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Make an editorial pass over the newly SGML-ified contrib documentation.
Fix lots of bad markup, bad English, bad explanations. Last ones ... whew. Man, that was tedious.
This commit is contained in:
Tom Lane
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<!-- $PostgreSQL: pgsql/doc/src/sgml/pgstandby.sgml,v 2.4 2007/12/16 23:00:42 tgl Exp $ -->
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<sect1 id="pgstandby">
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<title>pg_standby</title>
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<indexterm zone="pgstandby">
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<primary>pg_standby</primary>
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</indexterm>
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<para>
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<literal>pg_standby</literal> allows the creation of a Warm Standby server.
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Other configuration is required as well, all of which is described in the
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main server manual.
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</para>
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<para>
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The program is designed to be a wait-for <literal>restore_command</literal>,
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required to turn a normal archive recovery into a Warm Standby. Within the
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<literal>restore_command</literal> of the <literal>recovery.conf</literal>
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you could configure <literal>pg_standby</literal> in the following way:
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</para>
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<programlisting>
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restore_command = 'pg_standby archiveDir %f %p %r'
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</programlisting>
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<para>
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which would be sufficient to define that files will be restored from
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archiveDir.
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<application>pg_standby</> supports creation of a <quote>warm standby</>
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database server. It is designed to be a production-ready program, as well
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as a customizable template should you require specific modifications.
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</para>
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<para>
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<literal>pg_standby</literal> features include:
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<application>pg_standby</> is designed to be a waiting
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<literal>restore_command</literal>, which is needed to turn a standard
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archive recovery into a warm standby operation. Other
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configuration is required as well, all of which is described in the main
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server manual (see <xref linkend="warm-standby">).
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</para>
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<para>
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<application>pg_standby</application> features include:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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It is written in C. So it is very portable
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and easy to install.
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Supports copy or link for restoring WAL files
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</para>
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</listitem>
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<listitem>
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<para>
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Supports copy or link from a directory (only)
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Written in C, so very portable and easy to install
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</para>
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</listitem>
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<listitem>
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<para>
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Source easy to modify, with specifically designated
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sections to modify for your own needs, allowing
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interfaces to be written for additional Backup Archive Restore
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(BAR) systems
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Easy-to-modify source code, with specifically designated
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sections to modify for your own needs
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</para>
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</listitem>
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<listitem>
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<para>
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Already tested on Linux and Windows
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Already tested on Linux and Windows
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</para>
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</listitem>
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</itemizedlist>
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<sect2>
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<title>Usage</title>
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<para>
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<literal>pg_standby</literal> should be used within the
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<literal>restore_command</literal> of the <literal>recovery.conf</literal>
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file.
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</para>
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<para>
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The basic usage should be like this:
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To configure a standby
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server to use <application>pg_standby</>, put this into its
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<filename>recovery.conf</filename> configuration file:
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</para>
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<programlisting>
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restore_command = 'pg_standby archiveDir %f %p'
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restore_command = 'pg_standby <replaceable>archiveDir</> %f %p %r'
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</programlisting>
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<para>
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with the pg_standby command usage as
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</para>
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<programlisting>
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pg_standby [OPTION]... ARCHIVELOCATION NEXTWALFILE XLOGFILEPATH [RESTARTWALFILE]
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</programlisting>
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<para>
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When used within the <literal>restore_command</literal> the %f and %p macros
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will provide the actual file and path required for the restore/recovery.
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where <replaceable>archiveDir</> is the directory from which WAL segment
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files should be restored.
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</para>
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<para>
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<literal>pg_standby</literal> assumes that <literal>ARCHIVELOCATION</literal>
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is a directory accessible by the server-owning user.
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The full syntax of <application>pg_standby</>'s command line is
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</para>
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<synopsis>
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pg_standby <optional> <replaceable>option</> ... </optional> <replaceable>archivelocation</> <replaceable>nextwalfile</> <replaceable>xlogfilepath</> <optional> <replaceable>restartwalfile</> </optional>
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</synopsis>
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<para>
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When used within <literal>restore_command</literal>, the <literal>%f</> and
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<literal>%p</> macros should be specified for <replaceable>nextwalfile</>
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and <replaceable>xlogfilepath</> respectively, to provide the actual file
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and path required for the restore.
