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Implement streaming xlog for backup tools

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Add option for parallel streaming of the transaction log while a
base backup is running, to get the logfiles before the server has
removed them.

Also add a tool called pg_receivexlog, which streams the transaction
log into files, creating a log archive without having to wait for
segments to complete, thus decreasing the window of data loss without
having to waste space using archive_timeout. This works best in
combination with archive_command - suggested usage docs etc coming later.
This commit is contained in:
Magnus Hagander
2011-10-26 20:13:33 +02:00
parent 2b64f3f17a
commit d9bae53173
13 changed files with 1805 additions and 165 deletions
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65
doc/src/sgml/ref/pg_basebackup.sgml
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@@ -143,8 +143,8 @@ PostgreSQL documentation
</varlistentry>
<varlistentry>
<term><option>-x</option></term>
<term><option>--xlog</option></term>
<term><option>-x <replaceable class="parameter">method</replaceable></option></term>
<term><option>--xlog=<replaceable class="parameter">method</replaceable></option></term>
<listitem>
<para>
Includes the required transaction log files (WAL files) in the
@@ -154,16 +154,43 @@ PostgreSQL documentation
to consult the log archive, thus making this a completely standalone
backup.
</para>
<note>
<para>
The transaction log files are collected at the end of the backup.
Therefore, it is necessary for the
<xref linkend="guc-wal-keep-segments"> parameter to be set high
enough that the log is not removed before the end of the backup.
If the log has been rotated when it's time to transfer it, the
backup will fail and be unusable.
</para>
</note>
<para>
The following methods for collecting the transaction logs are
supported:
<variablelist>
<varlistentry>
<term><literal>f</literal></term>
<term><literal>fetch</literal></term>
<listitem>
<para>
The transaction log files are collected at the end of the backup.
Therefore, it is necessary for the
<xref linkend="guc-wal-keep-segments"> parameter to be set high
enough that the log is not removed before the end of the backup.
If the log has been rotated when it's time to transfer it, the
backup will fail and be unusable.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>s</literal></term>
<term><literal>stream</literal></term>
<listitem>
<para>
Stream the transaction log while the backup is created. This will
open a second connection to the server and start streaming the
transaction log in parallel while running the backup. Therefore,
it will use up two slots configured by the
<xref linkend="guc-max-wal-senders"> parameter. As long as the
client can keep up with transaction log received, using this mode
requires no extra transaction logs to be saved on the master.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
@@ -260,6 +287,20 @@ PostgreSQL documentation
The following command-line options control the database connection parameters.
<variablelist>
<varlistentry>
<term><option>-s <replaceable class="parameter">interval</replaceable></option></term>
<term><option>--statusint=<replaceable class="parameter">interval</replaceable></option></term>
<listitem>
<para>
Specifies the number of seconds between status packets sent back to the
server. This is required when streaming the transaction log (using
<literal>--xlog=stream</literal>) if replication timeout is configured
on the server, and allows for easier monitoring. The default value is
10 seconds.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-h <replaceable class="parameter">host</replaceable></option></term>
<term><option>--host=<replaceable class="parameter">host</replaceable></option></term>