path: root/lib/inets/doc/src/httpd.xml

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>1997</year><year>2018</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>httpd</title>
    <prepared>Ingela Anderton Andin</prepared>
    <docno></docno>
    <date>1997-10-14</date>
    <rev>2.2</rev>
    <file>httpd.sgml</file>
  </header>
  <module>httpd</module> 
  <modulesummary>
    HTTP server API
  </modulesummary>
  <description>
    <p>An implementation of an HTTP 1.1 compliant web server, as defined in 
    <url href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</url>. 
    Provides web server start options, administrative functions, and 
    an Erlang callback API.</p>
  </description>
  
  <section>
    <title>DATA TYPES</title>
    <p>Type definitions that are used more than once in
      this module:</p>
    <p><c>boolean() = true | false</c></p>
    <p><c>string()</c> = list of ASCII characters</p>
    <p><c>path() = string()</c> representing a file or a directory path</p>
    <p><c> ip_address() = {N1,N2,N3,N4} % IPv4
       | {K1,K2,K3,K4,K5,K6,K7,K8}  % IPv6</c></p>
    <p><c>hostname() = string()</c> representing a host, for example, 
    "foo.bar.com"</p>
    <p><c>property() = atom()</c></p>
    
  </section>

  <section>
    <title>ERLANG HTTP SERVER SERVICE START/STOP</title>
    <p>A web server can be configured to start when starting the <c>Inets</c>
    application, or dynamically in runtime by calling the
    <c>Inets</c> application API <c>inets:start(httpd, ServiceConfig)</c> or
    <c>inets:start(httpd, ServiceConfig, How)</c>,
    see <seealso marker="inets">inets(3)</seealso>.
    The configuration options, also called
    properties, are as follows:</p>

    <marker id="props_file"></marker>
    <p><em>File Properties</em></p>

    <p>When the web server is started
    at application start time, the properties are to be fetched from a
    configuration file that can consist of a regular Erlang property
    list, that is, <c>[{Option, Value}]</c>, where <c> Option = property()
    </c> and <c>Value = term()</c>, followed by a full stop, or for
    backwards compatibility, an Apache-like configuration file. If the
    web server is started dynamically at runtime,
    a file can still be specified but also the complete property
    list.</p>
    
    <taglist>
      <tag><marker id="prop_proplist_file"></marker>{proplist_file, path()}</tag>
      <item>
	<p>If this property is defined, <c>Inets</c> expects to find
	all other properties defined in this file. The
	file must include all properties listed under mandatory
	properties.</p>
      </item>

      <tag><marker id="prop_file"></marker>{file, path()}</tag>
      <item> 
	<p>If this property is defined, <c>Inets</c> expects to find all 
	other properties defined in this file, which uses Apache-like 
	syntax. The file must include all properties listed 
	under mandatory properties. The Apache-like syntax is the property, 
	written as one word where each new word begins with a capital, 
	followed by a white-space, followed by the value, followed by a 
	new line.</p>
	<p>Example:</p>
	<code>
{server_root, "/urs/local/www"} -> ServerRoot /usr/local/www</code>
	  
	<p>A few exceptions are documented
	  for each property that behaves differently,
	  and the special cases <c>{directory, {path(), PropertyList}}</c> 
	  and <c>{security_directory, {Dir, PropertyList}}</c>, are represented
	  as:</p>
	<pre>
	  <![CDATA[
<Directory Dir>
 <Properties handled as described above> 
</Directory>
         ]]></pre>
      </item>
    </taglist>
    <note>
	<p>The properties <c>proplist_file</c> and <c>file</c> are mutually exclusive. Also newer properties may not be supported as Apache-like options, this is a legacy feature.</p>
    </note>

    <marker id="props_mand"></marker>
    <p><em>Mandatory Properties</em></p>
    <taglist>
      <tag><marker id="prop_port"></marker>{port, integer()} </tag>
      <item> 
	<p>The port that the HTTP server listen to.
	If zero is specified as port, an arbitrary available port
	is picked and function <c>httpd:info/2</c> can be used to
	determine which port was picked.</p>
      </item>

      <tag><marker id="prop_server_name"></marker>{server_name, string()}</tag>
      <item>
	<p>The name of your server, normally a fully qualified domain name.</p>
      </item>

      <tag><marker id="prop_server_root"></marker>{server_root, path()}</tag>
      <item> 
	<p>Defines the home directory of the server, where log files, and so on, 
	can be stored. Relative paths specified in other properties refer
	to this directory.</p>
      </item>

      <tag> <marker id="prop_doc_root"></marker>{document_root, path()}</tag>
      <item>
	<p>Defines the top directory for the documents that
	are available on the HTTP server.</p>
      </item>
    </taglist>

    <marker id="props_comm"></marker>
    <p><em>Communication Properties</em></p>
    <taglist>
      <tag><marker id="prop_bind_address"></marker>{bind_address, ip_address() | hostname() | any}</tag>
      <item>
	<p>Default is <c>any</c>. <c>any</c> is denoted <em>*</em> 
	in the Apache-like configuration file.</p>
      </item>

      <tag><marker id="profile"></marker>{profile, atom()}</tag>
      <item>
        <p>Used together with <seealso marker="#prop_bind_address"><c>bind_address</c></seealso>
	and <seealso marker="#prop_port"><c>port</c></seealso> to uniquely identify
	a HTTP server. This can be useful in a virtualized environment,
	where there can
	be more that one server that has the same bind_address and port.
	If this property is not explicitly set, it is assumed that the
	<seealso marker="#prop_bind_address"><c>bind_address</c></seealso> and
	<seealso marker="#prop_port"><c>port</c></seealso>uniquely identifies the HTTP server.
	</p>
      </item>

