Merge pull request #2957 from rabbitmq/notify-systemd-using-erlang-systemd

Systemd: Use erlang-systemd to notify systemd of service status

Author: michaelklishin

deps/rabbit/Makefile

@@ -146,7 +146,7 @@ PLT_APPS += mnesia
 dep_syslog = git https://github.com/schlagert/syslog 4.0.0
 dep_osiris = git https://github.com/rabbitmq/osiris master
 # TODO: Use systemd from Hex.pm, once there is a new post-0.6.0 release.
-dep_systemd = git https://github.com/hauleth/erlang-systemd 0ce748edffcb72bb028733e9ca4707cb30add853
+dep_systemd = git https://github.com/hauleth/erlang-systemd e732727b0b637eb29e8adc77a4eb46d7ebc0f41a
 
 define usage_xml_to_erl
 $(subst __,_,$(patsubst $(DOCS_DIR)/rabbitmq%.1.xml, src/rabbit_%_usage.erl, $(subst -,_,$(1))))

deps/rabbit/apps/rabbitmq_prelaunch/src/rabbit_boot_state_systemd.erl

@@ -21,42 +21,20 @@
          terminate/2,
          code_change/3]).
 
--record(state, {mechanism,
-                sd_notify_module,
-                socket}).
-
 -define(LOG_PREFIX, "Boot state/systemd: ").
 
 start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
 
 init([]) ->
-    case os:type() of
-        {unix, _} ->
-            case code:load_file(sd_notify) of
-                {module, sd_notify} ->
-                    {ok, #state{mechanism = legacy,
-                                sd_notify_module = sd_notify}};
-                {error, _} ->
-                    case os:getenv("NOTIFY_SOCKET") of
-                        false ->
-                            ignore;
-                        "" ->
-                            ignore;
-                        Socket ->
-                            {ok, #state{mechanism = socat,
-                                        socket = Socket}}
-                    end
-            end;
-        _ ->
-            ignore
-    end.
+    {ok, _} = application:ensure_all_started(systemd),
+    {ok, #{}}.
 
 handle_call(_Request, _From, State) ->
     {noreply, State}.
 
 handle_cast({notify_boot_state, BootState}, State) ->
-    notify_boot_state(BootState, State),
+    _ = notify_boot_state(BootState),
     {noreply, State}.
 
 terminate(normal, _State) ->
@@ -65,124 +43,33 @@ terminate(normal, _State) ->
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
 
