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接前面例子， 简单的Slony-I设置实例
这次我增加一台机器C: 192.168.10.100，我尽量从该机器上发送slonik命令
机器A和机器B启动之后：
执行初始化cluster动作：
[postgres@pg102 ~]$ cat setup.sh #!/bin/sh CLUSTERNAME=testdb3_cluster MASTERDBNAME=testdb3 SLAVEDBNAME=testdb3 MASTERHOST=192.168.10.102 SLAVEHOST=192.168.10.101 REPLICATIONUSER=postgres /usr/local/slony/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 testdb3 tables'); set add table (set id=1, origin=1, id=1, fully qualified name = 'public.t1', comment='t1 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@pg102 ~]$
sh setup.sh
然后：
分别在机器A和机器B中，看到各自建立了一个名字空间(namespace，其实是schema)：
机器A:
[postgres@pg102 bin]$ ./psql psql (9.1.2) Type "help" for help. postgres=# \c testdb3 You are now connected to database "testdb3" as user "postgres". testdb3=# select * from pg_namespace; nspname | nspowner | nspacl --------------------+----------+------------------------------------- pg_toast | 10 | pg_temp_1 | 10 | pg_toast_temp_1 | 10 | pg_catalog | 10 | {postgres=UC/postgres,=U/postgres} public | 10 | {postgres=UC/postgres,=UC/postgres} information_schema | 10 | {postgres=UC/postgres,=U/postgres} _testdb3_cluster | 10 | {postgres=UC/postgres,=U/postgres} (7 rows) testdb3=# create table _testdb3_cluster.gao(id integer); CREATE TABLE testdb3=# drop table _testdb3_cluster; ERROR: table "_testdb3_cluster" does not exist testdb3=# drop table _testdb3_cluster.gao; DROP TABLE testdb3=#
机器B:
[postgres@pg101 bin]$ ./psql psql (9.1.2) Type "help" for help. postgres=# \c testdb3 You are now connected to database "testdb3" as user "postgres". testdb3=# select * from pg_namespace; nspname | nspowner | nspacl --------------------+----------+------------------------------------- pg_toast | 10 | pg_temp_1 | 10 | pg_toast_temp_1 | 10 | pg_catalog | 10 | {postgres=UC/postgres,=U/postgres} information_schema | 10 | {postgres=UC/postgres,=U/postgres} public | 10 | {postgres=UC/postgres,=UC/postgres} _testdb3_cluster | 10 | {postgres=UC/postgres,=U/postgres} (7 rows) testdb3=#
可以这样说，在slony的环境中，并不存在一个中心节点来存储cluster信息。
这种方式加上各种指令为中心的处理结构，导致其架构复杂化。
接下来，看看可否另slon daemon独立于DB节点运行：
我在机器C上执行：
/usr/local/slony/bin/slon testdb3_cluster "dbname=testdb3 user=postgres host=192.168.10.102" & /usr/local/slony/bin/slon testdb3_cluster "dbname=testdb3 user=postgres host=192.168.10.101" &
然后，此时，再在机器C上执行 subscribe 过程：
[postgres@pg102 ~]$ cat subscribe.sh #!/bin/sh CLUSTERNAME=testdb3_cluster MASTERDBNAME=testdb3 SLAVEDBNAME=testdb3 MASTERHOST=192.168.10.102 SLAVEHOST=192.168.10.101 REPLICATIONUSER=postgres /usr/local/slony/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=$REPLICATIONUSER'; # ---- # Node 2 subscribes set 1 # ---- subscribe set ( id = 1, provider = 1, receiver = 2, forward = no); _EOF_ [postgres@pg102 ~]$ sh subscribe.sh
验证：
在master数据库节点，增加数据：
testdb3=# INSERT INTO t1(comment) VALUES('replication test');
INSERT 0 1
testdb3=# select * from t1;
id | comment | ins_time
----+------------------+----------------------------
2 | replication test | 2013-07-18 13:47:30.023486
(1 row)
testdb3=#
此时，在 slave数据库节点，也可以看到同样的数据：已经成功。
[root@pg101 ~]# su - postgres [postgres@pg101 ~]$ psql testdb3 psql (9.1.2) Type "help" for help.
testdb3=# select * from t1;
id | comment | ins_time
----+------------------+----------------------------
2 | replication test | 2013-07-18 13:47:30.023486
(1 row)
testdb3=#
已经成功完成复制。
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磨砺技术珠矶，践行数据之道，追求卓越价值