auto-reload config on file change

Author: rnewson

rel/overlay/etc/default.ini

@@ -1233,3 +1233,8 @@ url = {{nouveau_url}}
 ; from the _first_ authentication failure.
 ; note: changing this setting requires a couchdb restart.
 ;max_lifetime = 300000
+
+[config]
+; periodically reload configuration from file.
+; Set to infinity to disable.
+;auto_reload_secs = infinity

src/config/src/config.erl

@@ -26,7 +26,7 @@
 -export([set/3, set/4, set/5]).
 -export([delete/2, delete/3, delete/4]).
 
--export([get_integer/3, set_integer/3, set_integer/4]).
+-export([get_integer/3, set_integer/3, set_integer/4, get_integer_or_infinity/3]).
 -export([get_float/3, set_float/3, set_float/4]).
 -export([get_boolean/3, set_boolean/3, set_boolean/4]).
 
@@ -38,7 +38,7 @@
 -export([subscribe_for_changes/1]).
 
 -export([init/1]).
--export([handle_call/3, handle_cast/2]).
+-export([handle_call/3, handle_cast/2, handle_info/2]).
 -export([terminate/2]).
 
 -export([is_sensitive/2]).
@@ -64,7 +64,9 @@
     % Just *.ini files: original *.ini + expanded *.d dirs
     ini_files,
     % The file we write config values to
-    write_filename
+    write_filename,
+    % Reload timer ref
+    reload_tref
 }).
 
 start_link(IniFilesDirs) ->
@@ -80,6 +82,17 @@ all() ->
     lists:sort(lists:filtermap(fun settings_fmap_fun/1, persistent_term:get())).
 
 get_integer(Section, Key, Default) when is_integer(Default) ->
+    get_integer_int(Section, Key, Default).
+
+get_integer_or_infinity(Section, Key, Default) when is_integer(Default); Default == infinity ->
+    case get_value(Section, Key, Default) of
+        infinity ->
+            infinity;
+        _Value ->
+            get_integer_int(Section, Key, Default)
+    end.
+
+get_integer_int(Section, Key, Default) ->
     try
         to_integer(get_value(Section, Key, Default))
     catch
@@ -294,7 +307,7 @@ init(IniFilesDirs) ->
     % correct node name and distribution mode.
     case check_distribution_mode() of
         ok ->
-            {ok, Config};
+            {ok, schedule_reload(Config)};
         {error, Msg} ->
             erlang:display(Msg),
             timer:sleep(500),
@@ -331,9 +344,9 @@ handle_call({set, Sec, Key, Val, Opts}, _From, Config) ->
                 ok ->
                     Event = {config_change, Sec, Key, Val, Persist},
                     gen_event:sync_notify(config_event, Event),
-                    {reply, ok, Config};
+                    {reply, ok, schedule_reload(Config)};
                 {error, Else} ->
-                    {reply, {error, Else}, Config}
+                    {reply, {error, Else}, schedule_reload(Config)}
             end
     end;
 handle_call({delete, Sec, Key, Persist, Reason}, _From, Config) ->
@@ -357,55 +370,21 @@ handle_call({delete, Sec, Key, Persist, Reason}, _From, Config) ->
         ok ->
             Event = {config_change, Sec, Key, deleted, Persist},
             gen_event:sync_notify(config_event, Event),
-            {reply, ok, Config};
+            {reply, ok, schedule_reload(Config)};
         Else ->
-            {reply, Else, Config}
+            {reply, Else, schedule_reload(Config)}
     end;
 handle_call(reload, _From, #config{} = Config) ->
-    #config{ini_files_dirs = IniFilesDirs} = Config,
-    IniFiles = expand_dirs(IniFilesDirs),
-    % Update persistent term with ini values.
-    IniMap = ini_map(IniFiles),
-    maps:foreach(
-        fun({Sec, Key}, V) ->
-            VExisting = get_value(Sec, Key, undefined),
-            case V =:= VExisting of
-                true ->
-                    ok;
-                false ->
-                    put_value(Sec, Key, V),
-                    Msg = "Reload detected config change ~s.~s = ~p",
-                    Args = [Sec, Key, maybe_conceal(V, is_sensitive(Sec, Key))],
-                    couch_log:notice(Msg, Args),
-                    Event = {config_change, Sec, Key, V, true},
-                    gen_event:sync_notify(config_event, Event)
-            end
-        end,
-        IniMap
-    ),
-    % And remove anything in persistent terms that wasn't on disk.
-    lists:foreach(
-        fun
-            ({{Sec, Key}, _}) when not is_map_key({Sec, Key}, IniMap) ->
-                NoticeMsg = "Reload deleting in-memory config ~s.~s",
-                couch_log:notice(NoticeMsg, [Sec, Key]),
-                erase_value(Sec, Key),
-                Event = {config_change, Sec, Key, deleted, true},
-                gen_event:sync_notify(config_event, Event);
-            (_) ->
-                ok
-        end,
-        all()
-    ),
-    Config1 = Config#config{
-        ini_files = IniFiles,
-        write_filename = get_write_file(IniFiles)
-    },
-    {reply, ok, Config1}.
+    {reply, ok, reload(Config)}.
 
 handle_cast(_Msg, State) ->
     {noreply, State}.
 