      <tag><marker id="prop_socket_type"></marker>{socket_type, ip_comm | {ip_comm,  Config::proplist()} | {essl, Config::proplist()}}</tag>
      <item>
	<p>For <c>ip_comm</c> configuration options, see 
	<seealso marker="kernel:gen_tcp#listen-2">gen_tcp:listen/2</seealso>, some options
	that are used internally by httpd can not be set.</p>
	<p>For <c>SSL</c> configuration options, see 
	<seealso marker="ssl:ssl#listen-2">ssl:listen/2</seealso>.</p>
	<p>Default is <c>ip_comm</c>.</p> 
      </item>

      <tag><marker id="prop_ipfamily"></marker>{ipfamily, inet | inet6}</tag>
      <item>
	<p>Default is <c>inet</c>, legacy option <c>inet6fb4</c> no longer makes sense and will be translated
	to inet.</p>
      </item>
      
      <tag><marker id="prop_minimum_bytes_per_second"></marker>{minimum_bytes_per_second, integer()}</tag>
      <item>
	<p>If given, sets a minimum of bytes per second value for connections.</p>
	<p>If the value is unreached, the socket closes for that connection.</p>
	<p>The option is good for reducing the risk of "slow DoS" attacks.</p>
      </item>
    </taglist>

    <marker id="props_api_modules"></marker>
    <p><em>Erlang Web Server API Modules</em> </p>
    <taglist>
      <tag><marker id="prop_modules"></marker>{modules, [atom()]} </tag>
      <item>
	<p>Defines which modules the HTTP server uses when handling
	requests. Default is <c>[mod_alias, mod_auth, mod_esi,
	mod_actions, mod_cgi, mod_dir, mod_get, mod_head, mod_log,
	mod_disk_log]</c>. 
	Notice that some <c>mod</c>-modules are dependent on
	others, so the order cannot be entirely arbitrary. See the
	<seealso marker="http_server">Inets Web Server Modules</seealso> in the
	User's Guide for details.</p>
      </item>
    </taglist>
    
    <marker id="props_limit"></marker>
    <p><em>Limit properties</em> </p>
    <taglist>

      <tag><marker id="prop_customize"></marker>{customize, atom()}</tag>
      <item> 
	<p>A callback module to customize the inets HTTP servers behaviour
	see <seealso marker="httpd_custom_api"> httpd_custom_api</seealso> </p>
      </item>
      
      <tag><marker id="prop_disable_chunked_encoding"></marker>{disable_chunked_transfer_encoding_send, boolean()}</tag>
      <item> 
	<p>Allows you to disable chunked
	transfer-encoding when sending a response to an HTTP/1.1
	client. Default is <c>false</c>.</p>
      </item>
      
      <tag><marker id="prop_keep_alive"></marker>{keep_alive, boolean()}</tag>
      <item>
	<p>Instructs the server whether to use persistent
	connections when the client claims to be HTTP/1.1
	compliant. Default is <c>true</c>.</p>
      </item>
      
      <tag><marker id="prop_keep_alive_timeout"></marker>{keep_alive_timeout, integer()}</tag>
      <item>
	<p>The number of seconds the server waits for a
	subsequent request from the client before closing the
	connection. Default is <c>150</c>.</p>
      </item>
      
      <tag><marker id="prop_max_body_size"></marker>{max_body_size, integer()}</tag>
      <item>
	<p>Limits the size of the message body of an HTTP request.
	Default is no limit.</p>
      </item>
      
      <tag><marker id="prop_max_clients"></marker>{max_clients, integer()}</tag>
      <item> 
	<p>Limits the number of simultaneous requests that can be
	supported. Default is <c>150</c>.</p>
      </item>

      <tag><marker id="prop_max_header_size"></marker>{max_header_size, integer()}</tag>
      <item>
	<p>Limits the size of the message header of an HTTP request.
	Default is <c>10240</c>.</p>
      </item>

      <tag><marker id="prop_max_content_length"></marker>{max_content_length, integer()}</tag>
      <item>
	<p>Maximum content-length in an incoming request, in bytes. Requests
	with content larger than this are answered with status 413.
	Default is <c>100000000</c> (100 MB).
	</p>
      </item>

      <tag><marker id="prop_max_uri"></marker>{max_uri_size, integer()}</tag>
      <item>
	<p>Limits the size of the HTTP request URI.
	Default is no limit.</p>
      </item>
      
      <tag><marker id="prop_max_keep_alive_req"></marker>{max_keep_alive_request, integer()}</tag>
      <item>
	<p>The number of requests that a client can do on one
	connection. When the server has responded to the number of
	requests defined by <c>max_keep_alive_requests</c>, the server 
	closes the connection. The server closes it even if there are 
	queued request. Default is no limit.</p>
      </item>

      
      <tag><marker id="max_client_body_chunk"></marker>{max_client_body_chunk, integer()}</tag>
      <item>
	<p>Enforces chunking of a HTTP PUT or POST body data to be deliverd
	to the mod_esi callback. Note this is not supported for mod_cgi. 
	Default is no limit e.i the whole body is deliverd as one entity, which could
	be very memory consuming. <seealso marker="mod_esi">mod_esi(3)</seealso>.
	</p>
      </item>
      
    </taglist>
    
    <marker id="props_admin"></marker>
    <p><em>Administrative Properties</em></p>
    <taglist> 
      <tag><marker id="prop_mime_types"></marker>{mime_types, [{MimeType, Extension}] | path()}</tag>
      <item>
	<p><c>MimeType = string()</c> and <c>Extension = string()</c>.
	  Files delivered to the client are MIME typed according to RFC
          1590. File suffixes are mapped to MIME types before file delivery.
          The mapping between file suffixes and MIME types can be specified
	  as an Apache-like file or directly in the property list. Such
          a file can look like the follwoing:</p>
        <pre>
# MIME type	Extension  
text/html	html htm
text/plain	asc txt</pre>
	
	<p>Default is [{"html","text/html"},{"htm","text/html"}].</p>
      </item>

      <tag><marker id="prop_mime_type"></marker>{mime_type, string()}</tag>
      <item>
	<p>When the server is asked to provide a document type that
	cannot be determined by the MIME Type Settings, the server
	uses this default type.</p>
      </item>
  
