implement a safer completeMultipart implementation (#20227)

- optimize writing part.N.meta by writing both part.N
  and its meta in sequence without network component.

- remove part.N.meta, part.N which were partially success
  ful, in quorum loss situations during renamePart()

- allow for strict read quorum check arbitrated via ETag
  for the given part number, this makes it double safer
  upon final commit.

- return an appropriate error when read quorum is missing,
  instead of returning InvalidPart{}, which is non-retryable
  error. This kind of situation can happen when many
  nodes are going offline in rotation, an example of such
  a restart() behavior is statefulset updates in k8s.

fixes #20091

cmd/erasure-common.go

@@ -19,13 +19,9 @@ package cmd
 
 import (
 	"context"
-	"fmt"
-	"io"
 	"math/rand"
 	"sync"
 	"time"
-
-	"github.com/minio/pkg/v3/sync/errgroup"
 )
 
 func (er erasureObjects) getOnlineDisks() (newDisks []StorageAPI) {
@@ -87,89 +83,3 @@ func (er erasureObjects) getLocalDisks() (newDisks []StorageAPI) {
 	}
 	return newDisks
 }
-
-// readMultipleFiles Reads raw data from all specified files from all disks.
-func readMultipleFiles(ctx context.Context, disks []StorageAPI, req ReadMultipleReq, readQuorum int) ([]ReadMultipleResp, error) {
-	resps := make([]chan ReadMultipleResp, len(disks))
-	for i := range resps {
-		resps[i] = make(chan ReadMultipleResp, len(req.Files))
-	}
-	g := errgroup.WithNErrs(len(disks))
-	// Read files in parallel across disks.
-	for index := range disks {
-		index := index
-		g.Go(func() (err error) {
-			if disks[index] == nil {
-				return errDiskNotFound
-			}
-			return disks[index].ReadMultiple(ctx, req, resps[index])
-		}, index)
-	}
-
-	dataArray := make([]ReadMultipleResp, 0, len(req.Files))
-	// Merge results. They should come in order from each.
-	for _, wantFile := range req.Files {
-		quorum := 0
-		toAdd := ReadMultipleResp{
-			Bucket: req.Bucket,
-			Prefix: req.Prefix,
-			File:   wantFile,
-		}
-		for i := range resps {
-			if disks[i] == nil {
-				continue
-			}
-			select {
-			case <-ctx.Done():
-			case gotFile, ok := <-resps[i]:
-				if !ok {
-					continue
-				}
-				if gotFile.Error != "" || !gotFile.Exists {
-					continue
-				}
-				if gotFile.File != wantFile || gotFile.Bucket != req.Bucket || gotFile.Prefix != req.Prefix {
-					continue
-				}
-				quorum++
-				if toAdd.Modtime.After(gotFile.Modtime) || len(gotFile.Data) < len(toAdd.Data) {
-					// Pick latest, or largest to avoid possible truncated entries.
-					continue
-				}
-				toAdd = gotFile
-			}
-		}
-		if quorum < readQuorum {
-			toAdd.Exists = false
-			toAdd.Error = errErasureReadQuorum.Error()
-			toAdd.Data = nil
-		}
-		dataArray = append(dataArray, toAdd)
-	}
-
-	ignoredErrs := []error{
-		errFileNotFound,
-		errVolumeNotFound,
-		errFileVersionNotFound,
-		io.ErrUnexpectedEOF, // some times we would read without locks, ignore these errors
-		io.EOF,              // some times we would read without locks, ignore these errors
-		context.DeadlineExceeded,
-		context.Canceled,
-	}
-	ignoredErrs = append(ignoredErrs, objectOpIgnoredErrs...)
-
-	errs := g.Wait()
-	for index, err := range errs {
-		if err == nil {
-			continue
-		}
-		if !IsErr(err, ignoredErrs...) {
-			storageLogOnceIf(ctx, fmt.Errorf("Drive %s, path (%s/%s) returned an error (%w)",
-				disks[index], req.Bucket, req.Prefix, err),
-				disks[index].String())
-		}
-	}
-
-	// Return all the metadata.
-	return dataArray, nil
-}