/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2013-2017, University of Amsterdam VU University Amsterdam All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module(http_unix_daemon, [ http_daemon/0, http_daemon/1 % +Options ]). :- use_module(library(error)). :- use_module(library(apply)). :- use_module(library(lists)). :- use_module(library(debug)). :- use_module(library(broadcast)). :- use_module(library(socket)). :- use_module(library(option)). :- use_module(library(uid)). :- use_module(library(unix)). :- use_module(library(syslog)). :- use_module(library(http/thread_httpd)). :- use_module(library(http/http_dispatch)). :- use_module(library(http/http_host)). :- use_module(library(main)). :- use_module(library(readutil)). :- if(exists_source(library(http/http_ssl_plugin))). :- use_module(library(ssl)). :- use_module(library(http/http_ssl_plugin)). :- endif. :- multifile http_server_hook/1, % +Options http_certificate_hook/3, % +CertFile, +KeyFile, -Password http:sni_options/2. % +HostName, +SSLOptions :- initialization(http_daemon, main). /** Run SWI-Prolog HTTP server as a Unix system daemon This module provides the logic that is needed to integrate a process into the Unix service (daemon) architecture. It deals with the following aspects, all of which may be used/ignored and configured using commandline options: - Select the port(s) to be used by the server - Run the startup of the process as root to perform privileged tasks and the server itself as unpriviledged user, for example to open ports below 1000. - Fork and detach from the controlling terminal - Handle console and debug output using a file and/or the syslog daemon. - Manage a _|pid file|_ The typical use scenario is to write a file that loads the following components: 1. The application code, including http handlers (see http_handler/3). 2. This library In the code below, =|?- [load].|= loads the remainder of the webserver code. This is often a sequence of use_module/1 directives. == :- use_module(library(http/http_unix_daemon)). :- [load]. == The program entry point is http_daemon/0, declared using initialization/2. This main be overruled using a new declaration after loading this library. The new entry point will typically call http_daemon/1 to start the server in a preconfigured way. == :- use_module(library(http/http_unix_daemon)). :- initialization(run, main). run :- ... http_daemon(Options). == Now, the server may be started using the command below. See http_daemon/0 for supported options. == % [sudo] swipl mainfile.pl [option ...] == Below are some examples. Our first example is completely silent, running on port 80 as user =www=. == % swipl mainfile.pl --user=www --pidfile=/var/run/http.pid == Our second example logs HTTP interaction with the syslog daemon for debugging purposes. Note that the argument to =|--debug|== is a Prolog term and must often be escaped to avoid misinterpretation by the Unix shell. The debug option can be repeated to log multiple debug topics. == % swipl mainfile.pl --user=www --pidfile=/var/run/http.pid \ --debug='http(request)' --syslog=http == *Broadcasting* The library uses broadcast/1 to allow hooking certain events: - http(pre_server_start) Run _after_ _fork_, just before starting the HTTP server. Can be used to load additional files or perform additional initialisation, such as starting additional threads. Recall that it is not possible to start threads _before_ forking. - http(post_server_start) Run _after_ starting the HTTP server. @tbd Cleanup issues wrt. loading and initialization of xpce. @see The file /doc/packages/examples/http/linux-init-script provides a /etc/init.d script for controlling a server as a normal Unix service. */ :- debug(daemon). % Do not run xpce in a thread. This disables forking. The problem here % is that loading library(pce) starts the event dispatching thread. This % should be handled lazily. :- set_prolog_flag(xpce_threaded, false). :- set_prolog_flag(message_ide, false). % cause xpce to trap messages :- dynamic interactive/0. %! http_daemon % % Start the HTTP server as a daemon process. This predicate % processes the commandline arguments below. Commandline arguments % that specify servers are processed in the order they appear % using the following schema: % % 1. Arguments that act as default for all servers. % 2. =|--http=Spec|= or =|--https=Spec|= is followed by % arguments for that server until the next =|--http=Spec|= % or =|--https=Spec|= or the end of the options. % 3. If no =|--http=Spec|= or =|--https=Spec|= appears, one % HTTP server is created from the specified parameters. % % Examples: % % == % --workers=10 --http --https % --http=8080 --https=8443 % --http=localhost:8080 --workers=1 --https=8443 --workers=25 % == % % $ --port=Port : % Start HTTP server at Port. It requires root permission and the % option =|--user=User|= to open ports below 1000. The default % port is 80. If =|--https|= is used, the default port is 443. % % $ --ip=IP : % Only listen to the given IP address. Typically used as % =|--ip=localhost|= to restrict access to connections from % _localhost_ if the server itself is behind an (Apache) % proxy server running on the same host. % % $ --debug=Topic : % Enable debugging Topic. See debug/3. % % $ --syslog=Ident : % Write debug messages to the syslog daemon using Ident % % $ --user=User : % When started as root to open a port below 1000, this option % must be provided to switch to the target user for operating % the server. The following actions are performed as root, i.e., % _before_ switching to User: % % - open the socket(s) % - write the pidfile % - setup syslog interaction % - Read the certificate, key and password file (=|--pwfile=File|=) % % $ --group=Group : % May be used in addition to =|--user|=. If omitted, the login % group of the target user is used. % % $ --pidfile=File : % Write the PID of the daemon process to File. % % $ --output=File : % Send output of the process to File. By default, all % Prolog console output is discarded. % % $ --fork[=Bool] : % If given as =|--no-fork|= or =|--fork=false|=, the process % runs in the foreground. % % $ --http[=(Bool|Port|BindTo:Port)] : % Create a plain HTTP server. If the argument is missing or % =true=, create at the specified or default address. Else % use the given port and interface. Thus, =|--http|= creates % a server at port 80, =|--http=8080|= creates one at port % 8080 and =|--http=localhost:8080|= creates one at port % 8080 that is only accessible from `localhost`. % % $ --https[=(Bool|Port|BindTo:Port)] : % As =|--http|=, but creates an HTTPS server. % Use =|--certfile|=, =|--keyfile|=, =|-pwfile|=, % =|--password|= and =|--cipherlist|= to configure SSL for % this server. % % $ --certfile=File : % The server certificate for HTTPS. % % $ --keyfile=File : % The server private key for HTTPS. % % $ --pwfile=File : % File holding the password for accessing the private key. This % is preferred over using =|--password=PW|= as it allows using % file protection to avoid leaking the password. The file is % read _before_ the server drops privileges when started with % the =|--user|= option. % % $ --password=PW : % The password for accessing the private key. See also `--pwfile`. % % $ --cipherlist=Ciphers : % One or more cipher strings separated by colons. See the OpenSSL % documentation for more information. Starting with SWI-Prolog % 7.5.11, the default value is always a set of ciphers that was % considered secure enough to prevent all critical attacks at the % time of the SWI-Prolog release. % % $ --interactive[=Bool] : % If =true= (default =false=) implies =|--no-fork|= and presents % the Prolog toplevel after starting the server. % % $ --gtrace=[Bool] : % Use the debugger to trace http_daemon/1. % % $ --sighup=Action : % Action to perform on =|kill -HUP |=. Default is `reload` % (running make/0). Alternative is `quit`, stopping the server. % % Other options are converted by argv_options/3 and passed to % http_server/1. For example, this allows for: % % $ --workers=Count : % Set the number of workers for the multi-threaded server. % % http_daemon/0 is defined as below. The start code for a specific % server can use this as a starting point, for example for specifying % defaults. % % ``` % http_daemon :- % current_prolog_flag(argv, Argv), % argv_options(Argv, _RestArgv, Options), % http_daemon(Options). % ``` % % @see http_daemon/1 http_daemon :- current_prolog_flag(argv, Argv), argv_options(Argv, _RestArgv, Options), http_daemon(Options). %! http_daemon(+Options) % % Start