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:
port(s) to be used by the serverThe typical use scenario is to write a file that loads the following components:
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 may 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=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.--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
--user=User
to open ports below 1000. The default port is 80. If --https
is used, the default port is 443.--ip=localhost to restrict access to connections from
localhost if the server itself is behind an (Apache) proxy server
running on the same host.
socket(s)--pwfile=File)--user. If omitted, the login
group of the target user is used.--no-fork or --fork=false, the
process runs in the foreground.|Port|BindTo:Port)]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.|Port|BindTo:Port)]--http, but creates an HTTPS server. Use --certfile, --keyfile, -pwfile,
--password and --cipherlist to configure SSL
for this server.--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.true (default false) implies --no-fork
and presents the Prolog toplevel after starting the server.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:
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 or additional options. This
uses guided options processing from argv_options/3
from library(main). The option definitions are available as http_opt_type/3, http_opt_help/2
and
http_opt_meta/2
http_daemon :-
current_prolog_flag(argv, Argv),
argv_options(Argv, _RestArgv, Options),
http_daemon(Options).
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_server(Handler, Options). The default is
provided by start_server/1.