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329 lines
14 KiB
XML
329 lines
14 KiB
XML
<?xml version="1.0"?>
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<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
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<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
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<!-- $LastChangedRevision$ -->
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<!--
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<modulesynopsis metafile="mod_isapi.xml.meta">
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<name>mod_isapi</name>
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<description>ISAPI Extensions within Apache for Windows</description>
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<status>Base</status>
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<sourcefile>mod_isapi.c</sourcefile>
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<identifier>isapi_module</identifier>
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<compatibility>Win32 only</compatibility>
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<summary>
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<p>This module implements the Internet Server extension API. It
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allows Internet Server extensions (<em>e.g.</em> ISAPI .dll
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modules) to be served by Apache for Windows, subject to the
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noted restrictions.</p>
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<p>ISAPI extension modules (.dll files) are written by third
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parties. The Apache Group does not author these modules, so we
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provide no support for them. Please contact the ISAPI's author
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directly if you are experiencing problems running their ISAPI
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extension. <strong>Please <em>do not</em> post such problems to
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Apache's lists or bug reporting pages.</strong></p>
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</summary>
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<section id="usage"><title>Usage</title>
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<p>In the server configuration file, use
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the <directive module="mod_mime">AddHandler</directive> directive to
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associate ISAPI files with the <code>isapi-handler</code> handler, and map
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it to them with their file extensions. To enable any .dll file to be
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processed as an ISAPI extension, edit the httpd.conf file and add the
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following line:</p>
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<example>
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AddHandler isapi-handler.dll
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</example>
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<note>In older versions of the Apache server,
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<code>isapi-isa</code> was the proper handler name, rather than
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<code>isapi-handler</code>. As of 2.3 development versions of the Apache
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server, <code>isapi-isa</code> is no longer valid. You will need to
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change your configuration to use <code>isapi-handler</code>
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instead.</note>
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<p>There is no capability within the Apache server to leave a
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requested module loaded. However, you may preload and keep a
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specific module loaded by using the following syntax in your
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httpd.conf:</p>
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<example>
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ISAPICacheFile c:/WebWork/Scripts/ISAPI/mytest.dll
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</example>
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<p>Whether or not you have preloaded an ISAPI extension, all
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ISAPI extensions are governed by the same permissions and
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restrictions as CGI scripts. That is, <directive module="core"
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>Options</directive> <code>ExecCGI</code> must be set for the
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directory that contains the ISAPI .dll file.</p>
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<p>Review the <a href="#notes">Additional Notes</a> and the <a
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href="#journal">Programmer's Journal</a> for additional details
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and clarification of the specific ISAPI support offered by
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<module>mod_isapi</module>.</p>
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</section>
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<section id="notes"><title>Additional Notes</title>
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<p>Apache's ISAPI implementation conforms to all of the ISAPI
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2.0 specification, except for some "Microsoft-specific"
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extensions dealing with asynchronous I/O. Apache's I/O model
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does not allow asynchronous reading and writing in a manner
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that the ISAPI could access. If an ISA tries to access
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unsupported features, including async I/O, a message is placed
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in the error log to help with debugging. Since these messages
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can become a flood, the directive <code>ISAPILogNotSupported
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Off</code> exists to quiet this noise.</p>
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<p>Some servers, like Microsoft IIS, load the ISAPI extension
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into the server and keep it loaded until memory usage is too
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high, or unless configuration options are specified. Apache
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currently loads and unloads the ISAPI extension each time it is
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requested, unless the <directive module="mod_isapi"
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>ISAPICacheFile</directive> directive is specified.