      <tag><marker id="prop_server_admin"></marker>{server_admin, string()}</tag>
      <item>
	<p>Defines the email-address of the server
	administrator to be included in any error messages returned by
	the server.</p>
      </item>

      <tag><marker id="prop_server_tokens"></marker>{server_tokens, none|prod|major|minor|minimal|os|full|{private, string()}}</tag>
      <item>
	<p>Defines the look of the value of the server header.</p>
	<p>Example: Assuming the version of <c>Inets</c> is 5.8.1, 
	the server header string can look as follows for
	the different values of server-tokens:</p>
	<taglist>
       <tag><c>none</c></tag>
       <item><p>""  % A Server: header will not be generated</p></item>
       <tag><c>prod</c></tag>
       <item><p>"inets"</p></item>
       <tag><c>major</c></tag>
       <item><p>"inets/5"</p></item>
       <tag><c>minor</c></tag>
       <item><p>"inets/5.8"</p></item>
       <tag><c>minimal</c></tag>
       <item><p>"inets/5.8.1"</p></item>
       <tag><c>os</c></tag>
       <item><p>"inets/5.8.1 (unix)"</p></item>
       <tag><c>full</c></tag>
       <item><p>"inets/5.8.1 (unix/linux) OTP/R15B"</p></item>
       <tag><c>{private, "foo/bar"}</c></tag>
       <item><p>"foo/bar"</p></item>
     </taglist>
	<p>By default, the value is as before, that is, <c>minimal</c>.</p>
      </item>

      <tag><marker id="prop_log_format"></marker>{log_format, common | combined}</tag>
      <item>
	<p>Defines if access logs are to be written according to the <c>common</c>
	log format or the extended common log format.
	The <c>common</c> format is one line looking like this:
        <c>remotehost rfc931 authuser [date] "request" status bytes</c>.</p> 
	<p>Here:</p>
	<taglist>
	  <tag><c>remotehost</c></tag>
	  <item>Remote.</item>
	  <tag><c>rfc931</c></tag>
	  <item>The remote username of the client (<url href="http://www.ietf.org/rfc/rfc931.txt">RFC 931</url>).</item>
	  <tag><c>authuser</c></tag>
	  <item>The username used for authentication.</item>
	  <tag><c>[date]</c></tag>
	  <item>Date and time of the request (<url href="http://www.ietf.org/rfc/rfc1123.txt">RFC 1123</url>).</item>
	  <tag><c>"request"</c></tag>
	  <item>The request line as it came from the client  (<url href="http://www.ietf.org/rfc/rfc1945.txt">RFC 1945</url>).</item>
	  <tag><c>status</c></tag>
	  <item>The HTTP status code returned to the client (<url href="http://www.ietf.org/rfc/rfc1945.txt">RFC 1945</url>).</item>
	  <tag><c>bytes</c></tag>
	  <item>The content-length of the document transferred.</item>
	</taglist>

	<p>The <c>combined</c> format is one line looking like this:
	<c>remotehost rfc931 authuser [date] "request" status bytes "referer" "user_agent" </c></p>
	<p>In addition to the earlier:</p>
	<taglist>
	  <tag><c>"referer"</c></tag>
	  <item>The URL the client was on before
	requesting the URL (if it could not be determined, 
	a minus sign is placed in this field).</item>
	  <tag><c>"user_agent"</c></tag>
	  <item>The software the client claims to be using (if it
	could not be determined, a minus sign is placed in
	this field).</item>
	</taglist>
	
	<p>This affects the access logs written by <c>mod_log</c> and 
	<c>mod_disk_log</c>.
	</p>	
      </item>      

      <tag><marker id="prop_elog_format"></marker>{error_log_format, pretty | compact}</tag>
      <item>
	<p>Default is <c>pretty</c>. If the error log is meant to be read
	directly by a human, <c>pretty</c> is the best option.</p>
	<p><c>pretty</c> has a format corresponding to:</p>
	
	<code>io:format("[~s] ~s, reason: ~n ~p ~n~n", [Date, Msg, Reason]).</code>

	<p><c>compact</c> has a format corresponding to:</p>
	
	<code>io:format("[~s] ~s, reason: ~w ~n", [Date, Msg, Reason]).</code>

	<p>This affects the error logs written by <c>mod_log</c> and 
	<c>mod_disk_log</c>.
	</p>
      </item>
      
    </taglist>
   
    <marker id="props_alias"></marker>
    <p><em>URL Aliasing Properties - Requires mod_alias</em></p>
    <taglist>
      <tag><marker id="prop_alias"></marker>{alias, {Alias, RealName}}</tag>
      <item>
	<p><c>Alias = string()</c> and <c>RealName = string()</c>. 
	<c>alias</c> allows documents to be stored in the local file
	system instead of the <c>document_root</c> location. URLs with a path
	beginning with url-path is mapped to local files beginning with
	directory-filename, for example:</p>
	
	<code>{alias, {"/image", "/ftp/pub/image"}}</code>
	
	<p>Access to http://your.server.org/image/foo.gif would refer to
	the file /ftp/pub/image/foo.gif.</p>
      </item>

      <tag><marker id="prop_re_write"></marker>{re_write, {Re, Replacement}}</tag>      
      <item>
	<p><c>Re = string()</c> and <c>Replacement = string()</c>. 
	<c>re_write</c> allows documents to be stored in the local file
	system instead of the <c>document_root</c> location. URLs are rewritten
        by <c>re:replace/3</c> to produce a path in the local file-system,
        for example:</p>
	
	<code>{re_write, {"^/[~]([^/]+)(.*)$", "/home/\\1/public\\2"}}</code>
	
	<p>Access to http://your.server.org/~bob/foo.gif would refer to
	the file /home/bob/public/foo.gif.

