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source.go
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source.go
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// Copyright (c) 2018 Palantir Technologies. All rights reserved.
//
// 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 periodic
import (
"context"
"fmt"
"sync"
"time"
conjurehealth "github.com/palantir/witchcraft-go-server/conjure/witchcraft/api/health"
"github.com/palantir/witchcraft-go-server/status"
"github.com/palantir/witchcraft-go-server/status/health"
)
type healthCheckSource struct {
gracePeriodReset time.Time
numRunsDuringGracePeriod int
lastErr error
poll func() error
gracePeriod time.Duration
retryInterval time.Duration
checkType conjurehealth.CheckType
mutex sync.RWMutex
}
// NewHealthCheckSource creates a health check source that calls poll every retryInterval in a goroutine. The goroutine
// is cancelled if ctx is cancelled. If gracePeriod elapses without poll returning nil, the returned health check
// source will give a health status of error. checkType is the key to be used in the health result returned by the
// health check source.
func NewHealthCheckSource(ctx context.Context, gracePeriod time.Duration, retryInterval time.Duration, checkType conjurehealth.CheckType, poll func() error) status.HealthCheckSource {
checker := &healthCheckSource{
gracePeriodReset: time.Now(),
lastErr: nil,
gracePeriod: gracePeriod,
retryInterval: retryInterval,
checkType: checkType,
poll: poll,
}
go checker.runPoll(ctx)
return checker
}
func (h *healthCheckSource) HealthStatus(ctx context.Context) conjurehealth.HealthStatus {
h.mutex.RLock()
defer func() {
h.mutex.RUnlock()
}()
if time.Now().Sub(h.gracePeriodReset) > h.gracePeriod {
if h.numRunsDuringGracePeriod > 0 {
return toHealthStatus(health.UnhealthyHealthCheckResult(h.checkType, fmt.Sprintf("have not seen a success during grace period, grace period reset: %s, grace period duration: %s, last error: %s", h.gracePeriodReset.String(), h.gracePeriod.String(), h.lastError())))
}
return toHealthStatus(health.UnhealthyHealthCheckResult(h.checkType, fmt.Sprintf("have not completed a poll during grace period, grace period reset: %s, grace period duration: %s", h.gracePeriodReset.String(), h.gracePeriod.String())))
}
return toHealthStatus(health.HealthyHealthCheckResult(h.checkType))
}
func (h *healthCheckSource) runPoll(ctx context.Context) {
ticker := time.NewTicker(h.retryInterval)
for {
select {
case <-ctx.Done():
return
case <-ticker.C:
h.doPoll()
}
}
}
func (h *healthCheckSource) doPoll() {
err := h.poll()
h.mutex.Lock()
defer func() {
h.mutex.Unlock()
}()
h.lastErr = err
if err == nil {
h.gracePeriodReset = time.Now()
h.numRunsDuringGracePeriod = 0
}
h.numRunsDuringGracePeriod++
}
func (h *healthCheckSource) lastError() string {
if h.lastErr == nil {
return ""
}
return h.lastErr.Error()
}
func toHealthStatus(result conjurehealth.HealthCheckResult) conjurehealth.HealthStatus {
return conjurehealth.HealthStatus{
Checks: map[conjurehealth.CheckType]conjurehealth.HealthCheckResult{
result.Type: result,
},
}
}