modules/graphite: support for Graphite/TCP

graphite module now supports sending over TCP,
if the connection is severed it will attempt to
reconnect periodically. the stats module is now
optional, if not loaded only core built-in stats
will be transmitted

modules/graphite/README.rst

@@ -12,7 +12,7 @@ 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.
+.. info:: 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
 
@@ -21,7 +21,8 @@ Only the ``host`` parameter is mandatory.
 			prefix = hostname(), -- optional metric prefix
 			host = '127.0.0.1',  -- graphite server address
 			port = 2003,         -- graphite server port
-			interval = 5 * sec   -- publish interval
+			interval = 5 * sec,  -- publish interval
+			tcp = false          -- set to true if want TCP mode
 		}
 	}
 

modules/graphite/graphite.lua

 --- @module graphite
 local graphite = {}
+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
+
+-- 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(graphite.cli) do
+			local ok, err = graphite.cli[i]:send(msg)
+			if not ok then
+				-- Best-effort reconnect once per two tries
+				local tcp = graphite.cli[i]['connect'] ~= nil
+				local host = graphite.info[i]
+				if tcp and host.seen + 2 * graphite.interval / 1000 <= now then
+					print(string.format('[graphite] reconnecting: %s#%d reason: %s',
+						  host.addr, host.port, err))
+					graphite.cli[i] = make_tcp(host.addr, host.port)
+					host.seen = now
+				end
+			end
+		end
+	end
+end
 
 function graphite.init(module)
-	graphite.socket = require('socket')
 	graphite.ev = nil
 	graphite.cli = {}
-	graphite.prefix = nil
+	graphite.info = {}
+	graphite.interval = 5 * sec
+	graphite.prefix = 'kresd.' .. hostname()
 	return 0
 end
 
@@ -17,44 +79,30 @@ end
 -- @function Publish results to the Graphite server(s)
 function graphite.publish()
 	local now = os.time()
+	-- Publish built-in statistics
 	if not graphite.cli then error("no graphite server configured") end
+	publish_table(cache.stats(), graphite.prefix..'.cache', now)
+	publish_table(worker.stats(), graphite.prefix..'.worker', now)
+	-- Publish extended statistics if available
+	if not stats then
+		return 0
+	end
 	local now_metrics = stats.list()
 	if type(now_metrics) ~= 'table' then
 		return 0 -- No metrics to watch
 	end
-	local function publish_table(metrics, prefix)
-		for key,val in pairs(metrics) do
-			local msg = key..' '..val..' '..now..'\n'
-			if prefix then
-				msg = prefix..'.'..msg
-			end
-			for i in ipairs(graphite.cli) do
-				graphite.cli[i]:send(msg)
-			end
-		end
-	end
-	publish_table(now_metrics, graphite.prefix)
-	publish_table(cache.stats(), graphite.prefix..'.cache')
-	publish_table(worker.stats(), graphite.prefix..'.worker')
+	publish_table(now_metrics, graphite.prefix, now)
 	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
+function graphite.add_server(graphite, host, port, tcp)
+	local s, err = tcp and make_tcp(host, port) or make_udp(host, port)
+	if not s then
 		error(err)
 	end
-	table.insert(graphite.cli, cli)
+	table.insert(graphite.cli, s)
+	table.insert(graphite.info, {addr = host, port = port, seen = 0})
 	return 0
 end
 
@@ -62,19 +110,19 @@ function graphite.config(conf)
 	-- config defaults
 	if not conf then return 0 end
 	if not conf.port then conf.port = 2003 end
-	if not conf.interval then conf.interval = 5 * sec end
+	if conf.interval then graphite.interval = conf.interval 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)
+			graphite:add_server(val, conf.port, conf.tcp)
 		end
 	else
-		graphite:add_server(conf.host, conf.port)
+		graphite:add_server(conf.host, conf.port, conf.tcp)
 	end
 	-- start publishing stats
 	if graphite.ev then event.cancel(graphite.ev) end
-	graphite.ev = event.recurrent(conf.interval, graphite.publish)
+	graphite.ev = event.recurrent(graphite.interval, graphite.publish)
 	return 0
 end