diff --git a/weed/s3api/filer_multipart.go b/weed/s3api/filer_multipart.go
index 7dd68466e..e8491fce7 100644
--- a/weed/s3api/filer_multipart.go
+++ b/weed/s3api/filer_multipart.go
@@ -1,9 +1,12 @@
 package s3api
 
 import (
+	"cmp"
 	"encoding/hex"
 	"encoding/xml"
 	"fmt"
+	"github.com/seaweedfs/seaweedfs/weed/stats"
+	"golang.org/x/exp/slices"
 	"math"
 	"path/filepath"
 	"sort"
@@ -11,18 +14,18 @@ import (
 	"strings"
 	"time"
 
-	"github.com/google/uuid"
-	"github.com/seaweedfs/seaweedfs/weed/s3api/s3err"
-	"golang.org/x/exp/slices"
-
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/s3"
+	"github.com/google/uuid"
+	"github.com/seaweedfs/seaweedfs/weed/s3api/s3err"
 
 	"github.com/seaweedfs/seaweedfs/weed/filer"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
 )
 
+const multipartExt = ".part"
+
 type InitiateMultipartUploadResult struct {
 	XMLName xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ InitiateMultipartUploadResult"`
 	s3.CreateMultipartUploadOutput
@@ -71,74 +74,97 @@ type CompleteMultipartUploadResult struct {
 func (s3a *S3ApiServer) completeMultipartUpload(input *s3.CompleteMultipartUploadInput, parts *CompleteMultipartUpload) (output *CompleteMultipartUploadResult, code s3err.ErrorCode) {
 
 	glog.V(2).Infof("completeMultipartUpload input %v", input)
-
-	completedParts := parts.Parts
-	slices.SortFunc(completedParts, func(a, b CompletedPart) int {
-		return a.PartNumber - b.PartNumber
-	})
-
+	completedPartNumbers := []int{}
+	completedPartMap := make(map[int][]string)
+	for _, part := range parts.Parts {
+		if _, ok := completedPartMap[part.PartNumber]; !ok {
+			completedPartNumbers = append(completedPartNumbers, part.PartNumber)
+		}
+		completedPartMap[part.PartNumber] = append(completedPartMap[part.PartNumber], part.ETag)
+	}
 	uploadDirectory := s3a.genUploadsFolder(*input.Bucket) + "/" + *input.UploadId
 
 	entries, _, err := s3a.list(uploadDirectory, "", "", false, maxPartsList)
 	if err != nil || len(entries) == 0 {
 		glog.Errorf("completeMultipartUpload %s %s error: %v, entries:%d", *input.Bucket, *input.UploadId, err, len(entries))
+		stats.S3HandlerCounter.WithLabelValues(stats.ErrorCompletedNoSuchUpload).Inc()
 		return nil, s3err.ErrNoSuchUpload
 	}
 
 	pentry, err := s3a.getEntry(s3a.genUploadsFolder(*input.Bucket), *input.UploadId)
 	if err != nil {
 		glog.Errorf("completeMultipartUpload %s %s error: %v", *input.Bucket, *input.UploadId, err)
+		stats.S3HandlerCounter.WithLabelValues(stats.ErrorCompletedNoSuchUpload).Inc()
 		return nil, s3err.ErrNoSuchUpload
 	}
 
