PostgreSQL Replication describes PostgreSQL Replicator, an open source solution for replicating PostgreSQL databases. Key features include asynchronous replication from a master to multiple slaves, supporting various replication types like role, grant, and large object replication without triggers. Replicator uses a Master Control Process to manage replication between nodes. It allows unlimited slaves without impacting the master and operates on any server.

1. PostgreSQL Replication
Joshua D. Drake / Command Prompt, Inc.
Major Contributor PostgreSQL.Org
President PgUS

2. Why
PostgreSQL + Replicator represents the easiest
and most flexible PostgreSQL replication
solution to date.

3. What features does it support?
● Master to many (Asynchronous) slaves
● Partial Sets
● Unique features
– Role replication
– Grant replication
– Large object replication
– Transaction logs, not triggers
● Failover/Promote
● Integrated, no triggers, easy DDL

4. Open Source + Supported
● BSD Licensed
● Open Community
● https://projects.commandprompt.com/public/replicator
● Supported
● Commercially from http://www.commandprompt.com

5. Get it!
● RPM:
– http://www.pgsqlrpms.org/
● Source:
● #! svn co
https://projects.commandprompt.com/public/replicator/repo
● Debian/Ubuntu
● Working on it

6. Compile it
● jd@hardy:~/repos$ cd REPLICATOR-8.3-1.8/
● jd@hardy:~/repos/REPLICATOR-8.3-1.8$ autoconf
● jd@hardy:~/repos/REPLICATOR-8.3-1.8$ ./configure
--prefix=/tmp/replicator
– checking build system type... i686-pc-linux-gnu
– checking host system type... i686-pc-linux-gnu
– checking which template to use... linux
– checking whether to build with 64-bit integer date/time support...
no
– checking whether NLS is wanted... no
– checking for default port number... 5432
– [...]

7. Install it
● jd@hardy:~/repos/REPLICATOR-8.3-1.8$ make -j2
install
– make -C doc install
– make[1]: Entering directory `/home/jd/repos/REPLICATOR-8.3-1.8/doc'
– make[1]: Nothing to be done for `install'.
– make[1]: Leaving directory `/home/jd/repos/REPLICATOR-8.3-1.8/doc'
– make -C src install
–
● [...]

8. Test it
● jd@hardy:~/repos/REPLICATOR-8.3-1.8$ cd src/test/
replication
● jd@hardy:~ PGROOT=/tmp/replicator ./test.pl | grep
-i succeeded

9. If only it could be... always
● test1 succeeded ● test12 succeeded
● test2 succeeded ● test14 succeeded
● test4 succeeded ● test15 succeeded
● test5 succeeded ● test16 succeeded
● test6 succeeded ● test17 succeeded
● test7 succeeded ● test_lo succeeded
● test8 succeeded
● test9 succeeded
● test10 succeeded
● test11 succeeded

10. Initialize Master
● jd@hardy:~/$ cd /tmp/replicator
● jd@hardy:/$ bin/initdb -D data
● jd@hardy:/$ bin/pg_ctl -D data start
● jd@hardy:/$ bin/createdb -U postgres repl_test;
● jd@hardy:/$ bin/pg_ctl -D data stop
● jd@hardy:/$ bin/init-mammoth-database -D data
repl_test
Database repl_test ready for
Mammoth Replicator

11. The postgresql.conf
● replication_enable = false
● replication_mode = master
● replication_slave_no = 0
● replication_database = 'repl_test'
● replication_mcp_address = '127.0.0.1'
● replication_mcp_port = 7777
● replication_mcp_authkey = 'mcp-key'
● replication_data_path = 'rlog'
●

12. postgresql.conf (2)
● replication_mcp_require_ssl = false
● replication_compression = true
● replication_use_utf8_encoding = true

13. Apply useful functions
● pg_ctl -D data start
● psql -U jd repl_test <
/tmp/replicator/share/postgresql/replicator-
functions.sql

14. The MCP
● Master Control Process
– Manages replication between nodes
● Transactions
● Promotion
● Status
– Has queueing mechanism
– Unlimited (in theory) slaves without impact on
master
– Operates on any server

15. mcp_server.conf
● mcp_listen_address = "0.0.0.0"
● mcp_listen_port = 7777
● mcp_authkey = "mcp-key"
● mcp_master_address = "127.0.0.1"
● mcp_max_slaves =5
● mcp_slave_addresses = "0:192.168.0.1, 1:192.168.0.1"
● mcp_promote_allow = ""

16. mcp_server.conf (2)
● mcp_queue_min_size = 16000000
● mcp_queue_max_size = 32000000
● mcp_require_ssl =0
● log_level = "log"
● replication_data_path = "rlog”

17. Fire up
● Start the mcp
– mcp_server -D /data/mcp_data
● Start Replication on relation
– Make sure you have a primary key
– ALTER TABLE foo ENABLE REPLICATION
– ALTER TABLE foo ENABLE REPLICATION ON SLAVE 0;
● Replicate the whole database
– SELECT enable_replication_global('{0}')

18. Check the status
type brecno frecno vrecno lrecno sync connected timestamp
master 888 888 0 497519 sync true Sat Jan 31 08:41:35
slave 0 - 497520 497519 - sync true Sat Jan 31 08:41:35
slave 1 - 888 0 - desync false Wed Dec 31 16:00:00
slave 2 - 888 0 - desync false Wed Dec 31 16:00:00
slave 3 - 888 0 - desync false Wed Dec 31 16:00:00
slave 4 - 888 0 - desync false Wed Dec 31 16:00:00
(In the normal output year is there too)

19. Fail over
Two modes:
– PROMOTE
– PROMOTE FORCE;