/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2002-2022, University of Amsterdam
VU University Amsterdam
CWI, 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(thread_httpd,
[ http_current_server/2, % ?:Goal, ?Port
http_server_property/2, % ?Port, ?Property
http_server/2, % :Goal, +Options
http_workers/2, % +Port, ?WorkerCount
http_add_worker/2, % +Port, +Options
http_current_worker/2, % ?Port, ?ThreadID
http_stop_server/2, % +Port, +Options
http_spawn/2, % :Goal, +Options
http_requeue/1, % +Request
http_close_connection/1, % +Request
http_enough_workers/3 % +Queue, +Why, +Peer
]).
:- use_module(library(debug)).
:- use_module(library(error)).
:- use_module(library(option)).
:- use_module(library(socket)).
:- use_module(library(thread_pool)).
:- use_module(library(gensym)).
:- use_module(http_wrapper).
:- use_module(http_path).
:- autoload(library(uri), [uri_resolve/3]).
:- predicate_options(http_server/2, 2,
[ port(any),
unix_socket(atom),
entry_page(atom),
tcp_socket(any),
workers(positive_integer),
timeout(number),
keep_alive_timeout(number),
silent(boolean),
ssl(list(any)), % if http/http_ssl_plugin is loaded
pass_to(system:thread_create/3, 3)
]).
:- predicate_options(http_spawn/2, 2,
[ pool(atom),
pass_to(system:thread_create/3, 3),
pass_to(thread_pool:thread_create_in_pool/4, 4)
]).
:- predicate_options(http_add_worker/2, 2,
[ timeout(number),
keep_alive_timeout(number),
max_idle_time(number),
pass_to(system:thread_create/3, 3)
]).
/** <module> Threaded HTTP server
Most code doesn't need to use this directly; instead use
library(http/http_server), which combines this library with the
typical HTTP libraries that most servers need.
This library defines the HTTP server frontend of choice for SWI-Prolog.
It is based on the multi-threading capabilities of SWI-Prolog and thus
exploits multiple cores to serve requests concurrently. The server
scales well and can cooperate with library(thread_pool) to control the
number of concurrent requests of a given type. For example, it can be
configured to handle 200 file download requests concurrently, 2 requests
that potentially uses a lot of memory and 8 requests that use a lot of
CPU resources.
On Unix systems, this library can be combined with
library(http/http_unix_daemon) to realise a proper Unix service process
that creates a web server at port 80, runs under a specific account,
optionally detaches from the controlling terminal, etc.
Combined with library(http/http_ssl_plugin) from the SSL package, this
library can be used to create an HTTPS server. See
<plbase>/doc/packages/examples/ssl/https for an example server using a
self-signed SSL certificate.
*/
:- meta_predicate
http_server(1, :),
http_current_server(1, ?),
http_spawn(0, +).
:- dynamic
current_server/6, % Port, Goal, Thread, Queue, Scheme, StartTime
queue_worker/2, % Queue, ThreadID
queue_options/2. % Queue, Options
:- multifile
make_socket_hook/3,
accept_hook/2,
close_hook/1,
open_client_hook/6,
discard_client_hook/1,
http:create_pool/1,
http:schedule_workers/1.
:- meta_predicate
thread_repeat_wait(0).
%! http_server(:Goal, :Options) is det.
%
% Create a server at Port that calls Goal for each parsed request.
% Options provide a list of options. Defined options are
%
% * port(?Address)
% Port to bind to. Address is either a port or a term
% Host:Port. The port may be a variable, causing the system
% to select a free port. See tcp_bind/2.
%
% * unix_socket(+Path)
% Instead of binding to a TCP port, bind to a _Unix Domain
% Socket_ at Path.
%
% * entry_page(+URI)
% Affects the message printed while the server is started.
% Interpreted as a URI relative to the server root.
%
% * tcp_socket(+Socket)
% If provided, use this socket instead of the creating one and
% binding it to an address. The socket must be bound to an
% address.
%
% * workers(+Count)
% Determine the number of worker threads. Default is 5. This
% is fine for small scale usage. Public servers typically need
% a higher number.
%
% * timeout(+Seconds)
% Maximum time of inactivity trying to read the request after a
% connection has been opened. Default is 60 seconds. See
% set_stream/1 using the _timeout_ option.