+	deleteEntries := []*filer_pb.Entry{}
 	partEntries := make(map[int][]*filer_pb.Entry, len(entries))
 	for _, entry := range entries {
+		foundEntry := false
 		glog.V(4).Infof("completeMultipartUpload part entries %s", entry.Name)
-		if strings.HasSuffix(entry.Name, ".part") && !entry.IsDirectory {
-			var partNumberString string
-			index := strings.Index(entry.Name, "_")
-			if index != -1 {
-				partNumberString = entry.Name[:index]
+		if entry.IsDirectory || !strings.HasSuffix(entry.Name, multipartExt) {
+			continue
+		}
+		partNumber, err := parsePartNumber(entry.Name)
+		if err != nil {
+			stats.S3HandlerCounter.WithLabelValues(stats.ErrorCompletedPartNumber).Inc()
+			glog.Errorf("completeMultipartUpload failed to pasre partNumber %s:%s", entry.Name, err)
+			continue
+		}
+		completedPartsByNumber, ok := completedPartMap[partNumber]
+		if !ok {
+			continue
+		}
+		for _, partETag := range completedPartsByNumber {
+			partETag = strings.Trim(partETag, `"`)
+			entryETag := hex.EncodeToString(entry.Attributes.GetMd5())
+			if partETag != "" && len(partETag) == 32 && entryETag != "" {
+				if entryETag != partETag {
+					glog.Errorf("completeMultipartUpload %s ETag mismatch chunk: %s part: %s", entry.Name, entryETag, partETag)
+					stats.S3HandlerCounter.WithLabelValues(stats.ErrorCompletedEtagMismatch).Inc()
+					continue
+				}
 			} else {
-				partNumberString = entry.Name[:len(entry.Name)-len(".part")]
+				glog.Warningf("invalid complete etag %s, partEtag %s", partETag, entryETag)
+				stats.S3HandlerCounter.WithLabelValues(stats.ErrorCompletedEtagInvalid).Inc()
 			}
-			partNumber, err := strconv.Atoi(partNumberString)
-			if err != nil {
-				glog.Errorf("completeMultipartUpload failed to pasre partNumber %s:%s", partNumberString, err)
+			if len(entry.Chunks) == 0 {
+				glog.Warningf("completeMultipartUpload %s empty chunks", entry.Name)
+				stats.S3HandlerCounter.WithLabelValues(stats.ErrorCompletedPartEmpty).Inc()
 				continue
 			}
 			//there maybe multi same part, because of client retry
 			partEntries[partNumber] = append(partEntries[partNumber], entry)
+			foundEntry = true
+		}
+		if !foundEntry {
+			deleteEntries = append(deleteEntries, entry)
 		}
-
 	}
 
 	mime := pentry.Attributes.Mime
 
 	var finalParts []*filer_pb.FileChunk
 	var offset int64
-	var deleteEntries []*filer_pb.Entry
-	for _, part := range completedParts {
-		entries := partEntries[part.PartNumber]
-		// check whether completedParts is more than received parts
-		if len(entries) == 0 {
-			glog.Errorf("part %d has no entry", part.PartNumber)
+	sort.Ints(completedPartNumbers)
+	for _, partNumber := range completedPartNumbers {
+		partEntriesByNumber, ok := partEntries[partNumber]
+		if !ok {
+			glog.Errorf("part %d has no entry", partNumber)
+			stats.S3HandlerCounter.WithLabelValues(stats.ErrorCompletedPartNotFound).Inc()
 			return nil, s3err.ErrInvalidPart
 		}
-
 		found := false
-		for _, entry := range entries {
+		if len(partEntriesByNumber) > 1 {
+			slices.SortFunc(partEntriesByNumber, func(a, b *filer_pb.Entry) int {
+				return cmp.Compare(b.Chunks[0].ModifiedTsNs, a.Chunks[0].ModifiedTsNs)
+			})
+		}
+		for _, entry := range partEntriesByNumber {
 			if found {
 				deleteEntries = append(deleteEntries, entry)
-				continue
-			}
-
-			partETag := strings.Trim(part.ETag, `"`)
-			entryETag := hex.EncodeToString(entry.Attributes.GetMd5())
-			glog.Warningf("complete etag %s, partEtag %s", partETag, entryETag)
-			if partETag != "" && len(partETag) == 32 && entryETag != "" && entryETag != partETag {
-				err = fmt.Errorf("completeMultipartUpload %s ETag mismatch chunk: %s part: %s", entry.Name, entryETag, partETag)
-				deleteEntries = append(deleteEntries, entry)
+				stats.S3HandlerCounter.WithLabelValues(stats.ErrorCompletedPartEntryMismatch).Inc()
 				continue
 			}
 			for _, chunk := range entry.GetChunks() {
@@ -154,13 +180,7 @@ func (s3a *S3ApiServer) completeMultipartUpload(input *s3.CompleteMultipartUploa
 				offset += int64(chunk.Size)
 			}
 			found = true
-			err = nil
 		}
-		if err != nil {
-			glog.Errorf("%s", err)
-			return nil, s3err.ErrInvalidPart
-		}
-
 	}
 
 	entryName := filepath.Base(*input.Key)
@@ -223,29 +243,15 @@ func (s3a *S3ApiServer) completeMultipartUpload(input *s3.CompleteMultipartUploa
 	return
 }
 
