darwin.go

//go:build darwin
// +build darwin

/*
   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 darwin

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

	"github.com/containerd/containerd/log"
	"github.com/containerd/containerd/mount"
	"github.com/containerd/containerd/snapshots"
	"github.com/containerd/containerd/snapshots/storage"

	"github.com/containerd/continuity/fs"
	"github.com/ukontainer/darwin-snapshotter/hdiu"
)

const (
	imageDirName = "images"
	imageSizeMB  = 512
)

type snapshotter struct {
	root string
	ms   *storage.MetaStore
}

// NewSnapshotter returns a Snapshotter which copies layers on the underlying
// file system. A metadata file is stored under the root.
func NewSnapshotter(root string) (snapshots.Snapshotter, error) {
	if err := os.MkdirAll(root, 0700); err != nil {
		return nil, err
	}
	ms, err := storage.NewMetaStore(filepath.Join(root, "metadata.db"))
	if err != nil {
		return nil, err
	}

	// create disk image directory
	if err := os.Mkdir(filepath.Join(root, imageDirName), 0700); err != nil && !os.IsExist(err) {
		return nil, fmt.Errorf("failed to create image directory: %s, %w", imageDirName, err)
	}

	return &snapshotter{
		root: root,
		ms:   ms,
	}, nil
}

// Stat returns the info for an active or committed snapshot by name or
// key.
//
// Should be used for parent resolution, existence checks and to discern
// the kind of snapshot.
func (o *snapshotter) Stat(ctx context.Context, key string) (snapshots.Info, error) {
	ctx, t, err := o.ms.TransactionContext(ctx, false)
	if err != nil {
		return snapshots.Info{}, err
	}
	defer func() {
		if rerr := t.Rollback(); rerr != nil {
			log.G(ctx).WithError(rerr).Warn("failed to rollback transaction")
		}
	}()
	_, info, _, err := storage.GetInfo(ctx, key)
	if err != nil {
		return snapshots.Info{}, err
	}

	return info, nil
}

func (o *snapshotter) Update(ctx context.Context, info snapshots.Info, fieldpaths ...string) (snapshots.Info, error) {
	ctx, t, err := o.ms.TransactionContext(ctx, true)
	if err != nil {
		return snapshots.Info{}, err
	}

	info, err = storage.UpdateInfo(ctx, info, fieldpaths...)
	if err != nil {
		if rerr := t.Rollback(); rerr != nil {
			log.G(ctx).WithError(rerr).Warn("failed to rollback transaction")
		}
		return snapshots.Info{}, err
	}

	if err := t.Commit(); err != nil {
		return snapshots.Info{}, err
	}

	return info, nil
}

func (o *snapshotter) Usage(ctx context.Context, key string) (snapshots.Usage, error) {
	return snapshots.Usage{}, errors.New("not implemented")
}

func (o *snapshotter) Prepare(ctx context.Context, key, parent string, opts ...snapshots.Opt) ([]mount.Mount, error) {
	return o.createSnapshot(ctx, snapshots.KindActive, key, parent, opts)
}

func (o *snapshotter) View(ctx context.Context, key, parent string, opts ...snapshots.Opt) ([]mount.Mount, error) {
	return o.createSnapshot(ctx, snapshots.KindView, key, parent, opts)
}

// Mounts returns a path to a disk image file identified by key. Can be
// called on an read-write or readonly transaction.
//
func (o *snapshotter) Mounts(ctx context.Context, key string) ([]mount.Mount, error) {
	ctx, t, err := o.ms.TransactionContext(ctx, false)
	if err != nil {
		return nil, err
	}
	s, err := storage.GetSnapshot(ctx, key)
	if rerr := t.Rollback(); rerr != nil {
		log.G(ctx).WithError(rerr).Warn("failed to rollback transaction")
	}
	if err != nil {
		return nil, fmt.Errorf("failed to get snapshot mount: %w", err)
	}
	return o.mounts(s), nil
}

func (o *snapshotter) Commit(ctx context.Context, name, key string, opts ...snapshots.Opt) error {
	ctx, t, err := o.ms.TransactionContext(ctx, true)
	if err != nil {
		return err
	}

	if _, err := storage.CommitActive(ctx, key, name, snapshots.Usage{}, opts...); err != nil {
		if rerr := t.Rollback(); rerr != nil {
			log.G(ctx).WithError(rerr).Warn("failed to rollback transaction")
		}
		return fmt.Errorf("failed to commit snapshot: %w", err)
	}
	return t.Commit()
}

