add systemd notify support

cogs/systemd.py

@@ -0,0 +1,33 @@
+import asyncio
+import os
+import socket
+
+from discord.ext import commands
+
+from utils.socket import open_datagram_endpoint
+
+class SystemdNotifier(commands.Cog):
+	def __init__(self):
+		self.os_sock = socket.socket(family=socket.AF_UNIX, type=socket.SOCK_DGRAM)
+		self.connect_task = asyncio.create_task(self.connect())
+		self.addr = os.environ['NOTIFY_SOCKET']
+
+	def send(self, msg):
+		self.sock.send(msg, self.addr)
+
+	async def connect(self):
+		self.sock = await open_datagram_endpoint(sock=self.os_sock)
+
+	def cog_unload(self):
+		self.connect_task.cancel()
+
+	@commands.Cog.listener()
+	async def on_shard_ready(self, shard_id):
+		self.send(b'STATUS=Ready on shard %d' % shard_id)
+
+	@commands.Cog.listener()
+	async def on_ready(self):
+		self.send(b'READY=1')
+
+def setup(bot):
+	bot.add_cog(SystemdNotifier())