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health.go
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health.go
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// Copyright 2024 The Bucketeer 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 health
import (
"context"
"fmt"
"net/http"
"sync/atomic"
"time"
)
type Status uint32
const (
// Healthy is returned when the health check was successful
Healthy Status = 0
// Unhealthy is returned when the health check was unsuccessful
Unhealthy Status = 1
)
func (s Status) String() string {
switch s {
case Healthy:
return "Healthy"
case Unhealthy:
return "Unhealthy"
default:
return "Unknown"
}
}
type check func(context.Context) Status
type checker struct {
status uint32
interval time.Duration
timeout time.Duration
checks map[string]check
}
type option func(*checker)
func WithCheck(name string, check check) option {
return func(c *checker) {
if _, ok := c.checks[name]; ok {
panic(fmt.Sprintf("health: %s already registered", name))
}
c.checks[name] = check
}
}
func WithInterval(interval time.Duration) option {
return func(c *checker) {
c.interval = interval
}
}
func WithTimeout(timeout time.Duration) option {
return func(c *checker) {
c.timeout = timeout
}
}
func newChecker(opts ...option) *checker {
checker := &checker{
status: uint32(Unhealthy),
interval: 10 * time.Second,
timeout: 5 * time.Second,
checks: make(map[string]check),
}
for _, o := range opts {
o(checker)
}
return checker
}
func (hc *checker) Run(ctx context.Context) {
ticker := time.NewTicker(hc.interval)
defer ticker.Stop()
hc.check(ctx)
for {
select {
case <-ctx.Done():
return
case <-ticker.C:
hc.check(ctx)
}
}
}
func (hc *checker) check(ctx context.Context) {
resultChan := make(chan Status, len(hc.checks))
ctx, cancel := context.WithTimeout(ctx, hc.timeout)
defer cancel()
for _, c := range hc.checks {
go func(c check) {
resultChan <- c(ctx)
}(c)
}
for i := 0; i < len(hc.checks); i++ {
if res := <-resultChan; res != Healthy {
hc.setStatus(Unhealthy)
return
}
}
hc.setStatus(Healthy)
}
func (hc *checker) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
if hc.getStatus() == Unhealthy {
resp.WriteHeader(http.StatusServiceUnavailable)
return
}
resp.WriteHeader(http.StatusOK)
}
func (hc *checker) getStatus() Status {
return Status(atomic.LoadUint32(&hc.status))
}
func (hc *checker) setStatus(s Status) {
atomic.StoreUint32(&hc.status, uint32(s))
}
func (hc *checker) Stop() {
hc.setStatus(Unhealthy)
}