o What is pg_standby?

pg_standby is a production-ready program that can be used to

create a Warm Standby server. Other configuration is required

as well, all of which is described in the main server manual.

pg_standby allows the creation of a Warm Standby server.

It is designed to be a production-ready program, as well as a

customisable template should you require specific modifications.

Other configuration is required as well, all of which is

described in the main server manual.

The program is designed to be a wait-for restore_command,

required to turn a normal archive recovery into a Warm Standby.

Within the restore_command of the recovery.conf you could

configure pg_standby in the following way:

restore_command = 'pg_standby archiveDir %f %p'

restore_command = 'pg_standby archiveDir %f %p %r'

which would be sufficient to define that files will be restored

from archiveDir.

The basic usage should be like this:

restore_command = 'pg_standby archiveDir %f %p'

restore_command = 'pg_standby archiveDir %f %p %r'

with the pg_standby command usage as

pg_standby [OPTION]...[ARCHIVELOCATION] [NEXTWALFILE] [XLOGFILEPATH]

pg_standby [OPTION]... ARCHIVELOCATIONNEXTWALFILEXLOGFILEPATH [RESTARTWALFILE]

When used within the restore_command the %f and %p macros

will provide the actual file and path required for the restore/recovery.

pg_standby assumes that ARCHIVELOCATION is directory accessible by the

server-owning user.

If RESTARTWALFILE is specified, typically by using the %r option, then all files

prior to this file will be removed from ARCHIVELOCATION. This then minimises

the number of files that need to be held, whilst at the same time maintaining

restart capability. This capability additionally assumes that ARCHIVELOCATION

directory is writable.

o options

pg_standbyhas number of options.

pg_standbyallows the following command line switches

-c

use copy/cp command to restore WAL files from archive

-k numfiles

Cleanup files in the archive so that we maintain no more

than this many files in the archive.

than this many files in the archive. This parameter will

be silently ignored if RESTARTWALFILE is specified, since

that specification method is more accurate in determining

the correct cut-off point in archive.

You should be wary against setting this number too low,

since this may mean you cannot restart the standby. This

It is wholly unrelated to the setting of checkpoint_segments

on either primary or standby.

Setting numfiles to be zero will disable deletion of files

from ARCHIVELOCATION.

If in doubt, use a large value or do not set a value at all.

If you specify neither RESTARTWALFILE nor -k, then -k 0

will be assumed, i.e. keep all files in archive.

Default=0, Min=0

-l

use ln command to restore WAL files from archive

WAL files will remain in archive

Link is more efficient, but the default is copy to

allow you to maintain the WAL archive for recovery

purposes as well as high-availability.

The default setting is not necessarily recommended,

consult the main database server manual for discussion.

This option uses the Windows Vista command mklink

to provide a file-to-file symbolic link. -l will

the failure back to the database server. This will be

interpreted as and end of recovery and the Standby will come

up fully as a result.

Default=3

Default=3, Min=0

-s sleeptime

the number of seconds to sleep between testing to see

if the file to be restored is available in the archive yet.

The default setting is not necessarily recommended,

consult the main database server manual for discussion.

Default=5

Default=5, Min=1, Max=60

-t triggerfile

the presence of the triggerfile will cause recovery to end

-w maxwaittime

the maximum number of seconds to wait for the next file,

after which recovery will end and the Standby will come up.

A setting of zero means wait forever.

The default setting is not necessarily recommended,

consult the main database server manual for discussion.

Default=0

Default=0, Min=0

Note: --help is not supported since pg_standby is not intended

for interactive use, except during dev/test

Note that backslashes need to be doubled in the archive_command, but

*not* in the restore_command, in 8.2, 8.1, 8.0 on Windows.

restore_command = 'pg_standby -c -d -s 5 -w 0 -t C:\pgsql.trigger.5442

..\archive %f %p 2>> standby.log'

restore_command = 'pg_standby -c -d -s 5 -w 0 -t C:\pgsql.trigger.5442 ..\archive %f %p 2>> standby.log'

which will

- use a copy command to restore WAL files from archive

- never timeout if file not found

- stop waiting when a trigger file called C:\pgsql.trigger.5442 appears

o supported versions

pg_standby is designed to work with PostgreSQL 8.2 and later. It is

currently compatible across minor changes between the way 8.3 and 8.2

operate.

PostgreSQL 8.3 provides the %r command line substitution, designed to

let pg_standby know the last file it needs to keep. If the last

parameter is omitted, no error is generated, allowing pg_standby to

function correctly with PostgreSQL 8.2 also. With PostgreSQL 8.2,

the -k option must be used if archive cleanup is required. This option

remains available in 8.3.

o reported test success

SUSE Linux 10.2

Windows XP Pro

o additional design notes

The use of a move command seems like it would be a good idea, but

this would prevent recovery from being restartable. Also, the last WAL

file is always requested twice from the archive.