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Posted to cvs@httpd.apache.org by co...@apache.org on 2005/08/24 10:18:48 UTC
svn commit: r239563 - in /httpd/httpd/trunk/docs/manual: caching.html.en
caching.xml
Author: colm
Date: Wed Aug 24 01:18:45 2005
New Revision: 239563
URL: http://svn.apache.org/viewcvs?rev=239563&view=rev
Log:
Remove over-zealous and invalid use of <indent></indent> in the Caching
User-guide.
Modified:
httpd/httpd/trunk/docs/manual/caching.html.en
httpd/httpd/trunk/docs/manual/caching.xml
Modified: httpd/httpd/trunk/docs/manual/caching.html.en
URL: http://svn.apache.org/viewcvs/httpd/httpd/trunk/docs/manual/caching.html.en?rev=239563&r1=239562&r2=239563&view=diff
==============================================================================
--- httpd/httpd/trunk/docs/manual/caching.html.en (original)
+++ httpd/httpd/trunk/docs/manual/caching.html.en Wed Aug 24 01:18:45 2005
@@ -112,8 +112,6 @@
<h3>Improving Cache Hits</h3>
- <span class="indent">
-
<p>When caching locally generated content, ensuring that
<code class="directive"><a href="./mod/core.html#usecanonicalname">UseCanonicalName</a></code> is set to
<code>On</code> can dramatically improve the ratio of cache hits. This
@@ -139,13 +137,11 @@
<p>If you are using Server Side Includes, and want the benefit of speedy
serves from the cache, you should use <code>virtual</code> include
types.</p>
- </span>
<h3>Expiry Periods</h3>
- <span class="indent">
<p>The default expiry period for cached entities is one hour, however
this can be easily over-ridden by using the <code class="directive"><a href="./mod/mod_cache.html#cachedefaultexpire">CacheDefaultExpire</a></code> directive. This
default is only used when the original source of the content does not
@@ -160,14 +156,12 @@
<p>The maximum expiry period may also be controlled by using the
<code class="directive"><a href="./mod/mod_cache.html#cachemaxexpire">CacheMaxExpire</a></code>.</p>
- </span>
<h3>A Brief Guide to Conditional Requests</h3>
- <span class="indent">
<p>When content expires from the cache and is re-requested from the
backend or content provider, rather than pass on the original request,
Aoache will use a conditional request instead.</p>
@@ -203,13 +197,11 @@
from the cache if it has not changed. As long as reading from the cache
store is faster than reading from the backend (e.g. an in-memory cache
compared to reading from disk).</p>
- </span>
<h3>What Can be Cached?</h3>
- <span class="indent">
<p>As mentioned already, the two styles of caching in Apache work
differently, <code class="module"><a href="./mod/mod_file_cache.html">mod_file_cache</a></code> caching maintains file
contents as they were when Apache was started. When a request is
@@ -260,15 +252,11 @@
<li>A response will not be stored if it includes a "Vary:" header
containing the match-all "*".</li>
</ol>
-
- </span>
<h3>What Should Not be Cached?</h3>
- <span class="indent">
-
<p>In short, any content which is highly time-sensitive, or which varies
depending on the particulars of the request that are not covered by
HTTP negotiation, should not be cached.</p>
@@ -280,13 +268,11 @@
<p>If on the other hand, the content served differs depending on the
values of various HTTP headers, it is possible that it might be possible
to cache it intelligently through the use of a "Vary" header.</p>
- </span>
<h3>Variable/Negotiated Content</h3>
- <span class="indent">
<p>If a response with a "Vary" header is received by
<code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code> when requesting content by the backend it
will attempt to handle it intelligently. If possible,
@@ -303,7 +289,6 @@
<p><code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code> will only serve the cached content to
requesters with matching accept-language and accept-charset headers
matching those of the original request.</p>
- </span>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
@@ -314,7 +299,6 @@
<h3>Local exploits</h3>
- <span class="indent">
<p>As requests to end-users can be served from the cache, the cache
