%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2011. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% 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.
%%
%% %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 :: atom(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start(Host) ->
L = atom_to_list(node()),
Name = upto($@, L),
start(Host, Name, [], no_link).
-spec start(Host, Name) -> {ok, Node} | {error, Reason} when
Host :: atom(),
Name :: atom(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start(Host, Name) ->
start(Host, Name, []).
-spec start(Host, Name, Args) -> {ok, Node} | {error, Reason} when
Host :: atom(),
Name :: atom(),
Args :: string(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start(Host, Name, Args) ->
start(Host, Name, Args, no_link).
-spec start_link(Host) -> {ok, Node} | {error, Reason} when
Host :: atom(),
Node :: node(),
Reason :: timeout | no_rsh | {already_running, Node}.
start_link(Host) ->
L = atom_to_list(node()),
Name = upto($@, L),
start(Host, Name, [], self()).
-spec start_link(Host, Name) -> {ok, Node} | {error, Reason} when
Host :: atom(),
Name :: atom(),
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 :: atom(),
Name :: atom(),
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) ->
% io:format("stop(~p)~n", [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} ->
%% io:format("Command: ~s~n", [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, Prog) ->
BasicCmd = lists:concat([Prog,
" -detached -noinput -master ", node(),
" ", long_or_short(), Name, "@", Host,
" -s slave slave_start ", node(),
" ", Waiter,
" ", Args]),
case after_char($@, atom_to_list(node())) of
Host ->
{ok, BasicCmd};
_ ->
case rsh() of
{ok, Rsh} ->
{ok, lists:concat([Rsh, " ", Host, " ", BasicCmd])};
Other ->
Other
end
end.
%% Give the user an opportunity to run another program,
%% than the "rsh". On HP-UX rsh is called remsh; thus HP users
%% must start erlang as erl -rsh remsh.
%%
%% Also checks that the given program exists.
%%
%% Returns: {ok, RshPath} | {error, Reason}
rsh() ->
Rsh =
case init:get_argument(rsh) of
{ok, [[Prog]]} -> Prog;
_ -> "rsh"
end,
case os:find_executable(Rsh) of
false -> {error, no_rsh};
Path -> {ok, Path}
end.
long_or_short() ->
case net_kernel:longnames() of
true -> " -name ";
false -> " -sname "
end.
%% This function will be invoked on the slave, using the -s option of erl.
%% It will wait for the master node to terminate.
slave_start([Master, Waiter]) ->
?dbg({?MODULE, slave_start}, [[Master, Waiter]]),
spawn(?MODULE, wait_for_master_to_die, [Master, Waiter]).
wait_for_master_to_die(Master, Waiter) ->
?dbg({?MODULE, wait_for_master_to_die}, [Master, Waiter]),
process_flag(trap_exit, true),
monitor_node(Master, true),
{Waiter, Master} ! {self(), slave_started},
wloop(Master).
wloop(Master) ->
receive
{nodedown, Master} ->
?dbg({?MODULE, wloop},
[[Master], {received, {nodedown, Master}}, halting_node] ),
halt();
_Other ->
wloop(Master)
end.
%% Just the short hostname, not the qualified, for convenience.
strip_host_name([]) -> [];
strip_host_name([$.|_]) -> [];
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).
