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 is no longer valid.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