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
|
%% The contents of this file are subject to the Mozilla Public License
%% Version 1.1 (the "License"); you may not use this file except in
%% compliance with the License. You may obtain a copy of the License
%% at http://www.mozilla.org/MPL/
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and
%% limitations under the License.
%%
%% The Original Code is RabbitMQ.
%%
%% The Initial Developer of the Original Code is VMware, Inc.
%% Copyright (c) 2007-2011 VMware, Inc. All rights reserved.
%%
-module(rabbit_guid).
-behaviour(gen_server).
-export([start_link/0]).
-export([guid/0, string_guid/1, binstring_guid/1]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2,
code_change/3]).
-define(SERVER, ?MODULE).
-define(SERIAL_FILENAME, "rabbit_serial").
-record(state, {serial}).
%%----------------------------------------------------------------------------
-ifdef(use_specs).
-export_type([guid/0]).
-type(guid() :: binary()).
-spec(start_link/0 :: () -> rabbit_types:ok_pid_or_error()).
-spec(guid/0 :: () -> guid()).
-spec(string_guid/1 :: (any()) -> string()).
-spec(binstring_guid/1 :: (any()) -> binary()).
-endif.
%%----------------------------------------------------------------------------
start_link() ->
gen_server:start_link({local, ?SERVER}, ?MODULE,
[update_disk_serial()], []).
update_disk_serial() ->
Filename = filename:join(rabbit_mnesia:dir(), ?SERIAL_FILENAME),
Serial = case rabbit_misc:read_term_file(Filename) of
{ok, [Num]} -> Num;
{error, enoent} -> 0;
{error, Reason} ->
throw({error, {cannot_read_serial_file, Filename, Reason}})
end,
case rabbit_misc:write_term_file(Filename, [Serial + 1]) of
ok -> ok;
{error, Reason1} ->
throw({error, {cannot_write_serial_file, Filename, Reason1}})
end,
Serial.
%% generate a GUID.
%%
%% The id is only unique within a single cluster and as long as the
%% serial store hasn't been deleted.
guid() ->
%% We don't use erlang:now() here because a) it may return
%% duplicates when the system clock has been rewound prior to a
%% restart, or ids were generated at a high rate (which causes
%% now() to move ahead of the system time), and b) it is really
%% slow since it takes a global lock and makes a system call.
%%
%% A persisted serial number, in combination with self/0 (which
%% includes the node name) uniquely identifies a process in space
%% and time. We combine that with a process-local counter to give
%% us a GUID.
G = case get(guid) of
undefined -> {{gen_server:call(?SERVER, serial, infinity), self()},
0};
{S, I} -> {S, I+1}
end,
put(guid, G),
erlang:md5(term_to_binary(G)).
%% generate a readable string representation of a GUID.
string_guid(Prefix) ->
Prefix ++ "-" ++ base64:encode_to_string(guid()).
binstring_guid(Prefix) ->
list_to_binary(string_guid(Prefix)).
%%----------------------------------------------------------------------------
init([Serial]) ->
{ok, #state{serial = Serial}}.
handle_call(serial, _From, State = #state{serial = Serial}) ->
{reply, Serial, State};
handle_call(_Request, _From, State) ->
{noreply, State}.
handle_cast(_Msg, State) ->
{noreply, State}.
handle_info(_Info, State) ->
{noreply, State}.
terminate(_Reason, _State) ->
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
|
