OmniPITR - omnipitr-backup-slave

USAGE

/some/path/omnipitr/bin/omnipitr-backup-slave [options]

Options:

--data-dir (-D)

Where PostgreSQL datadir is located (path)

--database (-d)

Which database to connect to to issue required SQL queries. Defaults to template1.

This is used only when --call-master is given.

--host (-h)

Which host to connect to when connecting to database to backup. Shouldn't really be changed in 99% of cases. Defaults to empty string - i.e. use UNIX sockets.

This is used only when --call-master is given.

--port (-P)

Which port to connect to when connecting to database. Defaults to 5432.

This is used only when --call-master is given.

--username (-U)

What username to use when connecting to database. Defaults to postgres.

This is used only when --call-master is given.

--source (-s)

Where are WAL files delivered by omnipitr-archive and used by omnipitr-restore

You can also specify compression for source. Check COMPRESSION section of the doc.

--dst-local (-dl)

Where to copy the hot backup files on current server (you can provide many of these).

You can also specify compression per-destination. Check COMPRESSION section of the doc.

--dst-remote (-dr)

Where to copy the hot backup files on remote server. Supported ways to transport files are rsync and rsync over ssh. Please see DESCRIPTION for more information (you can provide many of these)

You can also specify compression per-destination. Check COMPRESSION section of the doc.

--temp-dir (-t)

Where to create temporary files (defaults to /tmp or $TMPDIR environment variable location)

--log (-l)

Name of logfile (actually template, as it supports %% strftime(3) markers. Unfortunately due to the %x usage by PostgreSQL, We cannot use %% macros directly. Instead - any occurence of ^ character in log dir will be first changed to %, and later on passed to strftime.

--filename-template (-f)

Template for naming output files. Check FILENAMES section for details.

--pid-file

Name of file to use for pidfile. If it is specified, than only one copy of omnipitr-backup-slave (with this pidfile) can run at the same time.

Trying to run second copy of omnipitr-backup-slave will result in an error.

--removal-pause-trigger (-p)

name of file to be created to pause removal of old/obsolete segments. Should be the same as condigured removal-pause-trigger for omnipitr-restore.

--call-master (-cm)

If this option is given, omnipitr-backup-slave will issue

SELECT pg_start_backup( '...' );

and

SELECT pg_stop_backup()

on master database.

Backups on PostgreSQL 9.0+, on slave, without --call-master can fail when later used.

--verbose (-v)

Log verbosely what is happening.

--not-nice (-nn)

Do not use nice for compressions.

--digest (-dg)

Digest method to use (eg MD5 or SHA-1) for checksumming. Can be a comma seperated list to use multiple digest algorithms.

For details please check CHECKSUMMING below.

--gzip-path (-gp)

Full path to gzip program - in case you can't set proper PATH environment variable.

--bzip2-path (-bp)

Full path to bzip2 program - in case you can't set proper PATH environment variable.

--lzma-path (-lp)

Full path to lzma program - in case you can't set proper PATH environment variable.

--nice-path (-np)

Full path to nice program - in case you can't set proper PATH environment variable.

--tar-path (-tp)

Full path to tar program - in case you can't set proper PATH environment variable.

--tee-path (-ep)

Full path to tee program - in case you can't set proper PATH environment variable.

--psql-path (-sp)

Full path to psql program - in case you can't set proper PATH environment variable.

--rsync-path (-rp)

Full path to rsync program - in case you can't set proper PATH environment variable.

--pgcontroldata-path (-pp)

Full path to pg_controldata program - in case you can't set proper PATH environment variable.

--shell-path (-sh)

Full path to shell to be used when calling compression/archiving/checksumming.

It is important becaus the shell needs to support >( ... ) constructions.

One of the shells that do support it is bash, and this is the default value for --shell-path. You can substitute different shell if you're sure it supports mentioned construction.

DESCRIPTION

Running this program should be done by cronjob, or manually by database administrator.

As a result of running it there are 2 files, usually named HOST-data-YYYY-MM-DD.tar and HOST-xlog-YYYY-MM-DD.tar. These files can be optionally compressed and delivered to many places - both local (on the same server) or remote (via rsync).

Which options should be given depends only on installation, but generally you will need at least:

  • --data-dir

    Backup will process files in this directory.

  • --log

    to make sure that information is logged someplace about archiving progress

  • one of --dst-local or --dst-remote

    to specify where to send the backup files to

Of course you can provide many --dst-local or many --dst-remote or many mix of these.

Generally omnipitr-backup-slave will try to deliver WAL segment to all destinations. In case remote destination will fail, omnipitr-backup-slave will retry 3 times, with 5 minute delay between tries.

In case of errors when writing to local destination - it is skipped, and error is logged.

Backups will be transferred to destinations in this order:

1. All local destinations, in order provided in command line
2. All remote destinations, in order provided in command line

Remote destination specification

omnipitr-backup-slave delivers backup files to destination using rsync program. Both direct-rsync and rsync-over-ssh are supported (it's better to use direct rsync - it uses less resources due to lack of encryption.

Destination url/location should be in a format that is usable by rsync program.

For example you can use:

  • rsync://user@remote_host/module/path/

  • host:/path/

To allow remote delivery you need to have rsync program. In case you're using rsync over ssh, ssh program has also to be available.

In case your rsync/ssh programs are in custom directories simply set $PATH environemnt variable before starting PostgreSQL.

COMPRESSION

Every destination (and source of xlogs) can have specified compression. To use it you should prefix destination path/url with compression type followed by '=' sign.