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This is inefficient, but Apache's memory model makes this the
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most effective method. Many ISAPI modules are subtly
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incompatible with the Apache server, and unloading these
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modules helps to ensure the stability of the server.</p>
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<p>Also, remember that while Apache supports ISAPI Extensions,
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it <strong>does not support ISAPI Filters</strong>. Support for
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filters may be added at a later date, but no support is planned
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at this time.</p>
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</section>
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<section id="journal"><title>Programmer's Journal</title>
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<p>If you are programming Apache 2.0 <module>mod_isapi</module>
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modules, you must limit your calls to <code>ServerSupportFunction</code>
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to the following directives:</p>
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<dl>
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<dt><code>HSE_REQ_SEND_URL_REDIRECT_RESP</code></dt>
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<dd>Redirect the user to another location.<br />
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This must be a fully qualified URL (<em>e.g.</em>
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<code>http://server/location</code>).</dd>
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<dt><code>HSE_REQ_SEND_URL</code></dt>
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<dd>Redirect the user to another location.<br />
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This cannot be a fully qualified URL, you are not allowed to
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pass the protocol or a server name (<em>e.g.</em> simply
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<code>/location</code>).<br />
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This redirection is handled by the server, not the
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browser.<br />
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<note type="warning"><title>Warning</title>
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<p>In their recent documentation, Microsoft appears to have
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abandoned the distinction between the two
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<code>HSE_REQ_SEND_URL</code> functions. Apache continues to treat
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them as two distinct functions with different requirements
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and behaviors.</p>
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</note></dd>
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<dt><code>HSE_REQ_SEND_RESPONSE_HEADER</code></dt>
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<dd>Apache accepts a response body following the header if it
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follows the blank line (two consecutive newlines) in the
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headers string argument. This body cannot contain NULLs,
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since the headers argument is NULL terminated.</dd>
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<dt><code>HSE_REQ_DONE_WITH_SESSION</code></dt>
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<dd>Apache considers this a no-op, since the session will be
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finished when the ISAPI returns from processing.</dd>
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<dt><code>HSE_REQ_MAP_URL_TO_PATH</code></dt>
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<dd>Apache will translate a virtual name to a physical
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name.</dd>
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<dt><code>HSE_APPEND_LOG_PARAMETER</code></dt>
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<dd>
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This logged message may be captured in any of the following
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logs:
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<ul>
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<li>in the <code>\"%{isapi-parameter}n\"</code> component in a
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<directive module="mod_log_config">CustomLog</directive>
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directive</li>
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<li>in the <code>%q</code> log component with the
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<directive module="mod_isapi">ISAPIAppendLogToQuery</directive>
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<code>On</code> directive</li>
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<li>in the error log with the <directive module="mod_isapi"
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>ISAPIAppendLogToErrors</directive> <code>On</code> directive</li>
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</ul>
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<p>The first option, the <code>%{isapi-parameter}n</code> component,
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is always available and preferred.</p>
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</dd>
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<dt><code>HSE_REQ_IS_KEEP_CONN</code></dt>
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<dd>Will return the negotiated Keep-Alive status.</dd>
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<dt><code>HSE_REQ_SEND_RESPONSE_HEADER_EX</code></dt>
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<dd>Will behave as documented, although the <code>fKeepConn</code>
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flag is ignored.</dd>
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<dt><code>HSE_REQ_IS_CONNECTED</code></dt>
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<dd>Will report false if the request has been aborted.</dd>
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</dl>
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<p>Apache returns <code>FALSE</code> to any unsupported call to
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<code>ServerSupportFunction</code>, and sets the
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<code>GetLastError</code> value to
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<code>ERROR_INVALID_PARAMETER</code>.</p>
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<p><code>ReadClient</code> retrieves the request body exceeding the
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initial buffer (defined by <directive module="mod_isapi"
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>ISAPIReadAheadBuffer</directive>). Based on the
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<directive>ISAPIReadAheadBuffer</directive> setting (number of bytes
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to buffer prior to calling the ISAPI handler) shorter requests are sent
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complete to the extension when it is invoked. If the request is
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longer, the ISAPI extension must use <code>ReadClient</code> to
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retrieve the remaining request body.</p>
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<p><code>WriteClient</code> is supported, but only with the
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<code>HSE_IO_SYNC</code> flag or no option flag (value of
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<code>0</code>). Any other <code>WriteClient</code> request
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will be rejected with a return value of <code>FALSE</code>, and a
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<code>GetLastError</code> value of
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<code>ERROR_INVALID_PARAMETER</code>.</p>
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<p><code>GetServerVariable</code> is supported, although extended server
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variables do not exist (as defined by other servers.) All the
