XL: Refactor usage of reduceErrs and consistent behavior. (#2240)

This refactor is also needed in lieu of our quorum
requirement change for the newly understood logic behind
klauspost/reedsolom implementation.

object-api-multipart_test.go

@@ -129,7 +129,7 @@ func testPutObjectPartDiskNotFound(obj ObjectLayer, instanceType string, disks [
 	}
 
 	// Remove some random disk.
-	for _, disk := range disks[:7] {
+	for _, disk := range disks[:6] {
 		removeAll(disk)
 	}
 
@@ -165,7 +165,10 @@ func testPutObjectPartDiskNotFound(obj ObjectLayer, instanceType string, disks [
 	}
 
 	// This causes quorum failure verify.
-	removeAll(disks[len(disks)-1])
+	disks = disks[len(disks)-3:]
+	for _, disk := range disks {
+		removeAll(disk)
+	}
 
 	// Object part upload should fail with quorum not available.
 	testCase := createPartCases[len(createPartCases)-1]

xl-v1-common.go

@@ -25,7 +25,7 @@ import (
 // randomized quorum disk slice.
 func (xl xlObjects) getLoadBalancedQuorumDisks() (disks []StorageAPI) {
 	// It is okay to have readQuorum disks.
-	return xl.getLoadBalancedDisks()[:xl.readQuorum-1]
+	return xl.getLoadBalancedDisks()[0 : xl.readQuorum-1]
 }
 
 // getLoadBalancedDisks - fetches load balanced (sufficiently

xl-v1-metadata.go

@@ -314,7 +314,7 @@ func deleteAllXLMetadata(disks []StorageAPI, bucket, prefix string, errs []error
 }
 
 // writeUniqueXLMetadata - writes unique `xl.json` content for each disk in order.
-func writeUniqueXLMetadata(disks []StorageAPI, bucket, prefix string, xlMetas []xlMetaV1, writeQuorum, readQuorum int) error {
+func writeUniqueXLMetadata(disks []StorageAPI, bucket, prefix string, xlMetas []xlMetaV1, quorum int) error {
 	var wg = &sync.WaitGroup{}
 	var mErrs = make([]error, len(disks))
 
@@ -344,38 +344,17 @@ func writeUniqueXLMetadata(disks []StorageAPI, bucket, prefix string, xlMetas []
 	wg.Wait()
 
 	// Do we have write quorum?.
-	if !isDiskQuorum(mErrs, writeQuorum) {
-		// Validate if we have read quorum.
-		if isDiskQuorum(mErrs, readQuorum) {
-			// Return success.
-			return nil
-		}
+	if !isDiskQuorum(mErrs, quorum) {
 		// Delete all `xl.json` successfully renamed.
 		deleteAllXLMetadata(disks, bucket, prefix, mErrs)
 		return errXLWriteQuorum
 	}
 
-	// Reduce errors and verify quourm and return.
-	if errCount, reducedErr := reduceErrs(mErrs); reducedErr != nil {
-		if errCount < writeQuorum {
-			// Delete all `xl.json` successfully renamed.
-			deleteAllXLMetadata(disks, bucket, prefix, mErrs)
-			return errXLWriteQuorum
-		}
-		if isErrIgnored(reducedErr, []error{
+	return reduceErrs(mErrs, []error{
 		errDiskNotFound,
-			errDiskAccessDenied,
 		errFaultyDisk,
-			errVolumeNotFound,
-		}) {
-			// Success.
-			return nil
-		}
-		return reducedErr
-	}
-
-	// Success.
-	return nil
+		errDiskAccessDenied,
+	})
 }
 
 // writeSameXLMetadata - write `xl.json` on all disks in order.
@@ -410,36 +389,14 @@ func writeSameXLMetadata(disks []StorageAPI, bucket, prefix string, xlMeta xlMet
 
 	// Do we have write Quorum?.
 	if !isDiskQuorum(mErrs, writeQuorum) {
-		// Do we have readQuorum?.
-		if isDiskQuorum(mErrs, readQuorum) {
-			// Return success.
-			return nil
-		}
 		// Delete all `xl.json` successfully renamed.
 		deleteAllXLMetadata(disks, bucket, prefix, mErrs)
 		return errXLWriteQuorum
 	}
 
