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153 lines
4.9 KiB
HTML
153 lines
4.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<TITLE>Apache module mod_mmap_static</TITLE>
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<!--#include virtual="header.html" -->
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<H1 ALIGN="CENTER">Module mod_mmap_static</H1>
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<P>
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This module provides mmap()ing of a statically configured list
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of frequently requested but not changed files.
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<P><A
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HREF="module-dict.html#Status"
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REL="Help"
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><STRONG>Status:</STRONG></A> Experimental
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<BR>
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<A
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HREF="module-dict.html#SourceFile"
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REL="Help"
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><STRONG>Source File:</STRONG></A> mod_mmap_static.c
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<BR>
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<A
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HREF="module-dict.html#ModuleIdentifier"
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REL="Help"
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><STRONG>Module Identifier:</STRONG></A> mmap_static_module
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</P>
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<H2>Summary</H2>
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<P>
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This is an <STRONG>experimental</STRONG> module and should be used with
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care. You can easily create a broken site using this module, read this
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document carefully.
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<CODE>mod_mmap_static</CODE> maps a list of statically configured files (via
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<CODE>MMapFile</CODE> directives in the main server configuration) into
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memory through the system call <CODE>mmap()</CODE>. This system
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call is available on most modern Unix derivates, but not on all. There
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are sometimes system-specific limits on the size and number of files that
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can be mmap()d, experimentation is probably the easiest way to find out.
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</P>
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<P>
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This mmap()ing is done once at server start or restart, only. So whenever
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one of the mapped files changes on the filesystem you <EM>have</EM> to
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restart the server by at least sending it a HUP or USR1 signal (see the
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<A HREF="../stopping.html">Stopping and Restarting</A> documentation). To
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reiterate that point: if the files are modified <EM>in place</EM> without
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restarting the server you may end up serving requests that are completely
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bogus. You should update files by unlinking the old copy and putting a new
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copy in place. Most tools such as <CODE>rdist</CODE> and <CODE>mv</CODE> do
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this. The reason why this modules doesn't take care of changes to the files
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is that this check would need an extra <CODE>stat()</CODE> every time which
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is a waste and against the intent of I/O reduction.
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</P>
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<H2>Directives</H2>
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<UL>
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<LI><A HREF="#mmapfile">MMapFile</A>
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</LI>
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</UL>
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<HR>
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<H2><A NAME="mmapfile">MMapFile</A> directive</H2>
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<P>
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<A
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HREF="directive-dict.html#Syntax"
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REL="Help"
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><STRONG>Syntax:</STRONG></A> MMapFile <EM>filename</em>
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[<em>filename</em>] ...
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<BR>
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<A
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HREF="directive-dict.html#Default"
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REL="Help"
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><STRONG>Default:</STRONG></A> <EM>None</EM>
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<BR>
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<A
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HREF="directive-dict.html#Context"
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REL="Help"
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><STRONG>Context:</STRONG></A> server-config
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<BR>
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<A
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HREF="directive-dict.html#Override"
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REL="Help"
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><STRONG>Override:</STRONG></A> <EM>Not applicable</EM>
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<BR>
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<A
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HREF="directive-dict.html#Status"
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REL="Help"
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><STRONG>Status:</STRONG></A> Experimental
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<BR>
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<A
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HREF="directive-dict.html#Module"
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REL="Help"
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><STRONG>Module:</STRONG></A> mod_mmap_static
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<BR>
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<A
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HREF="directive-dict.html#Compatibility"
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REL="Help"
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><STRONG>Compatibility:</STRONG></A> Only available in Apache 1.3 or later
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<P>
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The <CODE>MMapFile</CODE> directive maps one or more files (given as
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whitespace separated arguments) into memory at server startup time. They
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are automatically unmapped on a server shutdown. When the files have changed
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on the filesystem at least a HUP or USR1 signal should be send to the server
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to re-mmap them.
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</P>
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<P>
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Be careful with the <EM>filename</EM> arguments: They have to literally
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match the filesystem path Apache's URL-to-filename translation handlers
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create. We cannot compare inodes or other stuff to match paths through
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symbolic links <EM>etc.</EM> because that again would cost extra <CODE>stat()</CODE>
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system calls which is not acceptable. This module may or may not work
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with filenames rewritten by <CODE>mod_alias</CODE> or
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<CODE>mod_rewrite</CODE>... it is an experiment after all.
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</P>
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<P>
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Notice: You cannot use this for speeding up CGI programs or other files
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which are served by special content handlers. It can only be used for
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regular files which are usually served by the Apache core content handler.
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</P>
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Example:
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<PRE>
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MMapFile /usr/local/apache/htdocs/index.html
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</PRE>
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<P>
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<STRONG>Note</STRONG>: don't bother asking for a for a <CODE>MMapDir</CODE>
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directive which
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recursively maps all the files in a directory. Use Unix the way it was
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meant to be used. For example, see the
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<A HREF="core.html#include">Include</A> directive, and consider this command:
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<PRE>
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find /www/htdocs -type f -print \
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| sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf
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</PRE>
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