micro/web/health.go

package web

import (
	"fmt"
	"net/http"
	"time"

	"github.com/go-chi/render"
	log "scm.yoorie.de/go-lib/gelf"
)

/*
healthChecker Class
*/
type healthChecker struct {
	message     string
	healthy     bool
	lastChecked time.Time
	startTime   time.Time
	period      int
	ticker      *time.Ticker
	done        chan bool
	//This is the healtchcheck you will have to provide.
	checkFunc func() (bool, string)
}

type HealthData struct {
	Message     string    `json:"message,omitempty"`
	LastChecked time.Time `json:"lastChecked"`
}

func newHealthChecker(checkFunction func() (bool, string)) *healthChecker {
	hc := &healthChecker{}
	hc.checkFunc = checkFunction
	hc.startTime = time.Now()
	return hc
}

func (h *healthChecker) start(checkPeriodInSeconds int) {
	h.period = checkPeriodInSeconds
	h.message = "service starting"
	h.healthy = false
	h.doCheck()
	h.ticker = time.NewTicker(time.Second * time.Duration(h.period))
	h.done = make(chan bool)
	go func() {
		for {
			select {
			case <-h.done:
				return
			case <-h.ticker.C:
				h.doCheck()
			}
		}
	}()
}

func (h *healthChecker) stop() {
	h.ticker.Stop()
	h.done <- true
	log.Debug("Health checker stopped.")
}

// internal function to process the health check
func (h *healthChecker) doCheck() {
	var msg string
	h.healthy, msg = h.checkFunc()
	if !h.healthy {
		h.message = msg
	} else {
		h.message = ""
	}
	h.lastChecked = time.Now()
}

/*
GetHealthyEndpoint is this service healthy
*/
func (h *healthChecker) healthyEndpoint(responseWriter http.ResponseWriter, request *http.Request) {
	t := time.Now()
	status := http.StatusOK
	healtData := &HealthData{
		Message:     "service up and running",
		LastChecked: h.lastChecked,
	}
	if t.Sub(h.lastChecked) > (time.Second * time.Duration(2*h.period)) {
		h.healthy = false
		h.message = "Healthcheck not running"
	}
	if !h.healthy {
		status = http.StatusServiceUnavailable
		healtData.Message = fmt.Sprintf("service is unavailable: %s", h.message)
	}
	responseWriter.WriteHeader(status)
	render.JSON(responseWriter, request, healtData)

}

/*
GetReadinessEndpoint is this service ready for taking requests
*/
func (h *healthChecker) readinessEndpoint(responseWriter http.ResponseWriter, request *http.Request) {
	render.JSON(responseWriter, request, &HealthData{
		Message:     "service is ready",
		LastChecked: h.startTime,
	})
}