The document explains the concept of Point-In-Time Recovery (PITR) and related functionalities such as log shipping, warm standby, and replication in PostgreSQL. It introduces PITR tools that streamline backup processes, detailing configuration steps for both archiving and standby/slave environments, along with commands and usage guidelines. The document further covers troubleshooting, monitor setup for alerts, and invites donations to support PostgreSQL development.

1. PITR made easy
Joshua Drake
United States PostgreSQL
Software in the Public Interest
Command Prompt, Inc.

2. What is PITR
Log shipping/Warm Standby/Replication

3. What can you do with it?
Simple asynchornous failover scenarios
Low impact backups
Simple archivals

4. What can't you do with it?
Read only slave

5. Why is PITR hard?
It was written by open source engineers.

6. Uses the many tools to one solution
rsync?
nfs?
walmgr?
scp?
Push or pull?
Something else?

7. What makes PITR easy?
PITR tools
BSD Licensed
Written in Python
(theoretically cross platform)

8. What is PITRTools
A simple wrapper around all the utilities you
already have.
ssh,rsync,pg_standby,postgresql

9. Features?
Warm standby
Cold Storage
Fail over (actionable)
Arbitrary alerts (monitoring)

10. How does it work?
success
Master Slave
else
Queue

11. The process on the archiver/master
On the archiver/Master:
● Configure ssh key for postgres user to
standby/slave
● Configure archiver.ini
● cmd_archiver -C /path/to/archiver.ini -I
● Edit the postgresql.conf change:
● archive_mode to on
● archive_command to:
● cmd_archiver -C /path/to/archiver.ini -F %p
● restart postgresql
● apply cmd_standby.sql to database of pitr user
(usually postgres)
● psql -U postgres < /path/to/cmd_standby/sql

12. The archiver
The archiver calls cmd_archive.py which calls rsync to “push” the
file to the slave or queue.
Usage: cmd_archiver [options] arg1 arg2
Options:
-h, --help show this help message and exit
-F FILE, --file=FILE Archive file
-C FILE, --config=FILE
the name of the archiver config file
-f, --flush Flush all remaining archives to slave
-I, --init Initialize master environment

13. The archiver config file
Useful but obvious parameters
[DEFAULT]
state: online
pgdata: /var/lib/postgresql/8.3/main
rsync_bin: /usr/bin/rsync
rsync_version = 2 # Because RH ships old software
user: postgres
timeout: 10
debug: on
ssh_debug: off

14. The “other” archiver options
r_archivedir: /var/lib/postgresql/archive
l_archivedir: /var/lib/postgresql/archive
rsync_version = 2
slaves: 192.168.1.201,192.168.1.202
notify_ok: /var/lib/postgresql/etc/archiver_ok.sh
notify_warning: /var/lib/postgresql/etc/archiver_warning.sh
notify_critical: /var/lib/postgresql/etc/archiver_critical.sh

15. cmd_standby.py
 Works in conjunction with pg_standby
 Supports failover
 Supports recovery to a point in time
 Included with 8.3, available for 8.1 and 8.2 (8.1
is flaky)

16. The process on the slave
On the standby/slave:
● Configure SSH key for postgres user to master
● Configure cmd_standby.ini
● Initialize environment
● cmd_standby -C /path/to/cmd_standby.ini -I
● Start base backup
● cmd_standby -C /path/to/cmd_standby.ini -B
● Start standby
● cmd_standby -C /path/to/cmd_standby.ini -S

17. The standby configuration
[DEFAULT]
pgversion: 8.2
numarchives: 10
ssh: /usr/bin/ssh
rsync: /usr/bin/rsync
pg_standby: /usr/lib/postgresql/8.3/bin/pg_standby
pg_ctl: /usr/lib/postgresql/8.3/bin/pg_ctl
r_psql: /usr/lib/postgresql/8.3/bin/psql
port: 6000
master_public_ip: 192.168.3.254
master_local_ip: 127.0.0.1
user: postgres
debug: off
ssh_timeout: 30

18. Configuring the standby cont...
archivedir: /data2/pgsql/archive/
pgdata: /data1/pgsql/data/
postgresql_conf: /var/lib/postgresql/etc/postgresql.conf
pg_hba_conf: /var/lib/postgresql/etc/pg_hba.conf
notify_critical: /var/lib/postgresql/etc/standby_critical.sh
notify_warning: /var/lib/postgresql/etc/standby_warning.sh
notify_ok: /var/lib/postgresql/etc/standby_ok.sh
action_failover: /var/lib/postgresql/pitr_tools/failover.sh

19. Start the standby
Usage: cmd_standby [options] arg1 arg2
Options:
-h, --help show this help message and exit
-A start|stop, --action=start|stop|stop_basebackup
Start or Stop PostgreSQL
-B, --basebackup Start/Stop a base backup
-C FILE, --config=FILE
Name of the archiver config file
-F VALUE, --failover=VALUE
If you are serious, set -F999
-I, --dbinit Use before -B
-P, --ping Is my master alive?
-R TIMESTAMP, --recovertotime=TIMESTAMP
To restore to a specific point in time
-S, --standby Enter standby mode

20. Is the archiver working?

21. Is the standby is working?

22. How do I?
 Use PITRTools to simplify backups?
 Take the archiver offline?
 Configure send_nsca (nagios) for alerts
 Donate to PostgreSQL?

23. Simplify backups
On the standby/slave:

 cmd_standby -C
/var/lib/postgresql/etc/cmd_standby.ini -Astop
 tar -czvf /backups/database.`date +%a`.tar.gz
/var/lib/pgsql/data
 cmd_standby -C
/var/lib/postgresql/etc/cmd_standby.ini -S
You could also use rsync with a network volume to make
the backup more efficient (after stopping the standby)

24. Take the archiver offline
 Edit /var/lib/postgresql/etc/cmd_archiver.ini
[DEFAULT]
; online or offline
state: offline
When you are ready to bring it back online, just change to
online. No restarts on archiver or standby required.

25. Configure send_nsca
 Example ok.sh for send_nsca
#!/bin/sh
echo "shoggoth;CMD_ARCHIVER;0;Archived to Yugg"|
/usr/sbin/send_nsca -to 10 -H monitor -d ';' -c /etc/
nagios/send_nsca.cfg

26. Donate to PostgreSQL
 For United States PostgreSQL:
 https://www.postgresql.us/donate
 For PostgreSQL Generally:
 http://www.postgresql.org/about/donate

27. Questions
Hit me