        In an Apache-like configuration file, <c>Re</c> is separated
        from <c>Replacement</c> with one single space, and as expected
        backslashes do not need to be backslash escaped, the
        same example would become:</p>

        <code>ReWrite ^/[~]([^/]+)(.*)$ /home/\1/public\2</code>

        <p>Beware of trailing space in <c>Replacement</c> to be used.
        If you must have a space in <c>Re</c>, use, for example, the character 
	encoding <c>\040</c>, see 
	<seealso marker="stdlib:re">re(3)</seealso>.</p>
      </item>

      <tag><marker id="prop_dir_idx"></marker>{directory_index, [string()]}</tag>      
      <item> 
	<p><c>directory_index</c> specifies a list of resources to look for
	if a client requests a directory using a <c>/</c> at the end of the
	directory name. <c>file</c> depicts the name of a file in the
	directory. Several files can be given, in which case the server
	returns the first it finds, for example:</p>
	
	<code>{directory_index, ["index.html", "welcome.html"]}</code>
	
	<p>Access to http://your.server.org/docs/ would return
	http://your.server.org/docs/index.html or
	http://your.server.org/docs/welcome.html if index.html does not
	exist.</p>
      </item> 
    </taglist>

    <marker id="props_cgi"></marker>
    <p><em>CGI Properties - Requires mod_cgi</em></p>
    <taglist> 
      <tag><marker id="prop_script_alias"></marker>{script_alias, {Alias, RealName}}</tag>
      <item>
	<p><c>Alias = string()</c> and <c>RealName = string()</c>.
	Have the same behavior as property <c>alias</c>, except that
	they also mark the target directory as containing CGI
	scripts. URLs with a path beginning with url-path are mapped to
	scripts beginning with directory-filename, for example:</p>
	
	<code>{script_alias, {"/cgi-bin/", "/web/cgi-bin/"}}</code>
	
	<p>Access to http://your.server.org/cgi-bin/foo would cause
	the server to run the script /web/cgi-bin/foo.</p>
      </item>
      
      <tag><marker id="prop_script_re_write"></marker>{script_re_write, {Re, Replacement}}</tag>
      <item>
	<p><c>Re = string()</c> and <c>Replacement = string()</c>.
	Have the same behavior as property <c>re_write</c>, except that
	they also mark the target directory as containing CGI
	scripts. URLs with a path beginning with url-path are mapped to
	scripts beginning with directory-filename, for example:</p>
	
	<code>{script_re_write, {"^/cgi-bin/(\\d+)/", "/web/\\1/cgi-bin/"}}</code>
	
	<p>Access to http://your.server.org/cgi-bin/17/foo would cause
	the server to run the script /web/17/cgi-bin/foo.</p>
      </item>
      
      <tag><marker id="prop_script_nocache"></marker>{script_nocache, boolean()}</tag>
      <item> 
	<p>If <c>script_nocache</c> is set to <c>true</c>, the HTTP server by
	default adds the header fields necessary to prevent proxies from
	caching the page. Generally this is preferred. 
	Default to <c>false</c>.</p>
      </item>
      
      <tag><marker id="prop_script_timeout"></marker>{script_timeout, integer()}</tag>
      <item>
	<p>The time in seconds the web server waits between each
	chunk of data from the script. If the CGI script does not deliver
	any data before the timeout, the connection to the client is
	closed. Default is <c>15</c>.</p>
      </item>
      
      <tag><marker id="prop_action"></marker>{action, {MimeType, CgiScript}} - requires mod_action</tag>
      <item>
	<p><c>MimeType = string()</c> and <c>CgiScript = string()</c>.
	<c>action</c> adds an action activating a CGI script
	whenever a file of a certain MIME type is requested. It
	propagates the URL and file path of the requested document using
	the standard CGI PATH_INFO and PATH_TRANSLATED environment
	variables.</p>
	<p>Example:</p>

	<code>{action, {"text/plain", "/cgi-bin/log_and_deliver_text"}}</code>
      </item>

      <tag><marker id="prop_script"></marker>{script, {Method, CgiScript}} - requires mod_action</tag>
      <item>
	<p><c>Method = string()</c> and <c>CgiScript = string()</c>.
	<c>script</c> adds an action activating a CGI script
	whenever a file is requested using a certain HTTP method. The
	method is either GET or POST, as defined in <url href="http://www.ietf.org/rfc/rfc1945.txt">RFC 1945</url>. It
	propagates the URL and file path of the requested document using
	the standard CGI PATH_INFO and PATH_TRANSLATED environment
	variables.</p>
	<p>Example:</p>
	
	<code>{script, {"PUT", "/cgi-bin/put"}}</code>
	
      </item>
    </taglist>
    
    <marker id="props_esi"></marker>
    <p><em>ESI Properties - Requires mod_esi</em></p>
    <taglist>
      <tag><marker id="prop_esi_alias"></marker>{erl_script_alias, {URLPath, [AllowedModule]}}</tag>      
      <item>
	<p><c>URLPath = string()</c> and <c>AllowedModule = atom()</c>.
	<c>erl_script_alias</c> marks all URLs matching url-path as erl
	scheme scripts. A matching URL is mapped into a specific module
	and function, for example:</p>
	
	<code>{erl_script_alias, {"/cgi-bin/example", [httpd_example]}}</code>
	
	<p>A request to
	http://your.server.org/cgi-bin/example/httpd_example:yahoo
	would refer to httpd_example:yahoo/3 or, if that does not exist,
	httpd_example:yahoo/2 and
	http://your.server.org/cgi-bin/example/other:yahoo would
	not be allowed to execute.</p>
      </item>

      <tag><marker id="prop_esi_nocache"></marker>{erl_script_nocache, boolean()}</tag>
      <item>
	<p>If <c>erl_script_nocache</c> is set to <c>true</c>, the server adds
	HTTP header fields preventing proxies from caching the
	page. This is generally a good idea for dynamic content, as
	the content often varies between each request. 
	Default is <c>false</c>.</p>
      </item>

      <tag><marker id="prop_esi_timeout"></marker>{erl_script_timeout, integer()}</tag>
      <item>
	<p>If <c>erl_script_timeout</c> sets the time in seconds the server
	waits between each chunk of data to be delivered through
	<c>mod_esi:deliver/2</c>. Default is <c>15</c>. This is only relevant
	for scripts that use the erl scheme.</p>
      </item>

