containerd/plugins/mount/manager.go

/*
   Copyright The containerd Authors.

   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 mount

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"

	bolt "go.etcd.io/bbolt"

	"github.com/containerd/log"
	"github.com/containerd/plugin"
	"github.com/containerd/plugin/registry"

	"github.com/containerd/containerd/v2/core/metadata"
	"github.com/containerd/containerd/v2/core/metadata/boltutil"
	"github.com/containerd/containerd/v2/core/mount"
	"github.com/containerd/containerd/v2/core/mount/manager"
	"github.com/containerd/containerd/v2/plugins"
)

func init() {
	registry.Register(&plugin.Registration{
		Type: plugins.MountManagerPlugin,
		ID:   "bolt",
		Requires: []plugin.Type{
			plugins.MetadataPlugin,
			plugins.MountHandlerPlugin,
		},
		InitFn: func(ic *plugin.InitContext) (any, error) {
			md, err := ic.GetSingle(plugins.MetadataPlugin)
			if err != nil {
				return nil, err
			}
			hp, err := ic.GetByType(plugins.MountHandlerPlugin)
			if err != nil && !errors.Is(err, plugin.ErrPluginNotFound) {
				return nil, err
			}
			var opts []manager.Opt
			for k, v := range hp {
				opts = append(opts, manager.WithMountHandler(k, v.(mount.Handler)))
			}

			root := ic.Properties[plugins.PropertyStateDir]

			// TODO: Allow overriding root and target directory from config

			targets := filepath.Join(root, "t")
			if merr := os.MkdirAll(targets, 0700); merr != nil {
				return nil, merr
			}

			// roots are the directories that mount handlers can operate in
			// TODO: support additional roots from config
			opts = append(opts, manager.WithAllowedRoot(filepath.Dir(ic.Properties[plugins.PropertyRootDir])))

			//if _, ok := mhandlers["mkdir"]; !ok {
			//	mkdir, err := handlers.MkdirHandler(roots...)
			//	if err != nil {
			//		return nil, fmt.Errorf("failed to create mkdir handler: %w", err)
			//	}
			//	mhandlers["mkdir"] = mkdir
			//}

			metadb := filepath.Join(root, "mounts.db")

			options := *bolt.DefaultOptions

			// Disable stat usage since we never consume the data.
			// This can reduce unnecessary contention during transactions.
			// https://github.com/etcd-io/bbolt/pull/977
			options.NoStatistics = true

			db, err := bolt.Open(metadb, 0600, &options)
			if err != nil {
				return nil, fmt.Errorf("failed to open database file: %w", err)
			}

			mm, err := manager.NewManager(db, targets, opts...)
			if err != nil {
				db.Close()
				return nil, fmt.Errorf("failed to create mount manager: %w", err)
			}

			//TODO: IF has sync
			if sync, ok := mm.(interface{ Sync(context.Context) error }); ok {

				// Start transaction and then background sync with mount state,
				// ensure startup waits until ready to continue
				tx, err := db.Begin(true)
				if err != nil {
					db.Close()
					return nil, fmt.Errorf("failed to open database for write: %w", err)
				}
				ctx := boltutil.WithTransaction(ic.Context, tx)

				ready := ic.RegisterReadiness()
				go func() {
					defer ready()
					if err := sync.Sync(ctx); err == nil {
						tx.Commit()
					} else {
						log.G(ctx).WithError(err).Errorf("failed to sync mounts")
						tx.Rollback()
					}
				}()
			}

			if collector, ok := mm.(metadata.Collector); ok {
				md.(*metadata.DB).RegisterCollectibleResource(metadata.ResourceMount, collector)
			}
			return mm, nil
		},
	})
}