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| --><title>mod_isapi - Apache HTTP Server</title><link href="../style/manual.css" type="text/css" rel="stylesheet"/></head><body><blockquote><div align="center"><img alt="[APACHE DOCUMENTATION]" src="../images/sub.gif"/><h3>Apache HTTP Server Version 2.0</h3></div><h1 align="center">Apache Module mod_isapi</h1><table cellspacing="1" cellpadding="0" bgcolor="#cccccc"><tr><td><table bgcolor="#ffffff"><tr><td valign="top"><span class="help">Description:</span></td><td><description>ISAPI Extensions within Apache for Windows</description></td></tr><tr><td><a href="module-dict.html#Status" class="help">Status:</a></td><td>Base</td></tr><tr><td><a href="module-dict.html#ModuleIdentifier" class="help">Module Identifier:</a></td><td>isapi_module</td></tr><tr><td align="left" valign="top"><a href="module-dict.html#Compatibility" class="help">Compatibility:</a></td><td><compatibility>Win32 only</compatibility></td></tr></table></td></tr></table><h2>Summary</h2><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 |
| extention. <strong>Please <em>do not</em> post such problems to |
| Apache's lists or bug reporting pages.</strong></p> |
| </summary><h2>Directives</h2><ul><li><a href="#isapiappendlogtoerrors">ISAPIAppendLogToErrors</a></li><li><a href="#isapiappendlogtoquery">ISAPIAppendLogToQuery</a></li><li><a href="#isapifilechache">ISAPIFileChache</a></li><li><a href="#isapilognotsupported">ISAPILogNotSupported</a></li><li><a href="#isapireadaheadbuffer">ISAPIReadAheadBuffer</a></li></ul><h2>Usage</h2> <p>In the server configuration file, use |
| the <a href="mod_mime.html#addhandler" class="directive"><code class="directive">AddHandler</code></a> directive to |
| associate ISAPI files with the <code>isapi-isa</code> handler, and map |
| it to the with their file extensions. To enable any .dll file to be |
| processed as an ISAPI extention, edit the httpd.conf file and add the |
| following line:</p> |
| <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code> |
| AddHandler isapi-isa .dll |
| </code></td></tr></table></blockquote> |
| |
| <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> |
| <blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code> |
| ISAPICacheFile c:/WebWork/Scripts/ISAPI/mytest.dll |
| </code></td></tr></table></blockquote> |
| |
| <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, <code>Options |
| 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 |
| mod_isapi.</p> |
| <h2><a name="notes">Additional Notes</a></h2> |
| |
| <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 ISAPICacheFile 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> |
| <h2><a name="journal">Programmer's Journal</a></h2> |
| |
| <p>If you are programming Apache 2.0 <code><a href="mod_isapi.html">mod_isapi</a></code> |
| modules, you must limit your calls to ServerSupportFunction to the |
| following directives:</p> |
| |
| <dl> |
| <dt>HSE_REQ_SEND_URL_REDIRECT_RESP</dt> |
| |
| <dd>Redirect the user to another location.<br> |
| This must be a fully qualified URL (e.g. |
| http://server/location).</dd> |
| |
| <dt>HSE_REQ_SEND_URL</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 (e.g. simply |
| /location).<br> |
| This redirection is handled by the server, not the |
| browser.<br> |
| <strong>Warning:</strong> in their recent documentation, |
| Microsoft appears to have abandoned the distinction between |
| the two HSE_REQ_SEND_URL functions. Apache continues to treat |
| them as two distinct functions with different requirements |
| and behaviors.</dd> |
| |
| <dt>HSE_REQ_SEND_RESPONSE_HEADER</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>HSE_REQ_DONE_WITH_SESSION</dt> |
| |
| <dd>Apache considers this a no-op, since the session will be |
| finished when the ISAPI returns from processing.</dd> |
| |
