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cache: Allow proactive caching of tree packs

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This commit adds a function to the cache which can decide to proactively
load the complete pack file and store it in the cache. This is helpful
for pack files containing only tree blobs, as it is likely that the same
file is accessed again in the future.
This commit is contained in:
Alexander Neumann 2017-09-24 22:50:35 +02:00
parent 5436154f0d
commit e1dfaf5d87
1 changed files with 38 additions and 22 deletions
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62
internal/cache/backend.go vendored
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@ -82,6 +82,25 @@ var autoCacheFiles = map[restic.FileType]bool{
restic.SnapshotFile: true,
}
func (b *Backend) cacheFile(ctx context.Context, h restic.Handle) error {
rd, err := b.Backend.Load(ctx, h, 0, 0)
if err != nil {
return err
}
if err = b.Cache.Save(h, rd); err != nil {
return err
}
if err = rd.Close(); err != nil {
// try to remove from the cache, ignore errors
_ = b.Cache.Remove(h)
return err
}
return nil
}
// Load loads a file from the cache or the backend.
func (b *Backend) Load(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
if b.Cache.Has(h) {
@ -91,41 +110,38 @@ func (b *Backend) Load(ctx context.Context, h restic.Handle, length int, offset
// partial file requested
if offset != 0 || length != 0 {
if b.Cache.PerformReadahead(h) {
debug.Log("performing readahead for %v", h)
err := b.cacheFile(ctx, h)
if err == nil {
return b.Cache.Load(h, length, offset)
}
debug.Log("error caching %v: %v", h, err)
}
debug.Log("Load(%v, %v, %v): partial file requested, delegating to backend", h, length, offset)
return b.Backend.Load(ctx, h, length, offset)
}
rd, err := b.Backend.Load(ctx, h, length, offset)
if err != nil {
if b.Backend.IsNotExist(err) {
// try to remove from the cache, ignore errors
_ = b.Cache.Remove(h)
}
return nil, err
}
// if we don't automatically cache this file type, fall back to the backend
if _, ok := autoCacheFiles[h.Type]; !ok {
return rd, nil
debug.Log("Load(%v, %v, %v): delegating to backend", h, length, offset)
return b.Backend.Load(ctx, h, length, offset)
}
debug.Log("auto-store %v in the cache", h)
err := b.cacheFile(ctx, h)
// cache the file, then return cached copy
if err = b.Cache.Save(h, rd); err != nil {
return nil, err
}
if err = rd.Close(); err != nil {
// try to remove from the cache, ignore errors
_ = b.Cache.Remove(h)
return nil, err
}
// load from the cache and save in the backend
if err == nil {
// load the cached version
return b.Cache.Load(h, 0, 0)
}
debug.Log("error caching %v: %v, falling back to backend", h, err)
return b.Backend.Load(ctx, h, length, offset)
}
// Stat tests whether the backend has a file. If it does not exist but still
// exists in the cache, it is removed from the cache.
func (b *Backend) Stat(ctx context.Context, h restic.Handle) (restic.FileInfo, error) {