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</para>
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<para>
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If <literal>RESTARTWALFILE</literal> is specified, typically by using the
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<literal>%r</literal> option, then all files prior to this file will be
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removed from <literal>ARCHIVELOCATION</literal>. This then minimises the
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number of files that need to be held, whilst at the same time maintaining
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restart capability. This capability additionally assumes that
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<literal>ARCHIVELOCATION</literal> directory is writable.
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If <replaceable>restartwalfile</> is specified, normally by using the
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<literal>%r</literal> macro, then all WAL files logically preceding this
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file will be removed from <replaceable>archivelocation</>. This minimizes
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the number of files that need to be retained, while preserving
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crash-restart capability. Use of this parameter is appropriate if the
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<replaceable>archivelocation</> is a transient staging area for this
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particular standby server, but <emphasis>not</> when the
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<replaceable>archivelocation</> is intended as a long-term WAL archive area.
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</para>
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<para>
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<application>pg_standby</application> assumes that
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<replaceable>archivelocation</> is a directory readable by the
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server-owning user. If <replaceable>restartwalfile</> (or <literal>-k</>)
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is specified,
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the <replaceable>archivelocation</> directory must be writable too.
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</para>
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<table>
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<title>Options</title>
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<tgroup cols="2">
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<title><application>pg_standby</> options</title>
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<tgroup cols="3">
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<thead>
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<row>
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<entry>Option</entry>
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<entry>Default</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>-c</entry>
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<entry> use copy/cp command to restore WAL files from archive</entry>
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</row>
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<row>
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<entry>-d</entry>
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<entry>debug/logging option.</entry>
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</row>
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<row>
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<entry>-k numfiles</entry>
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<entry><literal>-c</></entry>
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<entry>yes</entry>
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<entry>
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<para>
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Cleanup files in the archive so that we maintain no more than this
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many files in the archive. This parameter will be silently ignored if
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<literal>RESTARTWALFILE</literal> is specified, since that
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specification method is more accurate in determining the correct
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cut-off point in archive.
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</para>
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<para>
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You should be wary against setting this number too low,
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since this may mean you cannot restart the standby. This
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is because the last restartpoint marked in the WAL files
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may be many files in the past and can vary considerably.
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This should be set to a value exceeding the number of WAL
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files that can be recovered in 2*checkpoint_timeout seconds,
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according to the value in the warm standby postgresql.conf.
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It is wholly unrelated to the setting of checkpoint_segments
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on either primary or standby.
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</para>
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<para>
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Setting <literal>numfiles</literal> to be zero will disable deletion
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of files from <literal>ARCHIVELOCATION</literal>.
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</para>
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<para>
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If in doubt, use a large value or do not set a value at all.
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</para>
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<para>
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If you specify neither <literal>RESTARTWALFILE</> nor <literal>-k</>,
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then <literal>-k 0</> will be assumed, i.e. keep all files in archive.
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</para>
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Use <literal>cp</> or <literal>copy</> command to restore WAL files
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from archive.
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</entry>
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</row>
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<row>
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<entry>-l</entry>
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<entry><literal>-d</></entry>
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<entry>no</entry>
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<entry>Print lots of debug logging output on <filename>stderr</>.</entry>
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</row>
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<row>
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<entry><literal>-k</> <replaceable>numfiles</></entry>
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<entry>0</entry>
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<entry>
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<para>
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use ln command to restore WAL files from archive
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WAL files will remain in archive
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</para>
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<para>
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Link is more efficient, but the default is copy to allow you to
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maintain the WAL archive for recovery purposes as well as
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high-availability. The default setting is not necessarily recommended,
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consult the main database server manual for discussion.
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</para>
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<para>
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This option uses the Windows Vista command mklink
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to provide a file-to-file symbolic link. -l will
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not work on versions of Windows prior to Vista.
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Use the -c option instead.