the HTTP server as a daemon process. This predicate processes % a Prolog option list. It is normally called from http_daemon/0, % which derives the option list from the command line arguments. % % Error handling depends on whether or not interactive(true) is in % effect. If so, the error is printed before entering the toplevel. In % non-interactive mode this predicate calls halt(1). http_daemon(Options) :- catch(http_daemon_guarded(Options), Error, start_failed(Error)). start_failed(Error) :- interactive, !, print_message(warning, Error). start_failed(Error) :- print_message(error, Error), halt(1). %! http_daemon_guarded(+Options) % % Helper that is started from http_daemon/1. See http_daemon/1 for % options that are processed. http_daemon_guarded(Options) :- option(help(true), Options), !, print_message(information, http_daemon(help)), halt. http_daemon_guarded(Options) :- setup_debug(Options), kill_x11(Options), option_servers(Options, Servers0), maplist(make_socket, Servers0, Servers), ( option(fork(true), Options, true), option(interactive(false), Options, false), can_switch_user(Options) -> fork(Who), ( Who \== child -> halt ; disable_development_system, setup_syslog(Options), write_pid(Options), setup_output(Options), switch_user(Options), setup_signals(Options), start_servers(Servers), wait(Options) ) ; write_pid(Options), switch_user(Options), setup_signals(Options), start_servers(Servers), wait(Options) ). %! option_servers(+Options, -Sockets:list) % % Find all sockets that must be created according to Options. Each % socket is a term server(Scheme, Address, Opts), where Address is % either a plain port (integer) or Host:Port. The latter binds the % port to the interface belonging to Host. For example: % socket(http, localhost:8080, Opts) creates an HTTP socket that % binds to the localhost interface on port 80. Opts are the % options specific for the given server. option_servers(Options, Sockets) :- opt_sockets(Options, [], [], Sockets). opt_sockets([], Options, [], [Socket]) :- !, make_server(http(true), Options, Socket). opt_sockets([], _, Sockets, Sockets). opt_sockets([H|T], OptsH, Sockets0, Sockets) :- server_option(H), !, append(OptsH, [H], OptsH1), opt_sockets(T, OptsH1, Sockets0, Sockets). opt_sockets([H|T0], Opts, Sockets0, Sockets) :- server_start_option(H), !, server_options(T0, T, Opts, SOpts), make_server(H, SOpts, Socket), append(Sockets0, [Socket], Sockets1), opt_sockets(T, Opts, Sockets1, Sockets). opt_sockets([_|T], Opts, Sockets0, Sockets) :- opt_sockets(T, Opts, Sockets0, Sockets). server_options([], [], Options, Options). server_options([H|T], Rest, Options0, Options) :- server_option(H), !, generalise_option(H, G), delete(Options0, G, Options1), append(Options1, [H], Options2), server_options(T, Rest, Options2, Options). server_options([H|T], [H|T], Options, Options) :- server_start_option(H), !. server_options([_|T0], Rest, Options0, Options) :- server_options(T0, Rest, Options0, Options). generalise_option(H, G) :- H =.. [Name,_], G =.. [Name,_]. server_start_option(http(_)). server_start_option(https(_)). server_option(port(_)). server_option(ip(_)). server_option(certfile(_)). server_option(keyfile(_)). server_option(pwfile(_)). server_option(password(_)). server_option(cipherlist(_)). server_option(workers(_)). server_option(redirect(_)). make_server(http(Address0), Options0, server(http, Address, Options)) :- make_address(Address0, 80, Address, Options0, Options). make_server(https(Address0), Options0, server(https, Address, SSLOptions)) :- make_address(Address0, 443, Address, Options0, Options), merge_https_options(Options, SSLOptions). make_address(true, DefPort, Address, Options0, Options) :- !, option(port(Port), Options0, DefPort), ( option(ip(Bind), Options0) -> Address = (Bind:Port) ; Address = Port ), merge_options([port(Port)], Options0, Options). make_address(Bind:Port, _, Bind:Port, Options0, Options) :- !, must_be(atom, Bind), must_be(integer, Port), merge_options([port(Port), ip(Bind)], Options0, Options). make_address(Port, _, Address, Options0, Options) :- integer(Port), !, ( option(ip(Bind), Options0) -> Address = (Bind:Port) ; Address = Port, merge_options([port(Port)], Options0, Options) ). make_address(Spec, _, Address, Options0, Options) :- atomic(Spec), split_string(Spec, ":", "", [BindString, PortString]), number_string(Port, PortString), !, atom_string(Bind, BindString), Address = (Bind:Port), merge_options([port(Port), ip(Bind)], Options0, Options). make_address(Spec, _, _, _, _) :- domain_error(address, Spec). :- dynamic sni/3. merge_https_options(Options, [SSL|Options]) :- ( option(certfile(CertFile), Options), option(keyfile(KeyFile), Options) -> prepare_https_certificate(CertFile, KeyFile, Passwd0), read_file_to_string(CertFile, Certificate, []), read_file_to_string(KeyFile, Key, []), Pairs = [Certificate-Key] ; Pairs = [] ), ssl_secure_ciphers(SecureCiphers), option(cipherlist(CipherList), Options, SecureCiphers), ( string(Passwd0) -> Passwd = Passwd0 ; options_password(Options, Passwd) ), findall(HostName-HostOptions, http:sni_options(HostName, HostOptions), SNIs), maplist(sni_contexts, SNIs), SSL = ssl([ certificate_key_pairs(Pairs), cipher_list(CipherList), password(Passwd), sni_hook(http_unix_daemon:sni) ]). sni_contexts(Host-Options) :- ssl_context(server, SSL, Options), assertz(sni(_, Host, SSL)). %! http_certificate_hook(+CertFile, +KeyFile, -Password) is semidet. % % Hook called before starting the server if the --https option is % used. This hook may be used to create or refresh the % certificate. If the hook binds Password to a string, this string % will be used to decrypt the server private key as if the % --password=Password option was given. prepare_https_certificate(CertFile, KeyFile, Password) :- http_certificate_hook(CertFile, KeyFile, Password), !. prepare_https_certificate(_, _, _). options_password(Options, Passwd) :- option(password(Passwd), Options), !. options_password(Options, Passwd) :- option(pwfile(File), Options), !, read_file_to_string(File, String, []), split_string(String, "", "\r\n\t ", [Passwd]). options_password(_, ''). %! start_server(+Server) is det. % % Start the HTTP server. It performs the following steps: % % 1. Call broadcast(http(pre_server_start)) % 2. Call http_server(http_dispatch, Options) % 2. Call broadcast(http(post_server_start)) % % This predicate can be hooked using http_server_hook/1. This % predicate is executed after % % - Forking % - Setting I/O (e.g., to talk to the syslog daemon) % - Dropping root privileges (--user) % - Setting up signal handling start_servers(Servers) :- broadcast(http(pre_server_start)), maplist(start_server, Servers), broadcast(http(post_server_start)). start_server(server(_Scheme, Socket, Options)) :- option(redirect(To), Options), !, http_server(server_redirect(To), [tcp_socket(Socket)|Options]). start_server(server(_Scheme, Socket, Options)) :- http_server_hook([tcp_socket(Socket)|Options]), !. start_server(server(_Scheme, Socket, Options)) :- http_server(http_dispatch, [tcp_socket(Socket)|Options]). make_socket(server(Scheme, Address, Options), server(Scheme, Socket, Options)) :- tcp_socket(Socket), catch(bind_socket(Socket, Address), Error, make_socket_error(Error, Address)), debug(daemon(socket), 'Created socket ~p, listening on ~p', [Socket, Address]). bind_socket(Socket, Address) :- tcp_setopt(Socket, reuseaddr), tcp_bind(Socket, Address), tcp_listen(Socket, 5). make_socket_error(error(socket_error(_), _), Address) :- address_port(Address, Port), integer(Port), Port =< 1000, !, verify_root(open_port(Port)). make_socket_error(Error, _) :- throw(Error). address_port(_:Port, Port) :- !. address_port(Port, Port). %! disable_development_system % % Disable some development stuff. disable_development_system :- set_prolog_flag(editor, '/bin/false'). %! enable_development_system % % Re-enable the development environment. Currently re-enables xpce if % this was loaded, but not initialised and causes the interactive % toplevel to be re-enabled. enable_development_system :- assertz(interactive), set_prolog_flag(xpce_threaded, true), set_prolog_flag(message_ide, true), ( current_prolog_flag(xpce_version, _) -> call(pce_dispatch([])) ; true ), set_prolog_flag(toplevel_goal, prolog). %! setup_syslog(+Options) is det. % % Setup syslog interaction. setup_syslog(Options) :- option(syslog(Ident), Options), !, openlog(Ident, [pid], user). setup_syslog(_). %! setup_output(+Options) is