      <tag><marker id="prop_esi_timeout"></marker>{eval_script_alias, {URLPath, [AllowedModule]}}</tag>
      <item>
	<p><c>URLPath = string()</c> and <c>AllowedModule = atom()</c>.
	Same as <c>erl_script_alias</c> but for scripts
	using the eval scheme. This is only supported
	for backwards compatibility. The eval scheme is deprecated.</p>
      </item>
    </taglist>

    <marker id="props_log"></marker>
    <p><em>Log Properties - Requires mod_log</em></p>
    <taglist>
      <tag><marker id="prop_elog"></marker>{error_log, path()}</tag>
      <item>
	<p>Defines the filename of the error log file to be used to log
	server errors. If the filename does not begin with a slash (/),
	it is assumed to be relative to the <c>server_root</c>.</p>
      </item>

      <tag><marker id="prop_slog"></marker>{security_log, path()}</tag>
      <item>
	<p>Defines the filename of the access log file to be used to
	log security events. If the filename does not begin with a slash
	(/), it is assumed to be relative to the <c>server_root</c>.</p>
      </item>

      <tag><marker id="prop_tlog"></marker>{transfer_log, path()}</tag>
      <item> 
	<p>Defines the filename of the access log file to be used to
	log incoming requests. If the filename does not begin with a
	slash (/), it is assumed to be relative to the <c>server_root</c>.</p>
      </item>
    </taglist>

    <marker id="props_dlog"></marker>
    <p><em>Disk Log Properties - Requires mod_disk_log</em></p>
    <taglist>
      <tag><marker id="prop_dlog_format"></marker>{disk_log_format, internal | external}</tag>
      <item>
	<p>Defines the file format of the log files. See <c>disk_log</c> for
	details. If the internal file format is used, the
	log file is repaired after a crash. When a log file is
	repaired, data can disappear. When the external file format is
	used, <c>httpd</c> does not start if the log file is broken. Default is
	<c>external</c>.</p>
      </item>

      <tag><marker id="prop_edlog"></marker>{error_disk_log, path()}</tag>
      <item>
	<p>Defines the filename of the (<c>disk_log(3)</c>) error log file
	to be used to log server errors. If the filename does not begin
	with a slash (/), it is assumed to be relative to the <c>server_root</c>.</p>
      </item>

      <tag><marker id="prop_edlog_size"></marker>{error_disk_log_size, {MaxBytes, MaxFiles}}</tag>
      <item>
	<p><c>MaxBytes = integer()</c> and <c>MaxFiles = integer()</c>.
	Defines the properties of the (<c>disk_log(3)</c>) error log
	file. This file is of type wrap log and
	max bytes is written to each file and max files is
	used before the first file is truncated and reused.</p>
      </item>

      <tag><marker id="prop_sdlog"></marker>{security_disk_log, path()}</tag>
      <item>
	<p>Defines the filename of the (<c>disk_log(3)</c>) access log file
	logging incoming security events, that is, authenticated
	requests. If the filename does not begin with a slash (/), it
	is assumed to be relative to the <c>server_root</c>.</p>
      </item>

      <tag><marker id="prop_sdlog_size"></marker>{security_disk_log_size, {MaxBytes, MaxFiles}}</tag>
      <item>
	<p><c>MaxBytes = integer()</c> and <c>MaxFiles = integer()</c>. 
	Defines the properties of the <c>disk_log(3)</c> access log
	file. This file is of type wrap log and
	max bytes is written to each file and max files is
	used before the first file is truncated and reused.</p>
      </item>

      <tag><marker id="prop_tdlog"></marker>{transfer_disk_log, path()}</tag> 
      <item>
	<p>Defines the filename of the (<c>disk_log(3)</c>) access log file
	logging incoming requests. If the filename does not begin
	with a slash (/), it is assumed to be relative to the
	<c>server_root</c>.</p>
      </item>
      
      <tag><marker id="prop_tdlog_size"></marker>{transfer_disk_log_size, {MaxBytes, MaxFiles}}</tag>
      <item>
	<p><c>MaxBytes = integer()</c> and <c>MaxFiles = integer()</c>.  
	Defines the properties of the <c>disk_log(3)</c> access log
	file. This file is of type wrap log and
	max bytes is written to each file and max files is
	used before the first file is truncated and reused.</p>
      </item>
    </taglist>

    <marker id="props_auth"></marker>
    <p><em>Authentication Properties - Requires mod_auth</em></p>

    <marker id="prop_dri"></marker>
    <p><em>{directory, {path(), [{property(), term()}]}}</em></p>

    <marker id="props_dir"></marker>
    <p>The properties for directories are as follows:</p>
    
    <taglist>
      <tag><marker id="prop_allow_from"></marker>{allow_from, all | [RegxpHostString]}</tag>
      <item>
	<p>Defines a set of hosts to be granted access to a
	given directory, for example:</p>
	
	<code>{allow_from, ["123.34.56.11", "150.100.23"]}</code>
          
	<p>The host <c>123.34.56.11</c> and all machines on the <c>150.100.23</c>
	subnet are allowed access.</p>
      </item>
      
      <tag><marker id="prop_deny_from"></marker>{deny_from, all | [RegxpHostString]}</tag>
      <item>
	<p>Defines a set of hosts
	to be denied access to a given directory, for example:</p>
	
	<code>{deny_from, ["123.34.56.11", "150.100.23"]}</code>
          
	<p>The host <c>123.34.56.11</c> and all machines on the <c>150.100.23</c>
	subnet are not allowed access.</p>
      </item>

      <tag><marker id="prop_auth_type"></marker>{auth_type, plain | dets | mnesia}</tag>
      <item>
	<p>Sets the type of authentication database that is used for the
	directory. The key difference between the different methods is
	that dynamic data can be saved when Mnesia and Dets
	are used.
	This property is called <c>AuthDbType</c> in the Apache-like
	configuration files.</p>
      </item>

