Add self-healing feature (#7604)

- Background Heal routine receives heal requests from a channel, either to
heal format, buckets or objects
- Daily sweeper lists all objects in all buckets, these objects
don't necessarly have read quorum so they can be removed if
these objects are unhealable
- Heal daily ops receives objects from the daily sweeper
and send them to the heal routine.

cmd/background-heal-ops.go

@@ -0,0 +1,160 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 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 (
+	"context"
+	"time"
+
+	"github.com/minio/minio/cmd/logger"
+	"github.com/minio/minio/pkg/madmin"
+)
+
+// healTask represents what to heal along with options
+//   path: '/' =>  Heal disk formats along with metadata
+//   path: 'bucket/' or '/bucket/' => Heal bucket
+//   path: 'bucket/object' => Heal object
+type healTask struct {
+	path string
+	opts madmin.HealOpts
+	// Healing response will be sent here
+	responseCh chan healResult
+}
+
+// healResult represents a healing result with a possible error
+type healResult struct {
+	result madmin.HealResultItem
+	err    error
+}
+
+// healRoutine receives heal tasks, to heal buckets, objects and format.json
+type healRoutine struct {
+	tasks  chan healTask
+	doneCh chan struct{}
+}
+
+// Add a new task in the tasks queue
+func (h *healRoutine) queueHealTask(task healTask) {
+	h.tasks <- task
+}
+
+// Wait for heal requests and process them
+func (h *healRoutine) run() {
+	ctx := context.Background()
+	for {
+		select {
+		case task, ok := <-h.tasks:
+			if !ok {
+				break
+			}
+			if globalHTTPServer != nil {
+				// Wait at max 1 minute for an inprogress request
+				// before proceeding to heal
+				waitCount := 60
+				// Any requests in progress, delay the heal.
+				for globalHTTPServer.GetRequestCount() > 2 && waitCount > 0 {
+					waitCount--
+					time.Sleep(1 * time.Second)
+				}
+			}
+
+			var res madmin.HealResultItem
+			var err error
+			bucket, object := urlPath2BucketObjectName(task.path)
+			switch {
+			case bucket == "" && object == "":
+				res, err = bgHealDiskFormat(ctx, task.opts)
+			case bucket != "" && object == "":
+				res, err = bgHealBucket(ctx, bucket, task.opts)
+			case bucket != "" && object != "":
+				res, err = bgHealObject(ctx, bucket, object, task.opts)
+			}
+			task.responseCh <- healResult{result: res, err: err}
+		case <-h.doneCh:
+			return
+		case <-GlobalServiceDoneCh:
+			return
+		}
+	}
+}
+
+func initHealRoutine() *healRoutine {
+	return &healRoutine{
+		tasks:  make(chan healTask),
+		doneCh: make(chan struct{}),
+	}
+
+}
+
+func initBackgroundHealing() {
+	healBg := initHealRoutine()
+	go healBg.run()
+
+	globalBackgroundHealing = healBg
+}
+
+// bgHealDiskFormat - heals format.json, return value indicates if a
+// failure error occurred.
+func bgHealDiskFormat(ctx context.Context, opts madmin.HealOpts) (madmin.HealResultItem, error) {
+	// Get current object layer instance.
+	objectAPI := newObjectLayerFn()
+	if objectAPI == nil {
+		return madmin.HealResultItem{}, errServerNotInitialized
+	}
+
+	res, err := objectAPI.HealFormat(ctx, opts.DryRun)
+
+	// return any error, ignore error returned when disks have
+	// already healed.
+	if err != nil && err != errNoHealRequired {
+		return madmin.HealResultItem{}, err
+	}
+
+	// Healing succeeded notify the peers to reload format and re-initialize disks.
+	// We will not notify peers if healing is not required.
+	if err == nil {
+		for _, nerr := range globalNotificationSys.ReloadFormat(opts.DryRun) {
+			if nerr.Err != nil {
+				logger.GetReqInfo(ctx).SetTags("peerAddress", nerr.Host.String())
+				logger.LogIf(ctx, nerr.Err)
+			}
+		}
+	}
+
+	return res, nil
+}
+
+// bghealBucket - traverses and heals given bucket
+func bgHealBucket(ctx context.Context, bucket string, opts madmin.HealOpts) (madmin.HealResultItem, error) {
+	// Get current object layer instance.
+	objectAPI := newObjectLayerFn()
+	if objectAPI == nil {
+		return madmin.HealResultItem{}, errServerNotInitialized
+	}
+
+	return objectAPI.HealBucket(ctx, bucket, opts.DryRun, opts.Remove)
+}
+
+// bgHealObject - heal the given object and record result
+func bgHealObject(ctx context.Context, bucket, object string, opts madmin.HealOpts) (madmin.HealResultItem, error) {
+	// Get current object layer instance.
+	objectAPI := newObjectLayerFn()
+	if objectAPI == nil {
+		return madmin.HealResultItem{}, errServerNotInitialized
+	}
+	return objectAPI.HealObject(ctx, bucket, object, opts.DryRun, opts.Remove, opts.ScanMode)
+}