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
|
%% Copyright (c) 2017, 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.
-module(cowboy_tracer_h).
-behavior(cowboy_stream).
-export([init/3]).
-export([data/4]).
-export([info/3]).
-export([terminate/3]).
-export([early_error/5]).
-export([set_trace_patterns/0]).
-export([tracer_process/3]).
-export([system_continue/3]).
-export([system_terminate/4]).
-export([system_code_change/4]).
-type match_predicate()
:: fun((cowboy_stream:streamid(), cowboy_req:req(), cowboy:opts()) -> boolean()).
-type tracer_match_specs() :: [match_predicate()
| {method, binary()}
| {host, binary()}
| {path, binary()}
| {path_start, binary()}
| {header, binary()}
| {header, binary(), binary()}
| {peer_ip, inet:ip_address()}
].
-export_type([tracer_match_specs/0]).
-spec init(cowboy_stream:streamid(), cowboy_req:req(), cowboy:opts())
-> {cowboy_stream:commands(), any()}.
init(StreamID, Req, Opts) ->
init_tracer(StreamID, Req, Opts),
cowboy_stream:init(StreamID, Req, Opts).
-spec data(cowboy_stream:streamid(), cowboy_stream:fin(), cowboy_req:resp_body(), State)
-> {cowboy_stream:commands(), State} when State::any().
data(StreamID, IsFin, Data, Next) ->
cowboy_stream:data(StreamID, IsFin, Data, Next).
-spec info(cowboy_stream:streamid(), any(), State)
-> {cowboy_stream:commands(), State} when State::any().
info(StreamID, Info, Next) ->
cowboy_stream:info(StreamID, Info, Next).
-spec terminate(cowboy_stream:streamid(), cowboy_stream:reason(), any()) -> any().
terminate(StreamID, Reason, Next) ->
cowboy_stream:terminate(StreamID, Reason, Next).
-spec early_error(cowboy_stream:streamid(), cowboy_stream:reason(),
cowboy_stream:partial_req(), Resp, cowboy:opts()) -> Resp
when Resp::cowboy_stream:resp_command().
early_error(StreamID, Reason, PartialReq, Resp, Opts) ->
cowboy_stream:early_error(StreamID, Reason, PartialReq, Resp, Opts).
%% API.
%% These trace patterns are most likely not suitable for production.
-spec set_trace_patterns() -> ok.
set_trace_patterns() ->
erlang:trace_pattern({'_', '_', '_'}, [{'_', [], [{return_trace}]}], [local]),
erlang:trace_pattern(on_load, [{'_', [], [{return_trace}]}], [local]),
ok.
%% Internal.
init_tracer(StreamID, Req, Opts=#{tracer_match_specs := List, tracer_callback := _}) ->
case match(List, StreamID, Req, Opts) of
false ->
ok;
true ->
start_tracer(StreamID, Req, Opts)
end;
%% When the options tracer_match_specs or tracer_callback
%% are not provided we do not enable tracing.
init_tracer(_, _, _) ->
ok.
match([], _, _, _) ->
true;
match([Predicate|Tail], StreamID, Req, Opts) when is_function(Predicate) ->
case Predicate(StreamID, Req, Opts) of
true -> match(Tail, StreamID, Req, Opts);
false -> false
end;
match([{method, Value}|Tail], StreamID, Req=#{method := Value}, Opts) ->
match(Tail, StreamID, Req, Opts);
match([{host, Value}|Tail], StreamID, Req=#{host := Value}, Opts) ->
match(Tail, StreamID, Req, Opts);
match([{path, Value}|Tail], StreamID, Req=#{path := Value}, Opts) ->
match(Tail, StreamID, Req, Opts);
match([{path_start, PathStart}|Tail], StreamID, Req=#{path := Path}, Opts) ->
Len = byte_size(PathStart),
case Path of
<<PathStart:Len/binary, _/bits>> -> match(Tail, StreamID, Req, Opts);
_ -> false
end;
match([{header, Name}|Tail], StreamID, Req=#{headers := Headers}, Opts) ->
case Headers of
#{Name := _} -> match(Tail, StreamID, Req, Opts);
_ -> false
end;
match([{header, Name, Value}|Tail], StreamID, Req=#{headers := Headers}, Opts) ->
case Headers of
#{Name := Value} -> match(Tail, StreamID, Req, Opts);
_ -> false
end;
match([{peer_ip, IP}|Tail], StreamID, Req=#{peer := {IP, _}}, Opts) ->
match(Tail, StreamID, Req, Opts);
match(_, _, _, _) ->
false.
%% We only start the tracer if one wasn't started before.
start_tracer(StreamID, Req, Opts) ->
case erlang:trace_info(self(), tracer) of
{tracer, []} ->
TracerPid = proc_lib:spawn_link(?MODULE, tracer_process, [StreamID, Req, Opts]),
%% The default flags are probably not suitable for production.
Flags = maps:get(tracer_flags, Opts, [
send, 'receive', call, return_to,
procs, ports, monotonic_timestamp,
%% The set_on_spawn flag is necessary to catch events
%% from request processes.
set_on_spawn
]),
erlang:trace(self(), true, [{tracer, TracerPid}|Flags]),
ok;
_ ->
ok
end.
%% Tracer process.
-spec tracer_process(_, _, _) -> no_return().
tracer_process(StreamID, Req=#{pid := Parent}, Opts=#{tracer_callback := Fun}) ->
%% This is necessary because otherwise the tracer could stop
%% before it has finished processing the events in its queue.
process_flag(trap_exit, true),
State = Fun(init, {StreamID, Req, Opts}),
tracer_loop(Parent, Opts, State).
tracer_loop(Parent, Opts=#{tracer_callback := Fun}, State0) ->
receive
Msg when element(1, Msg) =:= trace_ts ->
State = Fun(Msg, State0),
tracer_loop(Parent, Opts, State);
{'EXIT', Parent, Reason} ->
tracer_terminate(Reason, Opts, State0);
{system, From, Request} ->
sys:handle_system_msg(Request, From, Parent, ?MODULE, [], {Opts, State0});
Msg ->
cowboy:log(warning, "~p: Tracer process received stray message ~9999p~n",
[?MODULE, Msg], Opts),
tracer_loop(Parent, Opts, State0)
end.
-spec tracer_terminate(_, _, _) -> no_return().
tracer_terminate(Reason, #{tracer_callback := Fun}, State) ->
_ = Fun(terminate, State),
exit(Reason).
%% System callbacks.
-spec system_continue(pid(), _, {cowboy:opts(), any()}) -> no_return().
system_continue(Parent, _, {Opts, State}) ->
tracer_loop(Parent, Opts, State).
-spec system_terminate(any(), _, _, _) -> no_return().
system_terminate(Reason, _, _, {Opts, State}) ->
tracer_terminate(Reason, Opts, State).
-spec system_code_change(Misc, _, _, _) -> {ok, Misc} when Misc::any().
system_code_change(Misc, _, _, _) ->
{ok, Misc}.
|
