Name

lua-telegraf - Lua/LuaJIT/OpenResty client writer for Telegraf/InfluxDB or any listener compatible with InfluxDB Line Protocol.

Table of Contents

• Name
• Status
• Description
• Installation
• Synopsis
  • OpenResty
  • Lua
• Methods
  • new
  • set
  • flush
• TODO
• Author
• Copyright and License

Status

This library is considered production ready.

Description

This library implements writer interface for InfluxDB line protocol. Focus is on simplicity and efficiency. Depending on runtime it will find most suitable backend/library for constructing and writing metrics.

When run in context of OpenResty it will use cosocket API, which ensures 100% nonblocking behavior, and nginx time primitives for fetching cached time (no syscall involved). Support for Lua, LuaJIT and nanosecond precision is covered by ljsyscall library.

Installation

Clone into your Lua module path or use opm:

  $ opm get lblasc/lua-telegraf

Synopsis

OpenResty

Simple (no batching)

# you do not need the following line if you installed
# module with `opm`
lua_package_path "/path/to/lua-telegraf/?.lua;;";

http {
  server {
    access_by_lua_block {
      local telegraf = require "telegraf"

      local t = telegraf.new({
        host = "127.0.0.1",
        port = 8094,
        global_tags = {
          gtag  = 1,
        },
      })

      local ok, err = t:set('test', {field = 123}, {tag = 'tagged'})
      if not ok then
        ngx.say(err)
      end
    }
  }
}

Batching

Create simple module (E.g. stats.lua) witch will use lua module caching to preserve lua-telegraf instance and make it available in all phases.

local telegraf = require 'telegraf'
local t

local _M = {}

function _M.init(conf)
  t = telegraf.new(conf)
  return t
end

function _M.get()
  assert(t)
  return t
end

return _M

lua_package_path "/path/to/stats/module/?.lua;;";

http {
  init_worker_by_lua_block {
    local function flush_stats(premature)
      if premature then
        return
      end

      local t = require('stats').get()
      t:flush()
    end

    local flush_every = 1 -- adjust flush interval (in seconds)
    require("stats").init({
      host = "127.0.0.1",
      port = 8094,
      batch_size = 20,
      global_tags = {
        gtag  = 1,
      },
    })

    local ok, err = ngx.timer.every(flush_every, flush_stats)
    if not ok then
      ngx.log(ngx.ERR, err)
      return
    end
  }

  server {
    access_by_lua_block {
      local t = require("stats").get()

      t:set('test', {field = 123}, {tag = 'tagged'})
    }

    log_by_lua_block {
      local t = require("stats").get()

      t:set('nginx_stats', {
        request_time = ngx.now() - ngx.req.start_time()
      }, {tag = 'mytag'})
    }
  }
}

Lua

local telegraf = require "telegraf"

local t = telegraf.new({
  host = "127.0.0.1",
  port = 8094,
  global_tags = {
    gtag  = 1,
  },
})

local ok, err = t:set('test', {field = 123}, {tag = 'tagged'})
if not ok then
  error(err)
end

Methods

new

syntax: t, err = telegraf.new(options?)

Creates telegraf instance with optional options table.

options

host

Default: 127.0.0.1

Sets the host address.

port

Default: 8094

Sets the host port.

proto

Default: udp

Sets the protocol, for now only supported is udp.

precision

Default: nil

Sets the timestamp precision. Currently, s, ms, u, and ns are supported, when precision is nil (default) no timestamp will be sent as part of the line protocol message, and the remote server will set timestamp based on the server-local clock.

global_tags

Default: {}

Tags that will be added to every metric. Field needs to be defined in set of tag/value pairs.

batch_size

Default: nil

Preallocates batch buffer by specified size and enables batching. Batch buffer is table which will exceed buffer size if not flushed in time, flushing is manual operation. By default (nil) batching is disabled and all metrics will be sent immediately.

set

syntax: ok, err = t:set(measurement, fields, tags?, timestamp?)

Generates new data point, depending on options, data point is pushed to a buffer or sent immediately.

• measurement: string denoting the measurement of the data point
• fields: table of key-value pairs denoting the field elements
• tags (optional): table of key-value pairs denoting the tag elements
• timestamp (optional): number which overrides generated or sets timestamp with time provided in UNIX time format

flush

syntax: t:flush()

Flushes batch buffer. If buffer is empty or not enabled method just returns.

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TODO

• http support

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Author

Luka Blašković lblasc@znode.net

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Copyright and License

See LICENSE

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