From 0528181ea4ea54e4db21b6ddccf78d7287e57e85 Mon Sep 17 00:00:00 2001
From: Peter Lemenkov <lemenkov@gmail.com>
Date: Tue, 7 Jul 2020 13:43:32 +0200
Subject: Add API proposed by Max Lapshin

Signed-off-by: Peter Lemenkov <lemenkov@gmail.com>
---
 src/sd_notify.erl       | 38 ++++++++++++++++++++++++++++++++++++++
 test/sd_notify_test.erl | 24 ++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/src/sd_notify.erl b/src/sd_notify.erl
index 72f1324..c0bb824 100644
--- a/src/sd_notify.erl
+++ b/src/sd_notify.erl
@@ -29,6 +29,44 @@
 
 -export([sd_notify/2, sd_notifyf/3, sd_pid_notify/3, sd_pid_notifyf/4, sd_pid_notify_with_fds/4]).
 
+-export([ready/0, reloading/0, stopping/0, watchdog/0]).
+-export([start_link/0]).
+-export([init/1, handle_info/2, terminate/2]).
+
+% API helpers
+
+ready() -> sd_pid_notify_with_fds(0, false, <<"READY=1">>, []).
+reloading() -> sd_pid_notify_with_fds(0, false, <<"RELOADING=1">>, []).
+stopping() -> sd_pid_notify_with_fds(0, false, <<"STOPPING=1">>, []).
+watchdog() -> sd_pid_notify_with_fds(0, false, <<"WATCHDOG=1">>, []).
+
+% gen_server API and callbacks
+
+start_link() ->
+	gen_server:start_link({local,?MODULE}, ?MODULE, [], []).
+
+init([]) ->
+	WatchdogMs = case os:getenv( "WATCHDOG_USEC" ) of
+		false -> none;
+		Value ->
+			Part = erlang:round(0.8 * erlang:list_to_integer(Value)),
+			erlang:convert_time_unit(Part, microsecond, millisecond)
+	end,
+	erlang:send_after(WatchdogMs, self(), watchdog),
+	error_logger:info_msg("watchdog: ~p ms", [WatchdogMs]),
+	{ok, WatchdogMs}.
+
+handle_info(watchdog, none) ->
+	{noreply, none};
+handle_info(watchdog, WatchdogMs) ->
+	watchdog(),
+	erlang:send_after(WatchdogMs, self(), watchdog),
+	{noreply, WatchdogMs}.
+
+terminate(_,_) -> ok.
+
+% Systemd API
+
 sd_notify(UnsetEnv, Data) ->
 	sd_pid_notify_with_fds(0, UnsetEnv, Data, []).
 
diff --git a/test/sd_notify_test.erl b/test/sd_notify_test.erl
index 21a9f9d..59df682 100644
--- a/test/sd_notify_test.erl
+++ b/test/sd_notify_test.erl
@@ -50,3 +50,27 @@ sd_notify_unsetenv_test_() ->
 		]
 
 	}.
+
+sd_notify_watchdog_test_() ->
+	{ok, CWD} = file:get_cwd(),
+	FakeNotifyUnixSockName = CWD ++ "/fake-sock-" ++ integer_to_list(erlang:phash2(make_ref())),
+	{ok, FakeNotifyUnixSock} = gen_udp:open(0, [{ifaddr, {local, FakeNotifyUnixSockName}}, {active, false}, list]),
+	os:putenv("NOTIFY_SOCKET", FakeNotifyUnixSockName),
+
+	{setup,
+		fun() -> ok end,
+		fun(_) -> ok = gen_udp:close(FakeNotifyUnixSock), ok = file:delete(FakeNotifyUnixSockName)  end,
+		[
+			{
+				"Try sending message",
+				fun() ->
+					os:putenv("WATCHDOG_USEC", "500000"),
+					sd_notify:start_link(),
+					{ok, {_Address, _Port, Packet}} = gen_udp:recv(FakeNotifyUnixSock, length("WATCHDOG=1"), 1000),
+					?assertEqual("WATCHDOG=1", Packet)
+				end
+			}
+
+		]
+
+	}.
-- 
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