%
% * keep_alive_timeout(+Seconds)
% Time to keep `Keep alive' connections alive. Default is
% 2 seconds.
%
% * stack_limit(+Bytes)
% Stack limit to use for the workers. The default is inherited
% from the `main` thread.
% If you need to control resource usage you may consider the
% `spawn` option of http_handler/3 and library(thread_pool).
%
% * silent(Bool)
% If `true` (default `false`), do not print an informational
% message that the server was started.
%
% A typical initialization for an HTTP server that uses
% http_dispatch/1 to relay requests to predicates is:
%
% ==
% :- use_module(library(http/thread_httpd)).
% :- use_module(library(http/http_dispatch)).
%
% start_server(Port) :-
% http_server(http_dispatch, [port(Port)]).
% ==
%
% Note that multiple servers can coexist in the same Prolog
% process. A notable application of this is to have both an HTTP
% and HTTPS server, where the HTTP server redirects to the HTTPS
% server for handling sensitive requests.
http_server(Goal, M:Options0) :-
server_address(Address, Options0),
!,
make_socket(Address, M:Options0, Options),
create_workers(Options),
create_server(Goal, Address, Options),
( option(silent(true), Options0)
-> true
; print_message(informational,
httpd_started_server(Address, Options0))
).
http_server(_Goal, _:Options0) :-
existence_error(server_address, Options0).
server_address(Address, Options) :-
( option(port(Port), Options)
-> Address = Port
; option(unix_socket(Path), Options)
-> Address = unix_socket(Path)
).
address_port(_IFace:Port, Port) :- !.
address_port(unix_socket(Path), Path) :- !.
address_port(Address, Address) :- !.
tcp_address(Port) :-
var(Port),
!.
tcp_address(Port) :-
integer(Port),
!.
tcp_address(_Iface:_Port).
address_domain(localhost:_Port, Domain) =>
Domain = inet.
address_domain(Iface:_Port, Domain) =>
( catch(ip_name(IP, Iface), error(_,_), fail),
functor(IP, ip, 8)
-> Domain = inet6
; Domain = inet
).
address_domain(_, Domain) =>
Domain = inet.
%! make_socket(+Address, :OptionsIn, -OptionsOut) is det.
%
% Create the HTTP server socket and worker pool queue. OptionsOut
% is quaranteed to hold the option queue(QueueId).
%
% @arg OptionsIn is qualified to allow passing the
% module-sensitive ssl option argument.
make_socket(Address, M:Options0, Options) :-
tcp_address(Address),
make_socket_hook(Address, M:Options0, Options),
!.
make_socket(Address, _:Options0, Options) :-
option(tcp_socket(_), Options0),
!,
make_addr_atom('httpd', Address, Queue),
Options = [ queue(Queue)
| Options0
].
make_socket(Address, _:Options0, Options) :-
tcp_address(Address),
!,
address_domain(Address, Domain),
socket_create(Socket, [domain(Domain)]),
tcp_setopt(Socket, reuseaddr),
tcp_bind(Socket, Address),
tcp_listen(Socket, 64),
make_addr_atom('httpd', Address, Queue),
Options = [ queue(Queue),
tcp_socket(Socket)
| Options0
].
:- if(current_predicate(unix_domain_socket/1)).
make_socket(Address, _:Options0, Options) :-
Address = unix_socket(Path),
!,
unix_domain_socket(Socket),
tcp_bind(Socket, Path),
tcp_listen(Socket, 64),
make_addr_atom('httpd', Address, Queue),
Options = [ queue(Queue),
tcp_socket(Socket)
| Options0
].
:- endif.
%! make_addr_atom(+Scheme, +Address, -Atom) is det.
%
% Create an atom that identifies the server's queue and thread
% resources.
make_addr_atom(Scheme, Address, Atom) :-
phrase(address_parts(Address), Parts),
atomic_list_concat([Scheme,@|Parts], Atom).
address_parts(Var) -->
{ var(Var),
!,
instantiation_error(Var)
}.
address_parts(Atomic) -->
{ atomic(Atomic) },
!,
[Atomic].
address_parts(Host:Port) -->
!,
address_parts(Host), [:], address_parts(Port).
address_parts(ip(A,B,C,D)) -->
!,
[ A, '.', B, '.', C, '.', D ].
address_parts(unix_socket(Path)) -->
[Path].
address_parts(Address) -->
{ domain_error(http_server_address, Address) }.
