walmgr - tools for managing WAL-based replication for PostgreSQL.
walmgr.py <config.ini> command
It is both admin and worker script for PostgreSQL PITR replication.
Set up passwordless ssh authentication from master to slave
master$ test -f ~/.ssh/id_dsa.pub || ssh-keygen -t dsa master$ cat ~/.ssh/id_dsa.pub | ssh slave cat \>\> .ssh/authorized_keys
master$ edit master.ini slave$ edit slave.ini
Make sure that walmgr.py executable has same pathname on slave and master.
Start archival process and create a base backup
master$ ./walmgr.py master.ini setup master$ ./walmgr.py master.ini backup
Note: starting from PostgreSQL 8.3 the archiving is enabled by setting archive_mode GUC to on. However changing this parameter requires the server to be restarted.
Prepare postgresql.conf and pg_hba.conf on slave and start replay
master$ scp $PGDATA/*.conf slave: slave$ ./walmgr.py slave.ini restore
For debian based distributions the standard configuration files are located in /etc/postgresql/x.x/main directory. If another scheme is used the postgresql.conf and pg_hba.conf should be copied to slave full_backup directory. Make sure to disable archive_command in slave config.
'walmgr.py restore' moves data in place, creates recovery.conf and starts postmaster in recovery mode.
In-progress WAL segments can be backup by command:
master$ ./walmgr.py master.ini sync
If need to stop replay on slave and boot into normal mode, do:
slave$ ./walmgr.py slave.ini boot
Common options to all walmgr.py commands.
- -h, --help
show this help message and exit
- -q, --quiet
make program silent
- -v, --verbose
make program more verbose
- -n, --not-really
Show what would be done without actually doing anything.
Sets up postgres archiving, creates necessary directory structures on slave.
Synchronizes in-progress WAL files to slave.
Start WAL synchronization in daemon mode. This will start periodically synching the in-progress WAL files to slave.
The following parameters are used to drive the syncdaemon: loop_delay - how long to sleep between the synchs. use_xlog_functions - use record based shipping to synchronize in-progress WAL segments.
Deconfigures postgres archiving.
Runs periodic command, if configured. This enables to execute arbitrary commands on interval, useful for synchronizing scripts, config files, crontabs etc.
List backup sets available on slave node.
Creates a new base backup from master database. Will purge expired backups and WAL files on slave if keep_backups is specified. During a backup a lock file is created in slave completed_wals directory. This is to prevent simultaneous backups and resulting corruption. If running backup is terminated, the BACKUPLOCK file may have to be removed manually.
restore <set> <dst>
EXPERIMENTAL. Attempts to restore the backup from slave to master.
Stop log playback and bring the database up.
Pauses WAL playback.
Continues previously paused WAL playback.
Lists available backups.
EXPERIMENTAL. Creates a new backup from slave data. Log replay is paused, slave data directory is backed up to full_backup directory and log replay resumed. Backups are rotated as needed. The idea is to move the backup load away from production node. Usable from postgres 8.2 and up.
Restores the specified backup set to target directory. If specified without arguments the latest backup is moved to slave data directory (doesn’t obey retention rules). If src backup is specified the backup is copied (instead of moving). Alternative destination directory can be specified with dst.
Optional. Indentifies this script, used in logging. Keep unique if using central logging.
Where to log.
Optional. If nonzero, skylog.ini is used for log configuration.
Pid file location for syncdaemon mode (if running with -d). Otherwise not required.
Database to connect to for pg_start_backup() etc. It is not a good idea to use dbname=template if running syncdaemon in record shipping mode.
Master data directory location.
Master postgresql.conf file location. This is where archive_command gets updated.
The command to restart master database, this used after changing archive_mode parameter. Leave unset, if you cannot afford to restart the database at setup/stop.
Slave host and base directory.
Configuration file location for the slave walmgr.
Slave directory where archived WAL files are copied.
Slave directory where incomplete WAL files are stored.
Slave directory where full backups are stored.
Slave directory where configuration file backups are stored. Optional.
The frequency of syncdaemon updates. In record shipping mode only incremental updates are sent, so smaller interval can be used.
Use pg_xlog functions for record based shipping (available in 8.2 and up).
If nonzero, a -z flag is added to rsync cmdline. Will reduce network traffic at the cost of extra CPU time.
Shell script to be executed at specified time interval. Can be used for synchronizing scripts, config files etc.
How ofter to run periodic command script. In seconds, and only evaluated at log switch times.
Boolean. If set to true, walmgr setup will set wal_level to hot_standby (9.0 and newer).
[wal-master] logfile = master.log pidfile = master.pid master_db = dbname=template1 master_data = /var/lib/postgresql/8.0/main master_config = /etc/postgresql/8.0/main/postgresql.conf slave = slave:/var/lib/postgresql/walshipping completed_wals = %(slave)s/logs.complete partial_wals = %(slave)s/logs.partial full_backup = %(slave)s/data.master loop_delay = 10.0 use_xlog_functions = 1 compression = 1
Postgres data directory for the slave. This is where the restored backup is copied/moved.
Directory for postgres configuration files. If specified, "walmgr restore" attempts to restore configuration files from config_backup directory.
Script to stop postmaster on slave.
Script to start postmaster on slave.
Base directory for slave files (logs.complete, data.master etc)
Specifies the location of postgres binaries (pg_controldata, etc). Needed if they are not already in the PATH.
Directory where complete WAL files are stored. Also miscellaneous control files are created in this directory (BACKUPLOCK, STOP, PAUSE, etc.).
Directory where partial WAL files are stored.
Directory where full backups are stored.
Number of backups to keep. Also all WAL files needed to bring earliest
backup up to date are kept. The backups are rotated before new backup is started, so at one point there is actually one less backup available.
It probably doesn’t make sense to specify keep_backups if periodic backups are not performed - the WAL files will pile up quickly.
Backups will be named data.master, data.master.0, data.master.1 etc.
Script to execute before rotating away the oldest backup. If it fails backups will not be rotated.
Set slave_pg_xlog to the directory on the slave where pg_xlog files get written to. On a restore to the slave walmgr.py will create a symbolic link from data/pg_xlog to this location.
Set backup_datadir to no to prevent walmgr.py from making a backup of the data directory when restoring to the slave. This defaults to yes
[wal-slave] logfile = slave.log slave_data = /var/lib/postgresql/8.0/main slave_stop_cmd = /etc/init.d/postgresql-8.0 stop slave_start_cmd = /etc/init.d/postgresql-8.0 start slave = /var/lib/postgresql/walshipping completed_wals = %(slave)s/logs.complete partial_wals = %(slave)s/logs.partial full_backup = %(slave)s/data.master keep_backups = 5 backup_datadir = yes