use object modTime for the event sequencer ID (#18285)

always set modTime after lock is acquired in
completemultipart stage to make sure that the
modTime is not racy.

cmd/erasure-multipart.go

@@ -1169,6 +1169,16 @@ func (er erasureObjects) CompleteMultipartUpload(ctx context.Context, bucket str
 			return oi, err
 		}
 	}
+
+	// Hold namespace to complete the transaction
+	lk := er.NewNSLock(bucket, object)
+	lkctx, err := lk.GetLock(ctx, globalOperationTimeout)
+	if err != nil {
+		return oi, err
+	}
+	ctx = lkctx.Context()
+	defer lk.Unlock(lkctx)
+
 	if checksumType.IsSet() {
 		checksumType |= hash.ChecksumMultipart | hash.ChecksumIncludesMultipart
 		cs := hash.NewChecksumFromData(checksumType, checksumCombined)
@@ -1212,15 +1222,6 @@ func (er erasureObjects) CompleteMultipartUpload(ctx context.Context, bucket str
 		}
 	}
 
-	// Hold namespace to complete the transaction
-	lk := er.NewNSLock(bucket, object)
-	lkctx, err := lk.GetLock(ctx, globalOperationTimeout)
-	if err != nil {
-		return oi, err
-	}
-	ctx = lkctx.Context()
-	defer lk.Unlock(lkctx)
-
 	// Remove parts that weren't present in CompleteMultipartUpload request.
 	for _, curpart := range currentFI.Parts {
 		// Remove part.meta which is not needed anymore.

cmd/event-notification.go

@@ -210,6 +210,9 @@ type eventArgs struct {
 func (args eventArgs) ToEvent(escape bool) event.Event {
 	eventTime := UTCNow()
 	uniqueID := fmt.Sprintf("%X", eventTime.UnixNano())
+	if !args.Object.ModTime.IsZero() {
+		uniqueID = fmt.Sprintf("%X", args.Object.ModTime.UnixNano())
+	}
 
 	respElements := map[string]string{
 		"x-amz-request-id": args.RespElements["requestId"],

cmd/object-api-options.go

@@ -194,8 +194,6 @@ func delOpts(ctx context.Context, r *http.Request, bucket, object string) (opts
 				Err:    fmt.Errorf("Unable to parse %s, failed with %w", xhttp.MinIOSourceMTime, err),
 			}
 		}
-	} else {
-		opts.MTime = UTCNow()
 	}
 	return opts, nil
 }
@@ -225,7 +223,7 @@ func putOpts(ctx context.Context, r *http.Request, bucket, object string, metada
 	}
 
 	mtimeStr := strings.TrimSpace(r.Header.Get(xhttp.MinIOSourceMTime))
-	mtime := UTCNow()
+	var mtime time.Time
 	if mtimeStr != "" {
 		mtime, err = time.Parse(time.RFC3339Nano, mtimeStr)
 		if err != nil {
@@ -237,7 +235,7 @@ func putOpts(ctx context.Context, r *http.Request, bucket, object string, metada
 		}
 	}
 	retaintimeStr := strings.TrimSpace(r.Header.Get(xhttp.MinIOSourceObjectRetentionTimestamp))
-	retaintimestmp := mtime
+	var retaintimestmp time.Time
 	if retaintimeStr != "" {
 		retaintimestmp, err = time.Parse(time.RFC3339, retaintimeStr)
 		if err != nil {
@@ -250,7 +248,7 @@ func putOpts(ctx context.Context, r *http.Request, bucket, object string, metada
 	}
 
 	lholdtimeStr := strings.TrimSpace(r.Header.Get(xhttp.MinIOSourceObjectLegalHoldTimestamp))
-	lholdtimestmp := mtime
+	var lholdtimestmp time.Time
 	if lholdtimeStr != "" {
 		lholdtimestmp, err = time.Parse(time.RFC3339, lholdtimeStr)
 		if err != nil {
@@ -262,7 +260,7 @@ func putOpts(ctx context.Context, r *http.Request, bucket, object string, metada
 		}
 	}
 	tagtimeStr := strings.TrimSpace(r.Header.Get(xhttp.MinIOSourceTaggingTimestamp))
-	taggingtimestmp := mtime
+	var taggingtimestmp time.Time
 	if tagtimeStr != "" {
 		taggingtimestmp, err = time.Parse(time.RFC3339, tagtimeStr)
 		if err != nil {
@@ -353,7 +351,7 @@ func copySrcOpts(ctx context.Context, r *http.Request, bucket, object string) (O
 // get ObjectOptions for CompleteMultipart calls
 func completeMultipartOpts(ctx context.Context, r *http.Request, bucket, object string) (opts ObjectOptions, err error) {
 	mtimeStr := strings.TrimSpace(r.Header.Get(xhttp.MinIOSourceMTime))
-	mtime := UTCNow()
+	var mtime time.Time
 	if mtimeStr != "" {
 		mtime, err = time.Parse(time.RFC3339Nano, mtimeStr)
 		if err != nil {