the cluster. Be sure to
# use host names that will resolve properly on all nodes
# (i.e. only use 'localhost' if all nodes are on the same host).
# Also, note that the user must be a superuser account.
add_node(node => 1,
host => '162.168.100.240',
dbname => 'masterdb',
port => 5432,
user => 'postgres',
password => 'postgres');
add_node(node => 2,
host => '192.168.100.241',
dbname => 'slavedb',
port => 5432,
user => 'postgres',
password => 'postgres');
#修改要同步的表或者序列
# This array contains a list of tables that already have primary keys.
"pkeyedtables" => [
'public.lyy',
],
#如果没有序列和无主键表需要同步，则将以下示例注释掉。
# For tables that have unique not null keys, but no primary
# key, enter their names and indexes here.
#lyy comment this
# "keyedtables" => {
# 'table3' => 'index_on_table3',
# 'table4' => 'index_on_table4',
# },
# Sequences that need to be replicated should be entered here.
# lyy comment this
# "sequences" => ['sequence1',
# 'sequence2',
# ],
},
#在主库，初始化slony cluster
[root@localhost etc]# slonik_init_cluster | /opt/pgsql92/bin/slonik
<stdin>:10: Set up replication nodes
<stdin>:13: Next: configure paths for each node/origin
<stdin>:16: Replication nodes prepared
<stdin>:17: Please start a slon replication daemon for each node
注释：同样的，本步执行完毕后，初始化完毕一个名为lyy_cluster1的slony集群。
并相应的产生一个名为_lyy_cluster1的模式，里面含有slony运行所需的配置表、序列、函数、触发器等(主要是通过slony-i安装过程中在/opt/pgsql92/share下生成的slony1_base.2.2.4.sql和slony1_funcs.2.2.4.sql)。
启动slon并进行数据集合订阅：
# 在主库，启动节点1的slon
[root@localhost etc]# slon_start 1
Invoke slon for node 1 - /opt/pgsql92/bin//slon -p /var/run/slony1/lyy_cluster2_node1.pid -s 1000 -d2 lyy_cluster1 'host=192.168.100.240 dbname=master user=postgres port=5432 password=postgres' > /var/log/slony1/node1/master-2015-09-15.log 2>&1 &
Slon successfully started for cluster lyy_cluster1, node node1
PID [7839]
Start the watchdog process as well...
# 在备库，启动节点2的slon
[root@localhost etc]# slon_start 2
Invoke slon for node 2 - /opt/pgsql92/bin//slon -p /var/run/slony1/cluster1_node2.pid -s 1000 -d2 cluster1 'host=192.168.100.241 dbname=slavedb user=postgres port=5432 password=postgres' > /var/log/slony1/node2/slavedb-2015-09-15.log 2>&1 &
Slon successfully started for cluster lyy_cluster1, node node2
PID [7613]
Start the watchdog process as well...
# 在主库，创建数据集合 (此处 1 是一个 set 集合号)
[root@localhost etc]# slonik_create_set 1 | /opt/pgsql92/bin/slonik
<stdin>:11: Subscription set 1 (set1_name) created
<stdin>:12: Adding tables to the subscription set
<stdin>:16: Add primary keyed table public.lyy
<stdin>:19: Adding sequences to the subscription set
<stdin>:20: All tables added
# 在主库，订阅 集合1 到 节点2 (1= set ID, 2= node ID)
[root@localhost etc]# slonik_subscribe_set 1 2 | /opt/pgsql92/bin/slonik
<stdin>:6: Subscribed nodes to set 1
目前，本次数据库的slony的同步复制已经配置完毕。
验证slony-I同步复制生效
在主库，向表lyy插入数据：
[postgres@localhost bin]$ ./psql -U postgres -d masterdb
psql (9.2.13)
Type "help" for help.
masterdb=# insert into lyy values(1,'lyy');
INSERT 0 1
在备库，查询表lyy中的数据情况：
postgres@localhost bin]$ ./psql -U postgres -d slavedb
psql (9.2.13)
Type "help" for help.
slavedb=# select * from lyy;
id | name
----+------
(0 rows)
slavedb=# select * from lyy;
id | name
----+------
1 | lyy
(1 row)
可以在主库执行增删操作，然后在备库执行查询操作，进行比对。
5.Slony-I的其他操作
slony的switchover操作（也就是把主节点改成从节点，从节点升级为主节点）：
slonik_move_set set1 node1 node2 | /opt/pgsql92/bin/slonik
slony的failver操作:
slonik_failover node1 node2 | /opt/pgsql92/bin/slonik
6.在pgadmin中配置使用slony-I
转至：http://my.oschina.net/liuyuanyuangogo/blog/507936
7.slony-I的使用限制
Slony-I只能同步以下内容：
1.表数据(不能同步DDL，表必须含有主键或者唯一键)
2.序列
Slony-I不能自动同步以下内容：
1.对大对象(BLOBS)的变更
2.对DDL（数据定义语句）的变更
3.对用户和角色的变更
这些使用限制的主要原因是：slony-I是通过触发器收集变更情况的，而触发器不能够捕获定义和大对象的修改。对于DDL的变更，slony-I提供了SLONIK EXECUTE SCRIPT命令来执行DDL的SQL脚本，但slony-I不会自动执行，你得手动组织变更的DDL sql语句并用SLONIK EXECUTE SCRIPT（当然这也可以通过直接到备库执行sql语句来实现定义修改）。
另外，如果表定义中with oid，那么原库中的表记录oid的取值不能同步为相同的值。
建议：如果您无法接受以上使用限制，那您值得尝试一下PostgrSQL 8.0之后的PITR（Point in Time Recovery），PITR对于远程节点是基于WAL日志的。
参考资料：
========
http://www.cnblogs.com/gaojian/p/3196244.html
http://blog.chinaunix.net/uid-15145533-id-2775796.html
也可以只用pgbench来测试slony-i的数据同步。
pgbench使用：http://www.postgresql.org/docs/9.2/static/pgbench.html
