feat: record flush_wait_ms in TxnInfo (#1342)

* feat: record flush_wait_ms in TxnInfo

Signed-off-by: ekexium <eke@fastmail.com>

* refactor: change FlushWaitDuration() to GetFlushMetrics()

Signed-off-by: ekexium <eke@fastmail.com>

---------

Signed-off-by: ekexium <eke@fastmail.com>

internal/unionstore/pipelined_memdb.go

@@ -55,6 +55,9 @@ type PipelinedMemDB struct {
 	//   Some([]) -> delete
 	batchGetCache map[string]util.Option[[]byte]
 	memChangeHook func(uint64)
+
+	// metrics
+	flushWaitDuration time.Duration
 }
 
 const (
@@ -358,12 +361,14 @@ func (p *PipelinedMemDB) needFlush() bool {
 // FlushWait will wait for all flushing tasks are done and return the error if there is a failure.
 func (p *PipelinedMemDB) FlushWait() error {
 	if p.flushingMemDB != nil {
+		now := time.Now()
 		err := <-p.errCh
 		if err != nil {
 			err = p.handleAlreadyExistErr(err)
 		}
 		// cleanup the flushingMemDB so the next call of FlushWait will not wait for the error channel.
 		p.flushingMemDB = nil
+		p.flushWaitDuration += time.Since(now)
 		return err
 	}
 	return nil
@@ -513,3 +518,10 @@ func (p *PipelinedMemDB) Checkpoint() *MemDBCheckpoint {
 func (p *PipelinedMemDB) RevertToCheckpoint(*MemDBCheckpoint) {
 	panic("RevertToCheckpoint is not supported for PipelinedMemDB")
 }
+
+// GetFlushMetrics implements MemBuffer interface.
+func (p *PipelinedMemDB) GetFlushMetrics() FlushMetrics {
+	return FlushMetrics{
+		WaitDuration: p.flushWaitDuration,
+	}
+}

internal/unionstore/union_store.go

@@ -37,6 +37,7 @@ package unionstore
 import (
 	"context"
 	"math"
+	"time"
 
 	tikverr "github.com/tikv/client-go/v2/error"
 	"github.com/tikv/client-go/v2/kv"
@@ -236,6 +237,12 @@ type MemBuffer interface {
 	Flush(force bool) (bool, error)
 	// FlushWait waits for the flushing task done and return error.
 	FlushWait() error
+	// GetFlushDetails returns the metrics related to flushing
+	GetFlushMetrics() FlushMetrics
+}
+
+type FlushMetrics struct {
+	WaitDuration time.Duration
 }
 
 var (
@@ -287,3 +294,6 @@ func (db *MemDBWithContext) BatchGet(ctx context.Context, keys [][]byte) (map[st
 	}
 	return m, nil
 }
+
+// GetFlushMetrisc implements the MemBuffer interface.
+func (db *MemDBWithContext) GetFlushMetrics() FlushMetrics { return FlushMetrics{} }

txnkv/transaction/txn.go

@@ -853,6 +853,7 @@ type TxnInfo struct {
 	OnePCFallback       bool   `json:"one_pc_fallback"`
 	ErrMsg              string `json:"error,omitempty"`
 	Pipelined           bool   `json:"pipelined"`
+	FlushWaitMs         int64  `json:"flush_wait_ms"`
 }
 
 func (txn *KVTxn) onCommitted(err error) {
@@ -875,6 +876,7 @@ func (txn *KVTxn) onCommitted(err error) {
 			AsyncCommitFallback: txn.committer.hasTriedAsyncCommit && !isAsyncCommit,
 			OnePCFallback:       txn.committer.hasTriedOnePC && !isOnePC,
 			Pipelined:           txn.IsPipelined(),
+			FlushWaitMs:         txn.GetMemBuffer().GetFlushMetrics().WaitDuration.Milliseconds(),
 		}
 		if err != nil {
 			info.ErrMsg = err.Error()