Merge pull request #2088 from josevalim/jv-start-distribution

Add start_distribution to kernel environment

OTP-15668

3 files changed, 62 insertions, 39 deletions

diff --git a/lib/kernel/doc/src/kernel_app.xml b/lib/kernel/doc/src/kernel_app.xml
index dbd83e1a6e..7f9609d5c1 100644
--- a/lib/kernel/doc/src/kernel_app.xml
+++ b/lib/kernel/doc/src/kernel_app.xml
@@ -369,6 +369,14 @@ MaxT = TickTime + TickTime / 4</code>
           performed. This option ensures that <c>global</c> is
           synchronized.</p>
       </item>
+      <tag><c>start_distribution = true | false</c></tag>
+      <item>
+        <p>Starts all distribution services, such as <c>rpc</c>,
+          <c>global</c>, and <c>net_kernel</c> if the parameter is
+          <c>true</c>. This parameter is to be set to <c>false</c>
+          for systems who want to disable all distribution functionality.</p>
+        <p>Defaults to <c>true</c>.</p>
+      </item>
       <tag><c>start_dist_ac = true | false</c></tag>
       <item>
         <p>Starts the <c>dist_ac</c> server if the parameter is
diff --git a/lib/kernel/src/kernel.erl b/lib/kernel/src/kernel.erl
index c68d04e279..111d103df2 100644
--- a/lib/kernel/src/kernel.erl
+++ b/lib/kernel/src/kernel.erl
@@ -145,26 +145,11 @@ init([]) ->
             {ok, {SupFlags,
                   [Code, File, StdError, User, LoggerSup, Config, RefC, 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]},
+            DistChildren =
+		case application:get_env(kernel, start_distribution) of
+		    {ok, false} -> [];
+		    _ -> start_distribution()
+		end,
 
             InetDb = #{id => inet_db,
                        start => {inet_db, start_link, []},
@@ -173,13 +158,6 @@ init([]) ->
                        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,
@@ -187,14 +165,11 @@ init([]) ->
                        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, RefC, SafeSup, LoggerSup] ++ Timer}}
+                  [Code, InetDb | DistChildren] ++
+                  [File, SigSrv, StdError, User, Config, RefC, SafeSup, LoggerSup] ++ Timer}}
     end;
 init(safe) ->
     SupFlags = #{strategy => one_for_one,
@@ -213,6 +188,39 @@ init(safe) ->
 
     {ok, {SupFlags, Boot ++ DiskLog ++ Pg2}}.
 
+start_distribution() ->
+    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]},
+
+    DistAC = start_dist_ac(),
+
+    NetSup = #{id => net_sup,
+               start => {erl_distribution, start_link, []},
+               restart => permanent,
+               shutdown => infinity,
+               type => supervisor,
+               modules => [erl_distribution]},
+
+    GlGroup = #{id => global_group,
+                start => {global_group,start_link,[]},
+                restart => permanent,
+                shutdown => 2000,
+                type => worker,
+                modules => [global_group]},
+
+    [Rpc, Global | DistAC] ++ [NetSup, GlGroup].
+
 start_dist_ac() ->
     Spec = [#{id => dist_ac,
               start => {dist_ac,start_link,[]},
diff --git a/lib/kernel/test/kernel_config_SUITE.erl b/lib/kernel/test/kernel_config_SUITE.erl
index 9207025a2c..57c44c2498 100644
--- a/lib/kernel/test/kernel_config_SUITE.erl
+++ b/lib/kernel/test/kernel_config_SUITE.erl
@@ -21,7 +21,8 @@
 
 -include_lib("common_test/include/ct.hrl").
 
--export([all/0, suite/0,groups/0,init_per_group/2,end_per_group/2, sync/1]).
+-export([all/0, suite/0,groups/0,init_per_group/2,end_per_group/2,
+	 start_distribution_false/1, sync/1]).
 
 -export([init_per_suite/1, end_per_suite/1]).
 
@@ -30,7 +31,7 @@ suite() ->
      {timetrap,{minutes,2}}].
 
 all() -> 
-    [sync].
+    [sync, start_distribution_false].
 
 groups() -> 
     [].
@@ -59,12 +60,9 @@ from(H, [H | T]) -> T;
 from(H, [_ | T]) -> from(H, T);
 from(_, []) -> [].
 
-%%-----------------------------------------------------------------
-%% Test suite for sync_nodes.   This is quite tricky.
-%%
+%% Test sync_nodes. This is quite tricky.
 %% Should be started in a CC view with:
 %% erl -sname XXX where XX not in [cp1, cp2]
-%%-----------------------------------------------------------------
 sync(Conf) when is_list(Conf) ->
     %% Write a config file
     Dir = proplists:get_value(priv_dir,Conf),
@@ -106,9 +104,18 @@ wait_for_node(Node) ->
 	_Other -> wait_for_node(Node)
     end.
 
-
 stop_node(Node) ->
     M = list_to_atom(lists:concat([Node,
 				   [$@],
 				   from($@,atom_to_list(node()))])),
     rpc:cast(M, erlang, halt, []).
+
+start_distribution_false(Config) when is_list(Config) ->
+    %% When distribution is disabled, -sname/-name has no effect
+    Str = os:cmd(ct:get_progname()
+		 ++ " -kernel start_distribution false"
+		 ++ " -sname no_distribution"
+		 ++ " -eval \"erlang:display(node())\""
+		 ++ " -noshell -s erlang halt"),
+    "'nonode@nohost'" ++ _ = Str,
+    ok.