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// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package reverseproxy
import (
"net/http"
"time"
)
// Upstream represents the interface that must be satisfied to use the healthchecker.
type Upstream interface {
SetHealthiness(bool)
}
// HealthChecker represents a worker that periodically evaluates if proxy upstream host is healthy.
type HealthChecker struct {
upstream Upstream
Ticker *time.Ticker
HTTPClient *http.Client
StopChan chan bool
}
// ScheduleChecks periodically runs health checks against an upstream host.
func (h *HealthChecker) ScheduleChecks(url string) {
// check if a host is healthy on start vs waiting for timer
h.upstream.SetHealthiness(h.IsHealthy(url))
stop := make(chan bool)
h.StopChan = stop
go func() {
for {
select {
case <-h.Ticker.C:
h.upstream.SetHealthiness(h.IsHealthy(url))
case <-stop:
return
}
}
}()
}
// Stop stops the healthchecker from makeing further requests.
func (h *HealthChecker) Stop() {
h.Ticker.Stop()
close(h.StopChan)
}
// IsHealthy attempts to check if a upstream host is healthy.
func (h *HealthChecker) IsHealthy(url string) bool {
req, err := http.NewRequest(http.MethodGet, url, nil)
if err != nil {
return false
}
resp, err := h.HTTPClient.Do(req)
if err != nil {
return false
}
if resp.StatusCode < 200 || resp.StatusCode >= 400 {
return false
}
return true
}
// NewHealthCheckWorker returns a new instance of a HealthChecker.
func NewHealthCheckWorker(u Upstream, interval time.Duration, client *http.Client) *HealthChecker {
return &HealthChecker{
upstream: u,
Ticker: time.NewTicker(interval),
HTTPClient: client,
}
}
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