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HTML
152 lines
7.1 KiB
HTML
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Chapter 22. Berkeley DB Extensions</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" />
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<link rel="up" href="index.html" title="Berkeley DB Programmer's Reference Guide" />
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<link rel="prev" href="tcl_faq.html" title="Tcl FAQ" />
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<link rel="next" href="ext_perl.html" title="Using Berkeley DB with Perl" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.2</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Chapter 22.
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Berkeley DB Extensions
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</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="tcl_faq.html">Prev</a> </td>
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<th width="60%" align="center"> </th>
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<td width="20%" align="right"> <a accesskey="n" href="ext_perl.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="chapter" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title"><a id="ext"></a>Chapter 22.
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Berkeley DB Extensions
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</h2>
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</div>
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</div>
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</div>
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<div class="toc">
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<p>
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<b>Table of Contents</b>
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</p>
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<dl>
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<dt>
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<span class="sect1">
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<a href="ext.html#ext_mod">Using Berkeley DB with Apache</a>
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</span>
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</dt>
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<dt>
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<span class="sect1">
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<a href="ext_perl.html">Using Berkeley DB with Perl</a>
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</span>
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</dt>
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<dt>
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<span class="sect1">
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<a href="ext_php.html">Using Berkeley DB with PHP</a>
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</span>
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</dt>
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</dl>
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="ext_mod"></a>Using Berkeley DB with Apache</h2>
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</div>
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</div>
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</div>
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<p>A mod_db4 Apache module is included in the Berkeley DB distribution, providing
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a safe framework for running Berkeley DB applications in an Apache 1.3
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environment. Apache natively provides no interface for communication
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between threads or processes, so the mod_db4 module exists to provide
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this communication.</p>
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<p>In general, it is dangerous to run Berkeley DB in a multiprocess system
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without some facility to coordinate database recovery between processes
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sharing the database environment after application or system failure.
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Failure to run recovery after failure can include process hangs and an
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inability to access the database environment. The mod_db4 Apache module
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oversees the proper management of Berkeley DB database environment resources.
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Developers building applications using Berkeley DB as the storage manager
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within an Apache module should employ this technique for proper resource
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management.</p>
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<p>Specifically, mod_db4 provides the following facilities:</p>
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<div class="orderedlist">
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<ol type="1">
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<li>New constructors for <a href="../api_reference/C/env.html" class="olink">DB_ENV</a> and <a href="../api_reference/C/db.html" class="olink">DB</a> handles, which install
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replacement open/close methods.</li>
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<li>Transparent caching of open <a href="../api_reference/C/env.html" class="olink">DB_ENV</a> and <a href="../api_reference/C/db.html" class="olink">DB</a> handles.</li>
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<li>Reference counting on all structures, allowing the module to detect the
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initial opening of any managed database and automatically perform recovery.</li>
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<li>Automatic detection of unexpected failures (segfaults, or a module
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actually calling exit() and avoiding shut down phases), and automatic
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termination of all child processes with open database resources to
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attempt consistency.</li>
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</ol>
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</div>
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<p>mod_db4 is designed to be used as an alternative interface to Berkeley DB. To
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have another Apache module (for example, mod_foo) use mod_db4, do not
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link mod_foo against the Berkeley DB library. In your mod_foo makefile, you
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should:</p>
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<pre class="programlisting">#include "mod_db4_export.h"</pre>
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<p>and add your Apache include directory to your CPPFLAGS.</p>
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<p>In mod_foo, to create a mod_db4 managed <a href="../api_reference/C/env.html" class="olink">DB_ENV</a> handle, use the
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following:</p>
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<pre class="programlisting">int mod_db4_db_env_create(DB_ENV **dbenvp, u_int32_t flags);</pre>
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<p>which takes identical arguments to <a href="../api_reference/C/envcreate.html" class="olink">db_env_create()</a>.</p>
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<p>To create a mod_db4 managed <a href="../api_reference/C/db.html" class="olink">DB</a> handle, use the following:</p>
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<pre class="programlisting">int mod_db4_db_create(DB **dbp, DB_ENV *dbenv, u_int32_t flags);</pre>
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<p>which takes identical arguments to <a href="../api_reference/C/dbcreate.html" class="olink">db_create()</a>.</p>
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<p>Otherwise the API is completely consistent with the standard Berkeley DB
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API.</p>
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<p>The mod_db4 module requires the Berkeley DB library be compiled with C++
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extensions and the MM library. (The MM library provides an abstraction
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layer which allows related processes to share data easily. On systems
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where shared memory or other inter-process communication mechanisms are
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not available, the MM library emulates them using temporary files. MM
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is used in several operating systems to provide shared memory pools to
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Apache modules.)</p>
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<p>To build this apache module, perform the following steps:</p>
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<pre class="programlisting">% ./configure --with-apxs=[path to the apxs utility] \
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--with-db4=[Berkeley DB library installation directory] \
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--with-mm=[libmm installation directory]
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% make
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% make install</pre>
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<p>Post-installation, modules can use this extension via the functions
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documented in $APACHE_INCLUDEDIR/mod_db4_export.h.</p>
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</div>
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</div>
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<div class="navfooter">
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<hr />
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|
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<table width="100%" summary="Navigation footer">
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|
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<tr>
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|||
|
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<td width="40%" align="left"><a accesskey="p" href="tcl_faq.html">Prev</a> </td>
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|||
|
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<td width="20%" align="center"> </td>
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|
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<td width="40%" align="right"> <a accesskey="n" href="ext_perl.html">Next</a></td>
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|
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</tr>
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|
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<tr>
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<td width="40%" align="left" valign="top">Tcl FAQ </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Using Berkeley DB with Perl</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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