buildkit/cache/refs.go

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package cache
import (
"context"
"sync"
"github.com/containerd/containerd/mount"
"github.com/moby/buildkit/cache/metadata"
"github.com/moby/buildkit/identity"
"github.com/moby/buildkit/util/flightcontrol"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
)
// Ref is a reference to cacheable objects.
type Ref interface {
Mountable
ID() string
Release(context.Context) error
Size(ctx context.Context) (int64, error)
Metadata() *metadata.StorageItem
}
type ImmutableRef interface {
Ref
Parent() ImmutableRef
Finalize(ctx context.Context) error // Make sure reference is flushed to driver
}
type MutableRef interface {
Ref
Commit(context.Context) (ImmutableRef, error)
}
type Mountable interface {
Mount(ctx context.Context, readonly bool) ([]mount.Mount, error)
}
type cacheRecord struct {
cm *cacheManager
mu *sync.Mutex // the mutex is shared by records sharing data
mutable bool
refs map[Mountable]struct{}
parent ImmutableRef
md *metadata.StorageItem
// dead means record is marked as deleted
dead bool
view string
viewMount []mount.Mount
sizeG flightcontrol.Group
// these are filled if multiple refs point to same data
equalMutable *mutableRef
equalImmutable *immutableRef
}
// hold ref lock before calling
func (cr *cacheRecord) ref() *immutableRef {
ref := &immutableRef{cacheRecord: cr}
cr.refs[ref] = struct{}{}
return ref
}
// hold ref lock before calling
func (cr *cacheRecord) mref() *mutableRef {
ref := &mutableRef{cacheRecord: cr}
cr.refs[ref] = struct{}{}
return ref
}
// hold ref lock before calling
func (cr *cacheRecord) isDead() bool {
return cr.dead || (cr.equalImmutable != nil && cr.equalImmutable.dead) || (cr.equalMutable != nil && cr.equalMutable.dead)
}
func (cr *cacheRecord) Size(ctx context.Context) (int64, error) {
// this expects that usage() is implemented lazily
s, err := cr.sizeG.Do(ctx, cr.ID(), func(ctx context.Context) (interface{}, error) {
cr.mu.Lock()
s := getSize(cr.md)
if s != sizeUnknown {
cr.mu.Unlock()
return s, nil
}
driverID := cr.ID()
if cr.equalMutable != nil {
driverID = cr.equalMutable.ID()
}
cr.mu.Unlock()
usage, err := cr.cm.ManagerOpt.Snapshotter.Usage(ctx, driverID)
if err != nil {
if cr.isDead() {
cr.mu.Unlock()
return int64(0), nil
}
return s, errors.Wrapf(err, "failed to get usage for %s", cr.ID())
}
cr.mu.Lock()
setSize(cr.md, usage.Size)
if err := cr.md.Commit(); err != nil {
return s, err
}
cr.mu.Unlock()
return usage.Size, nil
})
return s.(int64), err
}
func (cr *cacheRecord) Parent() ImmutableRef {
if cr.parent == nil {
return nil
}
p := cr.parent.(*immutableRef)
p.mu.Lock()
defer p.mu.Unlock()
return p.ref()
}
func (cr *cacheRecord) Mount(ctx context.Context, readonly bool) ([]mount.Mount, error) {
cr.mu.Lock()
defer cr.mu.Unlock()
if cr.mutable {
m, err := cr.cm.Snapshotter.Mounts(ctx, cr.ID())
if err != nil {
return nil, errors.Wrapf(err, "failed to mount %s", cr.ID())
}
if readonly {
m = setReadonly(m)
}
return m, nil
}
if cr.equalMutable != nil && readonly {
m, err := cr.cm.Snapshotter.Mounts(ctx, cr.equalMutable.ID())
if err != nil {
return nil, errors.Wrapf(err, "failed to mount %s", cr.equalMutable.ID())
}
return setReadonly(m), nil
}
if err := cr.finalize(ctx); err != nil {
return nil, err
}
if cr.viewMount == nil { // TODO: handle this better
cr.view = identity.NewID()
m, err := cr.cm.Snapshotter.View(ctx, cr.view, cr.ID())
if err != nil {
cr.view = ""
return nil, errors.Wrapf(err, "failed to mount %s", cr.ID())
}
cr.viewMount = m
}
return cr.viewMount, nil
}
// call when holding the manager lock
