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
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
|
%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2017. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
-module(slave).
%% If the macro DEBUG is defined during compilation,
%% debug printouts are done through erlang:display/1.
%% Activate this feature by starting the compiler
%% with> erlc -DDEBUG ...
%% or by> setenv ERL_COMPILER_FLAGS DEBUG
%% before running make (in the OTP make system)
%% (the example is for tcsh)
-export([pseudo/1,
pseudo/2,
start/1, start/2, start/3,
start/5,
start_link/1, start_link/2, start_link/3,
stop/1,
relay/1]).
%% Internal exports
-export([wait_for_slave/7, slave_start/1, wait_for_master_to_die/2]).
-import(error_logger, [error_msg/2]).
-ifdef(DEBUG).
-define(dbg(Tag,Data), erlang:display({Tag,Data})).
-else.
-define(dbg(Tag,Data), true).
-endif.
%% Start a list of pseudo servers on the local node
pseudo([Master | ServerList]) ->
pseudo(Master , ServerList);
pseudo(_) ->
error_msg("No master node given to slave:pseudo/1~n",[]).
-spec pseudo(Master, ServerList) -> ok when
Master :: node(),
ServerList :: [atom()].
pseudo(_, []) -> ok;
pseudo(Master, [S|Tail]) ->
start_pseudo(S, whereis(S), Master),
pseudo(Master, Tail).
start_pseudo(Name, undefined, Master) ->
X = rpc:call(Master,erlang, whereis,[Name]),
register(Name, spawn(slave, relay, [X]));
start_pseudo(_,_,_) -> ok. %% It's already there
%% This relay can be used to relay all messages directed to a process.
-spec relay(Pid) -> no_return() when
Pid :: pid().
relay({badrpc,Reason}) ->
error_msg(" ** exiting relay server ~w :~w **~n", [self(),Reason]),
exit(Reason);
relay(undefined) ->
error_msg(" ** exiting relay server ~w **~n", [self()]),
exit(undefined);
relay(Pid) when is_pid(Pid) ->
relay1(Pid).
relay1(Pid) ->
receive
X ->
Pid ! X
end,
relay1(Pid).
%% start/1,2,3 --
%% start_link/1,2,3 --
%%
%% The start/1,2,3 functions are used to start a slave Erlang node.
%% The node on which the start/N functions are used is called the
%% master in the description below.
%%
%% If hostname is the same for the master and the slave,
%% the Erlang node will simply be spawned. The only requirment for
%% this to work is that the 'erl' program can be found in PATH.
%%
%% If the master and slave are on different hosts, start/N uses
%% the 'rsh' program to spawn an Erlang node on the other host.
%% Alternative, if the master was started as
%% 'erl -sname xxx -rsh my_rsh...', then 'my_rsh' will be used instead
%% of 'rsh' (this is useful for systems where the rsh program is named
%% 'remsh').
%%
%% For this to work, the following conditions must be fulfilled:
%%
%% 1. There must be an Rsh program on computer; if not an error
%% is returned.
%%
%% 2. The hosts must be configured to allowed 'rsh' access without
%% prompts for password.
%%
%% The slave node will have its filer and user server redirected
%% to the master. When the master node dies, the slave node will
%% terminate. For the start_link functions, the slave node will
%% terminate also if the process which called start_link terminates.
%%
%% Returns: {ok, Name@Host} |
%% {error, timeout} |
%% {error, no_rsh} |
%% {error, {already_running, Name@Host}}
-spec start(Host) -> {ok, Node} | {error, Reason} when
Host :: inet:hostname(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start(Host) ->
L = atom_to_list(node()),
Name = upto($@, L),
start(Host, Name, [], no_link).
-spec start(Host, Name) -> {ok, Node} | {error, Reason} when
Host :: inet:hostname(),
Name :: atom() | string(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start(Host, Name) ->
start(Host, Name, []).
-spec start(Host, Name, Args) -> {ok, Node} | {error, Reason} when
Host :: inet:hostname(),
Name :: atom() | string(),
Args :: string(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start(Host, Name, Args) ->
start(Host, Name, Args, no_link).
-spec start_link(Host) -> {ok, Node} | {error, Reason} when
Host :: inet:hostname(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start_link(Host) ->
L = atom_to_list(node()),
Name = upto($@, L),
start(Host, Name, [], self()).
-spec start_link(Host, Name) -> {ok, Node} | {error, Reason} when
Host :: inet:hostname(),
Name :: atom() | string(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start_link(Host, Name) ->
start_link(Host, Name, []).
-spec start_link(Host, Name, Args) -> {ok, Node} | {error, Reason} when
Host :: inet:hostname(),
Name :: atom() | string(),
Args :: string(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start_link(Host, Name, Args) ->
start(Host, Name, Args, self()).
start(Host0, Name, Args, LinkTo) ->
Prog = lib:progname(),
start(Host0, Name, Args, LinkTo, Prog).
start(Host0, Name, Args, LinkTo, Prog) ->
Host =
case net_kernel:longnames() of
true -> dns(Host0);
false -> strip_host_name(to_list(Host0));
ignored -> exit(not_alive)
end,
Node = list_to_atom(lists:concat([Name, "@", Host])),
case net_adm:ping(Node) of
pang ->
start_it(Host, Name, Node, Args, LinkTo, Prog);
pong ->
{error, {already_running, Node}}
end.
%% Stops a running node.
-spec stop(Node) -> ok when
Node :: node().
stop(Node) ->
rpc:call(Node, erlang, halt, []),
ok.
%% Starts a new slave node.
start_it(Host, Name, Node, Args, LinkTo, Prog) ->
spawn(?MODULE, wait_for_slave, [self(), Host, Name, Node, Args, LinkTo,
Prog]),
receive
{result, Result} -> Result
end.
