Bootstrap logic to fix read-only volumes with `volume.check.disk`. (#7531)

* Bootstrap logic to fix read-only volumes with `volume.check.disk`.

The new implementation performs a second pass where read-only volumes are (optionally)
verified and fixed.

For each non-writable volume ID A:
  if volume is not full
    prune late volume entries not matching its index file
    select a writable volume replica B
    append missing entries from B into A
    mark the volume as writable (healthy)

* variable and parameter renaming

---------

Co-authored-by: chrislu <chris.lu@gmail.com>

weed/shell/command_volume_check_disk.go

@@ -37,6 +37,7 @@ type volumeCheckDisk struct {
 	verbose            bool
 	applyChanges       bool
 	syncDeletions      bool
+	fixReadOnly        bool
 	nonRepairThreshold float64
 }
 
@@ -48,19 +49,27 @@ func (c *commandVolumeCheckDisk) Help() string {
 	return `check all replicated volumes to find and fix inconsistencies. It is optional and resource intensive.
 
 	How it works:
-	
+
 	find all volumes that are replicated
-	  for each volume id, if there are more than 2 replicas, find one pair with the largest 2 in file count.
-      for the pair volume A and B
-        bi-directional sync (default): append entries in A and not in B to B, and entries in B and not in A to A
-        uni-directional sync (read-only repair): only sync from source to target without modifying source
+
+	for each writable volume ID, if there are more than 2 replicas, find one pair with the largest 2 in file count
+		for the pair volume A and B
+			append entries in A and not in B to B
+			append entries in B and not in A to A
+
+	optionally, for each non-writable volume replica A
+		if volume is not full
+			prune late volume entries not matching its index file
+			select a writable volume replica B
+			append missing entries from B into A
+			mark the volume as writable (healthy)
 
 	Options:
 	  -slow: check all replicas even if file counts are the same
 	  -v: verbose mode with detailed progress output
 	  -volumeId: check only a specific volume ID (0 for all)
 	  -apply: actually apply the fixes (default is simulation mode)
-	  -force-readonly: also check and repair read-only volumes using uni-directional sync
+	  -fixReadOnly: also check and repair read-only volumes using uni-directional sync
 	  -syncDeleted: sync deletion records during repair
 	  -nonRepairThreshold: maximum fraction of missing keys allowed for repair (default 0.3)
 
@@ -80,7 +89,7 @@ func (c *commandVolumeCheckDisk) Do(args []string, commandEnv *CommandEnv, write
 	applyChanges := fsckCommand.Bool("apply", false, "apply the fix")
 	// TODO: remove this alias
 	applyChangesAlias := fsckCommand.Bool("force", false, "apply the fix (alias for -apply)")
-	forceReadonly := fsckCommand.Bool("force-readonly", false, "apply the fix even on readonly volumes")
+	fixReadOnly := fsckCommand.Bool("fixReadOnly", false, "apply the fix even on readonly volumes (EXPERIMENTAL!)")
 	syncDeletions := fsckCommand.Bool("syncDeleted", false, "sync of deletions the fix")
 	nonRepairThreshold := fsckCommand.Float64("nonRepairThreshold", 0.3, "repair when missing keys is not more than this limit")
 	if err = fsckCommand.Parse(args); err != nil {
@@ -103,6 +112,7 @@ func (c *commandVolumeCheckDisk) Do(args []string, commandEnv *CommandEnv, write
 		verbose:            *verbose,
 		applyChanges:       *applyChanges,
 		syncDeletions:      *syncDeletions,
+		fixReadOnly:        *fixReadOnly,
 		nonRepairThreshold: *nonRepairThreshold,
 	}
 
@@ -123,24 +133,20 @@ func (c *commandVolumeCheckDisk) Do(args []string, commandEnv *CommandEnv, write
 		}
 	}
 
