HACK: Librato measurement sender

librato.go

package main

import (
	"bytes"
	"encoding/json"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"regexp"
	"strings"
	"time"
)

type librato struct {
	http.Client
	prefix      string
	user, token string
	counters    chan libratoCounter
	gauges      chan interface{}
}

func libratoTelemetry(prefix, user, token string) *librato {
	p := new(librato)
	p.prefix = prefix
	p.user = user
	p.token = token
	p.counters = make(chan libratoCounter, 1000)
	p.gauges = make(chan interface{}, 1000)
	go p.processTelemetry()
	return p
}

func (p *librato) processTelemetry() {
	const dt = 5 * time.Second
	timer := time.NewTimer(dt)
	m := new(libratoMeasurements)
	for {
		if m.size() >= 300 {
			go p.post(m)
			m = new(libratoMeasurements)
			timer.Reset(dt)
		}
		select {
		case c := <-p.counters:
			m.Counters = append(m.Counters, c)
		case g := <-p.gauges:
			m.Gauges = append(m.Gauges, g)
		case <-timer.C:
			if m.size() > 0 {
				go p.post(m)
				m = new(libratoMeasurements)
			}
			timer.Reset(dt)
		}
	}
}

func (p *librato) post(m *libratoMeasurements) {
	b, err := json.Marshal(m)
	if err != nil {
		log.Print(err)
		return
	}
	req, err := http.NewRequest("POST", "https://metrics-api.librato.com/v1/metrics", bytes.NewBuffer(b))
	if err != nil {
		log.Print(err)
	}
	req.SetBasicAuth(p.user, p.token)
	req.Header.Set("Content-Type", "application/json")
	resp, err := p.Client.Do(req)
	if err != nil {
		log.Print(err)
	}
	if resp != nil {
		if resp.StatusCode >= 400 {
			log.Printf("Librato response: %s", resp.Status)
		}
		io.Copy(ioutil.Discard, resp.Body) // discard the response
		resp.Body.Close()
	}
}

func replacer(re, repl string) func(string) string {
	pattern := regexp.MustCompile(re)
	return func(s string) string {
		return pattern.ReplaceAllString(s, repl)
	}
}

var namePreps = []func(string) string{
	strings.ToLower,
	replacer(`[:=]\s*`, "."),           // "request: total" -> "request.total" or "foo=bar" -> "foo.bar"
	replacer(`\s+`, "-"),               // "foo bar   qaz" -> "foo-bar-qaz"
	replacer(`-(\d+[a-z\-_]*)`, ".$1"), // "load-avg-15m" -> "load-avg.15m"
	replacer(`\.+`, "."),               // "oops...what" -> "oops.what"
	replacer(`[^a-z0-9_\-\.]`, "_"),    // replace any weird chars with _
}

func (p *librato) prepName(s string) string {
	for _, f := range namePreps {
		s = f(s)
	}
	if p.prefix == "" {
		return s
	}
	return p.prefix + "." + s
}

type libratoCounter struct {
	Name   string `json:"name"`
	Value  int    `json:"value"`
	Time   int64  `json:"measure_time,omitempty"`
	Source string `json:"source,omitempty"`
}

type libratoGauge struct {
	Name   string      `json:"name"`
	Value  interface{} `json:"value"`
	Time   int64       `json:"measure_time,omitempty"`
	Source string      `json:"source,omitempty"`
}

type libratoGaugeSummary struct {
	Name       string  `json:"name"`
	Count      int     `json:"count"`
	Sum        float64 `json:"sum"`
	Max        float64 `json:"max"`
	Min        float64 `json:"min"`
	SumSquares float64 `json:"sum_squares"`
	Time       int64   `json:"measure_time,omitempty"`
	Source     string  `json:"source,omitempty"`
}

type libratoMeasurements struct {
	Time     int64            `json:"measure_time,omitempty"`
	Source   string           `json:"source,omitempty"`
	Counters []libratoCounter `json:"counters,omitempty"`
	Gauges   []interface{}    `json:"gauges,omitempty"`
}

func (p *libratoMeasurements) size() int { return len(p.Counters) + len(p.Gauges) }

func (p *librato) put(measurement interface{}) {
	switch m := measurement.(type) {
	case libratoCounter:
		p.counters <- m
	case libratoGauge, libratoGaugeSummary:
		p.gauges <- m
	}
}

func (p *librato) Value(value interface{}, name string) {
	switch value.(type) {
	case float32, float64,
		int, int8, int16, int32, int64,
		uint, uint8, uint16, uint32, uint64:
	default:
		return
	}
	p.put(libratoGauge{Name: p.prepName(name), Value: value, Time: time.Now().Unix()})
}

func (p *librato) Count(value int, name string) {
	p.put(libratoCounter{Name: p.prepName(name), Value: value, Time: time.Now().Unix()})
}