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/
healthcheck.go
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/
healthcheck.go
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/*
Copyright 2018 The Kubernetes 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 metrics
import (
"fmt"
"net/http"
"sync"
"time"
)
// HealthCheck contains information about last activity time of the monitored component.
// NOTE: This started as a simplified version of ClusterAutoscaler's HealthCheck.
type HealthCheck struct {
activityTimeout time.Duration
checkTimeout bool
lastActivity time.Time
mutex *sync.Mutex
}
// NewHealthCheck builds new HealthCheck object with given timeout.
func NewHealthCheck(activityTimeout time.Duration, checkTimeout bool) *HealthCheck {
return &HealthCheck{
activityTimeout: activityTimeout,
checkTimeout: checkTimeout,
lastActivity: time.Now(),
mutex: &sync.Mutex{},
}
}
// checkLastActivity returns true if the last activity was too long ago, with duration from it.
func (hc *HealthCheck) checkLastActivity() (bool, time.Duration) {
hc.mutex.Lock()
defer hc.mutex.Unlock()
now := time.Now()
lastActivity := hc.lastActivity
activityTimedOut := now.After(lastActivity.Add(hc.activityTimeout))
timedOut := hc.checkTimeout && activityTimedOut
return timedOut, now.Sub(lastActivity)
}
// ServeHTTP implements http.Handler interface to provide a health-check endpoint.
func (hc *HealthCheck) ServeHTTP(w http.ResponseWriter, r *http.Request) {
timedOut, ago := hc.checkLastActivity()
if timedOut {
w.WriteHeader(500)
w.Write([]byte(fmt.Sprintf("Error: last activity more than %v ago", ago)))
} else {
w.WriteHeader(200)
w.Write([]byte("OK"))
}
}
// UpdateLastActivity updates last time of activity to now
func (hc *HealthCheck) UpdateLastActivity() {
hc.mutex.Lock()
defer hc.mutex.Unlock()
hc.lastActivity = time.Now()
}