%! create_server(:Goal, +Address, +Options) is det.
%
% Create the main server thread that runs accept_server/2 to
% listen to new requests.
create_server(Goal, Address, Options) :-
get_time(StartTime),
memberchk(queue(Queue), Options),
scheme(Scheme, Options),
autoload_https(Scheme),
address_port(Address, Port),
make_addr_atom(Scheme, Port, Alias),
thread_self(Initiator),
thread_create(accept_server(Goal, Initiator, Options), _,
[ alias(Alias)
]),
thread_get_message(server_started),
assert(current_server(Port, Goal, Alias, Queue, Scheme, StartTime)).
scheme(Scheme, Options) :-
option(scheme(Scheme), Options),
!.
scheme(Scheme, Options) :-
( option(ssl(_), Options)
; option(ssl_instance(_), Options)
),
!,
Scheme = https.
scheme(http, _).
autoload_https(https) :-
\+ clause(accept_hook(_Goal, _Options), _),
exists_source(library(http/http_ssl_plugin)),
!,
use_module(library(http/http_ssl_plugin)).
autoload_https(_).
%! http_current_server(:Goal, ?Port) is nondet.
%
% True if Goal is the goal of a server at Port.
%
% @deprecated Use http_server_property(Port, goal(Goal))
http_current_server(Goal, Port) :-
current_server(Port, Goal, _, _, _, _).
%! http_server_property(?Port, ?Property) is nondet.
%
% True if Property is a property of the HTTP server running at
% Port. Defined properties are:
%
% * goal(:Goal)
% Goal used to start the server. This is often
% http_dispatch/1.
% * scheme(-Scheme)
% Scheme is one of `http` or `https`.
% * start_time(?Time)
% Time-stamp when the server was created.
http_server_property(_:Port, Property) :-
integer(Port),
!,
server_property(Property, Port).
http_server_property(Port, Property) :-
server_property(Property, Port).
server_property(goal(Goal), Port) :-
current_server(Port, Goal, _, _, _, _).
server_property(scheme(Scheme), Port) :-
current_server(Port, _, _, _, Scheme, _).
server_property(start_time(Time), Port) :-
current_server(Port, _, _, _, _, Time).
%! http_workers(+Port, -Workers) is det.
%! http_workers(+Port, +Workers:int) is det.
%
% Query or set the number of workers for the server at this port.
% The number of workers is dynamically modified. Setting it to 1
% (one) can be used to profile the worker using tprofile/1.
http_workers(Port, Workers) :-
must_be(ground, Port),
current_server(Port, _, _, Queue, _, _),
!,
( integer(Workers)
-> resize_pool(Queue, Workers)
; findall(W, queue_worker(Queue, W), WorkerIDs),
length(WorkerIDs, Workers)
).
http_workers(Port, _) :-
existence_error(http_server, Port).
%! http_add_worker(+Port, +Options) is det.
%
% Add a new worker to the HTTP server for port Port. Options
% overrule the default queue options. The following additional
% options are processed:
%
% - max_idle_time(+Seconds)
% The created worker will automatically terminate if there is
% no new work within Seconds.
http_add_worker(Port, Options) :-
must_be(ground, Port),
current_server(Port, _, _, Queue, _, _),
!,
queue_options(Queue, QueueOptions),
merge_options(Options, QueueOptions, WorkerOptions),
atom_concat(Queue, '_', AliasBase),
create_workers(1, 1, Queue, AliasBase, WorkerOptions).
http_add_worker(Port, _) :-
existence_error(http_server, Port).
%! http_current_worker(?Port, ?ThreadID) is nondet.
%
% True if ThreadID is the identifier of a Prolog thread serving
% Port. This predicate is motivated to allow for the use of
% arbitrary interaction with the worker thread for development and
% statistics.
http_current_worker(Port, ThreadID) :-
current_server(Port, _, _, Queue, _, _),
queue_worker(Queue, ThreadID).
