tikv 重复事务

// 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 (
   "context"
   "math"
   "math/rand"
   "sync/atomic"
   "time"

   "github.com/pingcap/parser/terror"
   "github.com/pingcap/tidb/util/logutil"
   "go.uber.org/zap"
)

// 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 {
         logutil.BgLogger().Error("RunInNewTxn", zap.Error(err))
         return 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(err1)
         if retryable && IsTxnRetryableError(err) {
            logutil.BgLogger().Warn("RunInNewTxn",
               zap.Uint64("retry txn", txn.StartTS()),
               zap.Uint64("original txn", originalTxnTS),
               zap.Error(err))
            continue
         }
         return err
      }

      err = txn.Commit(context.Background())
      if err == nil {
         break
      }
      if retryable && IsTxnRetryableError(err) {
         logutil.BgLogger().Warn("RunInNewTxn",
            zap.Uint64("retry txn", txn.StartTS()),
            zap.Uint64("original txn", originalTxnTS),
            zap.Error(err))
         BackOff(i)
         continue
      }
      return err
   }
   return err
}

var (
   // maxRetryCnt represents maximum retry times 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)
}

// mockCommitErrorEnable uses to enable `mockCommitError` and only mock error once.
var mockCommitErrorEnable = int64(0)

// MockCommitErrorEnable exports for gofail testing.
func MockCommitErrorEnable() {
   atomic.StoreInt64(&mockCommitErrorEnable, 1)
}

// MockCommitErrorDisable exports for gofail testing.
func MockCommitErrorDisable() {
   atomic.StoreInt64(&mockCommitErrorEnable, 0)
}

// IsMockCommitErrorEnable exports for gofail testing.
func IsMockCommitErrorEnable() bool {
   return atomic.LoadInt64(&mockCommitErrorEnable) == 1
}

// TxnInfo is used to keep track the info of a committed transaction (mainly for diagnosis and testing)
type TxnInfo struct {
   StartTS  uint64 `json:"start_ts"`
   CommitTS uint64 `json:"commit_ts"`
   ErrMsg   string `json:"error,omitempty"`
}