-%%% Private
+%% Private
 
-notify_boot_state(ready = BootState,
-                  #state{mechanism = legacy, sd_notify_module = SDNotify}) ->
-    ?LOG_DEBUG(
-      ?LOG_PREFIX "notifying of state `~s` (via native module)",
-      [BootState],
-      #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
-    sd_notify_legacy(SDNotify);
-notify_boot_state(ready = BootState,
-                  #state{mechanism = socat, socket = Socket}) ->
+notify_boot_state(BootState)
+  when BootState =:= ready orelse BootState =:= stopping ->
+    Status = boot_state_to_desc(BootState),
     ?LOG_DEBUG(
-      ?LOG_PREFIX "notifying of state `~s` (via socat(1))",
-      [BootState],
-      #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
-    sd_notify_socat(Socket);
-notify_boot_state(BootState, _) ->
-    ?LOG_DEBUG(
-      ?LOG_PREFIX "ignoring state `~s`",
-      [BootState],
-      #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
-    ok.
-
-sd_notify_message() ->
-    "READY=1\nSTATUS=Initialized\nMAINPID=" ++ os:getpid() ++ "\n".
-
-sd_notify_legacy(SDNotify) ->
-    SDNotify:sd_notify(0, sd_notify_message()).
-
-%% socat(1) is the most portable way the sd_notify could be
-%% implemented in erlang, without introducing some NIF. Currently the
-%% following issues prevent us from implementing it in a more
-%% reasonable way:
-%% - systemd-notify(1) is unstable for non-root users
-%% - erlang doesn't support unix domain sockets.
-%%
-%% Some details on how we ended with such a solution:
-%%   https://github.com/rabbitmq/rabbitmq-server/issues/664
-sd_notify_socat(Socket) ->
-    case sd_current_unit() of
-        {ok, Unit} ->
-            ?LOG_DEBUG(
-              ?LOG_PREFIX "systemd unit for activation check: \"~s\"",
-              [Unit],
-              #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
-            sd_notify_socat(Socket, Unit);
-        _ ->
-            ok
-    end.
-
-sd_notify_socat(Socket, Unit) ->
-    try sd_open_port(Socket) of
-        Port ->
-            Port ! {self(), {command, sd_notify_message()}},
-            Result = sd_wait_activation(Port, Unit),
-            port_close(Port),
-            Result
-    catch
-        Class:Reason ->
-            ?LOG_DEBUG(
-              ?LOG_PREFIX "Failed to start socat(1): ~p:~p",
-              [Class, Reason],
-              #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
-            false
-    end.
-
-sd_current_unit() ->
-    CmdOut = os:cmd("ps -o unit= -p " ++ os:getpid()),
-    Ret = (catch re:run(CmdOut,
-                        "([-.@0-9a-zA-Z]+)",
-                        [unicode, {capture, all_but_first, list}])),
-    case Ret of
-        {'EXIT', _}     -> error;
-        {match, [Unit]} -> {ok, Unit};
-        _               -> error
-    end.
-
-socat_socket_arg("@" ++ AbstractUnixSocket) ->
-    "abstract-sendto:" ++ AbstractUnixSocket;
-socat_socket_arg(UnixSocket) ->
-    "unix-sendto:" ++ UnixSocket.
-
-sd_open_port(Socket) ->
-    open_port(
-        {spawn_executable, os:find_executable("socat")},
-        [{args, [socat_socket_arg(Socket), "STDIO"]},
-            use_stdio, out]).
-
-sd_wait_activation(Port, Unit) ->
-    case os:find_executable("systemctl") of
-        false ->
-            ?LOG_DEBUG(
-              ?LOG_PREFIX "systemctl(1) unavailable, falling back to sleep",
-              [],
-              #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
-            timer:sleep(5000),
-            ok;
-        _ ->
-            sd_wait_activation(Port, Unit, 10)
-    end.
-
-sd_wait_activation(_, _, 0) ->
+       ?LOG_PREFIX "notifying of state `~s`",
+       [BootState],
+       #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
+    systemd:notify([BootState, {status, Status}]);
+notify_boot_state(BootState) ->
+    Status = boot_state_to_desc(BootState),
     ?LOG_DEBUG(
-      ?LOG_PREFIX "service still in 'activating' state, bailing out",
-      [],
-      #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
-    ok;
-sd_wait_activation(Port, Unit, AttemptsLeft) ->
-    Ret = os:cmd("systemctl show --property=ActiveState -- '" ++ Unit ++ "'"),
-    case Ret of
-        "ActiveState=activating\n" ->
-            timer:sleep(1000),
-            sd_wait_activation(Port, Unit, AttemptsLeft - 1);
-        "ActiveState=" ++ _ ->
-            ok;
-        _ = Err ->
-            ?LOG_DEBUG(
-              ?LOG_PREFIX "unexpected status from systemd: ~p", [Err],
-              #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
-            ok
-    end.
+       ?LOG_PREFIX "sending non-systemd state (~s) as status description: ~s",
+       [BootState, Status],
+       #{domain => ?RMQLOG_DOMAIN_PRELAUNCH}),
+    systemd:notify({status, Status}).
+
+boot_state_to_desc(stopped) ->
+    "";
+boot_state_to_desc(booting) ->
+    "Startup in progress";
+boot_state_to_desc(core_started) ->
+    "Startup in progress (core ready, starting plugins)";
+boot_state_to_desc(ready) ->
+    "";
+boot_state_to_desc(stopping) ->
+    "";
+boot_state_to_desc(BootState) ->
+    atom_to_list(BootState).