itself can become a target for those wishing to deface or interfere with
content. It is important to bear in mind that the cache must at all
@@ -332,15 +316,12 @@
using <code class="module"><a href="./mod/mod_disk_cache.html">mod_disk_cache</a></code> you should bear this in mind -
ensure you upgrade Apache when security upgrades are announced and
run CGI processes as a non-Apache user using <a href="suexec.html">suEXEC</a> if possible.</p>
- </span>
<h3>Cache Poisoning</h3>
- <span class="indent">
-
<p>When running Apache as a caching proxy server, there is also the
potential for so-called cache poisoning. Cache Poisoning is a broad
term for attacks in which an attacker causes the proxy server to
@@ -358,7 +339,6 @@
a series of requests, and to exploit a vulnerability on an origin
webserver such that the attacker can entirely control the content
retrieved by the proxy.</p>
- </span>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
@@ -375,7 +355,6 @@
<h3>CacheFile</h3>
- <span class="indent">
<p>The most basic form of caching present in Apache is the file-handle
caching provided by <code class="module"><a href="./mod/mod_file_cache.html">mod_file_cache</a></code>. Rather than caching
file-contents, this cache maintains a table of open file descriptors. Files
@@ -406,13 +385,11 @@
will have been deleted, and not show up on the filesystem, extra free
space will not be recovered until Apache is stopped and the file
descriptor closed.</p>
- </span>
<h3>CacheEnable fd</h3>
- <span class="indent">
<p><code class="module"><a href="./mod/mod_mem_cache.html">mod_mem_cache</a></code> also provides its own file-handle
caching scheme, which can be enabled via the
<code class="directive"><a href="./mod/mod_cache.html#cacheenable">CacheEnable</a></code> directive.</p>
@@ -422,8 +399,6 @@
<p>As with all of <code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code> this type of file-handle
caching is intelligent, and handles will not be maintained beyond
the expiry time of the cached content.</p>
-
- </span>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
@@ -452,7 +427,6 @@
<h3>Operating System Caching</h3>
- <span class="indent">
<p>Almost all modern operating systems cache file-data in memory managed
directly by the kernel. This is a powerful feature, and for the most
part operating systems get it right. For example, on Linux, let's look at
@@ -482,7 +456,6 @@
deleted or modified, it can automatically remove file contents from the
cache when neccessary. This is a big advantage over Apache's in-memory
caching which has no way of knowing when a file has changed.</p>
- </span>
<p>Despite the performance and advantages of automatic operating system
@@ -497,7 +470,6 @@
<h3>MMapStatic Caching</h3>
- <span class="indent">
<p><code class="module"><a href="./mod/mod_file_cache.html">mod_file_cache</a></code> provides the
<code class="directive"><a href="./mod/mod_file_cache.html#mmapstatic">MMapStatic</a></code> directive, which
allows you to have Apache map a static file's contents into memory at
@@ -517,14 +489,11 @@
process will replicate this memory, so it is critically important
to ensure that the files mapped are not so large as to cause the
system to swap memory.</p>
- </span>
-
<h3>mod_mem_cache Caching</h3>
- <span class="indent">
<p><code class="module"><a href="./mod/mod_mem_cache.html">mod_mem_cache</a></code> provides a HTTP-aware intelligent
in-memory cache. It also uses heap memory directly, which means that
even if <var>MMap</var> is not supported on your system,
@@ -538,9 +507,6 @@
# Limit the size of the cache to 1 Megabyte
MCacheSize 1024</pre></div>
-
- </span>
-
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
@@ -571,7 +537,6 @@
<h3>Understanding the Cache-Store</h3>
- <span class="indent">
<p>To store items in the cache, <code class="module"><a href="./mod/mod_disk_cache.html">mod_disk_cache</a></code> creates
a 22 character hash of the url being requested. Thie hash incorporates
the hostname, protocol, port, path and any CGI arguments to the URL,
@@ -622,13 +587,11 @@
".vary" directory will be created for the url in question. This