%% Waits for the slave to start.
wait_for_slave(Parent, Host, Name, Node, Args, LinkTo, Prog) ->
Waiter = register_unique_name(0),
case mk_cmd(Host, Name, Args, Waiter, Prog) of
{ok, Cmd} ->
open_port({spawn, Cmd}, [stream]),
receive
{SlavePid, slave_started} ->
unregister(Waiter),
slave_started(Parent, LinkTo, SlavePid)
after 32000 ->
%% If it seems that the node was partially started,
%% try to kill it.
Node = list_to_atom(lists:concat([Name, "@", Host])),
case net_adm:ping(Node) of
pong ->
spawn(Node, erlang, halt, []),
ok;
_ ->
ok
end,
Parent ! {result, {error, timeout}}
end;
Other ->
Parent ! {result, Other}
end.
slave_started(ReplyTo, no_link, Slave) when is_pid(Slave) ->
ReplyTo ! {result, {ok, node(Slave)}};
slave_started(ReplyTo, Master, Slave) when is_pid(Master), is_pid(Slave) ->
process_flag(trap_exit, true),
link(Master),
link(Slave),
ReplyTo ! {result, {ok, node(Slave)}},
one_way_link(Master, Slave).
%% This function simulates a one-way link, so that the slave node
%% will be killed if the master process terminates, but the master
%% process will not be killed if the slave node terminates.
one_way_link(Master, Slave) ->
receive
{'EXIT', Master, _Reason} ->
unlink(Slave),
Slave ! {nodedown, node()};
{'EXIT', Slave, _Reason} ->
unlink(Master);
_Other ->
one_way_link(Master, Slave)
end.
register_unique_name(Number) ->
Name = list_to_atom(lists:concat(["slave_waiter_", Number])),
case catch register(Name, self()) of
true ->
Name;
{'EXIT', {badarg, _}} ->
register_unique_name(Number+1)
end.
%% Makes up the command to start the nodes.
%% If the node should run on the local host, there is
%% no need to use rsh.
mk_cmd(Host, Name, Args, Waiter, Prog0) ->
Prog = quote_progname(Prog0),
BasicCmd = lists:concat([Prog,
" -detached -noinput -master ", node(),
" ", long_or_short(), Name, "@", Host,
" -s slave slave_start ", node(),
" ", Waiter,
" ", Args]),
case after_char($@, atom_to_list(node())) of
Host ->
{ok, BasicCmd};
_ ->
case rsh() of
{ok, Rsh} ->
{ok, lists:concat([Rsh, " ", Host, " ", BasicCmd])};
Other ->
Other
end
end.
%% This is an attempt to distinguish between spaces in the program
%% path and spaces that separate arguments. The program is quoted to
%% allow spaces in the path.
%%
%% Arguments could exist either if the executable is excplicitly given
%% (through start/5) or if the -program switch to beam is used and
%% includes arguments (typically done by cerl in OTP test environment
%% in order to ensure that slave/peer nodes are started with the same
%% emulator and flags as the test node. The return from lib:progname()
%% could then typically be '/<full_path_to>/cerl -gcov').
quote_progname(Progname) ->
do_quote_progname(string:lexemes(to_list(Progname)," ")).
do_quote_progname([Prog]) ->
"\""++Prog++"\"";
do_quote_progname([Prog,Arg|Args]) ->
case os:find_executable(Prog) of
false ->
do_quote_progname([Prog++" "++Arg | Args]);
_ ->
%% this one has an executable - we assume the rest are arguments
"\""++Prog++"\""++
lists:flatten(lists:map(fun(X) -> [" ",X] end, [Arg|Args]))
end.
%% Give the user an opportunity to run another program,
%% than the "rsh". On HP-UX rsh is called remsh; thus HP users
%% must start erlang as erl -rsh remsh.
%%
%% Also checks that the given program exists.
%%
%% Returns: {ok, RshPath} | {error, Reason}
rsh() ->
Rsh =
case init:get_argument(rsh) of
{ok, [[Prog]]} -> Prog;
_ -> "rsh"
end,
case os:find_executable(Rsh) of
false -> {error, no_rsh};
Path -> {ok, Path}
end.
long_or_short() ->
case net_kernel:longnames() of
true -> " -name ";
false -> " -sname "
end.
%% This function will be invoked on the slave, using the -s option of erl.
%% It will wait for the master node to terminate.
slave_start([Master, Waiter]) ->
?dbg({?MODULE, slave_start}, [[Master, Waiter]]),
spawn(?MODULE, wait_for_master_to_die, [Master, Waiter]).
wait_for_master_to_die(Master, Waiter) ->
?dbg({?MODULE, wait_for_master_to_die}, [Master, Waiter]),
process_flag(trap_exit, true),
monitor_node(Master, true),
{Waiter, Master} ! {self(), slave_started},
wloop(Master).
wloop(Master) ->
receive
{nodedown, Master} ->
?dbg({?MODULE, wloop},
[[Master], {received, {nodedown, Master}}, halting_node] ),
halt();
_Other ->
wloop(Master)
end.
%% Just the short hostname, not the qualified, for convenience.
strip_host_name([]) -> [];
strip_host_name([$.|_]) -> [];
strip_host_name([H|T]) -> [H|strip_host_name(T)].
dns(H) -> {ok, Host} = net_adm:dns_hostname(H), Host.
to_list(X) when is_list(X) -> X;
to_list(X) when is_atom(X) -> atom_to_list(X).
upto(_, []) -> [];
upto(Char, [Char|_]) -> [];
upto(Char, [H|T]) -> [H|upto(Char, T)].
after_char(_, []) -> [];
after_char(Char, [Char|Rest]) -> Rest;
after_char(Char, [_|Rest]) -> after_char(Char, Rest).
|