1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2013-2018, University of Amsterdam
    7                              VU University Amsterdam
    8                              CWI, Amsterdam
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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   35*/
   36
   37:- module(http_unix_daemon,
   38          [ http_daemon/0,
   39            http_daemon/1                       % +Options
   40          ]).   41:- use_module(library(error)).   42:- use_module(library(apply)).   43:- use_module(library(lists)).   44:- use_module(library(debug)).   45:- use_module(library(broadcast)).   46:- use_module(library(socket)).   47:- use_module(library(option)).   48:- use_module(library(uid)).   49:- use_module(library(unix)).   50:- use_module(library(syslog)).   51:- use_module(library(http/thread_httpd)).   52:- use_module(library(http/http_dispatch)).   53:- use_module(library(http/http_host)).   54:- use_module(library(main)).   55:- use_module(library(readutil)).   56
   57:- if(( exists_source(library(http/http_ssl_plugin)),
   58        \+ current_prolog_flag(pldoc_to_tex,true))).   59:- use_module(library(ssl)).   60:- use_module(library(http/http_ssl_plugin)).   61:- endif.   62
   63:- multifile
   64    http_server_hook/1,                     % +Options
   65    http_certificate_hook/3,                % +CertFile, +KeyFile, -Password
   66    http:sni_options/2.                     % +HostName, +SSLOptions
   67
   68:- initialization(http_daemon, main).

:- use_module(library(http/http_unix_daemon)).

:- [load].

:- use_module(library(http/http_unix_daemon)).
:- initialization(run, main).

run :-
    ...
    http_daemon(Options).

% [sudo] swipl mainfile.pl [option ...]

% swipl mainfile.pl --user=www --pidfile=/var/run/http.pid

% swipl mainfile.pl --user=www --pidfile=/var/run/http.pid \
        --debug='http(request)' --syslog=http

  157:- debug(daemon).  158
  159% Do not run xpce in a thread. This disables forking. The problem here
  160% is that loading library(pce) starts the event dispatching thread. This
  161% should be handled lazily.
  162
  163:- set_prolog_flag(xpce_threaded,   false).  164:- set_prolog_flag(message_ide,     false). % cause xpce to trap messages
  165:- set_prolog_flag(message_context, [thread,time('%F %T.%3f')]).  166:- 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 <pid>. 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 also

- http_daemon/1

  300http_daemon :-
  301    current_prolog_flag(argv, Argv),
  302    argv_options(Argv, _RestArgv, Options),
  303    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).

  315http_daemon(Options) :-
  316    catch(http_daemon_guarded(Options), Error, start_failed(Error)).
  317
  318start_failed(Error) :-
  319    interactive,
  320    !,
  321    print_message(warning, Error).
  322start_failed(Error) :-
  323    print_message(error, Error),
  324    halt(1).

 http_daemon_guarded(+Options)

Helper that is started from http_daemon/1. See http_daemon/1 for options that are processed.

  331http_daemon_guarded(Options) :-
  332    option(help(true), Options),
  333    !,
  334    print_message(information, http_daemon(help)),
  335    halt.
  336http_daemon_guarded(Options) :-
  337    setup_debug(Options),
  338    kill_x11(Options),
  339    option_servers(Options, Servers0),
  340    maplist(make_socket, Servers0, Servers),
  341    (   option(fork(true), Options, true),
  342        option(interactive(false), Options, false),
  343        can_switch_user(Options)
  344    ->  fork(Who),
  345        (   Who \== child
  346        ->  halt
  347        ;   disable_development_system,
  348            setup_syslog(Options),
  349            write_pid(Options),
  350            setup_output(Options),
  351            switch_user(Options),
  352            setup_signals(Options),
  353            start_servers(Servers),
  354            wait(Options)
  355        )
  356    ;   write_pid(Options),
  357        switch_user(Options),
  358        setup_signals(Options),
  359        start_servers(Servers),
  360        wait(Options)
  361    ).

 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.