+handle_info(reload, #config{} = Config) ->
+    {noreply, schedule_reload(reload(Config))};
+handle_info(_Msg, State) ->
+    {noreply, State}.
+
 terminate(_Reason, _State) ->
     erase_all().
 
@@ -615,6 +594,58 @@ settings_fmap_fun({{?MODULE, ?SETTINGS, Sec, Key}, Val}) ->
 settings_fmap_fun(_) ->
     false.
 
+reload(Config) ->
+    #config{ini_files_dirs = IniFilesDirs} = Config,
+    IniFiles = expand_dirs(IniFilesDirs),
+    % Update ets with ini values.
+    IniMap = ini_map(IniFiles),
+    maps:foreach(
+        fun({Sec, Key}, V) ->
+            VExisting = get_value(Sec, Key, undefined),
+            case V =:= VExisting of
+                true ->
+                    ok;
+                false ->
+                    put_value(Sec, Key, V),
+                    Msg = "Reload detected config change ~s.~s = ~p",
+                    Args = [Sec, Key, maybe_conceal(V, is_sensitive(Sec, Key))],
+                    couch_log:notice(Msg, Args),
+                    Event = {config_change, Sec, Key, V, true},
+                    gen_event:sync_notify(config_event, Event)
+            end
+        end,
+        IniMap
+    ),
+    % And remove anything in ets that wasn't on disk.
+    lists:foreach(
+        fun
+            ({{Sec, Key}, _}) when not is_map_key({Sec, Key}, IniMap) ->
+                NoticeMsg = "Reload deleting in-memory config ~s.~s",
+                couch_log:notice(NoticeMsg, [Sec, Key]),
+                erase_value(Sec, Key),
+                Event = {config_change, Sec, Key, deleted, true},
+                gen_event:sync_notify(config_event, Event);
+            (_) ->
+                ok
+        end,
+        all()
+    ),
+    Config#config{
+        ini_files = IniFiles,
+        write_filename = get_write_file(IniFiles)
+    }.
+
+schedule_reload(#config{} = Config) ->
+    timer:cancel(Config#config.reload_tref),
+    case get_integer_or_infinity("config", "auto_reload_secs", infinity) of
+        infinity ->
+            Config;
+        AutoReloadSecs when AutoReloadSecs > 0 ->
+            AutoReloadMS = erlang:convert_time_unit(AutoReloadSecs, second, millisecond),
+            TRef = erlang:send_after(AutoReloadMS, ?MODULE, reload),
+            Config#config{reload_tref = TRef}
+    end.
+
 -ifdef(TEST).
 -include_lib("couch/include/couch_eunit.hrl").
 

test/elixir/test/config/suite.elixir

@@ -149,6 +149,7 @@
     "Non-term whitelist values allow further modification of the whitelist",
     "PORT `BUGGED` ?raw tests from config.js",
     "Reload config",
+    "Auto-reload config",
     "Server-side password hashing, and raw updates disabling that",
     "Settings can be altered with undefined whitelist allowing any change",
     "Standard config options are present",

test/elixir/test/config_test.exs

@@ -182,6 +182,22 @@ defmodule ConfigTest do
     assert resp.status_code == 200
   end
 
+  test "Auto-reload config", context do
+    {:ok, fd} = File.open "dev/lib/node1/etc/local.ini", [:append]
+    IO.puts(fd, "[foo]\nbar = baz")
+    File.close fd
+    assert !Map.has_key?(get_config(context, "foo"), "bar")
+
+    # enable config auto-reload
+    set_config(context, "config", "auto_reload_secs", "1")
+    on_exit(fn ->
+      delete_config(context, "config", "auto_reload_secs", nil)
+    end)
+
+    :timer.sleep(1200)
+    assert get_config(context, "foo", "bar") == "baz"
+  end
+
   # Those are negative test cases.  The positive cases are implicitly
   # tested by other ones.
   test "Only JSON strings are accepted", context do