XL: Implement ignore errors. (#2136)

Each metadata ops have a list of errors which can be
ignored, this is essentially needed when

  - disks are not found
  - disks are found but cannot be accessed (permission denied)
  - disks are there but fresh disks were added

This is needed since we don't have healing code in place where
it would have healed the fresh disks added.

Fixes #2072

fs-v1-multipart.go

@@ -85,7 +85,7 @@ func (fs fsObjects) listMultipartUploads(bucket, prefix, keyMarker, uploadIDMark
 			// For any walk error return right away.
 			if walkResult.err != nil {
 				// File not found or Disk not found is a valid case.
-				if walkResult.err == errFileNotFound || walkResult.err == errDiskNotFound || walkResult.err == errFaultyDisk {
+				if isErrIgnored(walkResult.err, walkResultIgnoredErrs) {
 					eof = true
 					break
 				}

object-common.go

@@ -43,6 +43,16 @@ func registerShutdown(callback func()) {
 	}()
 }
 
+// isErrIgnored should we ignore this error?, takes a list of errors which can be ignored.
+func isErrIgnored(err error, ignoredErrs []error) bool {
+	for _, ignoredErr := range ignoredErrs {
+		if ignoredErr == err {
+			return true
+		}
+	}
+	return false
+}
+
 // House keeping code needed for FS.
 func fsHouseKeeping(storageDisk StorageAPI) error {
 	// Cleanup all temp entries upon start.

tree-walk.go

@@ -21,6 +21,15 @@ import (
 	"strings"
 )
 
+// list of all errors that can be ignored in tree walk operation.
+var walkResultIgnoredErrs = []error{
+	errFileNotFound,
+	errVolumeNotFound,
+	errDiskNotFound,
+	errDiskAccessDenied,
+	errFaultyDisk,
+}
+
 // Tree walk result carries results of tree walking.
 type treeWalkResult struct {
 	entry string
@@ -48,32 +57,31 @@ func listDirFactory(isLeaf func(string, string) bool, disks ...StorageAPI) listD
 				continue
 			}
 			entries, err = disk.ListDir(bucket, prefixDir)
-			if err != nil {
+			if err == nil {
-				// For any reason disk was deleted or goes offline, continue
+				// Skip the entries which do not match the prefixEntry.
-				// and list from other disks if possible.
+				for i, entry := range entries {
-				if err == errDiskNotFound || err == errFaultyDisk {
+					if !strings.HasPrefix(entry, prefixEntry) {
-					continue
+						entries[i] = ""
-				}
+						continue
-				break
+					}
-			}
+					if isLeaf(bucket, pathJoin(prefixDir, entry)) {
-			// Skip the entries which do not match the prefixEntry.
+						entries[i] = strings.TrimSuffix(entry, slashSeparator)
-			for i, entry := range entries {
+					}
-				if !strings.HasPrefix(entry, prefixEntry) {
-					entries[i] = ""
-					continue
 				}
-				if isLeaf(bucket, pathJoin(prefixDir, entry)) {
+				sort.Strings(entries)
-					entries[i] = strings.TrimSuffix(entry, slashSeparator)
+				// Skip the empty strings
+				for len(entries) > 0 && entries[0] == "" {
+					entries = entries[1:]
 				}
+				return entries, nil
 			}
-			sort.Strings(entries)
+			// For any reason disk was deleted or goes offline, continue
-			// Skip the empty strings
+			// and list from other disks if possible.
-			for len(entries) > 0 && entries[0] == "" {
+			if isErrIgnored(err, walkResultIgnoredErrs) {
-				entries = entries[1:]
+				continue
 			}
-			return entries, nil
+			break
 		}
-
 		// Return error at the end.
 		return nil, err
 	}

xl-v1-bucket.go

@@ -102,6 +102,13 @@ func (xl xlObjects) undoMakeBucket(bucket string) {
 	wg.Wait()
 }
 
+// list all errors that can be ignored in a bucket metadata operation.
+var bucketMetadataOpIgnoredErrs = []error{
+	errDiskNotFound,
+	errDiskAccessDenied,
+	errFaultyDisk,
+}
+
 // getBucketInfo - returns the BucketInfo from one of the load balanced disks.
 func (xl xlObjects) getBucketInfo(bucketName string) (bucketInfo BucketInfo, err error) {
 	for _, disk := range xl.getLoadBalancedQuorumDisks() {
@@ -110,20 +117,20 @@ func (xl xlObjects) getBucketInfo(bucketName string) (bucketInfo BucketInfo, err
 		}
 		var volInfo VolInfo
 		volInfo, err = disk.StatVol(bucketName)
-		if err != nil {
+		if err == nil {
-			// For any reason disk went offline continue and pick the next one.
+			bucketInfo = BucketInfo{
-			if err == errDiskNotFound || err == errFaultyDisk {
+				Name:    volInfo.Name,
-				continue
+				Created: volInfo.Created,
 			}
-			return BucketInfo{}, err
+			return bucketInfo, nil
 		}
-		bucketInfo = BucketInfo{
+		// For any reason disk went offline continue and pick the next one.
-			Name:    volInfo.Name,
+		if isErrIgnored(err, bucketMetadataOpIgnoredErrs) {
-			Created: volInfo.Created,
+			continue
 		}
 		break
 	}
-	return bucketInfo, nil
+	return BucketInfo{}, err
 }
 