  373option_servers(Options, Sockets) :-
  374    opt_sockets(Options, [], [], Sockets).
  375
  376opt_sockets([], Options, [], [Socket]) :-
  377    !,
  378    make_server(http(true), Options, Socket).
  379opt_sockets([], _, Sockets, Sockets).
  380opt_sockets([H|T], OptsH, Sockets0, Sockets) :-
  381    server_option(H),
  382    !,
  383    append(OptsH, [H], OptsH1),
  384    opt_sockets(T, OptsH1, Sockets0, Sockets).
  385opt_sockets([H|T0], Opts, Sockets0, Sockets) :-
  386    server_start_option(H),
  387    !,
  388    server_options(T0, T, Opts, SOpts),
  389    make_server(H, SOpts, Socket),
  390    append(Sockets0, [Socket], Sockets1),
  391    opt_sockets(T, Opts, Sockets1, Sockets).
  392opt_sockets([_|T], Opts, Sockets0, Sockets) :-
  393    opt_sockets(T, Opts, Sockets0, Sockets).
  394
  395server_options([], [], Options, Options).
  396server_options([H|T], Rest, Options0, Options) :-
  397    server_option(H),
  398    !,
  399    generalise_option(H, G),
  400    delete(Options0, G, Options1),
  401    append(Options1, [H], Options2),
  402    server_options(T, Rest, Options2, Options).
  403server_options([H|T], [H|T], Options, Options) :-
  404    server_start_option(H),
  405    !.
  406server_options([_|T0], Rest, Options0, Options) :-
  407    server_options(T0, Rest, Options0, Options).
  408
  409generalise_option(H, G) :-
  410    H =.. [Name,_],
  411    G =.. [Name,_].
  412
  413server_start_option(http(_)).
  414server_start_option(https(_)).
  415
  416server_option(port(_)).
  417server_option(ip(_)).
  418server_option(certfile(_)).
  419server_option(keyfile(_)).
  420server_option(pwfile(_)).
  421server_option(password(_)).
  422server_option(cipherlist(_)).
  423server_option(workers(_)).
  424server_option(redirect(_)).
  425server_option(timeout(_)).
  426server_option(keep_alive_timeout(_)).
  427
  428make_server(http(Address0), Options0, server(http, Address, Options)) :-
  429    make_address(Address0, 80, Address, Options0, Options).
  430make_server(https(Address0), Options0, server(https, Address, SSLOptions)) :-
  431    make_address(Address0, 443, Address, Options0, Options),
  432    merge_https_options(Options, SSLOptions).
  433
  434make_address(true, DefPort, Address, Options0, Options) :-
  435    !,
  436    option(port(Port), Options0, DefPort),
  437    (   option(ip(Bind), Options0)
  438    ->  Address = (Bind:Port)
  439    ;   Address = Port
  440    ),
  441    merge_options([port(Port)], Options0, Options).
  442make_address(Bind:Port, _, Bind:Port, Options0, Options) :-
  443    !,
  444    must_be(atom, Bind),
  445    must_be(integer, Port),
  446    merge_options([port(Port), ip(Bind)], Options0, Options).
  447make_address(Port, _, Address, Options0, Options) :-
  448    integer(Port),
  449    !,
  450    (   option(ip(Bind), Options0)
  451    ->  Address = (Bind:Port)
  452    ;   Address = Port,
  453        merge_options([port(Port)], Options0, Options)
  454    ).
  455make_address(Spec, _, Address, Options0, Options) :-
  456    atomic(Spec),
  457    split_string(Spec, ":", "", [BindString, PortString]),
  458    number_string(Port, PortString),
  459    !,
  460    atom_string(Bind, BindString),
  461    Address = (Bind:Port),
  462    merge_options([port(Port), ip(Bind)], Options0, Options).
  463make_address(Spec, _, _, _, _) :-
  464    domain_error(address, Spec).
  465
  466:- dynamic sni/3.  467
  468merge_https_options(Options, [SSL|Options]) :-
  469    (   option(certfile(CertFile), Options),
  470        option(keyfile(KeyFile), Options)
  471    ->  prepare_https_certificate(CertFile, KeyFile, Passwd0),
  472        read_file_to_string(CertFile, Certificate, []),
  473        read_file_to_string(KeyFile, Key, []),
  474        Pairs = [Certificate-Key]
  475    ;   Pairs = []
  476    ),
  477    ssl_secure_ciphers(SecureCiphers),
  478    option(cipherlist(CipherList), Options, SecureCiphers),
  479    (   string(Passwd0)
  480    ->  Passwd = Passwd0
  481    ;   options_password(Options, Passwd)
  482    ),
  483    findall(HostName-HostOptions, http:sni_options(HostName, HostOptions), SNIs),
  484    maplist(sni_contexts, SNIs),
  485    SSL = ssl([ certificate_key_pairs(Pairs),
  486                cipher_list(CipherList),
  487                password(Passwd),
  488                sni_hook(http_unix_daemon:sni)
  489              ]).
  490
  491sni_contexts(Host-Options) :-
  492    ssl_context(server, SSL, Options),
  493    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.