-	// Reduce errors and verify quourm and return.
-	if errCount, reducedErr := reduceErrs(mErrs); reducedErr != nil {
-		if errCount < writeQuorum {
-			// Delete all `xl.json` successfully renamed.
-			deleteAllXLMetadata(disks, bucket, prefix, mErrs)
-			return errXLWriteQuorum
-		}
-		// Ignore specific errors if we are under write quorum.
-		if isErrIgnored(reducedErr, []error{
+	return reduceErrs(mErrs, []error{
 		errDiskNotFound,
-			errDiskAccessDenied,
 		errFaultyDisk,
-			errVolumeNotFound,
-		}) {
-			// Success.
-			return nil
-		}
-		return reducedErr
-	}
-
-	// Success.
-	return nil
+		errDiskAccessDenied,
+	})
 }

xl-v1-multipart-common.go

@@ -270,7 +270,7 @@ func (xl xlObjects) statPart(bucket, object, uploadID, partName string) (fileInf
 }
 
 // commitXLMetadata - commit `xl.json` from source prefix to destination prefix in the given slice of disks.
-func commitXLMetadata(disks []StorageAPI, srcPrefix, dstPrefix string, writeQuorum, readQuorum int) error {
+func commitXLMetadata(disks []StorageAPI, srcPrefix, dstPrefix string, quorum int) error {
 	var wg = &sync.WaitGroup{}
 	var mErrs = make([]error, len(disks))
 
@@ -303,35 +303,16 @@ func commitXLMetadata(disks []StorageAPI, srcPrefix, dstPrefix string, writeQuor
 	wg.Wait()
 
 	// Do we have write Quorum?.
-	if !isDiskQuorum(mErrs, writeQuorum) {
-		// Do we have readQuorum?.
-		if isDiskQuorum(mErrs, readQuorum) {
-			// Return success.
-			return nil
-		}
+	if !isDiskQuorum(mErrs, quorum) {
 		// Delete all `xl.json` successfully renamed.
 		deleteAllXLMetadata(disks, minioMetaBucket, dstPrefix, mErrs)
 		return errXLWriteQuorum
 	}
 
-	// Reduce errors and verify quourm and return.
-	if errCount, reducedErr := reduceErrs(mErrs); reducedErr != nil {
-		if errCount < writeQuorum {
-			// Delete all `xl.json` successfully renamed.
-			deleteAllXLMetadata(disks, minioMetaBucket, dstPrefix, mErrs)
-			return errXLWriteQuorum
-		}
-		if isErrIgnored(reducedErr, []error{
+	return reduceErrs(mErrs, []error{
 		errDiskNotFound,
 		errDiskAccessDenied,
 		errFaultyDisk,
 		errVolumeNotFound,
-		}) {
-			return nil
-		}
-		return reducedErr
-	}
-
-	// Success.
-	return nil
+	})
 }

xl-v1-multipart.go

@@ -285,7 +285,7 @@ func (xl xlObjects) newMultipartUpload(bucket string, object string, meta map[st
 	if err = writeSameXLMetadata(xl.storageDisks, minioMetaBucket, tempUploadIDPath, xlMeta, xl.writeQuorum, xl.readQuorum); err != nil {
 		return "", toObjectErr(err, minioMetaBucket, tempUploadIDPath)
 	}
-	rErr := renameObject(xl.storageDisks, minioMetaBucket, tempUploadIDPath, minioMetaBucket, uploadIDPath, xl.writeQuorum, xl.readQuorum)
+	rErr := renameObject(xl.storageDisks, minioMetaBucket, tempUploadIDPath, minioMetaBucket, uploadIDPath, xl.writeQuorum)
 	if rErr == nil {
 		// Return success.
 		return uploadID, nil
@@ -431,7 +431,7 @@ func (xl xlObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 
 	// Rename temporary part file to its final location.
 	partPath := path.Join(uploadIDPath, partSuffix)
-	err = renamePart(onlineDisks, minioMetaBucket, tmpPartPath, minioMetaBucket, partPath, xl.writeQuorum, xl.readQuorum)
+	err = renamePart(onlineDisks, minioMetaBucket, tmpPartPath, minioMetaBucket, partPath, xl.writeQuorum)
 	if err != nil {
 		return "", toObjectErr(err, minioMetaBucket, partPath)
 	}
@@ -466,12 +466,11 @@ func (xl xlObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 	newUUID := getUUID()
 	tempXLMetaPath := path.Join(tmpMetaPrefix, newUUID)
 
