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Merge pull request #1279 from restic/fix-eof-error
cache: Synchronize downloading
This commit is contained in:
commit
7e8bc8d362
3 changed files with 64 additions and 6 deletions
63
internal/cache/backend.go
vendored
63
internal/cache/backend.go
vendored
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@ -3,6 +3,7 @@ package cache
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import (
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"context"
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"io"
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"sync"
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"github.com/restic/restic/internal/debug"
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"github.com/restic/restic/internal/restic"
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@ -12,11 +13,25 @@ import (
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type Backend struct {
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restic.Backend
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*Cache
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// inProgress contains the handle for all files that are currently
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// downloaded. The channel in the value is closed as soon as the download
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// is finished.
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inProgressMutex sync.Mutex
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inProgress map[restic.Handle]chan struct{}
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}
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// ensure cachedBackend implements restic.Backend
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var _ restic.Backend = &Backend{}
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func newBackend(be restic.Backend, c *Cache) *Backend {
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return &Backend{
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Backend: be,
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Cache: c,
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inProgress: make(map[restic.Handle]chan struct{}),
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}
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}
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// Remove deletes a file from the backend and the cache if it has been cached.
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func (b *Backend) Remove(ctx context.Context, h restic.Handle) error {
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debug.Log("cache Remove(%v)", h)
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@ -83,6 +98,30 @@ var autoCacheFiles = map[restic.FileType]bool{
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}
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func (b *Backend) cacheFile(ctx context.Context, h restic.Handle) error {
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finish := make(chan struct{})
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defer func() {
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close(finish)
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// remove the finish channel from the map
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b.inProgressMutex.Lock()
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delete(b.inProgress, h)
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b.inProgressMutex.Unlock()
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}()
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b.inProgressMutex.Lock()
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other, alreadyDownloading := b.inProgress[h]
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if !alreadyDownloading {
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b.inProgress[h] = finish
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}
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b.inProgressMutex.Unlock()
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if alreadyDownloading {
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debug.Log("readahead %v is already performed by somebody else, delegating...", h)
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<-other
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debug.Log("download %v finished", h)
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return nil
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}
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rd, err := b.Backend.Load(ctx, h, 0, 0)
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if err != nil {
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return err
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@ -101,8 +140,29 @@ func (b *Backend) cacheFile(ctx context.Context, h restic.Handle) error {
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return nil
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}
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// loadFromCacheOrDelegate will try to load the file from the cache, and fall
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// back to the backend if that fails.
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func (b *Backend) loadFromCacheOrDelegate(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
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rd, err := b.Cache.Load(h, length, offset)
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if err == nil {
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return rd, nil
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}
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return b.Backend.Load(ctx, h, length, offset)
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}
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// Load loads a file from the cache or the backend.
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func (b *Backend) Load(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
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b.inProgressMutex.Lock()
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waitForFinish, inProgress := b.inProgress[h]
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b.inProgressMutex.Unlock()
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if inProgress {
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debug.Log("downloading %v is already in progress, waiting for finish", h)
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<-waitForFinish
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debug.Log("downloading %v finished", h)
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}
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if b.Cache.Has(h) {
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debug.Log("Load(%v, %v, %v) from cache", h, length, offset)
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rd, err := b.Cache.Load(h, length, offset)
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@ -116,9 +176,10 @@ func (b *Backend) Load(ctx context.Context, h restic.Handle, length int, offset
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if offset != 0 || length != 0 {
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if b.Cache.PerformReadahead(h) {
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debug.Log("performing readahead for %v", h)
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err := b.cacheFile(ctx, h)
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if err == nil {
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return b.Cache.Load(h, length, offset)
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return b.loadFromCacheOrDelegate(ctx, h, length, offset)
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}
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debug.Log("error caching %v: %v", h, err)
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5
internal/cache/cache.go
vendored
5
internal/cache/cache.go
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@ -155,10 +155,7 @@ func (c *Cache) IsNotExist(err error) bool {
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// Wrap returns a backend with a cache.
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func (c *Cache) Wrap(be restic.Backend) restic.Backend {
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return &Backend{
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Backend: be,
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Cache: c,
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}
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return newBackend(be, c)
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}
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// BaseDir returns the base directory.
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@ -163,7 +163,7 @@ func (sn *Snapshot) HasTagList(l []TagList) bool {
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for _, tags := range l {
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if sn.HasTags(tags) {
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debug.Log(" snapshot satisfies %v", tags, l)
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debug.Log(" snapshot satisfies %v %v", tags, l)
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return true
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}
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}
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