| <dt>HSE_REQ_MAP_URL_TO_PATH</dt> |
| |
| <dd>Apache will translate a virtual name to a physical |
| name.</dd> |
| |
| <dt>HSE_APPEND_LOG_PARAMETER</dt> |
| |
| <dd> |
| This logged message may be captured in any of the following |
| logs: |
| |
| <ul> |
| <li>in the \"%{isapi-parameter}n\" component in a |
| CustomLog directive</li> |
| |
| <li>in the %q log component with the |
| ISAPIAppendLogToQuery On directive</li> |
| |
| <li>in the error log with the ISAPIAppendLogToErrors On |
| directive</li> |
| </ul> |
| The first option, the %{isapi-parameter}n component, is |
| always available and prefered. |
| </dd> |
| |
| <dt>HSE_REQ_IS_KEEP_CONN</dt> |
| |
| <dd>Will return the negotiated Keep-Alive status.</dd> |
| |
| <dt>HSE_REQ_SEND_RESPONSE_HEADER_EX</dt> |
| |
| <dd>Will behave as documented, although the fKeepConn flag is |
| ignored.</dd> |
| |
| <dt>HSE_REQ_IS_CONNECTED</dt> |
| |
| <dd>Will report false if the request has been aborted.</dd> |
| </dl> |
| |
| <p>Apache returns FALSE to any unsupported call to |
| ServerSupportFunction, and sets the GetLastError value to |
| ERROR_INVALID_PARAMETER.</p> |
| |
| <p>ReadClient retrieves the request body exceeding the initial |
| buffer (defined by ISAPIReadAheadBuffer). Based on the |
| ISAPIReadAheadBuffer 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 ReadClient to retrieve the |
| remaining request body.</p> |
| |
| <p>WriteClient is supported, but only with the HSE_IO_SYNC flag |
| or no option flag (value of 0). Any other WriteClient request |
| will be rejected with a return value of FALSE, and a |
| GetLastError value of ERROR_INVALID_PARAMETER.</p> |
| |
| <p>GetServerVariable is supported, although extended server |
| variables do not exist (as defined by other servers.) All the |
| usual Apache CGI environment variables are available from |
| GetServerVariable, as well as the ALL_HTTP and ALL_RAW |
| values.</p> |
| |
| <p>Apache 2.0 <code><a href="mod_isapi.html">mod_isapi</a></code> supports additional |
| features introduced in later versions of the ISAPI specification, |
| as well as limited emulation of async I/O and the TransmitFile |
| semantics. Apache also supports preloading ISAPI .dlls for |
| performance, neither of which were not available under Apache 1.3 |
| mod_isapi.</p> |
| <hr/><h2><a name="ISAPIAppendLogToErrors">ISAPIAppendLogToErrors</a> <a name="isapiappendlogtoerrors">Directive</a></h2><table cellpadding="1" cellspacing="0" border="0" bgcolor="#cccccc"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Record HSE_APPEND_LOG_PARAMETER requests from ISAPI |
| extensions to the error log</td></tr><tr><td><a href="directive-dict.html#Syntax" class="help">Syntax:</a></td><td><syntax>ISAPIAppendLogToErrors on|off</syntax></td></tr><tr><td><a href="directive-dict.html#Default" class="help">Default:</a></td><td><code>ISAPIAppendLogToErrors off</code></td></tr><tr><td><a href="directive-dict.html#Context" class="help">Context:</a></td><td>server config</td></tr><tr><td><a href="directive-dict.html#Status" class="help">Status:</a></td><td>Base</td></tr><tr><td><a href="directive-dict.html#Module" class="help">Module:</a></td><td>mod_isapi</td></tr></table></td></tr></table><usage> |
| <p>Record HSE_APPEND_LOG_PARAMETER requests from ISAPI |
| extensions to the server error log.</p> |
| </usage><hr/><h2><a name="ISAPIAppendLogToQuery">ISAPIAppendLogToQuery</a> <a name="isapiappendlogtoquery">Directive</a></h2><table cellpadding="1" cellspacing="0" border="0" bgcolor="#cccccc"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Record HSE_APPEND_LOG_PARAMETER requests from ISAPI |
