xl: Make namespace locking granular for PutObject (#2199)

.travis.yml

@@ -4,9 +4,10 @@ language: go
 
 os:
 - linux
-- osx
+# Enable OSX builds when travis service is back.
+#- osx
 
-osx_image: xcode7.2
+#osx_image: xcode7.2
 
 env:
 - ARCH=x86_64

xl-v1-object.go

@@ -68,7 +68,10 @@ func (xl xlObjects) GetObject(bucket, object string, startOffset int64, length i
 	}
 
 	// If all the disks returned error, we return error.
-	if err := reduceErrs(errs); err != nil {
+	if errCount, err := reduceErrs(errs); err != nil {
+		if errCount < xl.readQuorum {
+			return toObjectErr(errXLReadQuorum, bucket, object)
+		}
 		return toObjectErr(err, bucket, object)
 	}
 
@@ -368,20 +371,25 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	minioMetaTmpBucket := path.Join(minioMetaBucket, tmpMetaPrefix)
 	tempObj := uniqueID
 
-	// Lock the object.
-	nsMutex.Lock(bucket, object)
-	defer nsMutex.Unlock(bucket, object)
-
-	// Initialize xl meta.
-	xlMeta := newXLMetaV1(object, xl.dataBlocks, xl.parityBlocks)
-
+	nsMutex.RLock(bucket, object)
 	// Read metadata associated with the object from all disks.
 	partsMetadata, errs := readAllXLMetadata(xl.storageDisks, bucket, object)
+	nsMutex.RUnlock(bucket, object)
+
 	// Do we have write quroum?.
 	if !isDiskQuorum(errs, xl.writeQuorum) {
 		return "", toObjectErr(errXLWriteQuorum, bucket, object)
 	}
 
+	// errFileNotFound is handled specially since it's OK for the object to
+	// not exists in the namespace yet.
+	if errCount, reducedErr := reduceErrs(errs); reducedErr != nil && reducedErr != errFileNotFound {
+		if errCount < xl.writeQuorum {
+			return "", toObjectErr(errXLWriteQuorum, bucket, object)
+		}
+		return "", toObjectErr(reducedErr, bucket, object)
+	}
+
 	// List all online disks.
 	onlineDisks, _ := xl.listOnlineDisks(partsMetadata, errs)
 
@@ -426,6 +434,9 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	// Tee reader combines incoming data stream and md5, data read from input stream is written to md5.
 	teeReader := io.TeeReader(limitDataReader, mw)
 
+	// Initialize xl meta.
+	xlMeta := newXLMetaV1(object, xl.dataBlocks, xl.parityBlocks)
+
 	// Collect all the previous erasure infos across the disk.
 	var eInfos []erasureInfo
 	for range onlineDisks {
@@ -483,6 +494,10 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 		}
 	}
 
+	// Lock the object.
+	nsMutex.Lock(bucket, object)
+	defer nsMutex.Unlock(bucket, object)
+
 	// Check if an object is present as one of the parent dir.
 	// -- FIXME. (needs a new kind of lock).
 	if xl.parentDirIsObject(bucket, path.Dir(object)) {
@@ -513,12 +528,12 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	}
 
 	// Write unique `xl.json` for each disk.
-	if err = writeUniqueXLMetadata(xl.storageDisks, minioMetaTmpBucket, tempObj, partsMetadata, xl.writeQuorum, xl.readQuorum); err != nil {
+	if err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempObj, partsMetadata, xl.writeQuorum, xl.readQuorum); err != nil {
 		return "", toObjectErr(err, bucket, object)
 	}
 
 	// Rename the successfully written temporary object to final location.
-	err = renameObject(xl.storageDisks, minioMetaTmpBucket, tempObj, bucket, object, xl.writeQuorum, xl.readQuorum)
+	err = renameObject(onlineDisks, minioMetaTmpBucket, tempObj, bucket, object, xl.writeQuorum, xl.readQuorum)
 	if err != nil {
 		return "", toObjectErr(err, bucket, object)
 	}

xl-v1-utils.go

@@ -23,57 +23,27 @@ import (
 	"path"
 )
 
