%%
%% %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(kernel).
-behaviour(supervisor).
%% External exports
-export([start/2, init/1, stop/1]).
-export([config_change/3]).
%%%-----------------------------------------------------------------
%%% The kernel is the first application started.
%%% Callback functions for the kernel application.
%%%-----------------------------------------------------------------
start(_, []) ->
case supervisor:start_link({local, kernel_sup}, kernel, []) of
{ok, Pid} ->
%% add signal handler
case whereis(erl_signal_server) of
%% in case of minimal mode
undefined -> ok;
_ ->
ok = gen_event:add_handler(erl_signal_server, erl_signal_handler, [])
end,
%% add error handler
Type = get_error_logger_type(),
case error_logger:swap_handler(Type) of
ok -> {ok, Pid, []};
Error ->
%% Not necessary since the node will crash anyway:
exit(Pid, shutdown),
Error
end;
Error -> Error
end.
stop(_State) ->
ok.
%%-------------------------------------------------------------------
%% Some configuration parameters for kernel are changed
%%-------------------------------------------------------------------
config_change(Changed, New, Removed) ->
do_distribution_change(Changed, New, Removed),
do_global_groups_change(Changed, New, Removed),
ok.
get_error_logger_type() ->
case application:get_env(kernel, error_logger) of
{ok, tty} -> tty;
{ok, {file, File}} when is_list(File) -> {logfile, File};
{ok, false} -> false;
{ok, silent} -> silent;
undefined -> tty; % default value
{ok, Bad} -> exit({bad_config, {kernel, {error_logger, Bad}}})
end.
%%%-----------------------------------------------------------------
%%% The process structure in kernel is as shown in the figure.
%%%
%%% ---------------
%%% | kernel_sup (A)|
%%% ---------------
%%% |
%%% -------------------------------
%%% | | |
%%% <std services> ------------- -------------
%%% (file,code, | erl_dist (A)| | safe_sup (1)|
%%% rpc, ...) ------------- -------------
%%% | |
%%% (net_kernel, (disk_log, pg2,
%%% auth, ...) ...)
%%%
%%% The rectangular boxes are supervisors. All supervisors except
%%% for kernel_safe_sup terminates the enitre erlang node if any of
%%% their children dies. Any child that can't be restarted in case
%%% of failure must be placed under one of these supervisors. Any
%%% other child must be placed under safe_sup. These children may
%%% be restarted. Be aware that if a child is restarted the old state
%%% and all data will be lost.
%%%-----------------------------------------------------------------
%%% Callback functions for the kernel_sup supervisor.
%%%-----------------------------------------------------------------
init([]) ->
SupFlags = #{strategy => one_for_all,
intensity => 0,
period => 1},
Config = #{id => kernel_config,
start => {kernel_config, start_link, []},
restart => permanent,
shutdown => 2000,
type => worker,
modules => [kernel_config]},
Code = #{id => code_server,
start => {code, start_link, []},
restart => permanent,
shutdown => 2000,
type => worker,
modules => [code]},
File = #{id => file_server_2,
start => {file_server, start_link, []},
restart => permanent,
shutdown => 2000,
type => worker,
modeules => [file, file_server, file_io_server, prim_file]},
StdError = #{id => standard_error,
start => {standard_error, start_link, []},
restart => temporary,
shutdown => 2000,
type => supervisor,
modules => [user_sup]},
User = #{id => user,
start => {user_sup, start, []},
restart => temporary,
shutdown => 2000,
type => supervisor,
modules => [user_sup]},
SafeSup = #{id => kernel_safe_sup,
start =>{supervisor, start_link, [{local, kernel_safe_sup}, ?MODULE, safe]},
restart => permanent,
shutdown => infinity,
type => supervisor,
modules => [?MODULE]},
case init:get_argument(mode) of
{ok, [["minimal"]]} ->
{ok, {SupFlags, [Code, File, StdError, User, Config, SafeSup]}};
_ ->
Rpc = #{id => rex,
start => {rpc, start_link, []},
restart => permanent,
shutdown => 2000,
type => worker,
modules => [rpc]},
Global = #{id => global_name_server,
start => {global, start_link, []},
restart => permanent,
shutdown => 2000,
type => worker,
modules => [global]},
GlGroup = #{id => global_group,
start => {global_group,start_link,[]},
restart => permanent,
shutdown => 2000,
type => worker,
modules => [global_group]},
InetDb = #{id => inet_db,
start => {inet_db, start_link, []},
restart => permanent,
shutdown => 2000,
type => worker,
modules => [inet_db]},
NetSup = #{id => net_sup,
start => {erl_distribution, start_link, []},
restart => permanent,
shutdown => infinity,
type => supervisor,
modules => [erl_distribution]},
SigSrv = #{id => erl_signal_server,
start => {gen_event, start_link, [{local, erl_signal_server}]},
restart => permanent,
shutdown => 2000,
type => worker,
modules => dynamic},
DistAC = start_dist_ac(),
Timer = start_timer(),
{ok, {SupFlags,
[Code, Rpc, Global, InetDb | DistAC] ++
[NetSup, GlGroup, File, SigSrv,
StdError, User, Config, SafeSup] ++ Timer}}
end;
init(safe) ->
SupFlags = #{strategy => one_for_one,
intensity => 4,
period => 3600},
Boot = start_boot_server(),
DiskLog = start_disk_log(),
Pg2 = start_pg2(),
%% Run the on_load handlers for all modules that have been
%% loaded so far. Running them at this point means that
%% on_load handlers can safely call kernel processes
%% (and in particular call code:priv_dir/1 or code:lib_dir/1).
