From: André Malo Date: Thu, 14 Nov 2002 04:06:08 +0000 (+0000) Subject: - add directive s X-Git-Tag: 2.0.44~62 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=896c2be348764291a3546c40e6935862f4318817;p=apache - add directive s - -> - some reformatting and markup improvement git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97511 13f79535-47bb-0310-9956-ffa450edef68 --- diff --git a/docs/manual/mod/mod_file_cache.xml b/docs/manual/mod/mod_file_cache.xml index 40ce5c4153..e8c754a522 100644 --- a/docs/manual/mod/mod_file_cache.xml +++ b/docs/manual/mod/mod_file_cache.xml @@ -11,20 +11,20 @@ - -This module should be used with care. You can easily - create a broken site using mod_file_cache, so read this - document carefully. - + + This module should be used with care. You can easily create a broken + site using mod_file_cache, so read this document + carefully. +

Caching frequently requested files that change very infrequently is a technique for reducing server load. - mod_file_cache provides two techniques for caching frequently - requested static files. Through configuration - directives, you can direct mod_file_cache to either open then - mmap()a file, or to pre-open a file and save the file's open - file handle. Both techniques reduce server load when - processing requests for these files by doing part of the work + mod_file_cache provides two techniques for caching + frequently requested static files. Through configuration + directives, you can direct mod_file_cache to either + open then mmap() a file, or to pre-open a file and save + the file's open file handle. Both techniques reduce server + load when processing requests for these files by doing part of the work (specifically, the file I/O) for serving the file when the server is started rather than during each request.

@@ -34,16 +34,15 @@ This module should be used with care. You can easily the Apache core content handler.

This module is an extension of and borrows heavily from the - mod_mmap_static module in Apache 1.3.

+ mod_mmap_static module in Apache 1.3.

 -
Using mod_file_cache +
Using mod_file_cache

mod_file_cache caches a list of statically - configured files via MMapFile or CacheFile directives in the - main server configuration.

+ configured files via MMapFile or CacheFile directives in the main server configuration.

Not all platforms support both directives. For example, Apache on Windows does not currently support the -

MmapFile Directive - -

The MmapFile - directive of mod_file_cache maps a list of - statically configured files into memory through the system call - mmap(). This system call is available on most modern - Unix derivates, but not on all. There are sometimes - system-specific limits on the size and number of files that can be - mmap()d, experimentation is probably the easiest way to find - out.

- -

This mmap()ing is done once at server start or restart, - only. So whenever one of the mapped files changes on the - filesystem you have to restart the server (see the Stopping and Restarting - documentation). To reiterate that point: if the files are - modified in place without restarting the server you - may end up serving requests that are completely bogus. You - should update files by unlinking the old copy and putting a new - copy in place. Most tools such as rdist and - mv do this. The reason why this modules doesn't - take care of changes to the files is that this check would need - an extra stat() every time which is a waste and - against the intent of I/O reduction.

-
- -
CacheFile Directive - -

The CacheFile - directive of mod_file_cache opens an active - handle or file descriptor to the file (or files) - listed in the configuration directive and places these open file - handles in the cache. When the file is requested, the server - retrieves the handle from the cache and passes it to the - sendfile() (or TransmitFile() on Windows), socket API.

- -

Insert more details about sendfile API...

- -

This file handle caching is done once at server start or - restart, only. So whenever one of the cached files changes on - the filesystem you have to restart the server (see the - Stopping and Restarting - documentation). To reiterate that point: if the files are - modified in place without restarting the server you - may end up serving requests that are completely bogus. You - should update files by unlinking the old copy and putting a new - copy in place. Most tools such as rdist and - mv do this.

-
- -Note Don't bother asking for a for a - directive which recursively caches all the files in a - directory. Try this instead... See the - Include directive, and consider - this command: - - find /www/htdocs -type f -print \
- | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf - - - +
MMapFile Directive + +

The MMapFile + directive of mod_file_cache maps a list of + statically configured files into memory through the system call + mmap(). This system call is available on most modern + Unix derivates, but not on all. There are sometimes system-specific + limits on the size and number of files that can be + mmap()ed, experimentation is probably the easiest way + to find out.

+ +

This mmap()ing is done once at server start or + restart, only. So whenever one of the mapped files changes on the + filesystem you have to restart the server (see the Stopping and Restarting documentation). + To reiterate that point: if the files are modified in place + without restarting the server you may end up serving requests that + are completely bogus. You should update files by unlinking the old + copy and putting a new copy in place. Most tools such as + rdist and mv do this. The reason why this + modules doesn't take care of changes to the files is that this check + would need an extra stat() every time which is a waste + and against the intent of I/O reduction.

+
+ +
CacheFile Directive + +

The CacheFile + directive of mod_file_cache opens an active + handle or file descriptor to the file (or files) + listed in the configuration directive and places these open file + handles in the cache. When the file is requested, the server + retrieves the handle from the cache and passes it to the + sendfile() (or TransmitFile() on Windows), + socket API.

+ + + +

This file handle caching is done once at server start or + restart, only. So whenever one of the cached files changes on + the filesystem you have to restart the server (see the + Stopping and Restarting + documentation). To reiterate that point: if the files are + modified in place without restarting the server you + may end up serving requests that are completely bogus. You + should update files by unlinking the old copy and putting a new + copy in place. Most tools such as rdist and + mv do this.

+
+ + Note +

Don't bother asking for a for a directive which recursively + caches all the files in a directory. Try this instead... See the + Include directive, and consider + this command:

+ + + find /www/htdocs -type f -print \
+ | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf + +
MMapFile -MMapFile file-path [file-path] ... +Map a list of files into memory at startup time +MMapFile file-path [file-path] ... server config @@ -128,10 +130,10 @@ This module should be used with care. You can easily (given as whitespace separated arguments) into memory at server startup time. They are automatically unmapped on a server shutdown. When the files have changed on the filesystem at - least a HUP or USR1 signal should be send to the server to - re-mmap them.

+ least a HUP or USR1 signal should be send to + the server to re-mmap() them.

-

Be careful with the file-path arguments: They have +

Be careful with the file-path arguments: They have to literally match the filesystem path Apache's URL-to-filename translation handlers create. We cannot compare inodes or other stuff to match paths through symbolic links etc. @@ -140,16 +142,16 @@ This module should be used with care. You can easily with filenames rewritten by mod_alias or mod_rewrite.

-Example - MMapFile /usr/local/apache/htdocs/index.html - + Example + MMapFile /usr/local/apache/htdocs/index.html + CacheFile -CacheFile - file-path [file-path] ... +Cache a list of file handles at startup time +CacheFile file-path [file-path] ... server config @@ -160,7 +162,7 @@ This module should be used with care. You can easily shutdown. When the files have changed on the filesystem, the server should be restarted to to re-cache them.

-

Be careful with the file-path arguments: They have +

Be careful with the file-path arguments: They have to literally match the filesystem path Apache's URL-to-filename translation handlers create. We cannot compare inodes or other stuff to match paths through symbolic links etc. @@ -169,10 +171,10 @@ This module should be used with care. You can easily with filenames rewritten by mod_alias or mod_rewrite.

-Example - CacheFile /usr/local/apache/htdocs/index.html - + Example + CacheFile /usr/local/apache/htdocs/index.html + - + \ No newline at end of file