det. % % Setup output from the daemon process. The default is to send all % output to a null-stream (see open_null_stream/1). With the % option output(File), all output is written to File. setup_output(Options) :- option(output(File), Options), !, open(File, write, Out, [encoding(utf8)]), set_stream(Out, buffer(line)), detach_IO(Out). setup_output(_) :- open_null_stream(Out), detach_IO(Out). %! write_pid(+Options) is det. % % If the option pidfile(File) is present, write the PID of the % daemon to this file. write_pid(Options) :- option(pidfile(File), Options), current_prolog_flag(pid, PID), !, setup_call_cleanup( open(File, write, Out), format(Out, '~d~n', [PID]), close(Out)), at_halt(catch(delete_file(File), _, true)). write_pid(_). %! switch_user(+Options) is det. % % Switch to the target user and group. If the server is started as % root, this option *must* be present. switch_user(Options) :- option(user(User), Options), !, verify_root(switch_user(User)), ( option(group(Group), Options) -> set_user_and_group(User, Group) ; set_user_and_group(User) ), prctl(set_dumpable(true)). % re-enable core dumps on Linux switch_user(_Options) :- verify_no_root. %! can_switch_user(Options) is det. % % Verify the user options before forking, so we can print the % message in time. can_switch_user(Options) :- option(user(User), Options), !, verify_root(switch_user(User)). can_switch_user(_Options) :- verify_no_root. verify_root(_Task) :- geteuid(0), !. verify_root(Task) :- print_message(error, http_daemon(no_root(Task))), halt(1). verify_no_root :- geteuid(0), !, throw(error(permission_error(open, server, http), context('Refusing to run HTTP server as root', _))). verify_no_root. :- if(\+current_predicate(prctl/1)). prctl(_). :- endif. %! server_redirect(+To, +Request) % % Redirect al requests for this server to the specified server. To % is one of: % % $ A port (integer) : % Redirect to the server running on that port in the same % Prolog process. % $ =true= : % Results from just passing =|--redirect|=. Redirects to % an HTTPS server in the same Prolog process. % $ A URL : % Redirect to the the given URL + the request uri. This can % be used if the server cannot find its public address. For % example: % % ``` % --http --redirect=https://myhost.org --https % ``` server_redirect(Port, Request) :- integer(Port), http_server_property(Port, scheme(Scheme)), http_public_host(Request, Host, _Port, []), memberchk(request_uri(Location), Request), ( default_port(Scheme, Port) -> format(string(To), '~w://~w~w', [Scheme, Host, Location]) ; format(string(To), '~w://~w:~w~w', [Scheme, Host, Port, Location]) ), throw(http_reply(moved_temporary(To))). server_redirect(true, Request) :- !, http_server_property(P, scheme(https)), server_redirect(P, Request). server_redirect(URI, Request) :- memberchk(request_uri(Location), Request), atom_concat(URI, Location, To), throw(http_reply(moved_temporary(To))). default_port(http, 80). default_port(https, 443). %! setup_debug(+Options) is det. % % Initialse debug/3 topics. The =|--debug|= option may be used % multiple times. setup_debug(Options) :- setup_trace(Options), nodebug(_), debug(daemon), enable_debug(Options). enable_debug([]). enable_debug([debug(Topic)|T]) :- !, atom_to_term(Topic, Term, _), debug(Term), enable_debug(T). enable_debug([_|T]) :- enable_debug(T). setup_trace(Options) :- option(gtrace(true), Options), !, gtrace. setup_trace(_). %! kill_x11(+Options) is det. % % Get rid of X11 access if interactive is false. kill_x11(Options) :- getenv('DISPLAY', Display), Display \== '', option(interactive(false), Options, false), !, setenv('DISPLAY', ''), set_prolog_flag(gui, false). kill_x11(_). %! setup_signals(+Options) % % Prepare the server for signal handling. By default SIGINT and % SIGTERM terminate the server. SIGHUP causes the server to run % make/0. setup_signals(Options) :- option(interactive(true), Options, false), !. setup_signals(Options) :- on_signal(int, _, quit), on_signal(term, _, quit), option(sighup(Action), Options, reload), must_be(oneof([reload,quit]), Action), on_signal(usr1, _, logrotate), on_signal(hup, _, Action). :- public quit/1, reload/1, logrotate/1. quit(Signal) :- debug(daemon, 'Dying