init:run_on_load_handlers(),
{ok, {SupFlags, Boot ++ DiskLog ++ Pg2}}.
start_dist_ac() ->
Spec = [#{id => dist_ac,
start => {dist_ac,start_link,[]},
restart => permanent,
shutdown => 2000,
type => worker,
modules => [dist_ac]}],
case application:get_env(kernel, start_dist_ac) of
{ok, true} -> Spec;
{ok, false} -> [];
undefined ->
case application:get_env(kernel, distributed) of
{ok, _} -> Spec;
_ -> []
end
end.
start_boot_server() ->
case application:get_env(kernel, start_boot_server) of
{ok, true} ->
Args = get_boot_args(),
[#{id => boot_server,
start => {erl_boot_server, start_link, [Args]},
restart => permanent,
shutdown => 1000,
type => worker,
modules => [erl_boot_server]}];
_ ->
[]
end.
get_boot_args() ->
case application:get_env(kernel, boot_server_slaves) of
{ok, Slaves} -> Slaves;
_ -> []
end.
start_disk_log() ->
case application:get_env(kernel, start_disk_log) of
{ok, true} ->
[#{id => disk_log_server,
start => {disk_log_server, start_link, []},
restart => permanent,
shutdown => 2000,
type => worker,
modules => [disk_log_server]},
#{id => disk_log_sup,
start => {disk_log_sup, start_link, []},
restart => permanent,
shutdown => 1000,
type => supervisor,
modules => [disk_log_sup]}];
_ ->
[]
end.
start_pg2() ->
case application:get_env(kernel, start_pg2) of
{ok, true} ->
[#{id => pg2,
start => {pg2, start_link, []},
restart => permanent,
shutdown => 1000,
type => worker,
modules => [pg2]}];
_ ->
[]
end.
start_timer() ->
case application:get_env(kernel, start_timer) of
{ok, true} ->
[#{id => timer_server,
start => {timer, start_link, []},
restart => permanent,
shutdown => 1000,
type => worker,
modules => [timer]}];
_ ->
[]
end.
%%-----------------------------------------------------------------
%% The change of the distributed parameter is taken care of here
%%-----------------------------------------------------------------
do_distribution_change(Changed, New, Removed) ->
%% check if the distributed parameter is changed. It is not allowed
%% to make a local application to a distributed one, or vice versa.
case is_dist_changed(Changed, New, Removed) of
%%{changed, new, removed}
{false, false, false} ->
ok;
{C, false, false} ->
%% At last, update the parameter.
gen_server:call(dist_ac, {distribution_changed, C}, infinity);
{false, _, false} ->
error_logger:error_report("Distribution not changed: "
"Not allowed to add the 'distributed' "
"parameter."),
{error, {distribution_not_changed, "Not allowed to add the "
"'distributed' parameter"}};
{false, false, _} ->
error_logger:error_report("Distribution not changed: "
"Not allowed to remove the "
"distribution parameter."),
{error, {distribution_not_changed, "Not allowed to remove the "
"'distributed' parameter"}}
end.
%%-----------------------------------------------------------------
%% Check if distribution is changed in someway.
%%-----------------------------------------------------------------
is_dist_changed(Changed, New, Removed) ->
C = case lists:keyfind(distributed, 1, Changed) of
false ->
false;
{distributed, NewDistC} ->
NewDistC
end,
N = case lists:keyfind(distributed, 1, New) of
false ->
false;
{distributed, NewDistN} ->
NewDistN
end,
R = lists:member(distributed, Removed),
{C, N, R}.
%%-----------------------------------------------------------------
%% The change of the global_groups parameter is taken care of here
%%-----------------------------------------------------------------
do_global_groups_change(Changed, New, Removed) ->
%% check if the global_groups parameter is changed.
case is_gg_changed(Changed, New, Removed) of
%%{changed, new, removed}
{false, false, false} ->
ok;
{C, false, false} ->
%% At last, update the parameter.
global_group:global_groups_changed(C);
{false, N, false} ->
global_group:global_groups_added(N);
{false, false, R} ->
global_group:global_groups_removed(R)
end.
%%-----------------------------------------------------------------
%% Check if global_groups is changed in someway.
%%-----------------------------------------------------------------
is_gg_changed(Changed, New, Removed) ->
C = case lists:keyfind(global_groups, 1, Changed) of
false ->
false;
{global_groups, NewDistC} ->
NewDistC
end,
N = case lists:keyfind(global_groups, 1, New) of
false ->
false;
{global_groups, NewDistN} ->
NewDistN
end,
R = lists:member(global_groups, Removed),
{C, N, R}.