%! accept_server(:Goal, +Initiator, +Options)
%
% The goal of a small server-thread accepting new requests and
% posting them to the queue of workers.
accept_server(Goal, Initiator, Options) :-
catch(accept_server2(Goal, Initiator, Options), http_stop, true),
thread_self(Thread),
debug(http(stop), '[~p]: accept server received http_stop', [Thread]),
retract(current_server(_Port, _, Thread, Queue, _Scheme, _StartTime)),
close_pending_accepts(Queue),
close_server_socket(Options).
accept_server2(Goal, Initiator, Options) :-
thread_send_message(Initiator, server_started),
repeat,
( catch(accept_server3(Goal, Options), E, true)
-> ( var(E)
-> fail
; accept_rethrow_error(E)
-> throw(E)
; print_message(error, E),
fail
)
; print_message(error, % internal error
goal_failed(accept_server3(Goal, Options))),
fail
).
accept_server3(Goal, Options) :-
accept_hook(Goal, Options),
!.
accept_server3(Goal, Options) :-
memberchk(tcp_socket(Socket), Options),
memberchk(queue(Queue), Options),
debug(http(connection), 'Waiting for connection', []),
tcp_accept(Socket, Client, Peer),
sig_atomic(send_to_worker(Queue, Client, Goal, Peer)),
http_enough_workers(Queue, accept, Peer).
send_to_worker(Queue, Client, Goal, Peer) :-
debug(http(connection), 'New HTTP connection from ~p', [Peer]),
thread_send_message(Queue, tcp_client(Client, Goal, Peer)).
accept_rethrow_error(http_stop).
accept_rethrow_error('$aborted').
%! close_server_socket(+Options)
%
% Close the server socket.
close_server_socket(Options) :-
close_hook(Options),
!.
close_server_socket(Options) :-
memberchk(tcp_socket(Socket), Options),
!,
tcp_close_socket(Socket).
%! close_pending_accepts(+Queue)
close_pending_accepts(Queue) :-
( thread_get_message(Queue, Msg, [timeout(0)])
-> close_client(Msg),
close_pending_accepts(Queue)
; true
).
close_client(tcp_client(Client, _Goal, _0Peer)) =>
debug(http(stop), 'Closing connection from ~p during shut-down', [_0Peer]),
tcp_close_socket(Client).
close_client(Msg) =>
( discard_client_hook(Msg)
-> true
; print_message(warning, http_close_client(Msg))
).
%! http_stop_server(+Port, +Options)
%
% Stop the indicated HTTP server gracefully. First stops all
% workers, then stops the server.
%
% @tbd Realise non-graceful stop
http_stop_server(Host:Port, Options) :- % e.g., localhost:4000
ground(Host),
!,
http_stop_server(Port, Options).
http_stop_server(Port, _Options) :-
http_workers(Port, 0), % checks Port is ground
current_server(Port, _, Thread, Queue, _Scheme, _Start),
retractall(queue_options(Queue, _)),
debug(http(stop), 'Signalling HTTP server thread ~p to stop', [Thread]),
thread_signal(Thread, throw(http_stop)),
catch(connect(localhost:Port), _, true),
thread_join(Thread, _0Status),
debug(http(stop), 'Joined HTTP server thread ~p (~p)', [Thread, _0Status]),
message_queue_destroy(Queue).
connect(Address) :-
setup_call_cleanup(
tcp_socket(Socket),
tcp_connect(Socket, Address),
tcp_close_socket(Socket)).
%! http_enough_workers(+Queue, +Why, +Peer) is det.
%
% Check that we have enough workers in our queue. If not, call the
% hook http:schedule_workers/1 to extend the worker pool. This
% predicate can be used by accept_hook/2.
http_enough_workers(Queue, _Why, _Peer) :-
message_queue_property(Queue, waiting(_0)),
!,
debug(http(scheduler), '~D waiting for work; ok', [_0]).
http_enough_workers(Queue, Why, Peer) :-
message_queue_property(Queue, size(Size)),
( enough(Size, Why)
-> debug(http(scheduler), '~D in queue; ok', [Size])
; current_server(Port, _, _, Queue, _, _),
Data = _{ port:Port,
reason:Why,
peer:Peer,
waiting:Size,
queue:Queue
},
debug(http(scheduler), 'Asking to reschedule: ~p', [Data]),
catch(http:schedule_workers(Data),
Error,
print_message(error, Error))
-> true
; true
).
enough(0, _).
enough(1, keep_alive). % I will be ready myself
%! http:schedule_workers(+Data:dict) is semidet.
