caddy/middleware/proxy/upstream.go

package proxy

import (
	"io"
	"io/ioutil"
	"net/http"
	"time"
)

type StaticUpstream struct {
	From   string
	Hosts  HostPool
	Policy Policy

	FailTimeout time.Duration
	MaxFails    int32
	HealthCheck struct {
		Path     string
		Interval time.Duration
	}
}

func (u *StaticUpstream) from() string {
	return u.From
}

func (u *StaticUpstream) healthCheck() {
	for _, host := range u.Hosts {
		hostUrl := host.Name + u.HealthCheck.Path
		if r, err := http.Get(hostUrl); err == nil {
			io.Copy(ioutil.Discard, r.Body)
			r.Body.Close()
			host.Unhealthy = r.StatusCode < 200 || r.StatusCode >= 400
		} else {
			host.Unhealthy = true
		}
	}
}

func (u *StaticUpstream) HealthCheckWorker(stop chan struct{}) {
	ticker := time.NewTicker(u.HealthCheck.Interval)
	u.healthCheck()
	for {
		select {
		case <-ticker.C:
			u.healthCheck()
		case <-stop:
			// TODO: the library should provide a stop channel and global
			// waitgroup to allow goroutines started by plugins a chance
			// to clean themselves up.
		}
	}
}

func (u *StaticUpstream) Select() *UpstreamHost {
	pool := u.Hosts
	if len(pool) == 1 {
		if pool[0].Down() {
			return nil
		}
		return pool[0]
	}
	allDown := true
	for _, host := range pool {
		if !host.Down() {
			allDown = false
			break
		}
	}
	if allDown {
		return nil
	}

	if u.Policy == nil {
		return (&Random{}).Select(pool)
	} else {
		return u.Policy.Select(pool)
	}
}