Add helpers for configuration reload

Makefile

@@ -20,10 +20,10 @@ test:
 	$(REBAR3) cover -v
 
 config/prod-sys.config: config/sys.config.example
-	[ -f $@ ] && diff $^ $@ || true
+	[ -f $@ ] && diff -u $@ $^ || true
 	cp -i -b $^ $@
 config/prod-vm.args: config/vm.args.example
-	[ -f $@ ] && diff $^ $@ || true
+	[ -f $@ ] && diff -u $@ $^ || true
 	cp -i -b $^ $@
 	@IP=$(shell curl -s -4 -m 10 http://ip.seriyps.ru  || curl -s -4 -m 10 https://digitalresistance.dog/myIp) \
 		&& sed -i s/@0\.0\.0\.0/@$${IP}/ $@
@@ -48,6 +48,11 @@ install: user $(LOGDIR)
 	fi
 	systemctl daemon-reload
 
+.PHONY: update-sysconfig
+update-sysconfig: config/prod-sys.config $(prefix)/mtp_proxy
+	REL_VSN=$(shell awk '{print $$2}' $(prefix)/mtp_proxy/releases/start_erl.data) && \
+		install -m 644 config/prod-sys.config "$(prefix)/mtp_proxy/releases/$${REL_VSN}/sys.config"
+
 uninstall:
 # TODO: ensure service is stopped
 	rm $(SERVICE)

README.md

@@ -22,7 +22,7 @@ Features
 * Protection from [replay attacks](https://habr.com/ru/post/452144/) used to detect proxies in some countries
 * Automatic telegram configuration reload (no need for restarts once per day)
 * IPv6 for client connections
-* Most of the configuration options can be updated without service restart
+* All configuration options can be updated without service restart
 * Small codebase compared to official one, code is covered by automated tests
 * A lots of metrics could be exported (optional)
 
@@ -46,7 +46,7 @@ curl -L -o mtp_install.sh https://git.io/fj5ru && bash mtp_install.sh -p 443 -s
 It does the same as described in [How to start OS-install - detailed](#how-to-start-os-install---detailed), but
 generates config-file for you automatically.
 
-How to start - docker
+How to start - Docker
 ---------------------
 
 ### To run with default settings
@@ -213,16 +213,20 @@ Default port is 1443 and default secret is `d0d6e111bada5511fcce9584deadbeef`.
 
 Secret key and proxy URLs will be printed on start.
 
-The easiest way to update config right now is to edit `config/prod-sys.config`
-and then re-install proxy by
+
+### Apply config changes without restart
+
+It's possible to reload config file without service restart (but if you want to update
+ad_tag on existing port, all clients of this port will be disconnected).
+
+This method doesn't work for Docker!
+
+To do that, make changes in `config/prod-sys.config` and run following command:
 
 ```bash
-sudo make uninstall && make && sudo make install
+sudo make update-sysconfig && sudo systemctl reload mtproto-proxy
 ```
 
-There are other ways as well. It's even possible to update configuration options
-without service restart / without downtime, but it's a bit trickier.
-
 ### Change default port / secret / ad tag
 
 To change default settings, change `mtproto_proxy` section of `prod-sys.config` as:

config/mtproto-proxy.service

@@ -24,6 +24,7 @@ LimitNOFILE=40960
 AmbientCapabilities=CAP_NET_BIND_SERVICE
 ExecStart=/opt/mtp_proxy/bin/mtp_proxy foreground
 ExecStop=/opt/mtp_proxy/bin/mtp_proxy stop
+ExecReload=/opt/mtp_proxy/bin/mtp_proxy rpcterms mtproto_proxy_app reload_config
 TimeoutStopSec=15s
 
 [Install]

src/mtproto_proxy_app.erl

@@ -9,7 +9,13 @@
 
 %% Application callbacks
 -export([start/2, prep_stop/1, stop/1, config_change/3]).
--export([mtp_listeners/0, running_ports/0, start_proxy/1, build_urls/4, get_port_secret/1]).
+%% Helpers
+-export([mtp_listeners/0,
+         reload_config/0,
+         running_ports/0,
+         start_proxy/1,
+         build_urls/4,
+         get_port_secret/1]).
 
 -define(APP, mtproto_proxy).
 
@@ -22,7 +28,7 @@
                         listen_ip => string()}.
 
 %%====================================================================
-%% API
+%% Application behaviour API
 %%====================================================================
 start(_StartType, _StartArgs) ->
     Res = {ok, _} = mtproto_proxy_sup:start_link(),
@@ -49,6 +55,41 @@ config_change(Changed, New, Removed) ->
     ok = lists:foreach(fun({K, V}) -> config_changed(new, K, V) end, New).
 
 %%--------------------------------------------------------------------
+%% Other APIs
+
+%% XXX: this is ad-hoc helper function; it is simplified version of code from OTP application_controller.erl
+reload_config() ->
+    PreEnv = application:get_all_env(?APP),
+    NewConfig = read_sys_config(),
+    [application:set_env(?APP, K, V) || {K, V} <- NewConfig],
+    NewEnv = application:get_all_env(?APP),
+    %% TODO: "Removed" will always be empty; to handle it properly we should merge env
+    %% from .app file with NewConfig
+    {Changed, New, Removed} = diff_env(NewEnv, PreEnv),
+    ?log(info, "Updating config; changed=~p, new=~p, deleted=~p", [Changed, New, Removed]),
+    config_change(Changed, New, Removed).
+
+read_sys_config() ->
+    {ok, [[File]]} = init:get_argument(config),
+    {ok, [Data]} = file:consult(File),
+    proplists:get_value(?APP, Data, []).
+
+diff_env(NewEnv, OldEnv) ->
+    NewEnvMap = maps:from_list(NewEnv),
+    OldEnvMap = maps:from_list(OldEnv),
+    NewKeySet = ordsets:from_list(maps:keys(NewEnvMap)),
+    OldKeySet = ordsets:from_list(maps:keys(OldEnvMap)),
+    DelKeys = ordsets:subtract(OldKeySet, NewKeySet),
+    AddKeys = ordsets:subtract(NewKeySet, OldKeySet),
+    ChangedKeys =
+        lists:filter(
+          fun(K) ->
+                  maps:get(K, NewEnvMap) =/= maps:get(K, OldEnvMap)
+          end, ordsets:intersection(OldKeySet, NewKeySet)),
+    {[{K, maps:get(K, NewEnvMap)} || K <- ChangedKeys],
+     [{K, maps:get(K, NewEnvMap)} || K <- AddKeys],
+     DelKeys}.
+
 
 %% @doc List of ranch listeners running mtproto_proxy
 -spec mtp_listeners() -> [tuple()].
@@ -200,3 +241,21 @@ report(Fmt, Args) ->
     io:format(Fmt ++ "\n", Args),
     ?log(info, Fmt, Args).
 -endif.
+
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+
+env_diff_test() ->
+    Pre = [{a, 1},
+           {b, 2},
+           {c, 3}],
+    Post = [{b, 2},
+            {c, 4},
+            {d, 5}],
+    ?assertEqual(
+       {[{c, 4}],
+        [{d, 5}],
+        [a]},
+       diff_env(Post, Pre)).
+
+-endif.