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http_unix_daemon.pl -- 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:
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.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
.--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.