%
% Hook called if a new connection or a keep-alive connection
% cannot be scheduled _immediately_ to a worker. Dict contains the
% following keys:
%
% - port:Port
% Port number that identifies the server.
% - reason:Reason
% One of =accept= for a new connection or =keep_alive= if a
% worker tries to reschedule itself.
% - peer:Peer
% Identify the other end of the connection
% - waiting:Size
% Number of messages waiting in the queue.
% - queue:Queue
% Message queue used to dispatch accepted messages.
%
% Note that, when called with `reason:accept`, we are called in
% the time critical main accept loop. An implementation of this
% hook shall typically send the event to thread dedicated to
% dynamic worker-pool management.
%
% @see http_add_worker/2 may be used to create (temporary) extra
% workers.
/*******************************
* WORKER QUEUE OPERATIONS *
*******************************/
%! create_workers(+Options)
%
% Create the pool of HTTP worker-threads. Each worker has the
% alias http_worker_N.
create_workers(Options) :-
option(workers(N), Options, 5),
option(queue(Queue), Options),
catch(message_queue_create(Queue), _, true),
atom_concat(Queue, '_', AliasBase),
create_workers(1, N, Queue, AliasBase, Options),
assert(queue_options(Queue, Options)).
create_workers(I, N, _, _, _) :-
I > N,
!.
create_workers(I, N, Queue, AliasBase, Options) :-
gensym(AliasBase, Alias),
thread_create(http_worker(Options), Id,
[ alias(Alias)
| Options
]),
assertz(queue_worker(Queue, Id)),
I2 is I + 1,
create_workers(I2, N, Queue, AliasBase, Options).
%! resize_pool(+Queue, +Workers) is det.
%
% Create or destroy workers. If workers are destroyed, the call
% waits until the desired number of waiters is reached.
resize_pool(Queue, Size) :-
findall(W, queue_worker(Queue, W), Workers),
length(Workers, Now),
( Now < Size
-> queue_options(Queue, Options),
atom_concat(Queue, '_', AliasBase),
I0 is Now+1,
create_workers(I0, Size, Queue, AliasBase, Options)
; Now == Size
-> true
; Now > Size
-> Excess is Now - Size,
thread_self(Me),
forall(between(1, Excess, _), thread_send_message(Queue, quit(Me))),
forall(between(1, Excess, _), thread_get_message(quitted(_)))
).
%! http_worker(+Options)
%
% Run HTTP worker main loop. Workers simply wait until they are
% passed an accepted socket to process a client.
%
% If the message quit(Sender) is read from the queue, the worker
% stops.
http_worker(Options) :-
debug(http(scheduler), 'New worker', []),
prolog_listen(this_thread_exit, done_worker),
option(queue(Queue), Options),
option(max_idle_time(MaxIdle), Options, infinite),
thread_repeat_wait(get_work(Queue, Message, MaxIdle)),
debug(http(worker), 'Waiting for a job ...', []),
debug(http(worker), 'Got job ~p', [Message]),
( Message = quit(Sender)
-> !,
thread_self(Self),
thread_detach(Self),
( Sender == idle
-> true
; retract(queue_worker(Queue, Self)),
thread_send_message(Sender, quitted(Self))
)
; open_client(Message, Queue, Goal, In, Out,
Options, ClientOptions),
( catch(http_process(Goal, In, Out, ClientOptions),
Error, true)
-> true
; Error = goal_failed(http_process/4)
),
( var(Error)
-> fail
; current_message_level(Error, Level),
print_message(Level, Error),
memberchk(peer(Peer), ClientOptions),
close_connection(Peer, In, Out),
fail
)
).
get_work(Queue, Message, infinite) :-
!,
thread_get_message(Queue, Message).
get_work(Queue, Message, MaxIdle) :-
( thread_get_message(Queue, Message, [timeout(MaxIdle)])
-> true
; Message = quit(idle)
).
%! open_client(+Message, +Queue, -Goal, -In, -Out,
%! +Options, -ClientOptions) is semidet.