on signal ~w', [Signal]), thread_send_message(main, quit). reload(Signal) :- debug(daemon, 'Reload on signal ~w', [Signal]), thread_send_message(main, reload). logrotate(Signal) :- debug(daemon, 'Closing log files on signal ~w', [Signal]), thread_send_message(main, logrotate). %! wait(+Options) % % This predicate runs in the main thread, waiting for messages % send by signal handlers to control the server. In addition, it % broadcasts maintenance(Interval, Deadline) messages every % Interval seconds. These messages may be trapped using listen/2 % for performing scheduled maintenance such as rotating log files, % cleaning stale data, etc. wait(Options) :- option(interactive(true), Options, false), !, enable_development_system. wait(Options) :- thread_self(Me), option(maintenance_interval(Interval), Options, 300), Interval > 0, !, first_deadline(Interval, FirstDeadline), State = deadline(0), repeat, State = deadline(Count), Deadline is FirstDeadline+Count*Interval, ( thread_get_message(Me, Msg, [deadline(Deadline)]) -> catch(ignore(handle_message(Msg)), E, print_message(error, E)), Msg == quit, halt(0) ; Count1 is Count + 1, nb_setarg(1, State, Count1), catch(broadcast(maintenance(Interval, Deadline)), E, print_message(error, E)), fail ). wait(_) :- thread_self(Me), repeat, thread_get_message(Me, Msg), catch(ignore(handle_message(Msg)), E, print_message(error, E)), Msg == quit, !, halt(0). handle_message(reload) :- make, broadcast(logrotate). handle_message(logrotate) :- broadcast(logrotate). first_deadline(Interval, Deadline) :- get_time(Now), Deadline is ((integer(Now) + Interval - 1)//Interval)*Interval. /******************************* * HOOKS * *******************************/ %! http_server_hook(+Options) is semidet. % % Hook that is called to start the HTTP server. This hook must be % compatible to http_server(Handler, Options). The default is % provided by start_server/1. %! http:sni_options(-HostName, -SSLOptions) is multi. % % Hook to provide Server Name Indication (SNI) for TLS % servers. When starting an HTTPS server, all solutions of this % predicate are collected and a suitable sni_hook/1 is defined % for ssl_context/3 to use different contexts depending on the % host name of the client request. This hook is executed % _before_ privileges are dropped. /******************************* * MESSAGES * *******************************/ :- multifile prolog:message//1. prolog:message(http_daemon(help)) --> [ 'Usage: option ...'-[], nl, 'Options:'-[], nl, nl, ' --port=port HTTP port to listen to'-[], nl, ' --ip=IP Only listen to this ip (--ip=localhost)'-[], nl, ' --debug=topic Print debug message for topic'-[], nl, ' --syslog=ident Send output to syslog daemon as ident'-[], nl, ' --user=user Run server under this user'-[], nl, ' --group=group Run server under this group'-[], nl, ' --pidfile=path Write PID to path'-[], nl, ' --output=file Send output to file (instead of syslog)'-[], nl, ' --fork=bool Do/do not fork'-[], nl, ' --http[=Address] Create HTTP server'-[], nl, ' --https[=Address] Create HTTPS server'-[], nl, ' --certfile=file The server certificate'-[], nl, ' --keyfile=file The server private key'-[], nl, ' --pwfile=file File holding password for the private key'-[], nl, ' --password=pw Password for the private key'-[], nl, ' --cipherlist=cs Cipher strings separated by colons'-[], nl, ' --redirect=to Redirect all requests to a URL or port'-[], nl, ' --interactive=bool Enter Prolog toplevel after starting server'-[], nl, ' --gtrace=bool Start (graphical) debugger'-[], nl, ' --sighup=action Action on SIGHUP: reload (default) or quit'-[], nl, ' --workers=count Number of HTTP worker threads'-[], nl, nl, 'Boolean options may be written without value (true) or as --no-name (false)'-[], nl, 'Address is a port number or host:port, e.g., 8080 or localhost:8080'-[], nl, 'Multiple servers can be started by repeating --http and --https'-[], nl, 'Each server merges the options before the first --http(s) and up the next'-[] ]. prolog:message(http_daemon(no_root(switch_user(User)))) --> [ 'Program must be started as root to use --user=~w.'-[User] ]. prolog:message(http_daemon(no_root(open_port(Port)))) --> [ 'Cannot open port ~w. Only root can open ports below 1000.'-[Port] ].