tidb txn 源码

tidb txn 代码

文件路径：/kv/txn.go

// 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,
// 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 kv

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"math"
	"math/rand"
	"sync"
	"time"

	"github.com/pingcap/failpoint"
	"github.com/pingcap/tidb/parser/terror"
	"github.com/pingcap/tidb/util/logutil"
	"github.com/tikv/client-go/v2/oracle"
	"go.uber.org/zap"
)

const (
	// TimeToPrintLongTimeInternalTxn is the duration if the internal transaction lasts more than it,
	// TiDB prints a log message.
	TimeToPrintLongTimeInternalTxn = time.Minute * 5
)

var globalInnerTxnTsBox = innerTxnStartTsBox{
	innerTSLock:        sync.Mutex{},
	innerTxnStartTsMap: make(map[uint64]struct{}, 256),
}

type innerTxnStartTsBox struct {
	innerTSLock        sync.Mutex
	innerTxnStartTsMap map[uint64]struct{}
}

func (ib *innerTxnStartTsBox) storeInnerTxnTS(startTS uint64) {
	ib.innerTSLock.Lock()
	ib.innerTxnStartTsMap[startTS] = struct{}{}
	ib.innerTSLock.Unlock()
}

func (ib *innerTxnStartTsBox) deleteInnerTxnTS(startTS uint64) {
	ib.innerTSLock.Lock()
	delete(ib.innerTxnStartTsMap, startTS)
	ib.innerTSLock.Unlock()
}

// GetMinInnerTxnStartTS get the min StartTS between startTSLowerLimit and curMinStartTS in globalInnerTxnTsBox.
func GetMinInnerTxnStartTS(now time.Time, startTSLowerLimit uint64,
	curMinStartTS uint64) uint64 {
	return globalInnerTxnTsBox.getMinStartTS(now, startTSLowerLimit, curMinStartTS)
}

func (ib *innerTxnStartTsBox) getMinStartTS(now time.Time, startTSLowerLimit uint64,
	curMinStartTS uint64) uint64 {
	minStartTS := curMinStartTS
	ib.innerTSLock.Lock()
	for innerTS := range ib.innerTxnStartTsMap {
		PrintLongTimeInternalTxn(now, innerTS, true)
		if innerTS > startTSLowerLimit && innerTS < minStartTS {
			minStartTS = innerTS
		}
	}
	ib.innerTSLock.Unlock()
	return minStartTS
}

// PrintLongTimeInternalTxn print the internal transaction information.
// runByFunction	true means the transaction is run by `RunInNewTxn`,
//
//	false means the transaction is run by internal session.
func PrintLongTimeInternalTxn(now time.Time, startTS uint64, runByFunction bool) {
	if startTS > 0 {
		innerTxnStartTime := oracle.GetTimeFromTS(startTS)
		if now.Sub(innerTxnStartTime) > TimeToPrintLongTimeInternalTxn {
			callerName := "internal session"
			if runByFunction {
				callerName = "RunInNewTxn"
			}
			infoHeader := fmt.Sprintf("An internal transaction running by %s lasts long time", callerName)

			logutil.BgLogger().Info(infoHeader,
				zap.Duration("time", now.Sub(innerTxnStartTime)), zap.Uint64("startTS", startTS),
				zap.Time("start time", innerTxnStartTime))
		}
	}
}

// RunInNewTxn will run the f in a new transaction environment, should be used by inner txn only.
func RunInNewTxn(ctx context.Context, store Storage, retryable bool, f func(ctx context.Context, txn Transaction) error) error {
	var (
		err           error
		originalTxnTS uint64
		txn           Transaction
	)

	defer func() {
		globalInnerTxnTsBox.deleteInnerTxnTS(originalTxnTS)
	}()

	for i := uint(0); i < maxRetryCnt; i++ {
		txn, err = store.Begin()
		if err != nil {
			logutil.BgLogger().Error("RunInNewTxn", zap.Error(err))
			return err
		}
		setRequestSourceForInnerTxn(ctx, txn)

		// originalTxnTS is used to trace the original transaction when the function is retryable.
		if i == 0 {
			originalTxnTS = txn.StartTS()
			globalInnerTxnTsBox.storeInnerTxnTS(originalTxnTS)
		}

		err = f(ctx, 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
		}

		failpoint.Inject("mockCommitErrorInNewTxn", func(val failpoint.Value) {
			if v := val.(string); len(v) > 0 {
				switch v {
				case "retry_once":
					//nolint:noloopclosure
					if i == 0 {
						err = ErrTxnRetryable
					}
				case "no_retry":
					failpoint.Return(errors.New("mock commit error"))
				}
			}
		})

		if err == nil {
			err = txn.Commit(ctx)
			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 // #nosec G404
	time.Sleep(sleep)
	return int(sleep)
}

func setRequestSourceForInnerTxn(ctx context.Context, txn Transaction) {
	if source := ctx.Value(RequestSourceKey); source != nil {
		requestSource := source.(RequestSource)
		if !requestSource.RequestSourceInternal {
			logutil.Logger(ctx).Warn("`RunInNewTxn` should be used by inner txn only")
		}
		txn.SetOption(RequestSourceInternal, requestSource.RequestSourceInternal)
		txn.SetOption(RequestSourceType, requestSource.RequestSourceType)
	} else {
		// panic in test mode in case there are requests without source in the future.
		// log warnings in production mode.
		if flag.Lookup("test.v") != nil || flag.Lookup("check.v") != nil {
			panic("unexpected no source type context, if you see this error, " +
				"the `RequestSourceTypeKey` is missing in your context")
		} else {
			logutil.Logger(ctx).Warn("unexpected no source type context, if you see this warning, " +
				"the `RequestSourceTypeKey` is missing in the context")
		}
	}
}

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