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NAME
httpd -
HTTP server API
DESCRIPTION
An implementation of an HTTP 1.1 compliant web server, as defined in RFC 2616. Provides web server start
options, administrative functions, and an Erlang callback API.
DATA TYPES
Type definitions that are used more than once in this module:
boolean() = true | false
string() = list of ASCII characters
path() = string() representing a file or a directory path
ip_address() = {N1,N2,N3,N4} % IPv4 | {K1,K2,K3,K4,K5,K6,K7,K8} % IPv6
hostname() = string() representing a host, for example, "foo.bar.com"
property() = atom()
ERLANG HTTP SERVER SERVICE START/STOP
A web server can be configured to start when starting the Inets application, or dynamically in runtime by
calling the Inets application API inets:start(httpd, ServiceConfig) or inets:start(httpd, ServiceConfig,
How), see inets(3erl). The configuration options, also called properties, are as follows:
File Properties
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, [{Option, Value}], where
Option = property() and Value = term(), followed by a full stop. If the web server is started
dynamically at runtime, a file can still be specified but also the complete property list.
{proplist_file, path()}:
If this property is defined, Inets expects to find all other properties defined in this file. The
file must include all properties listed under mandatory properties.
Note:
Note support for legacy configuration file with Apache syntax is dropped in OTP-23.
Mandatory Properties
{port, integer()} :
The port that the HTTP server listen to. If zero is specified as port, an arbitrary available port is
picked and function httpd:info/2 can be used to determine which port was picked.
{server_name, string()}:
The name of your server, normally a fully qualified domain name.
{server_root, path()}:
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.
{document_root, path()}:
Defines the top directory for the documents that are available on the HTTP server.
Communication Properties
{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.
Note:
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.
Erlang Web Server API Modules
{modules, [atom()]} :
Defines which modules the HTTP server uses when handling requests. Default is [mod_alias, mod_auth,
mod_esi, mod_actions, mod_cgi, mod_dir, mod_get, mod_head, mod_log, mod_disk_log]. Notice that some
mod-modules are dependent on others, so the order cannot be entirely arbitrary. See the Inets Web
Server Modules in the User's Guide for details.
Limit properties
{customize, atom()}:
A callback module to customize the inets HTTP servers behaviour see httpd_custom_api
{disable_chunked_transfer_encoding_send, boolean()}:
Allows you to disable chunked transfer-encoding when sending a response to an HTTP/1.1 client.
Default is false.
{keep_alive, boolean()}:
Instructs the server whether to use persistent connections when the client claims to be HTTP/1.1
compliant. Default is true.
{keep_alive_timeout, integer()}:
The number of seconds the server waits for a subsequent request from the client before closing the
connection. Default is 150.
{max_body_size, integer()}:
Limits the size of the message body of an HTTP request. Default is no limit.
{max_clients, integer()}:
Limits the number of simultaneous requests that can be supported. Default is 150.
{max_header_size, integer()}:
Limits the size of the message header of an HTTP request. Default is 10240.
{max_content_length, integer()}:
Maximum content-length in an incoming request, in bytes. Requests with content larger than this are
answered with status 413. Default is 100000000 (100 MB).
{max_uri_size, integer()}:
Limits the size of the HTTP request URI. Default is no limit.
{max_keep_alive_request, integer()}:
The number of requests that a client can do on one connection. When the server has responded to the
number of requests defined by max_keep_alive_requests, the server closes the connection. The server
closes it even if there are queued request. Default is no limit.
{max_client_body_chunk, integer()}:
Enforces chunking of a HTTP PUT or POST body data to be delivered to the mod_esi callback. Note this
is not supported for mod_cgi. Default is no limit e.i the whole body is delivered as one entity,
which could be very memory consuming. mod_esi(3erl).
Administrative Properties
{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]).
compact has a format corresponding to:
io:format("[~s] ~s, reason: ~w ~n", [Date, Msg, Reason]).
This affects the error logs written by mod_log and mod_disk_log.
URL Aliasing Properties - Requires mod_alias
{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"}}
Access to http://your.server.org/image/foo.gif would refer to the file /ftp/pub/image/foo.gif.
{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"}}
Access to http://your.server.org/~bob/foo.gif would refer to the file /home/bob/public/foo.gif.
{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"]}
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.
CGI Properties - Requires mod_cgi
{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/"}}
Access to http://your.server.org/cgi-bin/foo would cause the server to run the script /web/cgi-
bin/foo.
{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/"}}
Access to http://your.server.org/cgi-bin/17/foo would cause the server to run the script /web/17/cgi-
bin/foo.
{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"}}
ESI Properties - Requires mod_esi
{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]}}
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.
{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.
Log Properties - Requires mod_log
{error_log, path()}:
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 server_root.
{security_log, path()}:
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 server_root.
{transfer_log, path()}:
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 server_root.
Disk Log Properties - Requires mod_disk_log
{disk_log_format, internal | external}:
Defines the file format of the log files. See disk_log 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, httpd does not start if the log file is broken. Default is
external.