-func findByPartNumber(fileName string, parts []CompletedPart) (etag string, found bool) {
-	partNumber, formatErr := strconv.Atoi(fileName[:4])
-	if formatErr != nil {
-		return
-	}
-	x := sort.Search(len(parts), func(i int) bool {
-		return parts[i].PartNumber >= partNumber
-	})
-	if x >= len(parts) {
-		return
-	}
-	if parts[x].PartNumber != partNumber {
-		return
+func parsePartNumber(fileName string) (int, error) {
+	var partNumberString string
+	index := strings.Index(fileName, "_")
+	if index != -1 {
+		partNumberString = fileName[:index]
+	} else {
+		partNumberString = fileName[:len(fileName)-len(multipartExt)]
 	}
-	y := 0
-	for i, part := range parts[x:] {
-		if part.PartNumber == partNumber {
-			y = i
-		} else {
-			break
-		}
-	}
-	return parts[x+y].ETag, true
+	return strconv.Atoi(partNumberString)
 }
 
 func (s3a *S3ApiServer) abortMultipartUpload(input *s3.AbortMultipartUploadInput) (output *s3.AbortMultipartUploadOutput, code s3err.ErrorCode) {
@@ -361,7 +367,7 @@ func (s3a *S3ApiServer) listObjectParts(input *s3.ListPartsInput) (output *ListP
 		StorageClass:     aws.String("STANDARD"),
 	}
 
-	entries, isLast, err := s3a.list(s3a.genUploadsFolder(*input.Bucket)+"/"+*input.UploadId, "", fmt.Sprintf("%04d.part", *input.PartNumberMarker), false, uint32(*input.MaxParts))
+	entries, isLast, err := s3a.list(s3a.genUploadsFolder(*input.Bucket)+"/"+*input.UploadId, "", fmt.Sprintf("%04d%s", *input.PartNumberMarker, multipartExt), false, uint32(*input.MaxParts))
 	if err != nil {
 		glog.Errorf("listObjectParts %s %s error: %v", *input.Bucket, *input.UploadId, err)
 		return nil, s3err.ErrNoSuchUpload
@@ -373,15 +379,8 @@ func (s3a *S3ApiServer) listObjectParts(input *s3.ListPartsInput) (output *ListP
 	output.IsTruncated = aws.Bool(!isLast)
 
 	for _, entry := range entries {
-		if strings.HasSuffix(entry.Name, ".part") && !entry.IsDirectory {
-			var partNumberString string
-			index := strings.Index(entry.Name, "_")
-			if index != -1 {
-				partNumberString = entry.Name[:index]
-			} else {
-				partNumberString = entry.Name[:len(entry.Name)-len(".part")]
-			}
-			partNumber, err := strconv.Atoi(partNumberString)
+		if strings.HasSuffix(entry.Name, multipartExt) && !entry.IsDirectory {
+			partNumber, err := parsePartNumber(entry.Name)
 			if err != nil {
 				glog.Errorf("listObjectParts %s %s parse %s: %v", *input.Bucket, *input.UploadId, entry.Name, err)
 				continue
diff --git a/weed/s3api/filer_multipart_test.go b/weed/s3api/filer_multipart_test.go
index e76d903b8..7f75a40de 100644
--- a/weed/s3api/filer_multipart_test.go
+++ b/weed/s3api/filer_multipart_test.go
@@ -50,88 +50,27 @@ func TestListPartsResult(t *testing.T) {
 