-// Returns nil even if one of the slice elements is nil.
-// Else returns the error which occurs the most.
-func reduceErrs(errs []error) error {
-	// In case the error type is not in the known error list.
-	var unknownErr = errors.New("unknown error")
-	var errTypes = []struct {
-		err   error // error type
-		count int   // occurrence count
-	}{
-		// List of known error types. Any new type that can be returned from StorageAPI should
-		// be added to this list. Most common errors are listed here.
-		{errDiskNotFound, 0}, {errFaultyDisk, 0}, {errFileAccessDenied, 0},
-		{errFileNotFound, 0}, {errFileNameTooLong, 0}, {errVolumeNotFound, 0},
-		{errDiskFull, 0},
-		// unknownErr count - count of the number of unknown errors.
-		{unknownErr, 0},
-	}
-	// In case unknownErr count occurs maximum number of times, unknownErrType is used to
-	// to store it so that it can be used for the return error type.
-	var unknownErrType error
+// Returns number of errors that occurred the most (incl. nil) and the
+// corresponding error value. N B when there is more than one error value that
+// occurs maximum number of times, the error value returned depends on how
+// golang's map orders keys. This doesn't affect correctness as long as quorum
+// value is greater than or equal to simple majority, since none of the equally
+// maximal values would occur quorum or more number of times.
 
-	// For each err in []errs increment the corresponding count value.
+func reduceErrs(errs []error) (int, error) {
+	errorCounts := make(map[error]int)
 	for _, err := range errs {
-		if err == nil {
-			// Return nil even if one of the elements is nil.
-			return nil
-		}
-		for i := range errTypes {
-			if errTypes[i].err == err {
-				errTypes[i].count++
-				break
-			}
-			if errTypes[i].err == unknownErr {
-				errTypes[i].count++
-				unknownErrType = err
-				break
-			}
-		}
+		errorCounts[err]++
 	}
 	max := 0
-	// Get the error type which has the maximum count.
-	for i, errType := range errTypes {
-		if errType.count > errTypes[max].count {
-			max = i
+	var errMax error
+	for err, count := range errorCounts {
+		if max < count {
+			max = count
+			errMax = err
 		}
 	}
-	if errTypes[max].err == unknownErr {
-		// Return the unknown error.
-		return unknownErrType
-	}
-	return errTypes[max].err
+	return max, errMax
 }
 
 // Validates if we have quorum based on the errors related to disk only.

xl-v1-utils_test.go

@@ -17,27 +17,25 @@
 package main
 
 import "testing"
-import "syscall"
 
 // Test for reduceErrs.
 func TestReduceErrs(t *testing.T) {
 	testCases := []struct {
-		errs []error
-		err  error
+		errs  []error
+		err   error
+		count int
 	}{
-		{[]error{errDiskNotFound, errDiskNotFound, errDiskFull}, errDiskNotFound},
-		{[]error{errDiskNotFound, errDiskFull, errDiskFull}, errDiskFull},
-		{[]error{errDiskFull, errDiskNotFound, errDiskFull}, errDiskFull},
-		// A case for error not in the known errors list (refer to func reduceErrs)
-		{[]error{errDiskFull, syscall.EEXIST, syscall.EEXIST}, syscall.EEXIST},
-		{[]error{errDiskNotFound, errDiskNotFound, nil}, nil},
-		{[]error{nil, nil, nil}, nil},
+		{[]error{errDiskNotFound, errDiskNotFound, errDiskFull}, errDiskNotFound, 2},
+		{[]error{errDiskFull, errDiskNotFound, nil, nil}, nil, 2},
+		{[]error{}, nil, 0},
 	}
 	for i, testCase := range testCases {
-		expected := testCase.err
-		got := reduceErrs(testCase.errs)
-		if expected != got {
-			t.Errorf("Test %d : expected %s, got %s", i+1, expected, got)
+		gotMax, gotErr := reduceErrs(testCase.errs)
+		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)
 		}
 	}
 }