-	// Writes a unique `xl.json` each disk carrying new checksum
-	// related information.
-	if err = writeUniqueXLMetadata(onlineDisks, minioMetaBucket, tempXLMetaPath, partsMetadata, xl.writeQuorum, xl.readQuorum); err != nil {
+	// Writes a unique `xl.json` each disk carrying new checksum related information.
+	if err = writeUniqueXLMetadata(onlineDisks, minioMetaBucket, tempXLMetaPath, partsMetadata, xl.writeQuorum); err != nil {
 		return "", toObjectErr(err, minioMetaBucket, tempXLMetaPath)
 	}
-	rErr := commitXLMetadata(onlineDisks, tempXLMetaPath, uploadIDPath, xl.writeQuorum, xl.readQuorum)
+	rErr := commitXLMetadata(onlineDisks, tempXLMetaPath, uploadIDPath, xl.writeQuorum)
 	if rErr != nil {
 		return "", toObjectErr(rErr, minioMetaBucket, uploadIDPath)
 	}
@@ -696,10 +695,10 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 	}
 
 	// Write unique `xl.json` for each disk.
-	if err = writeUniqueXLMetadata(xl.storageDisks, minioMetaBucket, tempUploadIDPath, partsMetadata, xl.writeQuorum, xl.readQuorum); err != nil {
+	if err = writeUniqueXLMetadata(xl.storageDisks, minioMetaBucket, tempUploadIDPath, partsMetadata, xl.writeQuorum); err != nil {
 		return "", toObjectErr(err, minioMetaBucket, tempUploadIDPath)
 	}
-	rErr := commitXLMetadata(xl.storageDisks, tempUploadIDPath, uploadIDPath, xl.writeQuorum, xl.readQuorum)
+	rErr := commitXLMetadata(xl.storageDisks, tempUploadIDPath, uploadIDPath, xl.writeQuorum)
 	if rErr != nil {
 		return "", toObjectErr(rErr, minioMetaBucket, uploadIDPath)
 	}
@@ -722,7 +721,7 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 	// Rename if an object already exists to temporary location.
 	uniqueID := getUUID()
 	if xl.isObject(bucket, object) {
-		err = renameObject(xl.storageDisks, bucket, object, minioMetaBucket, path.Join(tmpMetaPrefix, uniqueID), xl.writeQuorum, xl.readQuorum)
+		err = renameObject(xl.storageDisks, bucket, object, minioMetaBucket, path.Join(tmpMetaPrefix, uniqueID), xl.writeQuorum)
 		if err != nil {
 			return "", toObjectErr(err, bucket, object)
 		}
@@ -742,7 +741,7 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 	}
 
 	// Rename the multipart object to final location.
-	if err = renameObject(xl.storageDisks, minioMetaBucket, uploadIDPath, bucket, object, xl.writeQuorum, xl.readQuorum); err != nil {
+	if err = renameObject(xl.storageDisks, minioMetaBucket, uploadIDPath, bucket, object, xl.writeQuorum); err != nil {
 		return "", toObjectErr(err, bucket, object)
 	}
 

xl-v1-object.go

@@ -67,12 +67,12 @@ func (xl xlObjects) GetObject(bucket, object string, startOffset int64, length i
 		return toObjectErr(errXLReadQuorum, bucket, object)
 	}
 
-	// If all the disks returned error, we return error.
-	if errCount, err := reduceErrs(errs); err != nil {
-		if errCount < xl.readQuorum {
-			return toObjectErr(errXLReadQuorum, bucket, object)
-		}
-		return toObjectErr(err, bucket, object)
+	if reducedErr := reduceErrs(errs, []error{
+		errDiskNotFound,
+		errFaultyDisk,
+		errDiskAccessDenied,
+	}); reducedErr != nil {
+		return toObjectErr(reducedErr, bucket, object)
 	}
 
 	// List all online disks.
@@ -237,7 +237,7 @@ func (xl xlObjects) getObjectInfo(bucket, object string) (objInfo ObjectInfo, er
 	return objInfo, nil
 }
 
-func undoRename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, isPart bool, errs []error, writeQuorum, readQuorum int) {
+func undoRename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, isPart bool, errs []error) {
 	var wg = &sync.WaitGroup{}
 	// Undo rename object on disks where RenameFile succeeded.
 
@@ -264,21 +264,9 @@ func undoRename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry str
 	wg.Wait()
 }
 
-// undoRenameObject - renames back the partially successful rename operations.
-func undoRenameObject(disks []StorageAPI, srcBucket, srcObject, dstBucket, dstObject string, errs []error, writeQuorum, readQuorum int) {
-	isPart := false
-	undoRename(disks, srcBucket, srcObject, dstBucket, dstObject, isPart, errs, writeQuorum, readQuorum)
-}
-
-// undoRenamePart - renames back the partially successful rename operation.
-func undoRenamePart(disks []StorageAPI, srcBucket, srcPart, dstBucket, dstPart string, errs []error, writeQuorum, readQuorum int) {
-	isPart := true
-	undoRename(disks, srcBucket, srcPart, dstBucket, dstPart, isPart, errs, writeQuorum, readQuorum)
-}
-
 // rename - common function that renamePart and renameObject use to rename
 // the respective underlying storage layer representations.
-func rename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, isPart bool, writeQuorum, readQuorum int) error {
+func rename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, isPart bool, quorum int) error {
 	// Initialize sync waitgroup.
 	var wg = &sync.WaitGroup{}
 