// Remove abandons the transaction identified by key. All resources
// associated with the key will be removed.
func (o *snapshotter) Remove(ctx context.Context, key string) (err error) {
	ctx, t, err := o.ms.TransactionContext(ctx, true)
	if err != nil {
		return err
	}
	defer func() {
		if err != nil && t != nil {
			if rerr := t.Rollback(); rerr != nil {
				log.G(ctx).WithError(rerr).Warn("failed to rollback transaction")
			}
		}
	}()

	id, _, err := storage.Remove(ctx, key)
	if err != nil {
		return fmt.Errorf("failed to remove: %w", err)
	}

	image := o.getImagePath(id)
	if err := os.RemoveAll(image); err != nil {
		return fmt.Errorf("failed to delete image '%s': %w", image, err)
	}

	err = t.Commit()
	if err != nil {
		return fmt.Errorf("failed to commit: %w", err)
	}

	return nil
}

// Walk the committed snapshots.
func (o *snapshotter) Walk(ctx context.Context, fn snapshots.WalkFunc, fs ...string) error {
	ctx, t, err := o.ms.TransactionContext(ctx, false)
	if err != nil {
		return err
	}
	defer func() {
		if rerr := t.Rollback(); rerr != nil {
			log.G(ctx).WithError(rerr).Warn("failed to rollback transaction")
		}
	}()
	return storage.WalkInfo(ctx, fn, fs...)
}

// Close closes the snapshotter
func (o *snapshotter) Close() error {
	return o.ms.Close()
}

func (o *snapshotter) createSnapshot(ctx context.Context, kind snapshots.Kind, key, parent string, opts []snapshots.Opt) (_ []mount.Mount, err error) {
	ctx, t, err := o.ms.TransactionContext(ctx, true)
	if err != nil {
		return nil, err
	}

	s, err := storage.CreateSnapshot(ctx, kind, key, parent, opts...)
	if err != nil {
		if rerr := t.Rollback(); rerr != nil {
			log.G(ctx).WithError(rerr).Warn("failed to rollback transaction")
		}
		return nil, fmt.Errorf("failed to create snapshot: %w", err)
	}

	if parent == "" {
		if err := hdiu.CreateSparseBundle(o.getImagePath(s.ID), imageSizeMB); err != nil {
			return nil, fmt.Errorf("CreateSparseBundle failed: %w", err)
		}
	} else {
		// Copy sparsebundle directory of parent
		copyDirOpts := []fs.CopyDirOpt{}
		if err := fs.CopyDir(o.getImagePath(s.ID), o.getImagePath(s.ParentIDs[0]), copyDirOpts...); err != nil {
			return nil, fmt.Errorf("failed copy parent layer: %w", err)
		}
	}

	if err := t.Commit(); err != nil {
		return nil, fmt.Errorf("commit failed: %w", err)
	}

	return o.mounts(s), nil
}

func (o *snapshotter) mounts(s storage.Snapshot) []mount.Mount {
	var (
		//source string
		options []string
	)

	if s.Kind == snapshots.KindView {
		options = append(options, "-readonly")
	} else {
		options = append(options, "-readwrite")
	}

	return []mount.Mount{
		{
			Source:  o.getImagePath(s.ID),
			Type:    "darwin",
			Options: options,
		},
	}
}

func (o *snapshotter) getImagePath(id string) string {
	return filepath.Join(o.root, imageDirName, id+".sparsebundle")
}