http.go

// Copyright (c) 2014 Ashley Jeffs
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, sub to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package metrics

import (
	"errors"
	"fmt"
	"net/http"
	"runtime"
	"sync"
	"time"

	"github.com/Jeffail/gabs"
)

//------------------------------------------------------------------------------

func init() {
	constructors["http_server"] = typeSpec{
		constructor: NewHTTP,
		description: `
Benthos can host its own stats endpoint, where a GET request will receive a JSON
blob of all metrics tracked within Benthos.`,
	}
}

//------------------------------------------------------------------------------

// Errors for the HTTP type.
var (
	ErrTimedOut = errors.New("timed out")
)

//------------------------------------------------------------------------------

// HTTP is an object with capability to hold internal stats as a JSON endpoint.
type HTTP struct {
	jsonRoot    *gabs.Container
	json        *gabs.Container
	flatMetrics map[string]int64
	pathPrefix  string
	timestamp   time.Time

	sync.Mutex
}

// NewHTTP creates and returns a new HTTP object.
func NewHTTP(config Config) (Type, error) {
	var jsonRoot, json *gabs.Container
	var pathPrefix string

	jsonRoot = gabs.New()
	if len(config.Prefix) > 0 {
		pathPrefix = config.Prefix + "."
		json, _ = jsonRoot.ObjectP(config.Prefix)
	} else {
		json = jsonRoot
	}

	t := &HTTP{
		jsonRoot:    jsonRoot,
		json:        json,
		flatMetrics: map[string]int64{},
		pathPrefix:  pathPrefix,
		timestamp:   time.Now(),
	}

	return t, nil
}

//------------------------------------------------------------------------------

// HandlerFunc returns an http.HandlerFunc for accessing metrics as a JSON blob.
func (h *HTTP) HandlerFunc() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		uptime := time.Since(h.timestamp).String()
		goroutines := runtime.NumGoroutine()

		h.Lock()

		h.json.SetP(fmt.Sprintf("%v", uptime), "uptime")
		h.json.SetP(goroutines, "goroutines")
		blob := h.jsonRoot.Bytes()

		h.Unlock()

		w.Header().Set("Content-Type", "application/json")
		w.Write(blob)
	}
}

// Incr increments a stat by a value.
func (h *HTTP) Incr(stat string, value int64) error {
	h.Lock()
	total, _ := h.flatMetrics[stat]
	total += value

	h.flatMetrics[stat] = total
	h.json.SetP(total, stat)
	h.Unlock()
	return nil
}

// Decr decrements a stat by a value.
func (h *HTTP) Decr(stat string, value int64) error {
	h.Lock()
	total, _ := h.flatMetrics[stat]
	total -= value

	h.flatMetrics[stat] = total
	h.json.SetP(total, stat)
	h.Unlock()
	return nil
}

// Timing sets a stat representing a duration.
func (h *HTTP) Timing(stat string, delta int64) error {
	readable := time.Duration(delta).String()

	h.Lock()
	h.json.SetP(delta, stat)
	h.json.SetP(readable, stat+"_readable")
	h.Unlock()
	return nil
}

// Gauge sets a stat as a gauge value.
func (h *HTTP) Gauge(stat string, value int64) error {
	h.Lock()
	h.json.SetP(value, stat)
	h.Unlock()
	return nil
}

// Close stops the HTTP object from aggregating metrics and cleans up resources.
func (h *HTTP) Close() error {
	return nil
}

//------------------------------------------------------------------------------