func (cr *cacheRecord) remove(ctx context.Context, removeSnapshot bool) error {
delete(cr.cm.records, cr.ID())
if cr.parent != nil {
if err := cr.parent.(*immutableRef).release(ctx); err != nil {
return err
}
}
if removeSnapshot {
if err := cr.cm.Snapshotter.Remove(ctx, cr.ID()); err != nil {
return err
}
}
if err := cr.cm.md.Clear(cr.ID()); err != nil {
return err
}
return nil
}
func (cr *cacheRecord) ID() string {
return cr.md.ID()
}
type immutableRef struct {
*cacheRecord
}
type mutableRef struct {
*cacheRecord
}
func (sr *immutableRef) Release(ctx context.Context) error {
sr.cm.mu.Lock()
defer sr.cm.mu.Unlock()
sr.mu.Lock()
defer sr.mu.Unlock()
return sr.release(ctx)
}
func (sr *immutableRef) release(ctx context.Context) error {
updateLastUsed(sr.md)
delete(sr.refs, sr)
if len(sr.refs) == 0 {
if sr.viewMount != nil { // TODO: release viewMount earlier if possible
if err := sr.cm.Snapshotter.Remove(ctx, sr.view); err != nil {
return err
}
sr.view = ""
sr.viewMount = nil
}
if sr.equalMutable != nil {
sr.equalMutable.release(ctx)
}
// go sr.cm.GC()
}
return nil
}
func (sr *immutableRef) Finalize(ctx context.Context) error {
sr.mu.Lock()
defer sr.mu.Unlock()
return sr.finalize(ctx)
}
func (cr *cacheRecord) Metadata() *metadata.StorageItem {
return cr.md
}
func (cr *cacheRecord) finalize(ctx context.Context) error {
mutable := cr.equalMutable
if mutable == nil {
return nil
}
err := cr.cm.Snapshotter.Commit(ctx, cr.ID(), mutable.ID())
if err != nil {
return errors.Wrapf(err, "failed to commit %s", mutable.ID())
}
mutable.dead = true
go func() {
cr.cm.mu.Lock()
defer cr.cm.mu.Unlock()
if err := mutable.remove(context.TODO(), false); err != nil {
logrus.Error(err)
}
}()
cr.equalMutable = nil
clearEqualMutable(cr.md)
return cr.md.Commit()
}
func (sr *mutableRef) commit(ctx context.Context) (ImmutableRef, error) {
if !sr.mutable || len(sr.refs) == 0 {
return nil, errors.Wrapf(errInvalid, "invalid mutable ref")
}
id := identity.NewID()
md, _ := sr.cm.md.Get(id)
rec := &cacheRecord{
mu: sr.mu,
cm: sr.cm,
parent: sr.Parent(),
equalMutable: sr,
refs: make(map[Mountable]struct{}),
md: md,
}
if descr := GetDescription(sr.md); descr != "" {
if err := queueDescription(md, descr); err != nil {
return nil, err
}
}
if err := initializeMetadata(rec); err != nil {
return nil, err
}
sr.cm.records[id] = rec
if err := sr.md.Commit(); err != nil {
return nil, err
}
setSize(md, sizeUnknown)
setEqualMutable(md, sr.ID())
if err := md.Commit(); err != nil {
return nil, err
}
ref := rec.ref()
sr.equalImmutable = ref
return ref, nil
}
func (sr *mutableRef) Commit(ctx context.Context) (ImmutableRef, error) {
sr.cm.mu.Lock()
defer sr.cm.mu.Unlock()
sr.mu.Lock()
defer sr.mu.Unlock()
return sr.commit(ctx)
}
func (sr *mutableRef) Release(ctx context.Context) error {
sr.cm.mu.Lock()
defer sr.cm.mu.Unlock()
sr.mu.Lock()
defer sr.mu.Unlock()
return sr.release(ctx)
}
func (sr *mutableRef) release(ctx context.Context) error {
delete(sr.refs, sr)
updateLastUsed(sr.md)
if getCachePolicy(sr.md) != cachePolicyRetain {
if sr.equalImmutable != nil {
if getCachePolicy(sr.equalImmutable.md) == cachePolicyRetain {
return nil
}
if err := sr.equalImmutable.remove(ctx, false); err != nil {
return err
}
}
if sr.parent != nil {
if err := sr.parent.(*immutableRef).release(ctx); err != nil {
return err
}
}
return sr.remove(ctx, true)
}
return nil
}
func setReadonly(mounts []mount.Mount) []mount.Mount {
for i, m := range mounts {
opts := make([]string, 0, len(m.Options))
for _, opt := range m.Options {
if opt != "rw" {
opts = append(opts, opt)
}
}
opts = append(opts, "ro")
mounts[i].Options = opts
}
return mounts
}