-	vcd.write("Pass #1 (writeable volumes)\n")
-	if err := vcd.checkWriteableVolumes(volumeReplicas); err != nil {
+	if err := vcd.checkWritableVolumes(volumeReplicas); err != nil {
 		return err
 	}
-	if *forceReadonly {
-		vcd.write("Pass #2 (read-only volumes)\n")
-		if err := vcd.checkReadOnlyVolumes(volumeReplicas); err != nil {
-			return err
-		}
-
+	if err := vcd.checkReadOnlyVolumes(volumeReplicas); err != nil {
+		return err
 	}
 
 	return nil
 }
 
-// checkWriteableVolumes fixes volume replicas which are not read-only.
-func (vcd *volumeCheckDisk) checkWriteableVolumes(volumeReplicas map[uint32][]*VolumeReplica) error {
-	// pick 1 pairs of volume replica
+// checkWritableVolumes fixes volume replicas which are not read-only.
+func (vcd *volumeCheckDisk) checkWritableVolumes(volumeReplicas map[uint32][]*VolumeReplica) error {
+	vcd.write("Pass #1 (writable volumes)\n")
+
 	for _, replicas := range volumeReplicas {
 		// filter readonly replica
 		var writableReplicas []*VolumeReplica
@@ -157,16 +163,14 @@ func (vcd *volumeCheckDisk) checkWriteableVolumes(volumeReplicas map[uint32][]*V
 		})
 		for len(writableReplicas) >= 2 {
 			a, b := writableReplicas[0], writableReplicas[1]
-			if !vcd.slowMode {
-				shouldSkip, err := vcd.shouldSkipVolume(a, b)
-				if err != nil {
-					vcd.write("error checking if volume %d should be skipped: %v\n", a.info.Id, err)
-					// Continue with sync despite error to be safe
-				} else if shouldSkip {
-					// always choose the larger volume to be the source
-					writableReplicas = append(writableReplicas[:1], writableReplicas[2:]...)
-					continue
-				}
+			shouldSkip, err := vcd.shouldSkipVolume(a, b)
+			if err != nil {
+				vcd.write("error checking if volume %d should be skipped: %v\n", a.info.Id, err)
+				// Continue with sync despite error to be safe
+			} else if shouldSkip {
+				// always choose the larger volume to be the source
+				writableReplicas = append(writableReplicas[:1], writableReplicas[2:]...)
+				continue
 			}
 			if err := vcd.syncTwoReplicas(a, b, true); err != nil {
 				vcd.write("sync volume %d on %s and %s: %v\n", a.info.Id, a.location.dataNode.Id, b.location.dataNode.Id, err)
@@ -183,9 +187,107 @@ func (vcd *volumeCheckDisk) checkWriteableVolumes(volumeReplicas map[uint32][]*V
 	return nil
 }
 
