1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
|
%% Copyright (c) 2011, Loïc Hoguin <[email protected]>
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
%% @doc Public API for managing listeners.
-module(cowboy_listener).
-behaviour(gen_server).
-export([start_link/2, stop/1,
add_connection/4, move_connection/3, remove_connection/2, check_upgrades/2,
get_protocol_options/1, set_protocol_options/2]). %% API.
-export([init/1, handle_call/3, handle_cast/2,
handle_info/2, terminate/2, code_change/3]). %% gen_server.
-type pools() :: [{atom(), non_neg_integer()}].
-record(state, {
req_pools = [] :: pools(),
reqs_table :: ets:tid(),
queue = undefined :: queue(),
max_conns = undefined :: non_neg_integer(),
proto_opts :: any(),
proto_opts_vsn = 1 :: non_neg_integer()
}).
%% API.
%% @private
%%
%% We set the process priority to high because cowboy_listener is the central
%% gen_server in Cowboy and is used to manage all the incoming connections.
%% Setting the process priority to high ensures the connection-related code
%% will always be executed when a connection needs it, allowing Cowboy to
%% scale far beyond what it would with a normal priority.
-spec start_link(non_neg_integer(), any()) -> {ok, pid()}.
start_link(MaxConns, ProtoOpts) ->
gen_server:start_link(?MODULE, [MaxConns, ProtoOpts],
[{spawn_opt, [{priority, high}]}]).
%% @private
-spec stop(pid()) -> stopped.
stop(ServerPid) ->
gen_server:call(ServerPid, stop).
%% @doc Add a connection to the given pool in the listener.
%%
%% Pools of connections are used to restrict the maximum number of connections
%% depending on their type. By default, Cowboy add all connections to the
%% pool <em>default</em>. It also checks for the maximum number of connections
%% in that pool before accepting again. This function only returns when there
%% is free space in the pool.
%%
%% When a process managing a connection dies, the process is removed from the
%% pool. If the socket has been sent to another process, it is up to the
%% protocol code to inform the listener of the new <em>ConnPid</em> by removing
%% the previous and adding the new one.
%%
%% This function also returns whether the protocol options have been modified.
%% If so, then an {upgrade, ProtoOpts, OptsVsn} will be returned instead of
%% the atom 'ok'. The acceptor can then continue with the new protocol options.
-spec add_connection(pid(), atom(), pid(), non_neg_integer())
-> ok | {upgrade, any(), non_neg_integer()}.
add_connection(ServerPid, Pool, ConnPid, OptsVsn) ->
gen_server:call(ServerPid, {add_connection, Pool, ConnPid, OptsVsn},
infinity).
%% @doc Move a connection from one pool to another.
-spec move_connection(pid(), atom(), pid()) -> ok.
move_connection(ServerPid, DestPool, ConnPid) ->
gen_server:cast(ServerPid, {move_connection, DestPool, ConnPid}).
%% @doc Remove the given connection from its pool.
-spec remove_connection(pid(), pid()) -> ok.
remove_connection(ServerPid, ConnPid) ->
gen_server:cast(ServerPid, {remove_connection, ConnPid}).
%% @doc Return whether a protocol upgrade is required.
-spec check_upgrades(pid(), non_neg_integer())
-> ok | {upgrade, any(), non_neg_integer()}.
check_upgrades(ServerPid, OptsVsn) ->
gen_server:call(ServerPid, {check_upgrades, OptsVsn}).
%% @doc Return the current protocol options.
-spec get_protocol_options(pid()) -> {ok, any()}.
get_protocol_options(ServerPid) ->
gen_server:call(ServerPid, get_protocol_options).
%% @doc Upgrade the protocol options.
-spec set_protocol_options(pid(), any()) -> ok.
set_protocol_options(ServerPid, ProtoOpts) ->
gen_server:call(ServerPid, {set_protocol_options, ProtoOpts}).
%% gen_server.
%% @private
-spec init(list()) -> {ok, #state{}}.
init([MaxConns, ProtoOpts]) ->
ReqsTable = ets:new(requests_table, [set, private]),
Queue = queue:new(),
{ok, #state{reqs_table=ReqsTable, max_conns=MaxConns,
proto_opts=ProtoOpts, queue=Queue}}.
