modules/graphite: push metrics to graphite server(s)

modules/graphite/README.rst

+.. _mod-graphite:
+
+Graphite module
+---------------
+
+The module sends statistics over the Graphite_ protocol to either Graphite_, Metronome_, InfluxDB_ or any compatible storage. This allows powerful visualization over metrics collected by Knot DNS Resolver. 
+
+.. tip:: The Graphite server is challenging to get up and running, InfluxDB_ combined with Grafana_ are much easier, and provide richer set of options and available front-ends. Metronome_ by PowerDNS alternatively provides a mini-graphite server for much simpler setups.
+
+Example configuration
+^^^^^^^^^^^^^^^^^^^^^
+
+Only the ``host`` parameter is mandatory.
+
+.. warning:: It uses UDP so it doesn't guarantee the delivery, make sure the target server supports UDP.
+
+.. code-block:: lua
+
+	modules = {
+		graphite = {
+			prefix = hostname(), -- optional metric prefix
+			host = '127.0.0.1',  -- graphite server address
+			port = 2003,         -- graphite server port
+			interval = 5 * sec   -- publish interval
+		}
+	}
+
+The module support sending data to multiple servers at once.
+
+.. code-block:: lua
+
+	modules = {
+		graphite = {
+			host = { '127.0.0.1', '1.2.3.4', '::1' },
+		}
+	}
+
+Dependencies
+^^^^^^^^^^^^
+
+* `luasocket <http://w3.impa.br/~diego/software/luasocket/>`_ available in LuaRocks
+
+    ``$ luarocks install socket``
+
+.. _Graphite: http://graphite.readthedocs.org/en/latest/feeding-carbon.html
+.. _InfluxDB: http://influxdb.com/
+.. _Metronome: https://github.com/ahuPowerDNS/metronome
+.. _Grafana: http://grafana.org/
\ No newline at end of file

modules/graphite/graphite.lua

+--- @module graphite
+local graphite = {}
+
+function graphite.init(module)
+	graphite.socket = require('socket')
+	graphite.ev = nil
+	graphite.cli = {}
+	graphite.prefix = nil
+	return 0
+end
+
+function graphite.deinit(module)
+	if graphite.ev then event.cancel(graphite.ev) end
+	return 0
+end
+
+-- @function Publish results to the Graphite server(s)
+function graphite.publish()
+	local now = os.time()
+	if not graphite.cli then error("no graphite server configured") end
+	local now_metrics = stats.list()
+	if type(now_metrics) ~= 'table' then
+		return 0 -- No metrics to watch
+	end
+	for key,val in pairs(now_metrics) do
+		for i in pairs(graphite.cli) do
+			msg = key..' '..val..' '..now..'\n'
+			if graphite.prefix then
+				msg = prefix..'.'..msg
+			end
+			graphite.cli[i]:send(msg)
+		end
+	end
+	return 0
+end
+
+-- @function Make connection to Graphite server.
+function graphite.add_server(graphite, host, port)
+	local cli, err, status
+	if host:find(':') then
+		cli, err = graphite.socket.udp6()
+	else
+		cli, err = graphite.socket.udp()
+	end
+	if not cli then
+		error(err)
+	end
+	status, err = cli:setpeername(host, port)
+	if not status then
+		error(err)
+	end
+	table.insert(graphite.cli, cli)
+	return 0
+end
+
+function graphite.config(conf)
+	-- config defaults
+	if not conf.port then conf.port = 2003 end
+	if not conf.interval then conf.interval = 5 * sec end
+	if conf.prefix then graphite.prefix = conf.prefix end
+	-- connect to host(s)
+	if type(conf.host) == 'table' then
+		for key, val in pairs(conf.host) do
+			graphite:add_server(val, conf.port)
+		end
+	else
+		graphite:add_server(conf.host, conf.port)
+	end
+	-- start publishing stats
+	if graphite.ev then event.cancel(graphite.ev) end
+	graphite.ev = event.recurrent(conf.interval, graphite.publish)
+	return 0
+end
+
+return graphite

modules/graphite/graphite.mk

+graphite_SOURCES := graphite.lua
+$(call make_lua_module,graphite)

modules/modules.mk

@@ -5,7 +5,8 @@ modules_TARGETS := hints \
 
 # List of Lua modules
 ifeq ($(HAS_lua),yes)
-modules_TARGETS += ketcd 
+modules_TARGETS += ketcd \
+                   graphite
 endif
 
 # List of Golang modules