 }
 
-func Test_findByPartNumber(t *testing.T) {
-	type args struct {
-		fileName string
-		parts    []CompletedPart
-	}
-
-	parts := []CompletedPart{
-		{
-			ETag:       "xxx",
-			PartNumber: 1,
-		},
-		{
-			ETag:       "lll",
-			PartNumber: 1,
-		},
-		{
-			ETag:       "yyy",
-			PartNumber: 3,
-		},
-		{
-			ETag:       "zzz",
-			PartNumber: 5,
-		},
-	}
-
+func Test_parsePartNumber(t *testing.T) {
 	tests := []struct {
-		name      string
-		args      args
-		wantEtag  string
-		wantFound bool
+		name     string
+		fileName string
+		partNum  int
 	}{
 		{
 			"first",
-			args{
-				"0001.part",
-				parts,
-			},
-			"lll",
-			true,
+			"0001_uuid.part",
+			1,
 		},
 		{
 			"second",
-			args{
-				"0002.part",
-				parts,
-			},
-			"",
-			false,
-		},
-		{
-			"third",
-			args{
-				"0003.part",
-				parts,
-			},
-			"yyy",
-			true,
-		},
-		{
-			"fourth",
-			args{
-				"0004.part",
-				parts,
-			},
-			"",
-			false,
-		},
-		{
-			"fifth",
-			args{
-				"0005.part",
-				parts,
-			},
-			"zzz",
-			true,
+			"0002.part",
+			2,
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			gotEtag, gotFound := findByPartNumber(tt.args.fileName, tt.args.parts)
-			assert.Equalf(t, tt.wantEtag, gotEtag, "findByPartNumber(%v, %v)", tt.args.fileName, tt.args.parts)
-			assert.Equalf(t, tt.wantFound, gotFound, "findByPartNumber(%v, %v)", tt.args.fileName, tt.args.parts)
+			partNumber, _ := parsePartNumber(tt.fileName)
+			assert.Equalf(t, tt.partNum, partNumber, "parsePartNumber(%v)", tt.fileName)
 		})
 	}
 }
diff --git a/weed/stats/metrics.go b/weed/stats/metrics.go
index f61f68e08..83391f047 100644
--- a/weed/stats/metrics.go
+++ b/weed/stats/metrics.go
@@ -241,7 +241,13 @@ var (
 			Name:      "request_total",
 			Help:      "Counter of s3 requests.",
 		}, []string{"type", "code", "bucket"})
-
+	S3HandlerCounter = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: Namespace,
+			Subsystem: "s3",
+			Name:      "handler_total",
+			Help:      "Counter of s3 server handlers.",
+		}, []string{"type"})
 	S3RequestHistogram = prometheus.NewHistogramVec(
 		prometheus.HistogramOpts{
 			Namespace: Namespace,
@@ -292,6 +298,7 @@ func init() {
 	Gather.MustRegister(VolumeServerResourceGauge)
 
 	Gather.MustRegister(S3RequestCounter)
+	Gather.MustRegister(S3HandlerCounter)
 	Gather.MustRegister(S3RequestHistogram)
 	Gather.MustRegister(S3TimeToFirstByteHistogram)
 }
diff --git a/weed/stats/metrics_names.go b/weed/stats/metrics_names.go
index ffb0c76f1..cfc0fbeb0 100644
--- a/weed/stats/metrics_names.go
+++ b/weed/stats/metrics_names.go
@@ -43,4 +43,13 @@ const (
 	ErrorChunkAssign         = "chunkAssign.failed"
 	ErrorReadCache           = "read.cache.failed"
 	ErrorReadStream          = "read.stream.failed"
+
+	// s3 handler
+	ErrorCompletedNoSuchUpload      = "errorCompletedNoSuchUpload"
+	ErrorCompletedPartEmpty         = "ErrorCompletedPartEmpty"
+	ErrorCompletedPartNumber        = "ErrorCompletedPartNumber"
+	ErrorCompletedPartNotFound      = "errorCompletedPartNotFound"
+	ErrorCompletedEtagInvalid       = "errorCompletedEtagInvalid"
+	ErrorCompletedEtagMismatch      = "errorCompletedEtagMismatch"
+	ErrorCompletedPartEntryMismatch = "errorCompletedPartEntryMismatch"
 )