xl: heal bucket should validate if bucket exists first. (#2953)

Fixes #2944

cmd/xl-v1-healing-common.go

@@ -0,0 +1,135 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import "time"
+
+// commonTime returns a maximally occurring time from a list of time.
+func commonTime(modTimes []time.Time) (modTime time.Time) {
+	var maxima int // Counter for remembering max occurrence of elements.
+	timeOccurenceMap := make(map[time.Time]int)
+	// Ignore the uuid sentinel and count the rest.
+	for _, time := range modTimes {
+		if time == timeSentinel {
+			continue
+		}
+		timeOccurenceMap[time]++
+	}
+	// Find the common cardinality from previously collected
+	// occurrences of elements.
+	for time, count := range timeOccurenceMap {
+		if count > maxima {
+			maxima = count
+			modTime = time
+		}
+	}
+	// Return the collected common uuid.
+	return modTime
+}
+
+// Beginning of unix time is treated as sentinel value here.
+var timeSentinel = time.Unix(0, 0).UTC()
+
+// Boot modTimes up to disk count, setting the value to time sentinel.
+func bootModtimes(diskCount int) []time.Time {
+	modTimes := make([]time.Time, diskCount)
+	// Boots up all the modtimes.
+	for i := range modTimes {
+		modTimes[i] = timeSentinel
+	}
+	return modTimes
+}
+
+// Extracts list of times from xlMetaV1 slice and returns, skips
+// slice elements which have errors. As a special error
+// errFileNotFound is treated as a initial good condition.
+func listObjectModtimes(partsMetadata []xlMetaV1, errs []error) (modTimes []time.Time) {
+	modTimes = bootModtimes(len(partsMetadata))
+	// Set a new time value, specifically set when
+	// error == errFileNotFound (this is needed when this is a
+	// fresh PutObject).
+	timeNow := time.Now().UTC()
+	for index, metadata := range partsMetadata {
+		if errs[index] == nil {
+			// Once the file is found, save the uuid saved on disk.
+			modTimes[index] = metadata.Stat.ModTime
+		} else if errs[index] == errFileNotFound {
+			// Once the file is not found then the epoch is current time.
+			modTimes[index] = timeNow
+		}
+	}
+	return modTimes
+}
+
+// Returns slice of online disks needed.
+// - slice returing readable disks.
+// - modTime of the Object
+func listOnlineDisks(disks []StorageAPI, partsMetadata []xlMetaV1, errs []error) (onlineDisks []StorageAPI, modTime time.Time) {
+	onlineDisks = make([]StorageAPI, len(disks))
+
+	// List all the file commit ids from parts metadata.
+	modTimes := listObjectModtimes(partsMetadata, errs)
+
+	// Reduce list of UUIDs to a single common value.
+	modTime = commonTime(modTimes)
+
+	// Create a new online disks slice, which have common uuid.
+	for index, t := range modTimes {
+		if t == modTime {
+			onlineDisks[index] = disks[index]
+		} else {
+			onlineDisks[index] = nil
+		}
+	}
+	return onlineDisks, modTime
+}
+
+// Return disks with the outdated or missing object.
+func outDatedDisks(disks []StorageAPI, partsMetadata []xlMetaV1, errs []error) (outDatedDisks []StorageAPI) {
+	outDatedDisks = make([]StorageAPI, len(disks))
+	latestDisks, _ := listOnlineDisks(disks, partsMetadata, errs)
+	for index, disk := range latestDisks {
+		if errorCause(errs[index]) == errFileNotFound {
+			outDatedDisks[index] = disks[index]
+			continue
+		}
+		if errs[index] != nil {
+			continue
+		}
+		if disk == nil {
+			outDatedDisks[index] = disks[index]
+		}
+	}
+	return outDatedDisks
+}
+
+// Returns if the object should be healed.
+func xlShouldHeal(partsMetadata []xlMetaV1, errs []error) bool {
+	modTime := commonTime(listObjectModtimes(partsMetadata, errs))
+	for index := range partsMetadata {
+		if errs[index] == errDiskNotFound {
+			continue
+		}
+		if errs[index] != nil {
+			return true
+		}
+		if modTime != partsMetadata[index].Stat.ModTime {
+			return true
+		}
+	}
+	return false
+}