directory will have multiple ".data" files corresponding to the
differently negotiated content.</p>
- </span>
<h3>Maintaining the Disk Cache</h3>
- <span class="indent">
<p>Although <code class="module"><a href="./mod/mod_disk_cache.html">mod_disk_cache</a></code> will remove cached content
as it is expired, it does not maintain any information on the total
size of the cache or how little free space may be left.</p>
@@ -655,8 +618,6 @@
to how much space is used you should ensure that
<a href="programs/htcacheclean.html">htcacheclean</a> is configured to
leave enough "grow room" following a clean.</p>
-
- </span>
</div></div>
Modified: httpd/httpd/trunk/docs/manual/caching.xml
URL: http://svn.apache.org/viewcvs/httpd/httpd/trunk/docs/manual/caching.xml?rev=239563&r1=239562&r2=239563&view=diff
==============================================================================
--- httpd/httpd/trunk/docs/manual/caching.xml (original)
+++ httpd/httpd/trunk/docs/manual/caching.xml Wed Aug 24 01:18:45 2005
@@ -127,8 +127,6 @@
<section>
<title>Improving Cache Hits</title>
- <indent>
-
<p>When caching locally generated content, ensuring that
<directive module="core">UseCanonicalName</directive> is set to
<code>On</code> can dramatically improve the ratio of cache hits. This
@@ -156,13 +154,11 @@
<p>If you are using Server Side Includes, and want the benefit of speedy
serves from the cache, you should use <code>virtual</code> include
types.</p>
- </indent>
</section>
<section>
<title>Expiry Periods</title>
- <indent>
<p>The default expiry period for cached entities is one hour, however
this can be easily over-ridden by using the <directive
module="mod_cache">CacheDefaultExpire</directive> directive. This
@@ -179,14 +175,12 @@
<p>The maximum expiry period may also be controlled by using the
<directive module="mod_cache">CacheMaxExpire</directive>.</p>
- </indent>
</section>
<section>
<title>A Brief Guide to Conditional Requests</title>
- <indent>
<p>When content expires from the cache and is re-requested from the
backend or content provider, rather than pass on the original request,
Aoache will use a conditional request instead.</p>
@@ -222,13 +216,11 @@
from the cache if it has not changed. As long as reading from the cache
store is faster than reading from the backend (e.g. an in-memory cache
compared to reading from disk).</p>
- </indent>
</section>
<section>
<title>What Can be Cached?</title>
- <indent>
<p>As mentioned already, the two styles of caching in Apache work
differently, <module>mod_file_cache</module> caching maintains file
contents as they were when Apache was started. When a request is
@@ -281,15 +273,11 @@
<li>A response will not be stored if it includes a "Vary:" header
containing the match-all "*".</li>
</ol>
-
- </indent>
</section>
<section>
<title>What Should Not be Cached?</title>
- <indent>
-
<p>In short, any content which is highly time-sensitive, or which varies
depending on the particulars of the request that are not covered by
HTTP negotiation, should not be cached.</p>
@@ -301,13 +289,11 @@
<p>If on the other hand, the content served differs depending on the
values of various HTTP headers, it is possible that it might be possible
to cache it intelligently through the use of a "Vary" header.</p>
- </indent>
</section>
<section>
<title>Variable/Negotiated Content</title>
- <indent>
<p>If a response with a "Vary" header is received by
<module>mod_cache</module> when requesting content by the backend it
will attempt to handle it intelligently. If possible,
@@ -324,7 +310,6 @@
<p><module>mod_cache</module> will only serve the cached content to
requesters with matching accept-language and accept-charset headers
matching those of the original request.</p>
- </indent>
</section>
</section>
@@ -335,7 +320,6 @@
<section>
<title>Local exploits</title>
- <indent>
<p>As requests to end-users can be served from the cache, the cache
itself can become a target for those wishing to deface or interfere with
content. It is important to bear in mind that the cache must at all
@@ -354,15 +338,12 @@
