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Copy pathdynamic-timeouts.go
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120 lines (101 loc) · 3.51 KB
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/*
* Minio Cloud Storage, (C) 2017 Minio, Inc.
*
* 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 cmd
import (
"sync"
"sync/atomic"
"time"
)
const (
dynamicTimeoutIncreaseThresholdPct = 0.33 // Upper threshold for failures in order to increase timeout
dynamicTimeoutDecreaseThresholdPct = 0.10 // Lower threshold for failures in order to decrease timeout
dynamicTimeoutLogSize = 16
maxDuration = time.Duration(1<<63 - 1)
)
// timeouts that are dynamically adapted based on actual usage results
type dynamicTimeout struct {
timeout int64
minimum int64
entries int64
log [dynamicTimeoutLogSize]time.Duration
mutex sync.Mutex
}
// newDynamicTimeout returns a new dynamic timeout initialized with timeout value
func newDynamicTimeout(timeout, minimum time.Duration) *dynamicTimeout {
return &dynamicTimeout{timeout: int64(timeout), minimum: int64(minimum)}
}
// Timeout returns the current timeout value
func (dt *dynamicTimeout) Timeout() time.Duration {
return time.Duration(atomic.LoadInt64(&dt.timeout))
}
// LogSuccess logs the duration of a successful action that
// did not hit the timeout
func (dt *dynamicTimeout) LogSuccess(duration time.Duration) {
dt.logEntry(duration)
}
// LogFailure logs an action that hit the timeout
func (dt *dynamicTimeout) LogFailure() {
dt.logEntry(maxDuration)
}
// logEntry stores a log entry
func (dt *dynamicTimeout) logEntry(duration time.Duration) {
entries := int(atomic.AddInt64(&dt.entries, 1))
index := entries - 1
if index < dynamicTimeoutLogSize {
dt.mutex.Lock()
dt.log[index] = duration
dt.mutex.Unlock()
}
if entries == dynamicTimeoutLogSize {
dt.mutex.Lock()
// Make copy on stack in order to call adjust()
logCopy := [dynamicTimeoutLogSize]time.Duration{}
copy(logCopy[:], dt.log[:])
// reset log entries
atomic.StoreInt64(&dt.entries, 0)
dt.mutex.Unlock()
dt.adjust(logCopy)
}
}
// adjust changes the value of the dynamic timeout based on the
// previous results
func (dt *dynamicTimeout) adjust(entries [dynamicTimeoutLogSize]time.Duration) {
failures, average := 0, int64(0)
for i := 0; i < len(entries); i++ {
if entries[i] == maxDuration {
failures++
} else {
average += int64(entries[i])
}
}
if failures < len(entries) {
average /= int64(len(entries) - failures)
}
timeOutHitPct := float64(failures) / float64(len(entries))
if timeOutHitPct > dynamicTimeoutIncreaseThresholdPct {
// We are hitting the timeout too often, so increase the timeout by 25%
timeout := atomic.LoadInt64(&dt.timeout) * 125 / 100
atomic.StoreInt64(&dt.timeout, timeout)
} else if timeOutHitPct < dynamicTimeoutDecreaseThresholdPct {
// We are hitting the timeout relatively few times, so decrease the timeout
average = average * 125 / 100 // Add buffer of 25% on top of average
timeout := (atomic.LoadInt64(&dt.timeout) + int64(average)) / 2 // Middle between current timeout and average success
if timeout < dt.minimum {
timeout = dt.minimum
}
atomic.StoreInt64(&dt.timeout, timeout)
}
}