minio/cmd/dynamic-timeouts.go
Klaus Post c851e022b7
Tweaks to dynamic locks (#10508)
* Fix cases where minimum timeout > default timeout.
* Add defensive code for too small/negative timeouts.
* Never set timeout below the maximum value of a request.
* Protect against (unlikely) int64 wraps.
* Decrease timeout slower.
* Don't re-lock before copying.
2020-09-18 09:18:18 -07:00

142 lines
3.9 KiB
Go

/*
* 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 (
"math"
"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 = math.MaxInt64
maxDynamicTimeout = 24 * time.Hour // Never set timeout bigger than this.
)
// 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 {
if timeout <= 0 || minimum <= 0 {
panic("newDynamicTimeout: negative or zero timeout")
}
if minimum > timeout {
minimum = timeout
}
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) {
if duration < 0 {
return
}
entries := int(atomic.AddInt64(&dt.entries, 1))
index := entries - 1
if index < dynamicTimeoutLogSize {
dt.mutex.Lock()
dt.log[index] = duration
// We leak entries while we copy
if entries == dynamicTimeoutLogSize {
// 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)
return
}
dt.mutex.Unlock()
}
}
// adjust changes the value of the dynamic timeout based on the
// previous results
func (dt *dynamicTimeout) adjust(entries [dynamicTimeoutLogSize]time.Duration) {
failures, max := 0, time.Duration(0)
for _, dur := range entries[:] {
if dur == maxDuration {
failures++
} else if dur > max {
max = dur
}
}
failPct := float64(failures) / float64(len(entries))
if failPct > dynamicTimeoutIncreaseThresholdPct {
// We are hitting the timeout too often, so increase the timeout by 25%
timeout := atomic.LoadInt64(&dt.timeout) * 125 / 100
// Set upper cap.
if timeout > int64(maxDynamicTimeout) {
timeout = int64(maxDynamicTimeout)
}
// Safety, shouldn't happen
if timeout < dt.minimum {
timeout = dt.minimum
}
atomic.StoreInt64(&dt.timeout, timeout)
} else if failPct < dynamicTimeoutDecreaseThresholdPct {
// We are hitting the timeout relatively few times,
// so decrease the timeout towards 25 % of maximum time spent.
max = max * 125 / 100
timeout := atomic.LoadInt64(&dt.timeout)
if max < time.Duration(timeout) {
// Move 50% toward the max.
timeout = (int64(max) + timeout) / 2
}
if timeout < dt.minimum {
timeout = dt.minimum
}
atomic.StoreInt64(&dt.timeout, timeout)
}
}