httpd.3erl - Man Page

{bind_address, ip_address() | hostname() | any}:

Default is any

{profile, atom()}:

Used together with bind_address and port 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 bind_address and port uniquely identifies the HTTP server.

{socket_type, ip_comm | {ip_comm, Config::proplist()} | {ssl, Config::proplist()}}:

For ip_comm configuration options, see gen_tcp:listen/2, some options that are used internally by httpd cannot be set.

For SSL configuration options, see ssl:listen/2.
Default is ip_comm.

OTP-25 deprecates the communication properties {socket_type, ip_comm | {ip_comm, Config::proplist()} | {essl, Config::proplist()}} replacing it by {socket_type, ip_comm | {ip_comm, Config::proplist()} | {ssl, Config::proplist()}}.

{ipfamily, inet | inet6}:

Default is inet, legacy option inet6fb4 no longer makes sense and will be translated to inet.

{minimum_bytes_per_second, integer()}:

If given, sets a minimum of bytes per second value for connections.

If the value is unreached, the socket closes for that connection.
The option is good for reducing the risk of "slow DoS" attacks.

{mime_types, [{MimeType, Extension}] | path()}:

MimeType = string() and Extension = string(). 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 in the property list.

Default is [{"html","text/html"},{"htm","text/html"}].

{mime_type, string()}:

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.

{server_admin, string()}:

Defines the email-address of the server administrator to be included in any error messages returned by the server.

{server_tokens, none|prod|major|minor|minimal|os|full|{private, string()}}:

Defines the look of the value of the server header.

Example: Assuming the version of Inets is 5.8.1, the server header string can look as follows for the different values of server-tokens:

none:

"" % A Server: header will not be generated

prod:

"inets"

major:

"inets/5"

minor:

"inets/5.8"

minimal:

"inets/5.8.1"

os:

"inets/5.8.1 (unix)"

full:

"inets/5.8.1 (unix/linux) OTP/R15B"

{private, "foo/bar"}:

"foo/bar"

By default, the value is as before, that is, minimal.

{logger, Options::list()}:

Currently only one option is supported:

{error, ServerID::atom()}:

Produces logger events on logger level error under the hierarchical logger domain: [otp, inets, httpd, ServerID, error] The built in logger formatting function produces log entries from the error reports:

#{server_name => string()
  protocol => internal | 'TCP' | 'TLS' | 'HTTP',
  transport => "TCP" | "TLS", %% Present when protocol = 'HTTP'
  uri => string(), %% Present when protocol = 'HTTP' and URI is valid
  peer => inet:peername(),
  host => inet:hostname(),
  reason => term()
}

An example of a log entry with only default settings of logger

=ERROR REPORT==== 9-Oct-2019::09:33:27.350235 ===
   Server: My Server
 Protocol: HTTP
Transport: TLS
      URI: /not_there
     Host: 127.0.1.1:80
     Peer: 127.0.0.1:45253
   Reason: [{statuscode,404},{description,"Object Not Found"}]

Using this option makes mod_log and mod_disk_log error logs redundant.
Add the filter

{fun logger_filters:domain/2,
	{log,equal,[otp,inets, httpd, ServerID, error]}

[{kernel,
 [{logger,
  [{handler, http_error_test, logger_std_h,
    #{config => #{ file => "log/http_error.log" },
      filters => [{inets_httpd, {fun logger_filters:domain/2,
                                 {log, equal,
                                  [otp, inets, httpd, my_server, error]
                                 }}}],
      filter_default => stop }}]}]}].

or if you want to add it to the default logger via an API:

logger:add_handler_filter(default,
                          inets_httpd,
                          {fun logger_filters:domain/2,
                           {log, equal,
                            [otp, inets, httpd, my_server, error]}}).

{log_format, common | combined}:

Defines if access logs are to be written according to the common log format or the extended common log format. The common format is one line looking like this: remotehost rfc931 authuser [date] "request" status bytes.

Here:

remotehost:

Remote.

rfc931:

The remote username of the client (RFC 931).

authuser:

The username used for authentication.

[date]:

Date and time of the request (RFC 1123).

"request":

The request line as it came from the client (RFC 1945).

status:

The HTTP status code returned to the client (RFC 1945).

bytes:

The content-length of the document transferred.

The combined format is one line looking like this: remotehost rfc931 authuser [date] "request" status bytes "referer" "user_agent"

In addition to the earlier:

"referer":

The URL the client was on before requesting the URL (if it could not be determined, a minus sign is placed in this field).

"user_agent":

The software the client claims to be using (if it could not be determined, a minus sign is placed in this field).

This affects the access logs written by mod_log and mod_disk_log.

{error_log_format, pretty | compact}:

Default is pretty. If the error log is meant to be read directly by a human, pretty is the best option.

pretty has a format corresponding to:

io:format("[~s] ~s, reason: ~n ~p ~n~n", [Date, Msg, Reason]).

io:format("[~s] ~s, reason: ~w ~n", [Date, Msg, Reason]).