  503prepare_https_certificate(CertFile, KeyFile, Password) :-
  504    http_certificate_hook(CertFile, KeyFile, Password),
  505    !.
  506prepare_https_certificate(_, _, _).
  507
  508
  509options_password(Options, Passwd) :-
  510    option(password(Passwd), Options),
  511    !.
  512options_password(Options, Passwd) :-
  513    option(pwfile(File), Options),
  514    !,
  515    read_file_to_string(File, String, []),
  516    split_string(String, "", "\r\n\t ", [Passwd]).
  517options_password(_, '').

 start_servers(+Servers) is det

Start the HTTP server. It performs the following steps:

1. Call broadcast(http(pre_server_start))
2. Foreach server a. Call broadcast(http(pre_server_start(Port))) b. Call http_server(http_dispatch, Options) c. Call broadcast(http(post_server_start(Port)))
3. 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

  538start_servers(Servers) :-
  539    broadcast(http(pre_server_start)),
  540    maplist(start_server, Servers),
  541    broadcast(http(post_server_start)).
  542
  543start_server(server(_Scheme, Socket, Options)) :-
  544    option(redirect(To), Options),
  545    !,
  546    http_server(server_redirect(To), [tcp_socket(Socket)|Options]).
  547start_server(server(_Scheme, Socket, Options)) :-
  548    http_server_hook([tcp_socket(Socket)|Options]),
  549    !.
  550start_server(server(_Scheme, Socket, Options)) :-
  551    option(port(Port), Options),
  552    broadcast(http(pre_server_start(Port))),
  553    http_server(http_dispatch, [tcp_socket(Socket)|Options]),
  554    broadcast(http(post_server_start(Port))).
  555
  556make_socket(server(Scheme, Address, Options),
  557            server(Scheme, Socket, Options)) :-
  558    tcp_socket(Socket),
  559    catch(bind_socket(Socket, Address), Error,
  560          make_socket_error(Error, Address)),
  561    debug(daemon(socket),
  562          'Created socket ~p, listening on ~p', [Socket, Address]).
  563
  564bind_socket(Socket, Address) :-
  565    tcp_setopt(Socket, reuseaddr),
  566    tcp_bind(Socket, Address),
  567    tcp_listen(Socket, 5).
  568
  569make_socket_error(error(socket_error(_,_), _), Address) :-
  570    address_port(Address, Port),
  571    integer(Port),
  572    Port =< 1000,
  573    !,
  574    verify_root(open_port(Port)).
  575make_socket_error(Error, _) :-
  576    throw(Error).
  577
  578address_port(_:Port, Port) :- !.
  579address_port(Port, Port).

 disable_development_system

Disable some development stuff.

  585disable_development_system :-
  586    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.

  594enable_development_system :-
  595    assertz(interactive),
  596    set_prolog_flag(xpce_threaded, true),
  597    set_prolog_flag(message_ide, true),
  598    (   current_prolog_flag(xpce_version, _)
  599    ->  call(pce_dispatch([]))
  600    ;   true
  601    ),
  602    set_prolog_flag(toplevel_goal, prolog).

 setup_syslog(+Options) is det

Setup syslog interaction.

  608setup_syslog(Options) :-
  609    option(syslog(Ident), Options),
  610    !,
  611    openlog(Ident, [pid], user).
  612setup_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.

  621setup_output(Options) :-
  622    option(output(File), Options),
  623    !,
  624    open(File, write, Out, [encoding(utf8)]),
  625    set_stream(Out, buffer(line)),
  626    detach_IO(Out).
  627setup_output(_) :-
  628    open_null_stream(Out),
  629    detach_IO(Out).

 write_pid(+Options) is det

If the option pidfile(File) is present, write the PID of the daemon to this file.

  637write_pid(Options) :-
  638    option(pidfile(File), Options),
  639    current_prolog_flag(pid, PID),
  640    !,
  641    setup_call_cleanup(
  642        open(File, write, Out),
  643        format(Out, '~d~n', [PID]),
  644        close(Out)),
  645    at_halt(catch(delete_file(File), _, true)).
  646write_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.