{error_disk_log, path()}:
Defines the filename of the (disk_log(3erl)) 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 server_root.
{error_disk_log_size, {MaxBytes, MaxFiles}}:
MaxBytes = integer() and MaxFiles = integer(). Defines the properties of the (disk_log(3erl)) 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.
{security_disk_log, path()}:
Defines the filename of the (disk_log(3erl)) 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 server_root.
{security_disk_log_size, {MaxBytes, MaxFiles}}:
MaxBytes = integer() and MaxFiles = integer(). Defines the properties of the disk_log(3erl) 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.
{transfer_disk_log, path()}:
Defines the filename of the (disk_log(3erl)) access log file logging incoming requests. If the
filename does not begin with a slash (/), it is assumed to be relative to the server_root.
{transfer_disk_log_size, {MaxBytes, MaxFiles}}:
MaxBytes = integer() and MaxFiles = integer(). Defines the properties of the disk_log(3erl) 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.
Authentication Properties - Requires mod_auth
{directory, {path(), [{property(), term()}]}}
The properties for directories are as follows:
{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"]}
The host 123.34.56.11 and all machines on the 150.100.23 subnet are allowed access.
{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"]}
The host 123.34.56.11 and all machines on the 150.100.23 subnet are not allowed access.
{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
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 mod_auth to create/edit the user database. This directive is
ignored if the Mnesia storage method is used. For security reasons, ensure that auth_user_file is
stored outside the document tree of the web server. If it is placed in the directory that it
protects, clients can download it.
{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
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 mod_auth to create/edit the group database. This directive is ignored
if the Mnesia storage method is used. For security reasons, ensure that the auth_group_file is stored
outside the document tree of the web server. If it is placed in the directory that it protects,
clients can download it.
{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.
Security Properties - Requires mod_security
{security_directory, {path(), [{property(), term()}]}}
The properties for the security directories are as follows:
{data_file, path()}:
Name of the security data file. The filename can either be absolute or relative to the server_root.
This file is used to store persistent data for module mod_security.
{max_retries, integer()}:
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 3. Can be set to infinity.
{block_time, integer()}:
Specifies the number of minutes a user is blocked. After this time has passed, the user automatically
regains access. Default is 60.
{fail_expire_time, integer()}:
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 30.
{auth_timeout, integer()}:
Specifies the number of seconds a successful user authentication is remembered. After this time has
passed, the authentication is no longer reported. Default is 30.
EXPORTS
info(Pid) -> HttpInformation
info(Pid, Properties) -> HttpInformation
Types:
Pid = pid()
Properties = [atom()]
HttpInformation =
[CommonOption] |
[CommunicationOption] |
[ModOption] |
[LimitOption] |
[AdminOption]
CommonOption =
{port, integer() >= 0} |
{server_name, string()} |
{server_root, Path} |
{document_root, Path}
CommunicationOption =
{bind_address, inet:ip_address() | inet:hostname() | any} |
{profile, atom()} |
{socket_type,
ip_comm |
{ip_comm, ssl:tls_option() | gen_tcp:option()} |
{ssl, ssl:tls_option() | gen_tcp:option()}} |
{ipfamily, inet | inet6} |
{minimum_bytes_per_second, integer()}
ModOption = {modules, atom()}
LimitOption =
{customize, atom()} |
{disable_chunked_transfer_encoding_send, boolean()} |
{keep_alive, boolean()} |
{keep_alive_timeout, integer()} |
{max_body_size, integer()} |
{max_clients, integer()} |
{max_header_size, integer()} |
{max_content_length, integer()} |
{max_uri_size, integer()} |
{max_keep_alive_request, integer()} |
{max_client_body_chunk, integer()}
AdminOption =
{mime_types,
[{MimeType :: string(), Extension :: string()}] | Path} |
{mime_type, string()} |
{server_admin, string()} |
{server_tokens,
none | prod | major | minor | minimal | os | full |
{private, string()}} |
{logger, Options :: list()} |
{log_format, common | combined} |
{error_log_format, pretty | compact}
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.
Note:
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(3erl).
