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// Copyright 2016 The etcd 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 contention
import (
"sync"
"time"
)
// TimeoutDetector detects routine starvations by
// observing the actual time duration to finish an action
// or between two events that should happen in a fixed
// interval. If the observed duration is longer than
// the expectation, the detector will report the result.
type TimeoutDetector struct {
mu sync.Mutex // protects all
maxDuration time.Duration
// map from event to time
// time is the last seen time of the event.
records map[uint64]time.Time
}
// NewTimeoutDetector creates the TimeoutDetector.
func NewTimeoutDetector(maxDuration time.Duration) *TimeoutDetector {
return &TimeoutDetector{
maxDuration: maxDuration,
records: make(map[uint64]time.Time),
}
}
// Reset resets the NewTimeoutDetector.
func (td *TimeoutDetector) Reset() {
td.mu.Lock()
defer td.mu.Unlock()
td.records = make(map[uint64]time.Time)
}
// Observe observes an event for given id. It returns false and exceeded duration
// if the interval is longer than the expectation.
func (td *TimeoutDetector) Observe(which uint64) (bool, time.Duration) {
td.mu.Lock()
defer td.mu.Unlock()
ok := true
now := time.Now()
exceed := time.Duration(0)
if pt, found := td.records[which]; found {
exceed = now.Sub(pt) - td.maxDuration
if exceed > 0 {
ok = false
}
}
td.records[which] = now
return ok, exceed
}
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