  654switch_user(Options) :-
  655    option(user(User), Options),
  656    !,
  657    verify_root(switch_user(User)),
  658    (   option(group(Group), Options)
  659    ->  set_user_and_group(User, Group)
  660    ;   set_user_and_group(User)
  661    ),
  662    prctl(set_dumpable(true)).      % re-enable core dumps on Linux
  663switch_user(_Options) :-
  664    verify_no_root.

 can_switch_user(Options) is det

Verify the user options before forking, so we can print the message in time.

  671can_switch_user(Options) :-
  672    option(user(User), Options),
  673    !,
  674    verify_root(switch_user(User)).
  675can_switch_user(_Options) :-
  676    verify_no_root.
  677
  678verify_root(_Task) :-
  679    geteuid(0),
  680    !.
  681verify_root(Task) :-
  682    print_message(error, http_daemon(no_root(Task))),
  683    halt(1).
  684
  685verify_no_root :-
  686    geteuid(0),
  687    !,
  688    throw(error(permission_error(open, server, http),
  689                context('Refusing to run HTTP server as root', _))).
  690verify_no_root.
  691
  692:- if(\+current_predicate(prctl/1)).  693prctl(_).
  694:- 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

  716server_redirect(Port, Request) :-
  717    integer(Port),
  718    http_server_property(Port, scheme(Scheme)),
  719    http_public_host(Request, Host, _Port, []),
  720    memberchk(request_uri(Location), Request),
  721    (   default_port(Scheme, Port)
  722    ->  format(string(To), '~w://~w~w', [Scheme, Host, Location])
  723    ;   format(string(To), '~w://~w:~w~w', [Scheme, Host, Port, Location])
  724    ),
  725    throw(http_reply(moved_temporary(To))).
  726server_redirect(true, Request) :-
  727    !,
  728    http_server_property(P, scheme(https)),
  729    server_redirect(P, Request).
  730server_redirect(URI, Request) :-
  731    memberchk(request_uri(Location), Request),
  732    atom_concat(URI, Location, To),
  733    throw(http_reply(moved_temporary(To))).
  734
  735default_port(http, 80).
  736default_port(https, 443).

 setup_debug(+Options) is det

Initialse debug/3 topics. The --debug option may be used multiple times.

  744setup_debug(Options) :-
  745    setup_trace(Options),
  746    nodebug(_),
  747    debug(daemon),
  748    enable_debug(Options).
  749
  750enable_debug([]).
  751enable_debug([debug(Topic)|T]) :-
  752    !,
  753    atom_to_term(Topic, Term, _),
  754    debug(Term),
  755    enable_debug(T).
  756enable_debug([_|T]) :-
  757    enable_debug(T).
  758
  759setup_trace(Options) :-
  760    option(gtrace(true), Options),
  761    !,
  762    gtrace.
  763setup_trace(_).

 kill_x11(+Options) is det

Get rid of X11 access if interactive is false.

  770kill_x11(Options) :-
  771    getenv('DISPLAY', Display),
  772    Display \== '',
  773    option(interactive(false), Options, false),
  774    !,
  775    setenv('DISPLAY', ''),
  776    set_prolog_flag(gui, false).
  777kill_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.

  786setup_signals(Options) :-
  787    option(interactive(true), Options, false),
  788    !.
  789setup_signals(Options) :-
  790    on_signal(int,  _, quit),
  791    on_signal(term, _, quit),
  792    option(sighup(Action), Options, reload),
  793    must_be(oneof([reload,quit]), Action),
  794    on_signal(usr1, _, logrotate),
  795    on_signal(hup,  _, Action).
  796
  797:- public
  798    quit/1,
  799    reload/1,
  800    logrotate/1.  801
  802quit(Signal) :-
  803    debug(daemon, 'Dying on signal ~w', [Signal]),
  804    thread_send_message(main, quit).
  805
  806reload(Signal) :-
  807    debug(daemon, 'Reload on signal ~w', [Signal]),
  808    thread_send_message(main, reload).
  809
  810logrotate(Signal) :-
  811    debug(daemon, 'Closing log files on signal ~w', [Signal]),
  812    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.