      <tag><marker id="prop_auth_user_file"></marker>{auth_user_file, path()}</tag>
      <item>
	<p>Sets the name of a file containing the list of users and
	passwords for user authentication. The filename can be either
	absolute or relative to the <c>server_root</c>. If using the
	plain storage method, this file is a plain text file where
	each line contains a username followed by a colon, followed
	by the non-encrypted password. If usernames are duplicated,
	the behavior is undefined.</p>
	<p>Example:</p>
	
	<code> ragnar:s7Xxv7
 edward:wwjau8 </code> 

	<p>If the Dets storage method is used, the user database is
	maintained by Dets and must not be edited by hand. Use the
	API functions in module <c>mod_auth</c> to create/edit the user
	database. This directive is ignored if the Mnesia
	storage method is used. For security reasons, ensure that
	<c>auth_user_file</c> is stored outside the document tree of the web
	server. If it is placed in the directory that it protects,
	clients can download it.</p>
      </item>
      
      <tag><marker id="prop_auth_group_file"></marker>{auth_group_file, path()}</tag>
      <item>
	<p>Sets the name of a file containing the list of user
	groups for user authentication. The filename can be either
	absolute or relative to the <c>server_root</c>. If the plain
	storage method is used, the group file is a plain text file, where
	each line contains a group name followed by a colon, followed
	by the members usernames separated by spaces.</p>
	<p>Example:</p>
	
	<code>group1: bob joe ante</code>
          
	<p>If the Dets storage method is used, the group database is
	maintained by Dets and must not be edited by hand. Use the
	API for module <c>mod_auth</c> to create/edit the group database.
	This directive is ignored if the Mnesia storage method is used.
	For security reasons, ensure that the <c>auth_group_file</c> is
	stored outside the document tree of the web server. If it is
	placed in the directory that it protects, clients
	can download it.</p>
      </item>

      <tag><marker id="prop_auth_name"></marker>{auth_name, string()}</tag>
      <item> 
	<p>Sets the name of the authorization realm (auth-domain) for
	a directory. This string informs the client about which 
	username and password to use.</p>
      </item>

      <tag><marker id="prop_auth_access_passwd"></marker>{auth_access_password, string()}</tag>
      <item>
	<p>If set to other than "NoPassword", the password is required
	for all API calls. If the password is set to "DummyPassword", the
	password must be changed before any other API calls. To secure
	the authenticating data, the password must be changed after the
	web server is started. Otherwise it is written in clear
	text in the configuration file.</p>
      </item>
      
      <tag><marker id="prop_req_user"></marker>{require_user, [string()]}</tag>
      <item> 
	<p>Defines users to grant access to a given
	directory using a secret password.</p>
      </item>

      <tag><marker id="prop_req_grp"></marker>{require_group, [string()]}</tag>
      <item>
	<p>Defines users to grant access to a given
	directory using a secret password.</p>
      </item>
      
    </taglist>

    <marker id="props_htaccess"></marker> 
    <p><em>Htaccess Authentication Properties - Requires mod_htaccess</em></p>
    <taglist>
      <tag><marker id="prop_access_files"></marker>{access_files, [path()]}</tag>
      <item>
	<p>Specifies the filenames that are used for
	access files. When a request comes, every directory in the path
	to the requested asset are searched after files with the
	names specified by this parameter. If such a file is found, the
	file is parsed and the restrictions specified in it are
	applied to the request.</p>
      </item>
    </taglist>

    <marker id="props_sec"></marker>
    <p><em>Security Properties - Requires mod_security</em></p>
 
    <marker id="prop_sec_dir"></marker>
    <p><em>{security_directory, {path(), [{property(), term()}]}}</em></p>
       
    <marker id="props_sdir"></marker>
    <p>The properties for the security directories are as follows:</p>
    <taglist>
      <tag><marker id="prop_data_file"></marker>{data_file, path()}</tag>      
      <item>
	<p>Name of the security data file. The filename can either be
	absolute or relative to the <c>server_root</c>. This file is used to
	store persistent data for module <c>mod_security</c>.</p>
      </item>
	  
      <tag><marker id="prop_max_retries"></marker>{max_retries, integer()}</tag>	  
      <item>
	<p>Specifies the maximum number of attempts to authenticate a
	user before the user is blocked out. If a user
	successfully authenticates while blocked, the
	user receives a 403 (Forbidden) response from the
	server. If the user makes a failed attempt while blocked, the
	server returns 401 (Unauthorized), for security
	reasons. 
	Default is <c>3</c>. Can be set to infinity.</p>
      </item>
	
      <tag><marker id="prop_block_time"></marker>{block_time, integer()}</tag>
      <item>
	<p>Specifies the number of minutes a user is blocked. After
	this timehas passed, the user automatically regains access.
	Default is <c>60</c>.</p>
      </item>
      
      <tag><marker id="prop_fail_exp_time"></marker>{fail_expire_time, integer()}</tag>
      <item>
	<p>Specifies the number of minutes a failed user authentication
	is remembered. If a user authenticates after this
	time has passed, the previous failed authentications are
	forgotten. 
	Default is <c>30</c>.</p>
      </item>
      
      <tag><marker id="prop_auth_timeout"></marker>{auth_timeout, integer()}</tag>
      <item>
	Specifies the number of seconds a successful user
	authentication is remembered. After this time has passed, the
	authentication is no longer reported. Default is <c>30</c>.
      </item>
    </taglist>    
  </section>

  <funcs>
    <func>
      <name>info(Pid) -></name>
      <name>info(Pid, Properties) -> [{Option, Value}]</name>
      <fsummary>Fetches information about the HTTP server.</fsummary>
      <type>
        <v>Properties = [property()]</v>
	<v>Option = property()</v>
	<v>Value = term()</v>
      </type>
      <desc>
        <p>Fetches information about the HTTP server. When called
	with only the pid, all properties are fetched. When called
	with a list of specific properties, they are fetched.
	The available properties are the same as the start options
	of the server. 
	</p>
	