info(Address, Port) -> HttpInformation
info(Address, Port, Profile) -> HttpInformation
info(Address, Port, Properties) -> HttpInformation
info(Address, Port, Profile, Properties) -> HttpInformation
Types:
Address = inet:ip_address() | any
Port = integer()
Profile = atom()
Properties = [atom()]
Path = file:name_all()
HttpInformation =
[CommonOption] |
[CommunicationOption] |
[ModOption] |
[LimitOption] |
[AdminOption]
CommonOption =
{port, integer() >= 0} |
{server_name, string()} |
{server_root, Path} |
{document_root, Path}
CommunicationOption =
{bind_address, inet:ip_address() | inet:hostname() | any} |
{profile, atom()} |
{socket_type,
ip_comm |
{ip_comm, ssl:tls_option() | gen_tcp:option()} |
{ssl, ssl:tls_option() | gen_tcp:option()}} |
{ipfamily, inet | inet6} |
{minimum_bytes_per_second, integer()}
ModOption = {modules, atom()}
LimitOption =
{customize, atom()} |
{disable_chunked_transfer_encoding_send, boolean()} |
{keep_alive, boolean()} |
{keep_alive_timeout, integer()} |
{max_body_size, integer()} |
{max_clients, integer()} |
{max_header_size, integer()} |
{max_content_length, integer()} |
{max_uri_size, integer()} |
{max_keep_alive_request, integer()} |
{max_client_body_chunk, integer()}
AdminOption =
{mime_types,
[{MimeType :: string(), Extension :: string()}] | Path} |
{mime_type, string()} |
{server_admin, string()} |
{server_tokens,
none | prod | major | minor | minimal | os | full |
{private, string()}} |
{logger, Options :: list()} |
{log_format, common | combined} |
{error_log_format, pretty | compact}
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.
Note:
The Address must be the IP address and cannot be the hostname.
reload_config(Config, Mode) -> ok | {error, Reason} | no_return()
Types:
Config = file:name_all() | [{Option, Value}]
Mode = non_disturbing | disturbing | blocked
Option = atom()
Value = Reason = term()
Reloads the HTTP server configuration without restarting the server. Incoming requests are
answered with a temporary down message during the reload time.
Note:
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.
ERLANG WEB SERVER API DATA TYPES
The Erlang web server API data types are as follows:
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
}).
To access the record in your callback-module use:
-include_lib("inets/include/httpd.hrl").
The fields of record mod have the following meaning:
data:
Type [{InteractionKey,InteractionValue}] is used to propagate data between modules. Depicted
interaction_data() in function type declarations.
socket_type:
socket_type() indicates whether it is an IP socket or an ssl socket.
socket:
The socket, in format ip_comm or ssl, depending on socket_type.
config_db:
The config file directives stored as key-value tuples in an ETS table. Depicted config_db() in
function type declarations.
method:
Type "GET" | "POST" | "HEAD" | "TRACE", that is, the HTTP method.
absolute_uri:
If the request is an HTTP/1.1 request, the URI can be in the absolute URI format. In that case, httpd
saves the absolute URI in this field. An Example of an absolute URI is "http://ServerName:Part/cgi-
bin/find.pl?person=jocke"
request_uri:
The Request-URI as defined in RFC 1945, for example, "/cgi-bin/find.pl?person=jocke".
http_version:
The HTTP version of the request, that is, "HTTP/1.0", or "HTTP/1.1".
request_line:
The Request-Line as defined inRFC 1945, for example, "GET /cgi-bin/find.pl?person=jocke HTTP/1.0".
parsed_header:
Type [{HeaderKey,HeaderValue}]. parsed_header contains all HTTP header fields from the HTTP request
stored in a list as key-value tuples. See RFC 2616 for a listing of all header fields. For example,
the date field is stored as {"date","Wed, 15 Oct 1997 14:35:17 GMT"}. RFC 2616 defines that HTTP is a
case-insensitive protocol and the header fields can be in lower case or upper case. httpd ensures
that all header field names are in lower case.
entity_body:
The entity-Body as defined in RFC 2616, for example, data sent from a CGI script using the POST
method.
connection:
true | false. If set to true, the connection to the client is a persistent connection and is not
closed when the request is served.
ERLANG WEB SERVER API CALLBACK FUNCTIONS
EXPORTS
Module:do(ModData)-> {proceed, OldData} | {proceed, NewData} | {break, NewData} | done
Types:
OldData = list()
NewData = [{response,{StatusCode,Body}}]
| [{response,{response,Head,Body}}]
| [{response,{already_sent,Statuscode,Size}}]
StatusCode = integer()
Body = io_list() | nobody | {Fun, Arg}
Head = [HeaderOption]
HeaderOption = {Option, Value} | {code, StatusCode}
Option = accept_ranges | allow
| cache_control | content_MD5
| content_encoding | content_language
| content_length | content_location
| content_range | content_type | date
| etag | expires | last_modified
| location | pragma | retry_after
| server | trailer | transfer_encoding
Value = string()
Fun = fun( Arg ) -> sent| close | Body
Arg = [term()]
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.
Module:remove(ConfigDB) -> ok | {error, Reason}
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.
Module:store({Option, Value}, Config)-> {ok, {Option, NewValue}} | {error, Reason}
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.
ERLANG WEB SERVER API HELP FUNCTIONS
EXPORTS
parse_query(QueryString) -> QueryList | uri_string:error()
Types:
QueryString = string()
QueryList = [{unicode:chardata(), unicode:chardata() | true}]
parse_query/1 parses incoming data to erl and eval scripts (see mod_esi(3erl)) as defined in the
standard URL format, that is, '+' becomes 'space' and decoding of hexadecimal characters (%xx).
SEE ALSO
RFC 2616, inets(3erl), ssl(3erl)
Ericsson AB inets 8.3.1.2 httpd(3erl)