  823wait(Options) :-
  824    option(interactive(true), Options, false),
  825    !,
  826    enable_development_system.
  827wait(Options) :-
  828    thread_self(Me),
  829    option(maintenance_interval(Interval), Options, 300),
  830    Interval > 0,
  831    !,
  832    first_deadline(Interval, FirstDeadline),
  833    State = deadline(0),
  834    repeat,
  835        State = deadline(Count),
  836        Deadline is FirstDeadline+Count*Interval,
  837        (   thread_idle(thread_get_message(Me, Msg, [deadline(Deadline)]),
  838                        long)
  839        ->  catch(ignore(handle_message(Msg)), E,
  840                  print_message(error, E)),
  841            Msg == quit,
  842            halt(0)
  843        ;   Count1 is Count + 1,
  844            nb_setarg(1, State, Count1),
  845            catch(broadcast(maintenance(Interval, Deadline)), E,
  846                  print_message(error, E)),
  847            fail
  848        ).
  849wait(_) :-
  850    thread_self(Me),
  851    repeat,
  852        thread_idle(thread_get_message(Me, Msg), long),
  853        catch(ignore(handle_message(Msg)), E,
  854              print_message(error, E)),
  855        Msg == quit,
  856        !,
  857        halt(0).
  858
  859handle_message(reload) :-
  860    make,
  861    broadcast(logrotate).
  862handle_message(logrotate) :-
  863    broadcast(logrotate).
  864
  865first_deadline(Interval, Deadline) :-
  866    get_time(Now),
  867    Deadline is ((integer(Now) + Interval - 1)//Interval)*Interval.
  868
  869
  870                 /*******************************
  871                 *            HOOKS             *
  872                 *******************************/

 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.

  891                 /*******************************
  892                 *           MESSAGES           *
  893                 *******************************/
  894
  895:- multifile
  896    prolog:message//1.  897
  898prolog:message(http_daemon(help)) -->
  899    [ 'Usage: <program> option ...'-[], nl,
  900      'Options:'-[], nl, nl,
  901      '  --port=port        HTTP port to listen to'-[], nl,
  902      '  --ip=IP            Only listen to this ip (--ip=localhost)'-[], nl,
  903      '  --debug=topic      Print debug message for topic'-[], nl,
  904      '  --syslog=ident     Send output to syslog daemon as ident'-[], nl,
  905      '  --user=user        Run server under this user'-[], nl,
  906      '  --group=group      Run server under this group'-[], nl,
  907      '  --pidfile=path     Write PID to path'-[], nl,
  908      '  --output=file      Send output to file (instead of syslog)'-[], nl,
  909      '  --fork=bool        Do/do not fork'-[], nl,
  910      '  --http[=Address]   Create HTTP server'-[], nl,
  911      '  --https[=Address]  Create HTTPS server'-[], nl,
  912      '  --certfile=file    The server certificate'-[], nl,
  913      '  --keyfile=file     The server private key'-[], nl,
  914      '  --pwfile=file      File holding password for the private key'-[], nl,
  915      '  --password=pw      Password for the private key'-[], nl,
  916      '  --cipherlist=cs    Cipher strings separated by colons'-[], nl,
  917      '  --redirect=to      Redirect all requests to a URL or port'-[], nl,
  918      '  --interactive=bool Enter Prolog toplevel after starting server'-[], nl,
  919      '  --gtrace=bool      Start (graphical) debugger'-[], nl,
  920      '  --sighup=action    Action on SIGHUP: reload (default) or quit'-[], nl,
  921      '  --workers=count    Number of HTTP worker threads'-[], nl,
  922      '  --timeout=sec      Time to wait for client to complete request'-[], nl,
  923      '  --keep_alive_timeout=sec'-[], nl,
  924      '                     Time to wait for a new request'-[], nl,
  925      nl,
  926      'Boolean options may be written without value (true) or as --no-name (false)'-[], nl,
  927      'Address is a port number or host:port, e.g., 8080 or localhost:8080'-[], nl,
  928      'Multiple servers can be started by repeating --http and --https'-[], nl,
  929      'Each server merges the options before the first --http(s) and up the next'-[]
  930    ].
  931prolog:message(http_daemon(no_root(switch_user(User)))) -->
  932    [ 'Program must be started as root to use --user=~w.'-[User] ].
  933prolog:message(http_daemon(no_root(open_port(Port)))) -->
  934    [ 'Cannot open port ~w.  Only root can open ports below 1000.'-[Port] ]