ensure you upgrade Apache when security upgrades are announced and
run CGI processes as a non-Apache user using <a
href="suexec.html">suEXEC</a> if possible.</p>
- </indent>
</section>
<section>
<title>Cache Poisoning</title>
- <indent>
-
<p>When running Apache as a caching proxy server, there is also the
potential for so-called cache poisoning. Cache Poisoning is a broad
term for attacks in which an attacker causes the proxy server to
@@ -380,7 +361,6 @@
a series of requests, and to exploit a vulnerability on an origin
webserver such that the attacker can entirely control the content
retrieved by the proxy.</p>
- </indent>
</section>
</section>
@@ -407,7 +387,6 @@
<section>
<title>CacheFile</title>
- <indent>
<p>The most basic form of caching present in Apache is the file-handle
caching provided by <module>mod_file_cache</module>. Rather than caching
file-contents, this cache maintains a table of open file descriptors. Files
@@ -440,13 +419,11 @@
will have been deleted, and not show up on the filesystem, extra free
space will not be recovered until Apache is stopped and the file
descriptor closed.</p>
- </indent>
</section>
<section>
<title>CacheEnable fd</title>
- <indent>
<p><module>mod_mem_cache</module> also provides its own file-handle
caching scheme, which can be enabled via the
<directive module="mod_cache">CacheEnable</directive> directive.</p>
@@ -458,8 +435,6 @@
<p>As with all of <module>mod_cache</module> this type of file-handle
caching is intelligent, and handles will not be maintained beyond
the expiry time of the cached content.</p>
-
- </indent>
</section>
</section>
@@ -498,7 +473,6 @@
<section>
<title>Operating System Caching</title>
- <indent>
<p>Almost all modern operating systems cache file-data in memory managed
directly by the kernel. This is a powerful feature, and for the most
part operating systems get it right. For example, on Linux, let's look at
@@ -529,7 +503,6 @@
deleted or modified, it can automatically remove file contents from the
cache when neccessary. This is a big advantage over Apache's in-memory
caching which has no way of knowing when a file has changed.</p>
- </indent>
</section>
<p>Despite the performance and advantages of automatic operating system
@@ -544,7 +517,6 @@
<section>
<title>MMapStatic Caching</title>
- <indent>
<p><module>mod_file_cache</module> provides the
<directive module="mod_file_cache">MMapStatic</directive> directive, which
allows you to have Apache map a static file's contents into memory at
@@ -566,14 +538,11 @@
process will replicate this memory, so it is critically important
to ensure that the files mapped are not so large as to cause the
system to swap memory.</p>
- </indent>
-
</section>
<section>
<title>mod_mem_cache Caching</title>
- <indent>
<p><module>mod_mem_cache</module> provides a HTTP-aware intelligent
in-memory cache. It also uses heap memory directly, which means that
even if <var>MMap</var> is not supported on your system,
@@ -588,9 +557,6 @@
# Limit the size of the cache to 1 Megabyte
MCacheSize 1024</pre>
</example>
-
- </indent>
-
</section>
</section>
@@ -631,7 +597,6 @@
<section>
<title>Understanding the Cache-Store</title>
- <indent>
<p>To store items in the cache, <module>mod_disk_cache</module> creates
a 22 character hash of the url being requested. Thie hash incorporates
the hostname, protocol, port, path and any CGI arguments to the URL,
@@ -682,13 +647,11 @@
".vary" directory will be created for the url in question. This
directory will have multiple ".data" files corresponding to the
differently negotiated content.</p>
- </indent>
</section>
<section>
<title>Maintaining the Disk Cache</title>
- <indent>
<p>Although <module>mod_disk_cache</module> will remove cached content
as it is expired, it does not maintain any information on the total
size of the cache or how little free space may be left.</p>
@@ -719,8 +682,6 @@
to how much space is used you should ensure that
<a href="programs/htcacheclean.html">htcacheclean</a> is configured to
leave enough "grow room" following a clean.</p>
-
- </indent>
</section>
</section>