3 files changed, 192 insertions, 0 deletions
diff --git a/modules/graphite/README.rst b/modules/graphite/README.rst
new file mode 100644
index 0000000..06efd82
--- /dev/null
+++ b/modules/graphite/README.rst
@@ -0,0 +1,49 @@
+.. _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 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.
+
+By default the module uses UDP so it doesn't guarantee the delivery, set ``tcp = true`` to enable Graphite over TCP. If the TCP consumer goes down or the connection with Graphite is lost, resolver will periodically attempt to reconnect with it.
+
+.. 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
+			tcp = false          -- set to true if want TCP mode
+		}
+	}
+
+The module supports 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 luasocket``
+
+.. _Graphite: https://graphite.readthedocs.io/en/latest/feeding-carbon.html
+.. _InfluxDB: https://influxdb.com/
+.. _Metronome: https://github.com/ahuPowerDNS/metronome
+.. _Grafana: http://grafana.org/
diff --git a/modules/graphite/graphite.lua b/modules/graphite/graphite.lua
new file mode 100644
index 0000000..bbf735a
--- /dev/null
+++ b/modules/graphite/graphite.lua
@@ -0,0 +1,141 @@
+-- Load dependent modules
+if not stats then modules.load('stats') end
+
+-- This is leader-only module
+if worker.id > 0 then return {} end
+local M = {}
+local socket = require('socket')
+
+-- Create connected UDP socket
+local function make_udp(host, port)
+	local s, err, status
+	if host:find(':') then
+		s, err = socket.udp6()
+	else
+		s, err = socket.udp()
+	end
+	if not s then
+		return nil, err
+	end
+	status, err = s:setpeername(host, port)
+	if not status then
+		return nil, err
+	end
+	return s
+end
+
+-- Create connected TCP socket
+local function make_tcp(host, port)
+	local s, err, status
+	if host:find(':') then
+		s, err = socket.tcp6()
+	else
+		s, err = socket.tcp()
+	end
+	if not s then
+		return nil, err
+	end
+	status, err = s:connect(host, port)
+	if not status then
+		return s, err
+	end
+	return s
+end
+
+local function merge(results)
+	local t = {}
+	for _, result in ipairs(results) do
+		for k, v in pairs(result) do
+			t[k] = (t[k] or 0) + v
+		end
+	end
+	return t
+end
+
+-- Send the metrics in a table to multiple Graphite consumers
+local function publish_table(metrics, prefix, now)
+	for key,val in pairs(metrics) do
+		local msg = key..' '..val..' '..now..'\n'
+		if prefix then
+			msg = prefix..'.'..msg
+		end
+		for i in ipairs(M.cli) do
+			local ok, err = M.cli[i]:send(msg)
+			if not ok then
+				-- Best-effort reconnect once per two tries
+				local tcp = M.cli[i]['connect'] ~= nil
+				local host = M.info[i]
+				if tcp and host.seen + 2 * M.interval / 1000 <= now then
+					print(string.format('[graphite] reconnecting: %s@%d reason: %s',
+						  host.addr, host.port, err))
+					M.cli[i] = make_tcp(host.addr, host.port)
+					host.seen = now
+				end
+			end
+		end
+	end
+end
+
+function M.init()
+	M.ev = nil
+	M.cli = {}
+	M.info = {}
+	M.interval = 5 * sec
+	M.prefix = 'kresd.' .. hostname()
+	return 0
+end
+
+function M.deinit()
+	if M.ev then event.cancel(M.ev) end
+	return 0
+end
+
+-- @function Publish results to the Graphite server(s)
+function M.publish()
+	local now = os.time()
+	-- Publish built-in statistics
+	if not M.cli then error("no graphite server configured") end
+	publish_table(merge(map 'cache.stats()'), M.prefix..'.cache', now)
+	publish_table(merge(map 'worker.stats()'), M.prefix..'.worker', now)
+	-- Publish extended statistics if available
+	publish_table(merge(map 'stats.list()'), M.prefix, now)
+	return 0
+end
+
+-- @function Make connection to Graphite server.
+function M.add_server(_, host, port, tcp)
+	local s, err
+	if tcp then
+		s, err = make_tcp(host, port)
+	else
+		s, err = make_udp(host, port)
+	end
+	if not s then
+		error(err)
+	end
+	table.insert(M.cli, s)
+	table.insert(M.info, {addr = host, port = port, seen = 0})
+	return 0
+end
+
+function M.config(conf)
+	-- config defaults
+	if not conf then return 0 end
+	if not conf.port then conf.port = 2003 end
+	if conf.interval then M.interval = conf.interval end
+	if conf.prefix then M.prefix = conf.prefix end
+	-- connect to host(s)
+	if type(conf.host) == 'table' then
+		for _, val in pairs(conf.host) do
+			M:add_server(val, conf.port, conf.tcp)
+		end
+	else
+		M:add_server(conf.host, conf.port, conf.tcp)
+	end
+	-- start publishing stats
+	if M.ev then event.cancel(M.ev) end
+	M.ev = event.recurrent(M.interval, M.publish)
+	return 0
+end
+
+return M
diff --git a/modules/graphite/graphite.mk b/modules/graphite/graphite.mk
new file mode 100644
index 0000000..615f8be
--- /dev/null
+++ b/modules/graphite/graphite.mk
@@ -0,0 +1,2 @@
+graphite_SOURCES := graphite.lua
+$(call make_lua_module,graphite)