 // Checks whether bucket exists.
@@ -166,10 +173,6 @@ func (xl xlObjects) listBuckets() (bucketsInfo []BucketInfo, err error) {
 		}
 		var volsInfo []VolInfo
 		volsInfo, err = disk.ListVols()
-		// Ignore any disks not found.
-		if err == errDiskNotFound || err == errFaultyDisk {
-			continue
-		}
 		if err == nil {
 			// NOTE: The assumption here is that volumes across all disks in
 			// readQuorum have consistent view i.e they all have same number
@@ -189,6 +192,10 @@ func (xl xlObjects) listBuckets() (bucketsInfo []BucketInfo, err error) {
 			}
 			return bucketsInfo, nil
 		}
+		// Ignore any disks not found.
+		if isErrIgnored(err, bucketMetadataOpIgnoredErrs) {
+			continue
+		}
 		break
 	}
 	return nil, err
@@ -245,8 +252,7 @@ func (xl xlObjects) DeleteBucket(bucket string) error {
 	// an unknown error.
 	for _, err := range dErrs {
 		if err != nil {
-			// We ignore error if errVolumeNotFound, errDiskNotFound or errFaultyDisk
+			if isErrIgnored(err, objMetadataOpIgnoredErrs) {
-			if err == errVolumeNotFound || err == errDiskNotFound || err == errFaultyDisk {
 				volumeNotFoundErrCnt++
 				continue
 			}

xl-v1-common.go

@@ -67,7 +67,7 @@ func (xl xlObjects) isObject(bucket, prefix string) (ok bool) {
 			return true
 		}
 		// Ignore for file not found,  disk not found or faulty disk.
-		if err == errFileNotFound || err == errDiskNotFound || err == errFaultyDisk {
+		if isErrIgnored(err, walkResultIgnoredErrs) {
 			continue
 		}
 		errorIf(err, "Unable to stat a file %s/%s/%s", bucket, prefix, xlMetaJSONFile)

xl-v1-metadata.go

@@ -194,6 +194,14 @@ func pickValidXLMeta(xlMetas []xlMetaV1) xlMetaV1 {
 	panic("Unable to look for valid XL metadata content")
 }
 
+// list of all errors that can be ignored in a metadata operation.
+var objMetadataOpIgnoredErrs = []error{
+	errDiskNotFound,
+	errDiskAccessDenied,
+	errFaultyDisk,
+	errVolumeNotFound,
+}
+
 // readXLMetadata - returns the object metadata `xl.json` content from
 // one of the disks picked at random.
 func (xl xlObjects) readXLMetadata(bucket, object string) (xlMeta xlMetaV1, err error) {
@@ -202,16 +210,18 @@ func (xl xlObjects) readXLMetadata(bucket, object string) (xlMeta xlMetaV1, err
 			continue
 		}
 		xlMeta, err = readXLMeta(disk, bucket, object)
-		if err != nil {
+		if err == nil {
-			// For any reason disk is not available continue and read from other disks.
+			return xlMeta, nil
-			if err == errDiskNotFound || err == errFaultyDisk {
+		}
-				continue
+		// For any reason disk or bucket is not available continue
-			}
+		// and read from other disks.
-			return xlMetaV1{}, err
+		if isErrIgnored(err, objMetadataOpIgnoredErrs) {
+			continue
 		}
 		break
 	}
-	return xlMeta, nil
+	// Return error here.
+	return xlMetaV1{}, err
 }
 
 // Undo rename xl metadata, renames successfully renamed `xl.json` back to source location.

xl-v1-multipart-common.go

@@ -178,16 +178,16 @@ func (xl xlObjects) isMultipartUpload(bucket, prefix string) bool {
 			continue
 		}
 		_, err := disk.StatFile(bucket, pathJoin(prefix, uploadsJSONFile))
-		if err != nil {
+		if err == nil {
-			// For any reason disk was deleted or goes offline, continue
+			return true
-			if err == errDiskNotFound || err == errFaultyDisk {
+		}
-				continue
+		// For any reason disk was deleted or goes offline, continue
-			}
+		if isErrIgnored(err, objMetadataOpIgnoredErrs) {
-			return false
+			continue
 		}
 		break
 	}
-	return true
+	return false
 }
 