%
% Opens the connection to the client in a worker from the message
% sent to the queue by accept_server/2.
open_client(requeue(In, Out, Goal, ClOpts),
_, Goal, In, Out, Opts, ClOpts) :-
!,
memberchk(peer(Peer), ClOpts),
option(keep_alive_timeout(KeepAliveTMO), Opts, 2),
check_keep_alive_connection(In, KeepAliveTMO, Peer, In, Out).
open_client(Message, Queue, Goal, In, Out, Opts,
[ pool(client(Queue, Goal, In, Out)),
timeout(Timeout)
| Options
]) :-
catch(open_client(Message, Goal, In, Out, Options, Opts),
E, report_error(E)),
option(timeout(Timeout), Opts, 60),
( debugging(http(connection))
-> memberchk(peer(Peer), Options),
debug(http(connection), 'Opened connection from ~p', [Peer])
; true
).
%! open_client(+Message, +Goal, -In, -Out,
%! -ClientOptions, +Options) is det.
open_client(Message, Goal, In, Out, ClientOptions, Options) :-
open_client_hook(Message, Goal, In, Out, ClientOptions, Options),
!.
open_client(tcp_client(Socket, Goal, Peer), Goal, In, Out,
[ peer(Peer),
protocol(http)
], _) :-
tcp_open_socket(Socket, In, Out).
report_error(E) :-
print_message(error, E),
fail.
%! check_keep_alive_connection(+In, +TimeOut, +Peer, +In, +Out) is semidet.
%
% Wait for the client for at most TimeOut seconds. Succeed if the
% client starts a new request within this time. Otherwise close
% the connection and fail.
check_keep_alive_connection(In, TMO, Peer, In, Out) :-
stream_property(In, timeout(Old)),
set_stream(In, timeout(TMO)),
debug(http(keep_alive), 'Waiting for keep-alive ...', []),
catch(peek_code(In, Code), E, true),
( var(E), % no exception
Code \== -1 % no end-of-file
-> set_stream(In, timeout(Old)),
debug(http(keep_alive), '\tre-using keep-alive connection', [])
; ( Code == -1
-> debug(http(keep_alive), '\tRemote closed keep-alive connection', [])
; debug(http(keep_alive), '\tTimeout on keep-alive connection', [])
),
close_connection(Peer, In, Out),
fail
).
%! done_worker
%
% Called when worker is terminated due to http_workers/2 or a
% (debugging) exception. In the latter case, recreate_worker/2
% creates a new worker.
done_worker :-
thread_self(Self),
thread_detach(Self),
retract(queue_worker(Queue, Self)),
thread_property(Self, status(Status)),
!,
( catch(recreate_worker(Status, Queue), _, fail)
-> print_message(informational,
httpd_restarted_worker(Self))
; done_status_message_level(Status, Level),
print_message(Level,
httpd_stopped_worker(Self, Status))
).
done_worker :- % received quit(Sender)
thread_self(Self),
thread_property(Self, status(Status)),
done_status_message_level(Status, Level),
print_message(Level,
httpd_stopped_worker(Self, Status)).
done_status_message_level(true, silent) :- !.
done_status_message_level(exception('$aborted'), silent) :- !.
done_status_message_level(_, informational).
%! recreate_worker(+Status, +Queue) is semidet.
%
% Deal with the possibility that threads are, during development,
% killed with abort/0. We recreate the worker to avoid that eventually
% we run out of workers. If we are aborted due to a halt/0 call,
% thread_create/3 will raise a permission error.
%
% The first clause deals with the possibility that we cannot write to
% `user_error`. This is possible when Prolog is started as a service
% using some service managers. Would be nice if we could write an
% error, but where?
recreate_worker(exception(error(io_error(write,user_error),_)), _Queue) :-
halt(2).
recreate_worker(exception(Error), Queue) :-
recreate_on_error(Error),
queue_options(Queue, Options),
atom_concat(Queue, '_', AliasBase),
create_workers(1, 1, Queue, AliasBase, Options).
recreate_on_error('$aborted').
recreate_on_error(time_limit_exceeded).
%! thread_httpd:message_level(+Exception, -Level)
%
% Determine the message stream used for exceptions that may occur
% during server_loop/5. Being multifile, clauses can be added by the
% application to refine error handling. See also message_hook/3 for
% further programming error handling.
:- multifile
message_level/2.
message_level(error(io_error(read, _), _), silent).
message_level(error(socket_error(epipe,_), _), silent).
message_level(error(http_write_short(_Obj,_Written), _), silent).
message_level(error(timeout_error(read, _), _), informational).
message_level(keep_alive_timeout, silent).
current_message_level(Term, Level) :-
( message_level(Term, Level)
-> true
; Level = error
).