%% @private
-spec handle_call(_, _, State)
-> {reply, ignored, State} | {stop, normal, stopped, State}.
handle_call({add_connection, Pool, ConnPid, AccOptsVsn}, From, State=#state{
req_pools=Pools, reqs_table=ReqsTable,
queue=Queue, max_conns=MaxConns,
proto_opts=ProtoOpts, proto_opts_vsn=LisOptsVsn}) ->
{NbConns, Pools2} = add_pid(ConnPid, Pool, Pools, ReqsTable),
State2 = State#state{req_pools=Pools2},
if AccOptsVsn =/= LisOptsVsn ->
{reply, {upgrade, ProtoOpts, LisOptsVsn}, State2};
NbConns > MaxConns ->
Queue2 = queue:in(From, Queue),
{noreply, State2#state{queue=Queue2}};
true ->
{reply, ok, State2}
end;
handle_call({check_upgrades, AccOptsVsn}, _From, State=#state{
proto_opts=ProtoOpts, proto_opts_vsn=LisOptsVsn}) ->
if AccOptsVsn =/= LisOptsVsn ->
{reply, {upgrade, ProtoOpts, LisOptsVsn}, State};
true ->
{reply, ok, State}
end;
handle_call(get_protocol_options, _From, State=#state{proto_opts=ProtoOpts}) ->
{reply, {ok, ProtoOpts}, State};
handle_call({set_protocol_options, ProtoOpts}, _From,
State=#state{proto_opts_vsn=OptsVsn}) ->
{reply, ok, State#state{proto_opts=ProtoOpts, proto_opts_vsn=OptsVsn + 1}};
handle_call(stop, _From, State) ->
{stop, normal, stopped, State};
handle_call(_Request, _From, State) ->
{reply, ignored, State}.
%% @private
-spec handle_cast(_, State) -> {noreply, State}.
handle_cast({move_connection, DestPool, ConnPid}, State=#state{
req_pools=Pools, reqs_table=ReqsTable}) ->
Pools2 = move_pid(ConnPid, DestPool, Pools, ReqsTable),
{noreply, State#state{req_pools=Pools2}};
handle_cast({remove_connection, ConnPid}, State=#state{
req_pools=Pools, reqs_table=ReqsTable, queue=Queue}) ->
{Pools2, Queue2} = remove_pid(ConnPid, Pools, ReqsTable, Queue),
{noreply, State#state{req_pools=Pools2, queue=Queue2}};
handle_cast(_Msg, State) ->
{noreply, State}.
%% @private
-spec handle_info(_, State) -> {noreply, State}.
handle_info({'DOWN', _Ref, process, Pid, _Info}, State=#state{
req_pools=Pools, reqs_table=ReqsTable, queue=Queue}) ->
{Pools2, Queue2} = remove_pid(Pid, Pools, ReqsTable, Queue),
{noreply, State#state{req_pools=Pools2, queue=Queue2}};
handle_info(_Info, State) ->
{noreply, State}.
%% @private
-spec terminate(_, _) -> ok.
terminate(_Reason, _State) ->
ok.
%% @private
-spec code_change(_, State, _) -> {ok, State}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
%% Internal.
%% @private
-spec add_pid(pid(), atom(), pools(), ets:tid())
-> {non_neg_integer(), pools()}.
add_pid(ConnPid, Pool, Pools, ReqsTable) ->
MonitorRef = erlang:monitor(process, ConnPid),
ConnPid ! {shoot, self()},
{NbConnsRet, Pools2} = case lists:keyfind(Pool, 1, Pools) of
false ->
{1, [{Pool, 1}|Pools]};
{Pool, NbConns} ->
NbConns2 = NbConns + 1,
{NbConns2, [{Pool, NbConns2}|lists:keydelete(Pool, 1, Pools)]}
end,
ets:insert(ReqsTable, {ConnPid, {MonitorRef, Pool}}),
{NbConnsRet, Pools2}.
%% @private
-spec move_pid(pid(), atom(), pools(), ets:tid()) -> pools().
move_pid(ConnPid, DestPool, Pools, ReqsTable) ->
{MonitorRef, SrcPool} = ets:lookup_element(ReqsTable, ConnPid, 2),
ets:insert(ReqsTable, {ConnPid, {MonitorRef, DestPool}}),
{SrcPool, SrcNbConns} = lists:keyfind(SrcPool, 1, Pools),
DestNbConns = case lists:keyfind(DestPool, 1, Pools) of
false -> 1;
{DestPool, NbConns} -> NbConns + 1
end,
Pools2 = lists:keydelete(SrcPool, 1, lists:keydelete(DestPool, 1, Pools)),
[{SrcPool, SrcNbConns - 1}, {DestPool, DestNbConns}|Pools2].
%% @private
-spec remove_pid(pid(), pools(), ets:tid(), queue()) -> {pools(), queue()}.
remove_pid(Pid, Pools, ReqsTable, Queue) ->
{MonitorRef, Pool} = ets:lookup_element(ReqsTable, Pid, 2),
erlang:demonitor(MonitorRef, [flush]),
{Pool, NbConns} = lists:keyfind(Pool, 1, Pools),
Pools2 = [{Pool, NbConns - 1}|lists:keydelete(Pool, 1, Pools)],
ets:delete(ReqsTable, Pid),
case queue:out(Queue) of
{{value, Client}, Queue2} ->
gen_server:reply(Client, ok),
{Pools2, Queue2};
_ ->
{Pools2, Queue}
end.
|