@@ -311,52 +299,35 @@ func rename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string,
 
 	// We can safely allow RenameFile errors up to len(xl.storageDisks) - xl.writeQuorum
 	// otherwise return failure. Cleanup successful renames.
-	if !isDiskQuorum(errs, writeQuorum) {
-		// Check we have successful read quorum.
-		if isDiskQuorum(errs, readQuorum) {
-			return nil // Return success.
-		} // else - failed to acquire read quorum.
+	if !isDiskQuorum(errs, quorum) {
 		// Undo all the partial rename operations.
-		undoRename(disks, srcBucket, srcEntry, dstBucket, dstEntry, isPart, errs, writeQuorum, readQuorum)
+		undoRename(disks, srcBucket, srcEntry, dstBucket, dstEntry, isPart, errs)
 		return errXLWriteQuorum
 	}
 	// Return on first error, also undo any partially successful rename operations.
-	if errCount, reducedErr := reduceErrs(errs); reducedErr != nil {
-		if errCount < writeQuorum {
-			// Undo all the partial rename operations.
-			undoRename(disks, srcBucket, srcEntry, dstBucket, dstEntry, isPart, errs, writeQuorum, readQuorum)
-			return errXLWriteQuorum
-		}
-		if isErrIgnored(reducedErr, []error{
+	return reduceErrs(errs, []error{
 		errDiskNotFound,
 		errDiskAccessDenied,
 		errFaultyDisk,
-			errVolumeNotFound,
-		}) {
-			// Return success.
-			return nil
-		}
-		return reducedErr
-	}
-	return nil
+	})
 }
 
 // renamePart - renames a part of the source object to the destination
 // across all disks in parallel. Additionally if we have errors and do
 // not have a readQuorum partially renamed files are renamed back to
 // its proper location.
-func renamePart(disks []StorageAPI, srcBucket, srcPart, dstBucket, dstPart string, writeQuorum, readQuorum int) error {
+func renamePart(disks []StorageAPI, srcBucket, srcPart, dstBucket, dstPart string, quorum int) error {
 	isPart := true
-	return rename(disks, srcBucket, srcPart, dstBucket, dstPart, isPart, writeQuorum, readQuorum)
+	return rename(disks, srcBucket, srcPart, dstBucket, dstPart, isPart, quorum)
 }
 
 // renameObject - renames all source objects to destination object
 // across all disks in parallel. Additionally if we have errors and do
 // not have a readQuorum partially renamed files are renamed back to
 // its proper location.
-func renameObject(disks []StorageAPI, srcBucket, srcObject, dstBucket, dstObject string, writeQuorum, readQuorum int) error {
+func renameObject(disks []StorageAPI, srcBucket, srcObject, dstBucket, dstObject string, quorum int) error {
 	isPart := false
-	return rename(disks, srcBucket, srcObject, dstBucket, dstObject, isPart, writeQuorum, readQuorum)
+	return rename(disks, srcBucket, srcObject, dstBucket, dstObject, isPart, quorum)
 }
 
 // PutObject - creates an object upon reading from the input stream
@@ -508,7 +479,7 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	// Rename if an object already exists to temporary location.
 	newUniqueID := getUUID()
 	if xl.isObject(bucket, object) {
-		err = renameObject(xl.storageDisks, bucket, object, minioMetaTmpBucket, newUniqueID, xl.writeQuorum, xl.readQuorum)
+		err = renameObject(xl.storageDisks, bucket, object, minioMetaTmpBucket, newUniqueID, xl.writeQuorum)
 		if err != nil {
 			return "", toObjectErr(err, bucket, object)
 		}
@@ -530,12 +501,12 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	}
 
 	// Write unique `xl.json` for each disk.
-	if err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempObj, partsMetadata, xl.writeQuorum, xl.readQuorum); err != nil {
+	if err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempObj, partsMetadata, xl.writeQuorum); err != nil {
 		return "", toObjectErr(err, bucket, object)
 	}
 
 	// Rename the successfully written temporary object to final location.
-	err = renameObject(onlineDisks, minioMetaTmpBucket, tempObj, bucket, object, xl.writeQuorum, xl.readQuorum)
+	err = renameObject(onlineDisks, minioMetaTmpBucket, tempObj, bucket, object, xl.writeQuorum)
 	if err != nil {
 		return "", toObjectErr(err, bucket, object)
 	}

xl-v1-utils.go

@@ -30,9 +30,12 @@ import (
 // value is greater than or equal to simple majority, since none of the equally
 // maximal values would occur quorum or more number of times.
 