%! http_requeue(+Header)
%
% Re-queue a connection to the worker pool. This deals with
% processing additional requests on keep-alive connections.
http_requeue(Header) :-
requeue_header(Header, ClientOptions),
memberchk(pool(client(Queue, Goal, In, Out)), ClientOptions),
memberchk(peer(Peer), ClientOptions),
http_enough_workers(Queue, keep_alive, Peer),
thread_send_message(Queue, requeue(In, Out, Goal, ClientOptions)),
!.
http_requeue(Header) :-
debug(http(error), 'Re-queue failed: ~p', [Header]),
fail.
requeue_header([], []).
requeue_header([H|T0], [H|T]) :-
requeue_keep(H),
!,
requeue_header(T0, T).
requeue_header([_|T0], T) :-
requeue_header(T0, T).
requeue_keep(pool(_)).
requeue_keep(peer(_)).
requeue_keep(protocol(_)).
%! http_process(Message, Queue, +Options)
%
% Handle a single client message on the given stream.
http_process(Goal, In, Out, Options) :-
debug(http(server), 'Running server goal ~p on ~p -> ~p',
[Goal, In, Out]),
option(timeout(TMO), Options, 60),
set_stream(In, timeout(TMO)),
set_stream(Out, timeout(TMO)),
http_wrapper(Goal, In, Out, Connection,
[ request(Request)
| Options
]),
next(Connection, Request).
next(Connection, Request) :-
next_(Connection, Request), !.
next(Connection, Request) :-
print_message(warning, goal_failed(next(Connection,Request))).
next_(switch_protocol(SwitchGoal, _SwitchOptions), Request) :-
!,
memberchk(pool(client(_Queue, _Goal, In, Out)), Request),
( catch(call(SwitchGoal, In, Out), E,
( print_message(error, E),
fail))
-> true
; http_close_connection(Request)
).
next_(spawned(ThreadId), _) :-
!,
debug(http(spawn), 'Handler spawned to thread ~w', [ThreadId]).
next_(Connection, Request) :-
downcase_atom(Connection, 'keep-alive'),
http_requeue(Request),
!.
next_(_, Request) :-
http_close_connection(Request).
%! http_close_connection(+Request)
%
% Close connection associated to Request. See also http_requeue/1.
http_close_connection(Request) :-
memberchk(pool(client(_Queue, _Goal, In, Out)), Request),
memberchk(peer(Peer), Request),
close_connection(Peer, In, Out).
%! close_connection(+Peer, +In, +Out)
%
% Closes the connection from the server to the client. Errors are
% currently silently ignored.
close_connection(Peer, In, Out) :-
debug(http(connection), 'Closing connection from ~p', [Peer]),
catch(close(In, [force(true)]), _, true),
catch(close(Out, [force(true)]), _, true).
%! http_spawn(:Goal, +Options) is det.
%
% Continue this connection on a new thread. A handler may call
% http_spawn/2 to start a new thread that continues processing the
% current request using Goal. The original thread returns to the
% worker pool for processing new requests. Options are passed to
% thread_create/3, except for:
%
% * pool(+Pool)
% Interfaces to library(thread_pool), starting the thread
% on the given pool.
%
% If a pool does not exist, this predicate calls the multifile
% hook http:create_pool/1 to create it. If this predicate succeeds
% the operation is retried.
http_spawn(Goal, Options) :-
select_option(pool(Pool), Options, ThreadOptions),
!,
current_output(CGI),
catch(thread_create_in_pool(Pool,
wrap_spawned(CGI, Goal), Id,
[ detached(true)
| ThreadOptions
]),
Error,
true),
( var(Error)
-> http_spawned(Id)
; Error = error(resource_error(threads_in_pool(_)), _)
-> throw(http_reply(busy))
; Error = error(existence_error(thread_pool, Pool), _),
create_pool(Pool)
-> http_spawn(Goal, Options)
; throw(Error)
).
http_spawn(Goal, Options) :-
current_output(CGI),
thread_create(wrap_spawned(CGI, Goal), Id,
[ detached(true)
| Options
]),
http_spawned(Id).
wrap_spawned(CGI, Goal) :-
set_output(CGI),
http_wrap_spawned(Goal, Request, Connection),
next(Connection, Request).
