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// Copyright 2015 PingCAP, 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package kv
import (
"math"
"math/rand"
"time"
"github.com/juju/errors"
"github.com/pingcap/tidb/terror"
log "github.com/sirupsen/logrus"
"golang.org/x/net/context"
)
// RunInNewTxn will run the f in a new transaction environment.
func RunInNewTxn(store Storage, retryable bool, f func(txn Transaction) error) error {
var (
err error
originalTxnTS uint64
txn Transaction
)
for i := uint(0); i < maxRetryCnt; i++ {
txn, err = store.Begin()
if err != nil {
log.Errorf("[kv] RunInNewTxn error - %v", err)
return errors.Trace(err)
}
// originalTxnTS is used to trace the original transaction when the function is retryable.
if i == 0 {
originalTxnTS = txn.StartTS()
}
err = f(txn)
if err != nil {
err1 := txn.Rollback()
terror.Log(errors.Trace(err1))
if retryable && IsRetryableError(err) {
log.Warnf("[kv] Retry txn %v original txn %v err %v", txn, originalTxnTS, err)
continue
}
return errors.Trace(err)
}
err = txn.Commit(context.Background())
if err == nil {
break
}
if retryable && IsRetryableError(err) {
log.Warnf("[kv] Retry txn %v original txn %v err %v", txn, originalTxnTS, err)
BackOff(i)
continue
}
return errors.Trace(err)
}
return errors.Trace(err)
}
var (
// Max retry count in RunInNewTxn
maxRetryCnt uint = 100
// retryBackOffBase is the initial duration, in microsecond, a failed transaction stays dormancy before it retries
retryBackOffBase = 1
// retryBackOffCap is the max amount of duration, in microsecond, a failed transaction stays dormancy before it retries
retryBackOffCap = 100
)
// BackOff Implements exponential backoff with full jitter.
// Returns real back off time in microsecond.
// See http://www.awsarchitectureblog.com/2015/03/backoff.html.
func BackOff(attempts uint) int {
upper := int(math.Min(float64(retryBackOffCap), float64(retryBackOffBase)*math.Pow(2.0, float64(attempts))))
sleep := time.Duration(rand.Intn(upper)) * time.Millisecond
time.Sleep(sleep)
return int(sleep)
}
// BatchGetValues gets values in batch.
// The values from buffer in transaction and the values from the storage node are merged together.
func BatchGetValues(txn Transaction, keys []Key) (map[string][]byte, error) {
if txn.IsReadOnly() {
return txn.GetSnapshot().BatchGet(keys)
}
bufferValues := make([][]byte, len(keys))
shrinkKeys := make([]Key, 0, len(keys))
for i, key := range keys {
val, err := txn.GetMemBuffer().Get(key)
if IsErrNotFound(err) {
shrinkKeys = append(shrinkKeys, key)
continue
}
if err != nil {
return nil, errors.Trace(err)
}
if len(val) != 0 {
bufferValues[i] = val
}
}
storageValues, err := txn.GetSnapshot().BatchGet(shrinkKeys)
if err != nil {
return nil, errors.Trace(err)
}
for i, key := range keys {
if bufferValues[i] == nil {
continue
}
storageValues[string(key)] = bufferValues[i]
}
return storageValues, nil
}
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