-// checkReadOnlyVolumes fixes read-only volume replicas.
+// makeVolumeWritable flags a volume as writable, by volume ID.
+func (vcd *volumeCheckDisk) makeVolumeWritable(vid uint32, vr *VolumeReplica) error {
+	if !vcd.applyChanges {
+		return nil
+	}
+
+	err := operation.WithVolumeServerClient(false, pb.NewServerAddressFromDataNode(vr.location.dataNode), vcd.grpcDialOption(), func(volumeServerClient volume_server_pb.VolumeServerClient) error {
+		_, vsErr := volumeServerClient.VolumeMarkWritable(context.Background(), &volume_server_pb.VolumeMarkWritableRequest{
+			VolumeId: vid,
+		})
+		return vsErr
+	})
+	if err != nil {
+		return err
+	}
+
+	vcd.write("volume %d on %s is now writable\n", vid, vr.location.dataNode.Id)
+	return nil
+}
+
+// makeVolumeReadOnly flags a volume as read-only, by volume ID.
+func (vcd *volumeCheckDisk) makeVolumeReadonly(vid uint32, vr *VolumeReplica) error {
+	if !vcd.applyChanges {
+		return nil
+	}
+
+	err := operation.WithVolumeServerClient(false, pb.NewServerAddressFromDataNode(vr.location.dataNode), vcd.grpcDialOption(), func(volumeServerClient volume_server_pb.VolumeServerClient) error {
+		_, vsErr := volumeServerClient.VolumeMarkReadonly(context.Background(), &volume_server_pb.VolumeMarkReadonlyRequest{
+			VolumeId: vid,
+		})
+		return vsErr
+	})
+	if err != nil {
+		return err
+	}
+
+	vcd.write("volume %d on %s is now read-only\n", vid, vr.location.dataNode.Id)
+	return nil
+}
+
 func (vcd *volumeCheckDisk) checkReadOnlyVolumes(volumeReplicas map[uint32][]*VolumeReplica) error {
-	return fmt.Errorf("not yet implemented (https://github.com/seaweedfs/seaweedfs/issues/7442)")
+	if !vcd.fixReadOnly {
+		return nil
+	}
+	vcd.write("Pass #2 (read-only volumes)\n")
+
+	for vid, replicas := range volumeReplicas {
+		var source *VolumeReplica = nil
+		roReplicas := []*VolumeReplica{}
+
+		for _, r := range replicas {
+			if r.info.ReadOnly {
+				roReplicas = append(roReplicas, r)
+			} else {
+				// we assume all writable replicas are identical by this point, after the checkWritableVolumes() pass.
+				source = r
+			}
+		}
+		if len(roReplicas) == 0 {
+			vcd.write("no read-only replicas for volume %d\n", vid)
+			continue
+		}
+		if source == nil {
+			vcd.write("got %d read-only replicas for volume %d and no writable replicas to fix from\n", len(roReplicas), vid)
+			continue
+		}
+
+		// attempt to fix read-only replicas from the know good source
+		for _, r := range roReplicas {
+			// TODO: skip full readonly volumes.
+			skip, err := vcd.shouldSkipVolume(r, source)
+			if err != nil {
+				vcd.write("error checking if volume %d should be skipped: %v\n", r.info.Id, err)
+				continue
+			}
+			if skip {
+				continue
+			}
+
+			// make volume writable...
+			if err := vcd.makeVolumeWritable(vid, r); err != nil {
+				return err
+			}
+
+			// ...fix it...
+			// TODO: test whether syncTwoReplicas() is enough to prune garbage entries on broken volumes.
+			if err := vcd.syncTwoReplicas(source, r, false); err != nil {
+				vcd.write("sync read-only volume %d on %s from %s: %v\n", vid, r.location.dataNode.Id, source.location.dataNode.Id, err)
+
+				// ...or revert it back to read-only, if something went wrong.
+				if roErr := vcd.makeVolumeReadonly(vid, r); roErr != nil {
+					return fmt.Errorf("failed to make volume %d on %s readonly after: %v: %v", vid, r.location.dataNode.Id, err, roErr)
+				}
+				vcd.write("volume %d on %s is now read-only\n", vid, r.location.dataNode.Id)
+
+				return err
+			}
+		}
+	}
+
+	return nil
 }
 
 func (vcd *volumeCheckDisk) grpcDialOption() grpc.DialOption {
@@ -260,6 +362,11 @@ func (vcd *volumeCheckDisk) eqVolumeFileCount(a, b *VolumeReplica) (bool, bool,
 // Error Handling: Errors from eqVolumeFileCount are wrapped with context and propagated.
 // The Do method logs these errors and continues processing to ensure other volumes are checked.
 func (vcd *volumeCheckDisk) shouldSkipVolume(a, b *VolumeReplica) (bool, error) {
+	if vcd.slowMode {
+		// never skip volumes on slow mode
+		return false, nil
+	}
+
 	pulseTimeAtSecond := vcd.now.Add(-constants.VolumePulsePeriod * 2).Unix()
 	doSyncDeletedCount := false
 	if vcd.syncDeletions && a.info.DeleteCount != b.info.DeleteCount {