--- name: "walmgr" section: "1" platform: "linux" package: "skytools" version: "2.1.8-2.2" release: "Debian 6.0 (Squeeze)" platforms: ["linux"] url: "https://new.carta.tech/walmgr" --- # walmgr(1) tools for managing WAL-based replication for PostgreSQL. ## NAME walmgr - tools for managing WAL-based replication for PostgreSQL. ## SYNOPSIS ``` walmgr.py command ``` ## DESCRIPTION It is both admin and worker script for PostgreSQL PITR replication. ## QUICK START 1\. 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 ``` 2\. Configure paths ``` master$ edit master.ini slave$ edit slave.ini ``` ``` Make sure that walmgr.py executable has same pathname on slave and master. ``` 3\. Start archival process and create a base backup ``` master$ ./walmgr.py master.ini setup master$ ./walmgr.py master.ini backup ``` 4\. 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. ``` 5\. In-progress WAL segments can be backup by command: ``` master$ ./walmgr.py master.ini sync ``` 6\. If need to stop replay on slave and boot into normal mode, do: ``` slave$ ./walmgr.py slave.ini boot ``` ## GENERAL OPTIONS 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. ## MASTER COMMANDS ### setup Sets up postgres archiving, creates necessary directory structures on slave. ### sync Synchronizes in-progress WAL files to slave. ### syncdaemon Start WAL synchronization in daemon mode. This will start periodically synching the in-progress WAL files to slave. loop\_delay use\_xlog\_functions ### stop Deconfigures postgres archiving. ### periodic Runs periodic command, if configured. This enables to execute arbitrary commands on interval, useful for synchronizing scripts, config files, crontabs etc. ### listbackups List backup sets available on slave node. ### backup 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 \ \ EXPERIMENTAL. Attempts to restore the backup from slave to master. ## SLAVE COMMANDS ### boot Stop log playback and bring the database up. ### pause Pauses WAL playback. ### continue Continues previously paused WAL playback. ### listbackups Lists available backups. ### backup 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. ### restore \[src\]\[dst\] 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. ## CONFIGURATION ### Common settings job\_name Optional. Indentifies this script, used in logging. Keep unique if using central logging. logfile Where to log. use\_skylog Optional. If nonzero, skylog.ini is used for log configuration. ### Master settings pidfile Pid file location for syncdaemon mode (if running with -d). Otherwise not required. master\_db 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 Master data directory location. master\_config Master postgresql.conf file location. This is where archive\_command gets updated. slave Slave host and base directory. completed\_wals Slave directory where archived WAL files are copied. partial\_wals Slave directory where incomplete WAL files are stored. full\_backup Slave directory where full backups are stored. loop\_delay The frequency of syncdaemon updates. In record shipping mode only incremental updates are sent, so smaller interval can be used. use\_xlog\_functions Use pg\_xlog functions for record based shipping (available in 8.2 and up). compression If nonzero, a -z flag is added to rsync cmdline. Will reduce network traffic at the cost of extra CPU time. periodic\_command Shell script to be executed at specified time interval. Can be used for synchronizing scripts, config files etc. command\_interval How ofter to run periodic command script. In seconds, and only evaluated at log switch times. ### Sample master.ini ``` [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 ``` ### Slave settings slave\_data Postgres data directory for the slave. This is where the restored backup is copied/moved. slave\_stop\_cmd Script to stop postmaster on slave. slave\_start\_cmd Script to start postmaster on slave. slave Base directory for slave files (logs.comlete, data.master etc) completed\_wals Directory where complete WAL files are stored. Also miscellaneous control files are created in this directory (BACKUPLOCK, STOP, PAUSE, etc.). partial\_wals Directory where partial WAL files are stored. full\_backup Directory where full backups are stored. keep\_backups 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. archive\_command Script to execute before rotating away the oldest backup. If it fails backups will not be rotated. ### Sample slave.ini ``` [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 ```