packages/utils/prometheus-node-exporter-lua/files/usr/bin/prometheus-node-exporter-lua

#!/usr/bin/lua

-- Metrics web server

-- Copyright (c) 2016 Jeff Schornick <jeff@schornick.org>
-- Copyright (c) 2015 Kevin Lyda <kevin@lyda.ie>
-- Licensed under the Apache License, Version 2.0

socket = require("socket")

-- Parsing

function space_split(s)
  local elements = {}
  for element in s:gmatch("%S+") do
    table.insert(elements, element)
  end
  return elements
end

function get_contents(filename)
  local f = io.open(filename, "rb")
  local contents = ""
  if f then
    contents = f:read "*a"
    f:close()
  end

  return contents
end

-- Metric printing

function print_metric(metric, labels, value)
  if type(value) == "nil" then
    return
  end
  out:write(metric)
  if labels then
    out:write("{")
    coma = ""
    for label,value in pairs(labels) do
      out:write(coma, label, '="', value, '"')
      coma = ","
    end
    out:write("}")
  end
  out:write(" ", value, "\n")
end

function metric(name, mtype, labels, value)
  out:write("# TYPE ", name, " ", mtype, "\n")
  local outputter = function(labels, value)
    print_metric(name, labels, value)
  end
  if value then
    outputter(labels, value)
  end
  return outputter
end

function timed_scrape(collector)
  local start_time = socket.gettime()
  local success = 1
  local status, err = pcall(collector.scrape)
  if not status then
    success = 0
    io.stderr:write(err .. '\n')
  end
  return (socket.gettime() - start_time), success
end

function run_all_collectors(collectors)
  local metric_duration = metric("node_scrape_collector_duration_seconds", "gauge")
  local metric_success = metric("node_scrape_collector_success", "gauge")
  for _,cname in pairs(collectors) do
    if col_mods[cname] ~= nil then
      local duration, success = timed_scrape(col_mods[cname])
      local labels = {collector=cname}
      metric_duration(labels, duration)
      metric_success(labels, success)
    end
  end
end

-- Web server-specific functions

function handle_request(env)
  -- use buffered output instead uhttpd.send()
  out = io.open("/proc/self/fd/1", "a+")
  out:setvbuf("full")
  if env.PATH_INFO ~= '/metrics' then
    out:write("Status: 404 Not Found\r\n")
    out:write("Server: lua-metrics\r\n")
    out:write("Content-Type: text/plain\r\n\r\n")
    out:write("ERROR: File Not Found.")
  else
    out:write("Status: 200 OK\r\n")
    out:write("Server: lua-metrics\r\n")
    out:write("Content-Type: text/plain; version=0.0.4\r\n\r\n")
    local cols = {}
    for c in env.QUERY_STRING:gmatch("collect[^=]*=([^&]+)") do
      cols[#cols+1] = c
    end
    if #cols == 0 then
      cols = col_names
    end
    run_all_collectors(cols)
  end
  out:flush()
end

-- Main program

col_mods = {}
col_names = {}
ls_fd = io.popen("ls -1 /usr/lib/lua/prometheus-collectors/*.lua")
for c in ls_fd:lines() do
  c = c:match("([^/]+)%.lua$")
  col_mods[c] = require('prometheus-collectors.'..c)
  col_names[#col_names+1] = c
end
ls_fd:close()

if arg ~= nil then
  out = io.output()
  run_all_collectors(col_names)
end