PITR made easy

Joshua Drake

United States PostgreSQL

Software in the Public Interest

Command Prompt, Inc.Creative Commons Attribution-Share Alike 3.0 United States License

What is PITR

Log shipping/Warm Standby/Replication

What can you do with it?

Simple asynchronous fail over scenariosLow impact backups

Simple archiving

What can't you do with it?

Read only slave

Why is PITR hard?

It was written by open source engineers.

Uses the many tools to one solution

rsync?nfs?

walmgr?scp?

Push or pull?Something else?

What makes PITR easy?

PITR toolsBSD Licensed

Written in Python(theoretically cross platform)

What is PITRTools

A simple wrapper around all the utilities you already have.

ssh,rsync,pg_standby,postgresql

Designed by a consultant (KISS)

PITRTools Features?

Warm standbyCold Storage

Fail over (actionable)Arbitrary alerts (monitoring)

Single protocol (security)

How does it work?

Queue

SlaveMastersuccess

else

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

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

The archiver config file

Useful but obvious parameters

[DEFAULT]state: onlinepgdata: /var/lib/postgresql/8.3/mainrsync_bin: /usr/bin/rsyncrsync_version = 2 # Because RH ships old softwareuser: postgrestimeout: 10debug: onssh_debug: off

The “other” archiver options

r_archivedir: /var/lib/postgresql/archivel_archivedir: /var/lib/postgresql/archiversync_version = 2slaves: 192.168.1.201,192.168.1.202notify_ok: /var/lib/postgresql/etc/archiver_ok.shnotify_warning: /var/lib/postgresql/etc/archiver_warning.shnotify_critical: /var/lib/postgresql/etc/archiver_critical.sh

Configuring archiver with pitrtools

● 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

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)

The process on the slave/standby

On the standby/slave:● Configure SSH key for postgres user to master● Configure cmd_standby.ini

The standby configuration

[DEFAULT]pgversion: 8.2numarchives: 10ssh: /usr/bin/sshrsync: /usr/bin/rsyncpg_standby: /usr/lib/postgresql/8.3/bin/pg_standbypg_ctl: /usr/lib/postgresql/8.3/bin/pg_ctlr_psql: /usr/lib/postgresql/8.3/bin/psqlport: 6000master_public_ip: 192.168.3.254master_local_ip: 127.0.0.1user: postgresdebug: off ssh_timeout: 30

Configuring the standby cont...

archivedir: /data2/pgsql/archive/pgdata: /data1/pgsql/data/postgresql_conf: /var/lib/postgresql/etc/postgresql.confpg_hba_conf: /var/lib/postgresql/etc/pg_hba.confnotify_critical: /var/lib/postgresql/etc/standby_critical.shnotify_warning: /var/lib/postgresql/etc/standby_warning.shnotify_ok: /var/lib/postgresql/etc/standby_ok.shaction_failover: /var/lib/postgresql/pitr_tools/failover.sh

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

Initializing the slave/standby

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

Is the archiver working?

With debug: on

Is the standby is working?

How do I?

Use PITRTools to simplify backups? Take the archiver offline? Configure send_nsca (nagios) for alerts Get PITRTools Donate to PostgreSQL?

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)

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.

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

Get PITRTools

svn co \https://projects.commandprompt.com/public \/pitrtools/repo

Donate to PostgreSQL

For United States PostgreSQL: https://www.postgresql.us/donate

For PostgreSQL Generally: http://www.postgresql.org/about/donate

Questions

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