-func reduceErrs(errs []error) (int, error) {
+func reduceErrs(errs []error, ignoredErrs []error) error {
 	errorCounts := make(map[error]int)
 	for _, err := range errs {
+		if isErrIgnored(err, ignoredErrs) {
+			continue
+		}
 		errorCounts[err]++
 	}
 	max := 0
@@ -43,7 +46,7 @@ func reduceErrs(errs []error) (int, error) {
 			errMax = err
 		}
 	}
-	return max, errMax
+	return errMax
 }
 
 // Validates if we have quorum based on the errors related to disk only.

xl-v1-utils_test.go

@@ -20,23 +20,40 @@ import "testing"
 
 // Test for reduceErrs.
 func TestReduceErrs(t *testing.T) {
+	// List all of all test cases to validate various cases of reduce errors.
 	testCases := []struct {
 		errs        []error
+		ignoredErrs []error
 		err         error
-		count int
 	}{
-		{[]error{errDiskNotFound, errDiskNotFound, errDiskFull}, errDiskNotFound, 2},
-		{[]error{errDiskFull, errDiskNotFound, nil, nil}, nil, 2},
-		{[]error{}, nil, 0},
+		// Validate if have reduced properly.
+		{[]error{
+			errDiskNotFound,
+			errDiskNotFound,
+			errDiskFull,
+		}, []error{}, errDiskNotFound},
+		// Validate if have no consensus.
+		{[]error{
+			errDiskFull,
+			errDiskNotFound,
+			nil, nil,
+		}, []error{}, nil},
+		// Validate if have consensus and errors ignored.
+		{[]error{
+			errVolumeNotFound,
+			errVolumeNotFound,
+			errVolumeNotFound,
+			errDiskNotFound,
+			errDiskNotFound,
+		}, []error{errDiskNotFound}, errVolumeNotFound},
+		{[]error{}, []error{}, nil},
 	}
+	// Validates list of all the testcases for returning valid errors.
 	for i, testCase := range testCases {
-		gotMax, gotErr := reduceErrs(testCase.errs)
+		gotErr := reduceErrs(testCase.errs, testCase.ignoredErrs)
 		if testCase.err != gotErr {
 			t.Errorf("Test %d : expected %s, got %s", i+1, testCase.err, gotErr)
 		}
-		if testCase.count != gotMax {
-			t.Errorf("Test %d : expected %d, got %d", i+1, testCase.count, gotMax)
-		}
 	}
 }
 

xl-v1.go

@@ -45,7 +45,7 @@ const (
 	maxErasureBlocks = 16
 
 	// Minimum erasure blocks.
-	minErasureBlocks = 6
+	minErasureBlocks = 4
 )
 
 // xlObjects - Implements XL object layer.
@@ -84,7 +84,7 @@ func checkSufficientDisks(disks []string) error {
 	}
 
 	// Verify if we have even number of disks.
-	// only combination of 6, 8, 10, 12, 14, 16 are supported.
+	// only combination of 4, 6, 8, 10, 12, 14, 16 are supported.
 	if !isEven(totalDisks) {
 		return errXLNumDisks
 	}
@@ -194,9 +194,9 @@ func newXLObjects(disks, ignoredDisks []string) (ObjectLayer, error) {
 	}
 
 	// Figure out read and write quorum based on number of storage disks.
-	// READ and WRITE quorum is always set to (N/2 + 1) number of disks.
-	xl.readQuorum = len(xl.storageDisks)/2 + 1
-	xl.writeQuorum = len(xl.storageDisks)/2 + 1
+	// READ and WRITE quorum is always set to (N/2) number of disks.
+	xl.readQuorum = len(xl.storageDisks) / 2
+	xl.writeQuorum = len(xl.storageDisks) / 2
 
 	// Return successfully initialized object layer.
 	return xl, nil

xl-v1_test.go

@@ -73,7 +73,7 @@ func TestCheckSufficientDisks(t *testing.T) {
 		},
 		// Lesser than minimum number of disks < 6.
 		{
-			disks[0:5],
+			disks[0:3],
 			errXLMinDisks,
 		},
 		// Odd number of disks, not divisible by '2'.