	<note><p>Pid is the pid returned from <c>inets:start/[2,3]</c>. 
	    Can also be retrieved form <c>inets:services/0</c> and
	    <c>inets:services_info/0</c>,
	    see <seealso marker="inets">inets(3)</seealso>.
	  </p></note>
      </desc>
    </func>

    <func>
      <name>info(Address, Port) ->  </name>
      <name>info(Address, Port, Profile) ->  </name>
      <name since="OTP 18.0">info(Address, Port, Profile, Properties) -> [{Option, Value}] </name>
      <name>info(Address, Port, Properties) -> [{Option, Value}] </name>
      <fsummary>Fetches information about the HTTP server.</fsummary>
      <type>
	<v>Address = ip_address()</v>
	<v>Port = integer()</v>
	<v>Profile = atom()</v>
	<v>Properties = [property()]</v>
        <v>Option = property()</v>
	<v>Value = term()</v>
      </type>
      <desc>
        <p>Fetches information about the HTTP server. When called with
        only <c>Address</c> and <c>Port</c>, all properties are
        fetched.  When called with a list of specific properties, they
        are fetched.  The available properties are the same as the
        start options of the server.
	</p>

	<note><p>The address must be the IP address and cannot be
	    the hostname.
	  </p></note>	
      </desc>
    </func>
    
    <func>
      <name>reload_config(Config, Mode) -> ok | {error, Reason}</name>
      <fsummary>Reloads the HTTP server configuration without
	restarting the server.</fsummary>
      <type>
        <v>Config = path() | [{Option, Value}]</v>
	<v>Option = property()</v>
	<v>Value = term()</v>
	<v>Mode = non_disturbing | disturbing</v>
      </type>
      <desc>
	<p>Reloads the HTTP server configuration without restarting the
	  server. Incoming requests are answered with a temporary
	  down message during the reload time.</p>
	
	<note><p>Available properties are the same as the
	    start options of the server, but the properties 
	    <c>bind_address</c> and <c>port</c> 
	    cannot be changed.</p></note>
	
	<p>If mode is disturbing, the server is blocked forcefully,
	  all ongoing requests terminates, and the reload
	  starts immediately. If mode is non-disturbing, no new
	  connections are accepted, but ongoing requests are
	  allowed to complete before the reload is done.</p>
      </desc>
    </func>
  </funcs>

  <section>
    <title>ERLANG WEB SERVER API DATA TYPES</title>
    <p>The Erlang web server API data types are as follows:</p>
    <code type="none">
      ModData = #mod{}

      -record(mod, {
		data = [],
		socket_type = ip_comm,
		socket, 
		config_db,
		method,
		absolute_uri,
		request_uri,
		http_version,
		request_line,
		parsed_header = [],
		entity_body,
		connection
	}).</code>

    <p>To acess the record in your callback-module use:</p>
    <code> -include_lib("inets/include/httpd.hrl").</code>

    <p>The fields of record <c>mod</c> have the following meaning:
      </p>
    <taglist>
      <tag><c>data</c></tag>
      <item><p>Type <c>[{InteractionKey,InteractionValue}]</c> is used to
       propagate data between modules. Depicted
      <c>interaction_data()</c> in function type declarations.</p>
      </item>
      <tag><c>socket_type</c></tag>
      <item><p><c>socket_type()</c>
       indicates whether it is an IP socket or an <c>ssl</c> socket.</p>
      </item>
      <tag><c>socket</c></tag>
      <item><p>The socket, in format <c>ip_comm</c> or <c>ssl</c>,
       depending on <c>socket_type</c>.</p>
      </item>
      <tag><c>config_db</c></tag>
      <item><p>The config file directives stored as key-value tuples in
       an ETS table. Depicted <c>config_db()</c> in function type
       declarations.</p>
      </item>
      <tag><c>method</c></tag>
      <item><p>Type <c>"GET" | "POST" | "HEAD" | "TRACE"</c>, that is, the
       HTTP method.</p>
      </item>
      <tag><c>absolute_uri</c></tag>
      <item><p>If the request is an HTTP/1.1
       request, the URI can be in the absolute URI format. In that
       case, <c>httpd</c> saves the absolute URI in this field. An Example
       of an absolute URI is 
      <c>"http://ServerName:Part/cgi-bin/find.pl?person=jocke"</c></p></item>
      <tag><c>request_uri</c></tag>
      <item><p>The <c>Request-URI</c> as defined
       in <url href="http://www.ietf.org/rfc/rfc1945.txt">RFC 1945</url>, for example, <c>"/cgi-bin/find.pl?person=jocke"</c>.</p>
      </item>
      <tag><c>http_version</c></tag>
      <item><p>The <c>HTTP</c> version of the
       request, that is, "HTTP/0.9", "HTTP/1.0", or "HTTP/1.1".</p>
      </item>
      <tag><c>request_line</c></tag>
      <item><p>The <c>Request-Line</c> as
       defined in<url href="http://www.ietf.org/rfc/rfc1945.txt">RFC 1945</url>, for example, 
       <c>"GET /cgi-bin/find.pl?person=jocke HTTP/1.0"</c>.</p>
      </item>
      <tag><c>parsed_header</c></tag>
      <item>Type <c>[{HeaderKey,HeaderValue}]</c>.
      <c>parsed_header</c> contains all HTTP header fields from the
      HTTP request stored in a list as key-value tuples. See
      <url href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</url>
      for a listing of all header fields. For example, the date field
      is stored as <c>{"date","Wed, 15 Oct 1997 14:35:17 GMT"}</c>.
      RFC 2616 defines that HTTP is a case-insensitive protocol and
      the header fields can be in lower case or upper case. <c>httpd</c>
      ensures that all header field names are in lower case.
      </item>
      <tag><c>entity_body</c></tag>
      <item><p>The <c>entity-Body</c> as defined
       in <url href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</url>, for example, data sent from a CGI script using the
       POST method.</p>
      </item>
      <tag><c>connection</c></tag>
      <item><p><c>true | false</c>. If set to <c>true</c>, the connection to the
       client is a persistent connection and is not closed when
       the request is served.</p></item>
    </taglist>
  </section>