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see <ulink url="http://en.wikipedia.org/wiki/NTFS_symbolic_link"></ulink>
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</para>
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Remove files from <replaceable>archivelocation</replaceable> so that
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no more than this many WAL files before the current one are kept in the
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archive. Zero (the default) means not to remove any files from
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<replaceable>archivelocation</replaceable>.
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This parameter will be silently ignored if
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<replaceable>restartwalfile</replaceable> is specified, since that
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specification method is more accurate in determining the correct
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archive cut-off point.
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Use of this parameter is <emphasis>deprecated</> as of
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<productname>PostgreSQL</> 8.3; it is safer and more efficient to
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specify a <replaceable>restartwalfile</replaceable> parameter. A too
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small setting could result in removal of files that are still needed
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for a restart of the standby server, while a too large setting wastes
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archive space.
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</entry>
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</row>
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<row>
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<entry>-r maxretries</entry>
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<entry><literal>-l</></entry>
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<entry>no</entry>
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<entry>
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<para>
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the maximum number of times to retry the restore command if it
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fails. After each failure, we wait for sleeptime * num_retries
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so that the wait time increases progressively, so by default
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we will wait 5 secs, 10 secs then 15 secs before reporting
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the failure back to the database server. This will be
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interpreted as and end of recovery and the Standby will come
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up fully as a result. <literal>Default=3 Min=0</literal>
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</para>
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Use <literal>ln</> command to restore WAL files from archive.
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Link is more efficient than copy, but the default is copy since link
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will not work in all scenarios.
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On Windows, this option uses the <literal>mklink</> command
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to provide a file-to-file symbolic link. <literal>-l</> will
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not work on versions of Windows prior to Vista.
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</entry>
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</row>
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<row>
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<entry>-s sleeptime</entry>
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<entry><literal>-r</> <replaceable>maxretries</></entry>
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<entry>3</entry>
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<entry>
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the number of seconds to sleep between testing to see
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if the file to be restored is available in the archive yet.
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The default setting is not necessarily recommended,
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consult the main database server manual for discussion.
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<literal>Default=5, Min=1, Max=60</literal>
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Set the maximum number of times to retry the copy or link command if it
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fails. After each failure, we wait for <replaceable>sleeptime</> *
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<replaceable>num_retries</>
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so that the wait time increases progressively. So by default,
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we will wait 5 secs, 10 secs, then 15 secs before reporting
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the failure back to the standby server. This will be
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interpreted as end of recovery and the standby will come
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up fully as a result.
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</entry>
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</row>
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<row>
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<entry>-t triggerfile</entry>
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<entry><literal>-s</> <replaceable>sleeptime</></entry>
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<entry>5</entry>
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<entry>
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the presence of the triggerfile will cause recovery to end
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whether or not the next file is available
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It is recommended that you use a structured filename to
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Set the number of seconds (up to 60) to sleep between tests to see
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if the WAL file to be restored is available in the archive yet.
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The default setting is not necessarily recommended;
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consult <xref linkend="warm-standby"> for discussion.
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</entry>
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</row>
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<row>
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<entry><literal>-t</> <replaceable>triggerfile</></entry>
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<entry>none</entry>
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<entry>
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Specify a trigger file whose presence should cause recovery to end
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whether or not the next WAL file is available.
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It is recommended that you use a structured filename to
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avoid confusion as to which server is being triggered
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when multiple servers exist on same system.
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e.g. /tmp/pgsql.trigger.5432
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when multiple servers exist on the same system; for example
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<filename>/tmp/pgsql.trigger.5432</>.
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</entry>
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</row>
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<row>
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<entry>-w maxwaittime</entry>
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<entry><literal>-w</> <replaceable>maxwaittime</></entry>
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<entry>0</entry>
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<entry>
|
||||
the maximum number of seconds to wait for the next file,
|
||||
after which recovery will end and the Standby will come up.
|
||||
The default setting is not necessarily recommended,
|
||||
consult the main database server manual for discussion. A setting of
|
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zero means wait forever.
|
||||
<literal>Default=0, Min=0</literal>
|
||||
Set the maximum number of seconds to wait for the next WAL file,
|
||||
after which recovery will end and the standby will come up.
|
||||
A setting of zero (the default) means wait forever.
