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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 51. Archive Modules</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="replication-origins.html" title="Chapter 50. Replication Progress Tracking" /><link rel="next" href="archive-module-init.html" title="51.1. Initialization Functions" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">Chapter 51. Archive Modules</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="replication-origins.html" title="Chapter 50. Replication Progress Tracking">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="server-programming.html" title="Part V. Server Programming">Up</a></td><th width="60%" align="center">Part V. Server Programming</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="archive-module-init.html" title="51.1. Initialization Functions">Next</a></td></tr></table><hr /></div><div class="chapter" id="ARCHIVE-MODULES"><div class="titlepage"><div><div><h2 class="title">Chapter 51. Archive Modules</h2></div></div></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="archive-module-init.html">51.1. Initialization Functions</a></span></dt><dt><span class="sect1"><a href="archive-module-callbacks.html">51.2. Archive Module Callbacks</a></span></dt><dd><dl><dt><span class="sect2"><a href="archive-module-callbacks.html#ARCHIVE-MODULE-STARTUP">51.2.1. Startup Callback</a></span></dt><dt><span class="sect2"><a href="archive-module-callbacks.html#ARCHIVE-MODULE-CHECK">51.2.2. Check Callback</a></span></dt><dt><span class="sect2"><a href="archive-module-callbacks.html#ARCHIVE-MODULE-ARCHIVE">51.2.3. Archive Callback</a></span></dt><dt><span class="sect2"><a href="archive-module-callbacks.html#ARCHIVE-MODULE-SHUTDOWN">51.2.4. Shutdown Callback</a></span></dt></dl></dd></dl></div><a id="id-1.8.16.2" class="indexterm"></a><p>
PostgreSQL provides infrastructure to create custom modules for continuous
archiving (see <a class="xref" href="continuous-archiving.html" title="26.3. Continuous Archiving and Point-in-Time Recovery (PITR)">Section 26.3</a>). While archiving via
a shell command (i.e., <a class="xref" href="runtime-config-wal.html#GUC-ARCHIVE-COMMAND">archive_command</a>) is much
simpler, a custom archive module will often be considerably more robust and
performant.
</p><p>
When a custom <a class="xref" href="runtime-config-wal.html#GUC-ARCHIVE-LIBRARY">archive_library</a> is configured, PostgreSQL
will submit completed WAL files to the module, and the server will avoid
recycling or removing these WAL files until the module indicates that the files
were successfully archived. It is ultimately up to the module to decide what
to do with each WAL file, but many recommendations are listed at
<a class="xref" href="continuous-archiving.html#BACKUP-ARCHIVING-WAL" title="26.3.1. Setting Up WAL Archiving">Section 26.3.1</a>.
</p><p>
Archiving modules must at least consist of an initialization function (see
<a class="xref" href="archive-module-init.html" title="51.1. Initialization Functions">Section 51.1</a>) and the required callbacks (see
<a class="xref" href="archive-module-callbacks.html" title="51.2. Archive Module Callbacks">Section 51.2</a>). However, archive modules are
also permitted to do much more (e.g., declare GUCs and register background
workers).
</p><p>
The <code class="filename">contrib/basic_archive</code> module contains a working
example, which demonstrates some useful techniques.
</p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="replication-origins.html" title="Chapter 50. Replication Progress Tracking">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="server-programming.html" title="Part V. Server Programming">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="archive-module-init.html" title="51.1. Initialization Functions">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 50. Replication Progress Tracking </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 51.1. Initialization Functions</td></tr></table></div></body></html>