%! create_pool(+Pool)
%
% Lazy creation of worker-pools for the HTTP server. This
% predicate calls the hook http:create_pool/1. If the hook fails
% it creates a default pool of size 10. This should suffice most
% typical usecases. Note that we get a permission error if the
% pool is already created. We can ignore this.
create_pool(Pool) :-
E = error(permission_error(create, thread_pool, Pool), _),
catch(http:create_pool(Pool), E, true).
create_pool(Pool) :-
print_message(informational, httpd(created_pool(Pool))),
thread_pool_create(Pool, 10, []).
/*******************************
* WAIT POLICIES *
*******************************/
:- meta_predicate
thread_repeat_wait(0).
%! thread_repeat_wait(:Goal) is multi.
%
% Acts as `repeat, thread_idle(Goal)`, choosing whether to use a
% `long` or `short` idle time based on the average firing rate.
thread_repeat_wait(Goal) :-
new_rate_mma(5, 1000, State),
repeat,
update_rate_mma(State, MMA),
long(MMA, IsLong),
( IsLong == brief
-> call(Goal)
; thread_idle(Goal, IsLong)
).
long(MMA, brief) :-
MMA < 0.05,
!.
long(MMA, short) :-
MMA < 1,
!.
long(_, long).
%! new_rate_mma(+N, +Resolution, -State) is det.
%! update_rate_mma(!State, -MMA) is det.
%
% Implement _Modified Moving Average_ computing the average time
% between requests as an exponential moving averate with alpha=1/N.
%
% @arg Resolution is the time resolution in 1/Resolution seconds. All
% storage is done in integers to avoid the need for stack freezing in
% nb_setarg/3.
%
% @see https://en.wikipedia.org/wiki/Moving_average
new_rate_mma(N, Resolution, rstate(Base, 0, MaxI, Resolution, N, 0)) :-
current_prolog_flag(max_tagged_integer, MaxI),
get_time(Base).
update_rate_mma(State, MMAr) :-
State = rstate(Base, Last, MaxI, Resolution, N, MMA0),
get_time(Now),
Stamp is round((Now-Base)*Resolution),
( Stamp > MaxI
-> nb_setarg(1, State, Now),
nb_setarg(2, State, 0)
; true
),
Diff is Stamp-Last,
nb_setarg(2, State, Stamp),
MMA is round(((N-1)*MMA0+Diff)/N),
nb_setarg(6, State, MMA),
MMAr is MMA/float(Resolution).
/*******************************
* MESSAGES *
*******************************/
:- multifile
prolog:message/3.
prolog:message(httpd_started_server(Port, Options)) -->
[ 'Started server at '-[] ],
http_root(Port, Options).
prolog:message(httpd_stopped_worker(Self, Status)) -->
[ 'Stopped worker ~p: ~p'-[Self, Status] ].
prolog:message(httpd_restarted_worker(Self)) -->
[ 'Replaced aborted worker ~p'-[Self] ].
prolog:message(httpd(created_pool(Pool))) -->
[ 'Created thread-pool ~p of size 10'-[Pool], nl,
'Create this pool at startup-time or define the hook ', nl,
'http:create_pool/1 to avoid this message and create a ', nl,
'pool that fits the usage-profile.'
].
http_root(Address, Options) -->
{ landing_page(Address, URI, Options) },
[ '~w'-[URI] ].
landing_page(Host:Port, URI, Options) :-
!,
must_be(atom, Host),
must_be(integer, Port),
http_server_property(Port, scheme(Scheme)),
( default_port(Scheme, Port)
-> format(atom(Base), '~w://~w', [Scheme, Host])
; format(atom(Base), '~w://~w:~w', [Scheme, Host, Port])
),
entry_page(Base, URI, Options).
landing_page(unix_socket(Path), URI, _Options) :-
!,
format(string(URI), 'Unix domain socket "~w"', [Path]).
landing_page(Port, URI, Options) :-
landing_page(localhost:Port, URI, Options).
default_port(http, 80).
default_port(https, 443).
entry_page(Base, URI, Options) :-
option(entry_page(Entry), Options),
!,
uri_resolve(Entry, Base, URI).
entry_page(Base, URI, _) :-
http_absolute_location(root(.), Entry, []),
uri_resolve(Entry, Base, URI).