 // listUploadsInfo - list all uploads info.
@@ -199,20 +199,20 @@ func (xl xlObjects) listUploadsInfo(prefixPath string) (uploadsInfo []uploadInfo
 		splitPrefixes := strings.SplitN(prefixPath, "/", 3)
 		var uploadsJSON uploadsV1
 		uploadsJSON, err = readUploadsJSON(splitPrefixes[1], splitPrefixes[2], disk)
-		if err != nil {
+		if err == nil {
-			// For any reason disk was deleted or goes offline, continue
+			uploadsInfo = uploadsJSON.Uploads
-			if err == errDiskNotFound || err == errFaultyDisk {
+			return uploadsInfo, nil
-				continue
+		}
-			}
+		if err == errFileNotFound {
-			if err == errFileNotFound {
+			return []uploadInfo{}, nil
-				return []uploadInfo{}, nil
+		}
-			}
+		// For any reason disk was deleted or goes offline, continue
-			return nil, err
+		if isErrIgnored(err, objMetadataOpIgnoredErrs) {
+			continue
 		}
-		uploadsInfo = uploadsJSON.Uploads
 		break
 	}
-	return uploadsInfo, nil
+	return []uploadInfo{}, err
 }
 
 // isUploadIDExists - verify if a given uploadID exists and is valid.
@@ -249,16 +249,16 @@ func (xl xlObjects) statPart(bucket, object, uploadID, partName string) (fileInf
 			continue
 		}
 		fileInfo, err = disk.StatFile(minioMetaBucket, partNamePath)
-		if err != nil {
+		if err == nil {
-			// For any reason disk was deleted or goes offline, continue
+			return fileInfo, nil
-			if err == errDiskNotFound {
+		}
-				continue
+		// For any reason disk was deleted or goes offline, continue
-			}
+		if isErrIgnored(err, objMetadataOpIgnoredErrs) {
-			return FileInfo{}, err
+			continue
 		}
 		break
 	}
-	return fileInfo, nil
+	return FileInfo{}, err
 }
 
 // commitXLMetadata - commit `xl.json` from source prefix to destination prefix.

xl-v1-multipart.go

@@ -68,7 +68,10 @@ func (xl xlObjects) listMultipartUploads(bucket, prefix, keyMarker, uploadIDMark
 				continue
 			}
 			uploads, _, err = listMultipartUploadIDs(bucket, keyMarker, uploadIDMarker, maxUploads, disk)
-			if err == errDiskNotFound || err == errFaultyDisk {
+			if err == nil {
+				break
+			}
+			if isErrIgnored(err, objMetadataOpIgnoredErrs) {
 				continue
 			}
 			break
@@ -100,7 +103,7 @@ func (xl xlObjects) listMultipartUploads(bucket, prefix, keyMarker, uploadIDMark
 			// For any walk error return right away.
 			if walkResult.err != nil {
 				// File not found or Disk not found is a valid case.
-				if walkResult.err == errFileNotFound || walkResult.err == errDiskNotFound || walkResult.err == errFaultyDisk {
+				if isErrIgnored(walkResult.err, walkResultIgnoredErrs) {
 					continue
 				}
 				return ListMultipartsInfo{}, err
@@ -130,14 +133,17 @@ func (xl xlObjects) listMultipartUploads(bucket, prefix, keyMarker, uploadIDMark
 					continue
 				}
 				newUploads, end, err = listMultipartUploadIDs(bucket, entry, uploadIDMarker, maxUploads, disk)
-				if err == errDiskNotFound || err == errFaultyDisk {
+				if err == nil {
+					break
+				}
+				if isErrIgnored(err, objMetadataOpIgnoredErrs) {
 					continue
 				}
 				break
 			}
 			nsMutex.RUnlock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, entry))
 			if err != nil {
-				if err == errFileNotFound || walkResult.err == errDiskNotFound || walkResult.err == errFaultyDisk {
+				if isErrIgnored(err, walkResultIgnoredErrs) {
 					continue
 				}
 				return ListMultipartsInfo{}, err
@@ -723,7 +729,10 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 			continue
 		}
 		uploadsJSON, err = readUploadsJSON(bucket, object, disk)
-		if err == errDiskNotFound || err == errFaultyDisk {
+		if err == nil {
+			break
+		}
+		if isErrIgnored(err, objMetadataOpIgnoredErrs) {
 			continue
 		}
 		break
@@ -774,7 +783,10 @@ func (xl xlObjects) abortMultipartUpload(bucket, object, uploadID string) (err e
 			continue
 		}
 		uploadsJSON, err = readUploadsJSON(bucket, object, disk)
-		if err == errDiskNotFound || err == errFaultyDisk {
+		if err == nil {
+			break
+		}
+		if isErrIgnored(err, objMetadataOpIgnoredErrs) {
 			continue
 		}
 		break