{alias, {Alias, RealName}}:

Alias = string() and RealName = string(). alias allows documents to be stored in the local file system instead of the document_root location. URLs with a path beginning with url-path is mapped to local files beginning with directory-filename, for example:

{alias, {"/image", "/ftp/pub/image"}}

{re_write, {Re, Replacement}}:

Re = string() and Replacement = string(). re_write allows documents to be stored in the local file system instead of the document_root location. URLs are rewritten by re:replace/3 to produce a path in the local file-system, for example:

{re_write, {"^/[~]([^/]+)(.*)$", "/home/\\1/public\\2"}}

{directory_index, [string()]}:

directory_index specifies a list of resources to look for if a client requests a directory using a / at the end of the directory name. file 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:

{directory_index, ["index.html", "welcome.html"]}

{script_alias, {Alias, RealName}}:

Alias = string() and RealName = string(). Have the same behavior as property alias, 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:

{script_alias, {"/cgi-bin/", "/web/cgi-bin/"}}

{script_re_write, {Re, Replacement}}:

Re = string() and Replacement = string(). Have the same behavior as property re_write, 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:

{script_re_write, {"^/cgi-bin/(\\d+)/", "/web/\\1/cgi-bin/"}}

{script_nocache, boolean()}:

If script_nocache is set to true, the HTTP server by default adds the header fields necessary to prevent proxies from caching the page. Generally this is preferred. Default to false.

{script_timeout, integer()}:

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 15.

{action, {MimeType, CgiScript}} - requires mod_action:

MimeType = string() and CgiScript = string(). action 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.

Example:

{action, {"text/plain", "/cgi-bin/log_and_deliver_text"}}

{script, {Method, CgiScript}} - requires mod_action:

Method = string() and CgiScript = string(). script 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 RFC 1945. It propagates the URL and file path of the requested document using the standard CGI PATH_INFO and PATH_TRANSLATED environment variables.

Example:

{script, {"PUT", "/cgi-bin/put"}}

{erl_script_alias, {URLPath, [AllowedModule]}}:

URLPath = string() and AllowedModule = atom(). erl_script_alias marks all URLs matching url-path as erl scheme scripts. A matching URL is mapped into a specific module and function, for example:

{erl_script_alias, {"/cgi-bin/example", [httpd_example]}}

{erl_script_nocache, boolean()}:

If erl_script_nocache is set to true, 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 false.

{erl_script_timeout, integer()}:

If erl_script_timeout sets the time in seconds the server waits between each chunk of data to be delivered through mod_esi:deliver/2. Default is 15. This is only relevant for scripts that use the erl scheme.

{allow_from, all | [RegxpHostString]}:

Defines a set of hosts to be granted access to a given directory, for example:

{allow_from, ["123.34.56.11", "150.100.23"]}

{deny_from, all | [RegxpHostString]}:

Defines a set of hosts to be denied access to a given directory, for example:

{deny_from, ["123.34.56.11", "150.100.23"]}

{auth_type, plain | dets | mnesia}:

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.

{auth_user_file, path()}:

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 server_root. 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.

Example:

 ragnar:s7Xxv7
 edward:wwjau8

{auth_group_file, path()}:

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 server_root. 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.

Example:

group1: bob joe ante

{auth_name, string()}:

Sets the name of the authorization realm (auth-domain) for a directory. This string informs the client about which username and password to use.

{auth_access_password, string()}:

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.

{require_user, [string()]}:

Defines users to grant access to a given directory using a secret password.

{require_group, [string()]}:

Defines users to grant access to a given directory using a secret password.

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.

Pid is the pid returned from inets:start/[2,3]. Can also be retrieved form inets:services/0 and inets:services_info/0, see inets(3).

Fetches information about the HTTP server. When called with only Address and Port, 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.

The Address must be the IP address and cannot be the hostname.

Reloads the HTTP server configuration without restarting the server. Incoming requests are answered with a temporary down message during the reload time.

Available properties are the same as the start options of the server, but the properties bind_address and port cannot be changed.

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.

When a valid request reaches httpd, it calls do/1 in each module, defined by the configuration option of Module. The function can generate data for other modules or a response that can be sent back to the client.

The field data in ModData is a list. This list is the list returned from the last call to do/1.

Body is the body of the HTTP response that is sent back to the client. An appropriate header is appended to the message. StatusCode is the status code of the response, see RFC 2616 for the appropriate values.

Head is a key value list of HTTP header fields. The server constructs an HTTP header from this data. See RFC 2616 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.

If Body is returned and equal to {Fun,Arg}, the web server tries apply/2 on Fun with Arg as argument. The web server expects that the fun either returns a list (Body) that is an HTTP response, or the atom sent if the HTTP response is sent back to the client. If close is returned from the fun, something has gone wrong and the server signals this to the client by closing the connection.

Types:

ConfigDB = ets_table()
Reason = term()

When httpd is shut down, it tries to execute remove/1 in each Erlang web server callback module. The programmer can use this function to clean up resources created in the store function.

Types:

Line = string()
Option = property()
Config = [{Option, Value}]
Value = term()
Reason = term()

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.

Types:

QueryString = string()
QueryList = [{unicode:chardata(), unicode:chardata() | true}]

parse_query/1 parses incoming data to erl and eval scripts (see mod_esi(3)) as defined in the standard URL format, that is, '+' becomes 'space' and decoding of hexadecimal characters (%xx).