Allowed compression types:

  • gzip

    Compresses with gzip program, used file extension is .gz

  • bzip2

    Compresses with bzip2 program, used file extension is .bz2

  • lzma

    Compresses with lzma program, used file extension is .lzma

If you want to pass any extra arguments to compression program, you can either:

  • make a wrapper

    Write a program/script that will be named in the same way your actual compression program is named, but adding some parameters to call

  • use environment variables

    All of supported compression programs use environment variables:

    • gzip - GZIP

    • bzip2 - BZIP2

    • lzma - XZ_OPT

    For details - please consult manual to your choosen compression tool.

It is strongly suggest to use only 1 compression method for all destinations

CHECKSUMMING

OmniPITR can (since version 0.2.0) calculate checksums of created files.

To calculate the checksums, OmniPITR uses Digest Perl module (part of standard Perl distribution).

Digest module supports (now) 5 different types of checksums:

  • MD5 - standard md5 algorithm

  • SHA-1 - SHA-1 algorithm

  • SHA-256 - SHA-2 algorithm with hash size of 256 bits

  • SHA-384 - SHA-2 algorithm with hash size of 384 bits

  • SHA-512 - SHA-2 algorithm with hash size of 512 bits

If you'll choose to use checksums, for every type of checksum (you can specify --digest=MD5,SHA-512) there will be one additional file created, named just like data and xlog tarbals, but with __FILETYPE__ part of filename (details in FILENAMES) changed to digest name.

So, with filename template being __FILETYPE__.tar__CEXT__, gzip compression and MD5 checksumming, you will get 3 files:

  • data.tar.gz

  • xlog.tar.gz

  • MD5.tar.gz

It is important to understand that the checksum file is plain text, and the parts of its name that suggest tar.gz as just "leftovers" from filename template.

After creation, such checksum file can be verified with:

md5sum -c MD5.tar.gz

FILENAMES

Naming of files for backups might be important depending on deployment.

Generally, generated filenames are named using templates, with default template being:

__HOSTNAME__-__FILETYPE__-^Y-^m-^d.tar__CEXT__

Within template (specified with --filename-template option) you can use following markers:

  • __HOSTNAME__

    Name of server backup is made on - as reported by hostname(1) program.

  • __FILETYPE__

    It is actually required to have __FILETYPE__ - it specifies whether the file contains data (data) or xlog segments (xlog)

  • __CEXT__

    Based on compression algorithm choosen for given delivery. Can be empty (no compression), or contains dot (.) and literal extension associated with choosen compression program.

  • any ^? markers

    like in strftime(3) call, but ^ will be first changed to %.

Filename template is evaluated at start, so any timestamp (^? markers) will relate to date/time of beginning of backup process.

TABLESPACES

If omnipitr-backup-master detects additional tablespaces, they will be also compressed to generated tarball.

Since the full path to the tablespace directory is important, and should be preserved, and normally tar doesn't let you store files which path starts with "/" (as it would be dangerous), omnipitr-backup-master uses the following approach:

all tablespaces will be stored in tar, and upon extraction they will be put in the directory "tablespaces", and under it - there will be the full path to the tablespace directory.

For example:

Assuming PostgreSQL PGDATA is in /var/lib/pgsql/data, and it has 3 extra tablespaces placed in:

  • /mnt/san/tablespace

  • /home/whatever/xxx

  • /media/ssd

generated DATA tarball will contain 2 directories:

  • data - copy of /var/lib/pgsql/data

  • tablespaces - which contains full directory structure leading to:

    • tablespaces/mnt/san/tablespace - copy of /mnt/san/tablespace

    • tablespaces/home/whatever/xxx - copy of /home/whatever/xxx

    • tablespaces/media/ssd - copy of /media/ssd

Thanks to this approach, if you'll create symlink "tablespaces" pointing to root directory (ln -s / tablespaces) before exploding tarball - all tablespace files will be created already in the correct places. This is of course not necessary, but will help if you'd ever need to recover from such backup.

EXAMPLES

Minimal setup, with copying file to local directory:

/.../omnipitr-backup-slave -D /mnt/data -l /var/log/omnipitr/backup.log -dl /mnt/backups/

Minimal setup, with compression, and copying file to remote directory over rsync:

/.../omnipitr-backup-slave -D /mnt/data/ -l /var/log/omnipitr/backup.log -dr bzip2=rsync://slave/postgres/backups/

2 remote, compressed destinations, 1 local, with auto rotated logfile, and modified filenames

/.../omnipitr-backup-slave -D /mnt/data/ -l /var/log/omnipitr/backup-^Y-^m-^d.log -dr bzip2=rsync://slave/postgres/backups/ -dr gzip=backups:/mnt/hotbackups/ -dl /mnt/backups/ -f "main-__FILETYPE__-^Y^m^d_^H^M^S.tar__CEXT__"

IMPORTANT NOTICES

  • If you're using compressed source dir (wal archive) - omnipitr-backup-slave has to uncompress all of xlogs before putting them in .tar.XX. This means that you should have enough free disk space for this purpose in the place where you create temporary directories. Alternarively - do not use compression for sending WAL segments to standby server - in this case - decompression will not be necessary.

  • omnipitr-backup-slave compresses whole source directory - i.e. all files from there. This means that if you're using delay recovery (-w option to omnipitr-restore) - there will be more files there, and backup will be larger. This is especially important if you're using compressed wal archive (please see note above)

  • If you're using omnipitr-backup-slave on PostgreSQL 9.0+ you have to use --call-master. Otherwise created backup might fail when used as base for another replication slave that later on is promoted to standalone.

The OmniPITR project is Copyright (c) 2009-2010 OmniTI. All rights reserved.

POD ERRORS

Hey! The above document had some coding errors, which are explained below:

Around line 425:

'=item' outside of any '=over'