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||||
The default setting is not necessarily recommended;
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||||
consult <xref linkend="warm-standby"> for discussion.
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</entry>
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</row>
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</tbody>
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@ -209,89 +201,129 @@ restore_command = 'pg_standby archiveDir %f %p %r'
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</table>
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<note>
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<para>
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<literal>--help</literal> is not supported since
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<literal>pg_standby</literal> is not intended for interactive use, except
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during development and testing.
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<literal>--help</literal> is not supported since
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||||
<application>pg_standby</application> is not intended for interactive use,
|
||||
except during development and testing.
|
||||
</para>
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||||
</note>
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||||
</sect2>
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<sect2>
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<title>Supported versions</title>
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||||
<para>
|
||||
<literal>pg_standby</literal> is designed to work with PostgreSQL 8.2 and
|
||||
and later. It is currently compatible across minor changes between the way
|
||||
8.3 and 8.2 operate.
|
||||
</para>
|
||||
<para>
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||||
PostgreSQL 8.3 provides the <literal>%r</literal> command line substitution,
|
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designed to let <literal>pg_standby</literal> know the last file it needs to
|
||||
keep. If the last parameter is omitted, no error is generated, allowing
|
||||
<literal>pg_standby</literal> to function correctly with PostgreSQL 8.2
|
||||
also. With PostgreSQL 8.2, the <literal>-k</literal> option must be used if
|
||||
archive cleanup is required. This option remains available in 8.3.
|
||||
</para>
|
||||
</sect2>
|
||||
|
||||
<sect2>
|
||||
<title>Additional design notes</title>
|
||||
<para>
|
||||
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.
|
||||
</para>
|
||||
</sect2>
|
||||
|
||||
<sect2>
|
||||
<title>Examples</title>
|
||||
|
||||
<para>On Linux or Unix systems, you might use:</para>
|
||||
|
||||
<programlisting>
|
||||
archive_command = 'cp %p .../archive/%f'
|
||||
|
||||
restore_command = 'pg_standby -l -d -s 2 -t /tmp/pgsql.trigger.5442 .../archive %f %p %r 2>>standby.log'
|
||||
</programlisting>
|
||||
<para>
|
||||
where the archive directory is physically located on the standby server,
|
||||
so that the <literal>archive_command</> is accessing it across NFS,
|
||||
but the files are local to the standby (enabling use of <literal>ln</>).
|
||||
This will:
|
||||
</para>
|
||||
<itemizedlist>
|
||||
<listitem>
|
||||
<para>Example on Linux</para>
|
||||
<programlisting>
|
||||
archive_command = 'cp %p ../archive/%f'
|
||||
|
||||
restore_command = 'pg_standby -l -d -k 255 -r 2 -s 2 -w 0 -t /tmp/pgsql.trigger.5442 $PWD/../archive %f %p 2>> standby.log'
|
||||
</programlisting>
|
||||
<para>
|
||||
which will
|
||||
use the <literal>ln</> command to restore WAL files from archive
|
||||
</para>
|
||||
<itemizedlist>
|
||||
<listitem><para>use a ln command to restore WAL files from archive</para></listitem>
|
||||
<listitem><para>produce logfile output in standby.log</para></listitem>
|
||||
<listitem><para>keep the last 255 full WAL files, plus the current one</para></listitem>
|
||||
<listitem><para>sleep for 2 seconds between checks for next WAL file is full</para></listitem>
|
||||
<listitem><para>never timeout if file not found</para></listitem>
|
||||
<listitem><para>stop waiting when a trigger file called /tmp/pgsql.trigger.5442 appears</para></listitem>
|
||||
</itemizedlist>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>
|
||||
Example on Windows
|
||||
produce debugging output in <filename>standby.log</>
|
||||
</para>
|
||||
<programlisting>
|
||||
archive_command = 'copy %p ..\\archive\\%f'
|
||||
</programlisting>
|
||||
</listitem>
|
||||
<listitem>
|
||||
<para>
|
||||
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.