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usual Apache CGI environment variables are available from
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<code>GetServerVariable</code>, as well as the <code>ALL_HTTP</code>
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and <code>ALL_RAW</code> values.</p>
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<p>Apache 2.0 <module>mod_isapi</module> supports additional
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features introduced in later versions of the ISAPI specification,
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as well as limited emulation of async I/O and the
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<code>TransmitFile</code> semantics. Apache also supports preloading
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ISAPI .dlls for performance, neither of which were not available under
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Apache 1.3 <code>mod_isapi</code>.</p>
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</section>
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<directivesynopsis>
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<name>ISAPICacheFile</name>
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<description>ISAPI .dll files to be loaded at startup</description>
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<syntax>ISAPICacheFile <var>file-path</var> [<var>file-path</var>]
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...</syntax>
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<contextlist><context>server config</context><context>virtual host</context>
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</contextlist>
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<usage>
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<p>Specifies a space-separated list of file names to be loaded
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when the Apache server is launched, and remain loaded until the
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server is shut down. This directive may be repeated for every
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ISAPI .dll file desired. The full path name of each file should
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be specified. If the path name is not absolute, it will be treated
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relative to <directive module="core">ServerRoot</directive>.</p>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>ISAPIReadAheadBuffer</name>
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<description>Size of the Read Ahead Buffer sent to ISAPI
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extensions</description>
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<syntax>ISAPIReadAheadBuffer <var>size</var></syntax>
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<default>ISAPIReadAheadBuffer 49152</default>
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<contextlist><context>server config</context><context>virtual host</context>
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<context>directory</context><context>.htaccess</context></contextlist>
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<override>FileInfo</override>
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<usage>
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<p>Defines the maximum size of the Read Ahead Buffer sent to
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ISAPI extensions when they are initially invoked. All remaining
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data must be retrieved using the <code>ReadClient</code> callback; some
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ISAPI extensions may not support the <code>ReadClient</code> function.
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Refer questions to the ISAPI extension's author.</p>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>ISAPILogNotSupported</name>
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<description>Log unsupported feature requests from ISAPI
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extensions</description>
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<syntax>ISAPILogNotSupported on|off</syntax>
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<default>ISAPILogNotSupported off</default>
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<contextlist><context>server config</context><context>virtual host</context>
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<context>directory</context><context>.htaccess</context></contextlist>
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<override>FileInfo</override>
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<usage>
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<p>Logs all requests for unsupported features from ISAPI
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extensions in the server error log. This may help administrators
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to track down problems. Once set to on and all desired ISAPI modules
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are functioning, it should be set back to off.</p>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>ISAPIAppendLogToErrors</name>
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<description>Record <code>HSE_APPEND_LOG_PARAMETER</code> requests from
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ISAPI extensions to the error log</description>
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<syntax>ISAPIAppendLogToErrors on|off</syntax>
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<default>ISAPIAppendLogToErrors off</default>
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<contextlist><context>server config</context><context>virtual host</context>
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<context>directory</context><context>.htaccess</context></contextlist>
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<override>FileInfo</override>
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<usage>
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<p>Record <code>HSE_APPEND_LOG_PARAMETER</code> requests from ISAPI
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extensions to the server error log.</p>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>ISAPIAppendLogToQuery</name>
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<description>Record <code>HSE_APPEND_LOG_PARAMETER</code> requests from
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ISAPI extensions to the query field</description>
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<syntax>ISAPIAppendLogToQuery on|off</syntax>
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<default>ISAPIAppendLogToQuery on</default>
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<contextlist><context>server config</context><context>virtual host</context>
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<context>directory</context><context>.htaccess</context></contextlist>
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<override>FileInfo</override>
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<usage>
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<p>Record <code>HSE_APPEND_LOG_PARAMETER</code> requests from ISAPI
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extensions to the query field (appended to the <directive
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module="mod_log_config">CustomLog</directive> <code>%q</code>
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component).</p>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>ISAPIFakeAsync</name>
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<description>Fake asynchronous support for ISAPI callbacks</description>
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<syntax>ISAPIFakeAsync on|off</syntax>
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<default>ISAPIFakeAsync off</default>
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<contextlist><context>server config</context><context>virtual host</context>
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<context>directory</context><context>.htaccess</context></contextlist>
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<override>FileInfo</override>
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<usage>
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<p>While set to on, asynchronous support for ISAPI callbacks is
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simulated.</p>
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</usage>
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</directivesynopsis>
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</modulesynopsis>
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