From 45fb375c41c5e9e73553dd9c1f4f44c8e4a1c34e Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Thu, 3 Aug 2023 02:18:18 -0700
Subject: [PATCH] allow healing to prefer local disks over remote (#17788)

---
 cmd/erasure-decode.go    | 5 ++++-
 cmd/erasure-heal_test.go | 2 +-
 cmd/erasure-healing.go   | 5 ++++-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/cmd/erasure-decode.go b/cmd/erasure-decode.go
index 12f17f574..98696bb9f 100644
--- a/cmd/erasure-decode.go
+++ b/cmd/erasure-decode.go
@@ -289,12 +289,15 @@ func (e Erasure) Decode(ctx context.Context, writer io.Writer, readers []io.Read
 }
 
 // Heal reads from readers, reconstruct shards and writes the data to the writers.
-func (e Erasure) Heal(ctx context.Context, writers []io.Writer, readers []io.ReaderAt, totalLength int64) (derr error) {
+func (e Erasure) Heal(ctx context.Context, writers []io.Writer, readers []io.ReaderAt, totalLength int64, prefer []bool) (derr error) {
 	if len(writers) != e.parityBlocks+e.dataBlocks {
 		return errInvalidArgument
 	}
 
 	reader := newParallelReader(readers, e, 0, totalLength)
+	if len(readers) == len(prefer) {
+		reader.preferReaders(prefer)
+	}
 
 	startBlock := int64(0)
 	endBlock := totalLength / e.blockSize
diff --git a/cmd/erasure-heal_test.go b/cmd/erasure-heal_test.go
index 35ef42cb6..baba08978 100644
--- a/cmd/erasure-heal_test.go
+++ b/cmd/erasure-heal_test.go
@@ -132,7 +132,7 @@ func TestErasureHeal(t *testing.T) {
 		}
 
 		// test case setup is complete - now call Heal()
-		err = erasure.Heal(context.Background(), staleWriters, readers, test.size)
+		err = erasure.Heal(context.Background(), staleWriters, readers, test.size, nil)
 		closeBitrotReaders(readers)
 		closeBitrotWriters(staleWriters)
 		if err != nil && !test.shouldFail {
diff --git a/cmd/erasure-healing.go b/cmd/erasure-healing.go
index 54ab84510..bb5335a98 100644
--- a/cmd/erasure-healing.go
+++ b/cmd/erasure-healing.go
@@ -661,6 +661,7 @@ func (er *erasureObjects) healObject(ctx context.Context, bucket string, object
 			partChecksums := latestMeta.Parts[partIndex].Checksums
 			tillOffset := erasure.ShardFileOffset(0, partSize, partSize)
 			readers := make([]io.ReaderAt, len(latestDisks))
+			prefer := make([]bool, len(latestDisks))
 			checksumAlgo := erasureInfo.GetChecksumInfo(partNumber).Algorithm
 			for i, disk := range latestDisks {
 				if disk == OfflineDisk {
@@ -670,6 +671,8 @@ func (er *erasureObjects) healObject(ctx context.Context, bucket string, object
 				partPath := pathJoin(object, srcDataDir, fmt.Sprintf("part.%d", partNumber))
 				readers[i] = newBitrotReader(disk, copyPartsMetadata[i].Data, bucket, partPath, tillOffset, checksumAlgo,
 					checksumInfo.Hash, erasure.ShardSize())
+				prefer[i] = disk.Hostname() == ""
+
 			}
 			writers := make([]io.Writer, len(outDatedDisks))
 			for i, disk := range outDatedDisks {
@@ -689,7 +692,7 @@ func (er *erasureObjects) healObject(ctx context.Context, bucket string, object
 			// Heal each part. erasure.Heal() will write the healed
 			// part to .minio/tmp/uuid/ which needs to be renamed
 			// later to the final location.
-			err = erasure.Heal(ctx, writers, readers, partSize)
+			err = erasure.Heal(ctx, writers, readers, partSize, prefer)
 			closeBitrotReaders(readers)
 			closeBitrotWriters(writers)
 			if err != nil {