  <section>
    <title>ERLANG WEB SERVER API CALLBACK FUNCTIONS</title>
  </section>
  <funcs>
    <func>
      <name>Module:do(ModData)-> {proceed, OldData} | {proceed, NewData} | {break, NewData} | done</name>
      <fsummary>Called for each request to the web server.</fsummary>
      <type>
        <v>OldData = list()</v>
        <v>NewData = [{response,{StatusCode,Body}}]</v>
	<v>| [{response,{response,Head,Body}}]</v>
	<v>| [{response,{already_sent,Statuscode,Size}}]</v>
        <v>StatusCode = integer()</v>
        <v>Body = io_list() | nobody | {Fun, Arg}</v>
        <v>Head = [HeaderOption]</v>
        <v>HeaderOption = {Option, Value} | {code, StatusCode}</v>
        <v>Option = accept_ranges | allow</v>
	<v>| cache_control | content_MD5</v>
	<v>| content_encoding | content_language</v>
	<v>| content_length | content_location</v>
	<v>| content_range | content_type | date</v>
	<v>| etag | expires | last_modified</v>
	<v>| location | pragma | retry_after</v>
	<v>| server | trailer | transfer_encoding</v>
        <v>Value = string()</v>
        <v>Fun = fun( Arg ) -> sent| close | Body </v>
        <v>Arg = [term()]</v>
      </type>
      <desc>
        <p>When a valid request reaches <c>httpd</c>, it calls <c>do/1</c> in
          each module, defined by the configuration
          option of <c>Module</c>. The function can generate data for other
	  modules or a response that can be sent back to the client.</p>
        <p>The field <c>data</c> in <c>ModData</c> is a list. This list is
          the list returned from the last call to
          <c>do/1</c>.</p>
        <p><c>Body</c> is the body of the HTTP response that is
          sent back to the client. An appropriate header is
          appended to the message. <c>StatusCode</c> is the
          status code of the response, see 
	  <url href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</url> 
	  for the appropriate values.</p>
        <p><c>Head</c> is a key value list of HTTP header fields. The
        server constructs an HTTP header from this data. See <url href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</url>  for the appropriate value for each header field. If the
        client is an HTTP/1.0 client, the server filters the
        list so that only HTTP/1.0 header fields are sent back
        to the client.</p>
        <p>If <c>Body</c> is returned and equal to <c>{Fun,Arg}</c>,
          the web server tries <c>apply/2</c> on <c>Fun</c> with
          <c>Arg</c> as argument. The web server expects that the fun either
          returns a list <c>(Body)</c> that is an HTTP repsonse, or the
          atom <c>sent</c> if the HTTP response is sent back to the
          client. If <c>close</c> is returned from the fun, something has gone
          wrong and the server signals this to the client by
          closing the connection.</p>
      </desc>
    </func>

    <func>
      <name>Module:load(Line, AccIn)-> eof | ok | {ok, AccOut} | {ok, AccOut, {Option, Value}} | {ok, AccOut, [{Option, Value}]} | {error, Reason}</name>
      <fsummary>Converts a line in an Apache-like config 
	file to an <c>{Option, Value}</c> tuple.</fsummary>
      <type>
        <v>Line = string()</v>
        <v>AccIn = [{Option, Value}]</v>
	<v>AccOut = [{Option, Value}]</v>
        <v>Option = property()</v>
        <v>Value = term() </v>
        <v>Reason = term()</v>
      </type>
      <desc>
	<p>Converts a line in an Apache-like
	  configuration file to an <c>{Option, Value}</c> tuple. Some
	  more complex configuration options, such as <c>directory</c>
	  and <c>security_directory</c>, create an
	  accumulator. This function only needs clauses for the
	  options implemented by this particular callback module.
	</p>
      </desc>
    </func>
    
    <func>
      <name>Module:remove(ConfigDB) -> ok | {error, Reason} </name>
      <fsummary>Callback function that is called when the web server is closed.</fsummary>
      <type>
        <v>ConfigDB = ets_table()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>When <c>httpd</c> is shut down, it tries to execute
          <c>remove/1</c> in each Erlang web server callback module. The
          programmer can use this function to clean up resources
          created in the store function.</p>
      </desc>
    </func>
    
    <func>
      <name>Module:store({Option, Value}, Config)-> {ok, {Option, NewValue}} | {error, Reason}</name>
      <fsummary>Checks the validity of the configuration options.</fsummary>
      <type>
        <v>Line = string()</v>
        <v>Option = property()</v>
	<v>Config = [{Option, Value}]</v>
        <v>Value = term()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
	<p>Checks the validity of the
	  configuration options before saving them in the internal
	  database. This function can also have a side effect,
	  that is, setup of necessary extra resources implied by the
	  configuration option. It can also
	  resolve possible dependencies among
	  configuration options by changing the value of the option.
	  This function only needs clauses for the options
	  implemented by this particular callback module.</p>
      </desc>
    </func>
  </funcs>

  <section>
    <title>ERLANG WEB SERVER API HELP FUNCTIONS</title>
  </section>
  <funcs>
    <func>
      <name>parse_query(QueryString) -> [{Key,Value}]</name>
      <fsummary>Parses incoming data to <c>erl</c> and <c>eval</c> scripts.</fsummary>
      <type>
        <v>QueryString = string()</v>
	<v>Key = string()</v>
	<v>Value = string()</v>
      </type>
      <desc>
        <p><c>parse_query/1</c> parses incoming data to <c>erl</c> and
          <c>eval</c> scripts (see <seealso marker="mod_esi">mod_esi(3)</seealso>) 
	  as defined in the standard
          URL format, that is, '+' becomes 'space' and decoding of
          hexadecimal characters (<c>%xx</c>).</p>
      </desc>
    </func>
  </funcs>

  <section>
    <title>SEE ALSO</title>
    <p><url href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</url>, 
    <seealso marker="inets">inets(3)</seealso>,
    <seealso marker="ssl:ssl">ssl(3)</seealso>
    </p>
  </section>

</erlref>