|
||||
sleep for 2 seconds between checks for next WAL file availability
|
||||
</para>
|
||||
<programlisting>
|
||||
restore_command = 'pg_standby -c -d -s 5 -w 0 -t C:\pgsql.trigger.5442 ..\archive %f %p 2>> standby.log'
|
||||
</programlisting>
|
||||
</listitem>
|
||||
<listitem>
|
||||
<para>
|
||||
which will
|
||||
stop waiting only when a trigger file called
|
||||
<filename>/tmp/pgsql.trigger.5442</> appears
|
||||
</para>
|
||||
</listitem>
|
||||
<listitem>
|
||||
<para>
|
||||
remove no-longer-needed files from the archive directory
|
||||
</para>
|
||||
<itemizedlist>
|
||||
<listitem><para>use a copy command to restore WAL files from archive</para></listitem>
|
||||
<listitem><para>produce logfile output in standby.log</para></listitem>
|
||||
<listitem><para>sleep for 5 seconds between checks for next WAL file is full</para></listitem>
|
||||
<listitem><para>never timeout if file not found</para></listitem>
|
||||
<listitem><para>stop waiting when a trigger file called C:\pgsql.trigger.5442 appears</para></listitem>
|
||||
</itemizedlist>
|
||||
</listitem>
|
||||
</itemizedlist>
|
||||
|
||||
<para>On Windows, you might use:</para>
|
||||
|
||||
<programlisting>
|
||||
archive_command = 'copy %p ...\\archive\\%f'
|
||||
|
||||
restore_command = 'pg_standby -d -s 5 -t C:\pgsql.trigger.5442 ...\archive %f %p %r 2>>standby.log'
|
||||
</programlisting>
|
||||
<para>
|
||||
Note that backslashes need to be doubled in the
|
||||
<literal>archive_command</>, but <emphasis>not</emphasis> in the
|
||||
<literal>restore_command</>. This will:
|
||||
</para>
|
||||
<itemizedlist>
|
||||
<listitem>
|
||||
<para>
|
||||
use the <literal>copy</> command to restore WAL files from archive
|
||||
</para>
|
||||
</listitem>
|
||||
<listitem>
|
||||
<para>
|
||||
produce debugging output in <filename>standby.log</>
|
||||
</para>
|
||||
</listitem>
|
||||
<listitem>
|
||||
<para>
|
||||
sleep for 5 seconds between checks for next WAL file availability
|
||||
</para>
|
||||
</listitem>
|
||||
<listitem>
|
||||
<para>
|
||||
stop waiting only when a trigger file called
|
||||
<filename>C:\pgsql.trigger.5442</> appears
|
||||
</para>
|
||||
</listitem>
|
||||
<listitem>
|
||||
<para>
|
||||
remove no-longer-needed files from the archive directory
|
||||
</para>
|
||||
</listitem>
|
||||
</itemizedlist>
|
||||
|
||||
<para>
|
||||
Since the Windows example uses <literal>copy</> at both ends, either
|
||||
or both servers might be accessing the archive directory across the
|
||||
network.
|
||||
</para>
|
||||
|
||||
</sect2>
|
||||
|
||||
|
||||
<sect2>
|
||||
<title>Supported server versions</title>
|
||||
|
||||
<para>
|
||||
<application>pg_standby</application> is designed to work with
|
||||
<productname>PostgreSQL</> 8.2 and later.
|
||||
</para>
|
||||
<para>
|
||||
<productname>PostgreSQL</> 8.3 provides the <literal>%r</literal> macro,
|
||||
which is designed to let <application>pg_standby</application> know the
|
||||
last file it needs to keep. With <productname>PostgreSQL</> 8.2, the
|
||||
<literal>-k</literal> option must be used if archive cleanup is
|
||||
required. This option remains available in 8.3, but its use is deprecated.
|
||||
</para>
|
||||
</sect2>
|
||||
|
||||
<sect2>
|
||||
<title>Author</title>
|
||||
|
||||
<para>
|
||||
Simon Riggs
|
||||
</para>
|
||||
</sect2>
|
||||
|
||||
</sect1>
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user