| extensions to the query field</td></tr><tr><td><a href="directive-dict.html#Syntax" class="help">Syntax:</a></td><td><syntax>ISAPIAppendLogToQuery on|off</syntax></td></tr><tr><td><a href="directive-dict.html#Default" class="help">Default:</a></td><td><code>ISAPIAppendLogToQuery off</code></td></tr><tr><td><a href="directive-dict.html#Context" class="help">Context:</a></td><td>server config</td></tr><tr><td><a href="directive-dict.html#Status" class="help">Status:</a></td><td>Base</td></tr><tr><td><a href="directive-dict.html#Module" class="help">Module:</a></td><td>mod_isapi</td></tr></table></td></tr></table><usage> |
| <p>Record HSE_APPEND_LOG_PARAMETER requests from ISAPI |
| extensions to the query field (appended to the CustomLog %q |
| component).</p> |
| </usage><hr/><h2><a name="ISAPIFileChache">ISAPIFileChache</a> <a name="isapifilechache">Directive</a></h2><table cellpadding="1" cellspacing="0" border="0" bgcolor="#cccccc"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>ISAPI .dll files to be loaded at startup</td></tr><tr><td><a href="directive-dict.html#Syntax" class="help">Syntax:</a></td><td><syntax>ISAPIFileCache <em>file-path</em> [<em>file-path</em>] ...</syntax></td></tr><tr><td><a href="directive-dict.html#Context" class="help">Context:</a></td><td>server config</td></tr><tr><td><a href="directive-dict.html#Status" class="help">Status:</a></td><td>Base</td></tr><tr><td><a href="directive-dict.html#Module" class="help">Module:</a></td><td>mod_isapi</td></tr></table></td></tr></table><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.</p> |
| </usage><hr/><h2><a name="ISAPILogNotSupported">ISAPILogNotSupported</a> <a name="isapilognotsupported">Directive</a></h2><table cellpadding="1" cellspacing="0" border="0" bgcolor="#cccccc"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Log unsupported feature requests from ISAPI |
| extensions</td></tr><tr><td><a href="directive-dict.html#Syntax" class="help">Syntax:</a></td><td><syntax>ISAPILogNotSupported on|off</syntax></td></tr><tr><td><a href="directive-dict.html#Default" class="help">Default:</a></td><td><code>ISAPILogNotSupported on</code></td></tr><tr><td><a href="directive-dict.html#Context" class="help">Context:</a></td><td>server config</td></tr><tr><td><a href="directive-dict.html#Status" class="help">Status:</a></td><td>Base</td></tr><tr><td><a href="directive-dict.html#Module" class="help">Module:</a></td><td>mod_isapi</td></tr></table></td></tr></table><usage> |
| <p>Logs all requests for unsupported features from ISAPI |
| extensions in the server error log. While this should be turned |
| off once all desired ISAPI modules are functioning, it defaults |
| to on to help administrators track down problems.</p> |
| </usage><hr/><h2><a name="ISAPIReadAheadBuffer">ISAPIReadAheadBuffer</a> <a name="isapireadaheadbuffer">Directive</a></h2><table cellpadding="1" cellspacing="0" border="0" bgcolor="#cccccc"><tr><td><table bgcolor="#ffffff"><tr><td><strong>Description: </strong></td><td>Size of the Read Ahead Buffer sent to ISAPI |
| extensions</td></tr><tr><td><a href="directive-dict.html#Syntax" class="help">Syntax:</a></td><td><syntax>ISAPIReadAheadBuffer <em>size</em></syntax></td></tr><tr><td><a href="directive-dict.html#Default" class="help">Default:</a></td><td><code>ISAPIReadAheadBuffer 49152</code></td></tr><tr><td><a href="directive-dict.html#Context" class="help">Context:</a></td><td>server config</td></tr><tr><td><a href="directive-dict.html#Status" class="help">Status:</a></td><td>Base</td></tr><tr><td><a href="directive-dict.html#Module" class="help">Module:</a></td><td>mod_isapi</td></tr></table></td></tr></table><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 ReadClient callback; some |
| ISAPI extensions may not support the ReadClient function. Refer |
| questions to the ISAPI extension's author.</p> |
| </usage><hr/><h3 align="center">Apache HTTP Server Version 2.0</h3><a href="./"><img alt="Index" src="../images/index.gif"/></a><a href="../"><img alt="Home" src="../images/home.gif"/></a></blockquote></body></html> |