statsd interface for nginx (via ngx_lua)

statsd.lua

-- ----------------------------------------------------------------------------
-- statsd interface for nginx
-- (c) 2014 Anton Tolchanov
-- https://gist.github.com/knyar/8905045
--
-- Usage:
-- 1. install nginx with ngx_lua;
-- 2. put this file as statsd.lua somewhere (/var/lib/nginx/lua/ will do);
-- 3. initialize stats in init_by_lua:
--   http {
--    ...
--    lua_package_path "/var/lib/nginx/lua/?.lua";
--    init_by_lua 'statsd = require("statsd")';
--    ...
--   }
-- 4. send data to statsd from log_by_lua:
--   server {
--    ...
--    log_by_lua '
--     statsd.log(
--      statsd.incr("nginx.site01.status." .. ngx.var.status),
--      statsd.time("nginx.site01.req_time", ngx.now() - ngx.req.start_time())
--     )
--    ';
--   }
--
-- See http://wiki.nginx.org/HttpLuaModule for more information about ngx_lua
-- ----------------------------------------------------------------------------
local Statsd = {}

Statsd.time = function (counter, n) return counter .. ":" .. n .. "|ms" end
Statsd.count = function (counter, n) return counter .. ":" .. n .. "|c" end
Statsd.incr = function (counter) return Statsd.count(counter, 1) end

Statsd.send = function (premature, metrics)
    local udp = ngx.socket.udp()
    udp:setpeername("127.0.0.1", 8125)
    udp:send(metrics)
    udp:close()
end

Statsd.log = function (...)
    -- This function will be run from log_by_lua where socket operations are
    -- not available. A work-around is to schedule a nginx timer to run
    -- Statsd.send() for us. `arg` contains all parameters to this function.
    local ok, err = ngx.timer.at(0, Statsd.send, table.concat(arg, "\n"))
    if not ok then
        ngx.log(ngx.ERR, "cannot create timer: ", err)
    end
end

return Statsd