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restic/internal/repository/index_parallel.go
greatroar 2e0f1f5113 repository: Remove RunWorkers, report ctx.Err()
This removes RunWorkers, which had become mere overhead by successive
refactors. It also ensures that each former user of that function
returns any context error that occurs, so failure to complete an
operation is always reported as an error.
2022-05-10 22:26:00 +02:00

78 lines
1.8 KiB
Go

package repository
import (
"context"
"sync"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/restic"
"golang.org/x/sync/errgroup"
)
const loadIndexParallelism = 5
// ForAllIndexes loads all index files in parallel and calls the given callback.
// It is guaranteed that the function is not run concurrently. If the callback
// returns an error, this function is cancelled and also returns that error.
func ForAllIndexes(ctx context.Context, repo restic.Repository,
fn func(id restic.ID, index *Index, oldFormat bool, err error) error) error {
debug.Log("Start")
type FileInfo struct {
restic.ID
Size int64
}
var m sync.Mutex
// track spawned goroutines using wg, create a new context which is
// cancelled as soon as an error occurs.
wg, ctx := errgroup.WithContext(ctx)
ch := make(chan FileInfo)
// send list of index files through ch, which is closed afterwards
wg.Go(func() error {
defer close(ch)
return repo.List(ctx, restic.IndexFile, func(id restic.ID, size int64) error {
select {
case <-ctx.Done():
return ctx.Err()
case ch <- FileInfo{id, size}:
}
return nil
})
})
// a worker receives an index ID from ch, loads the index, and sends it to indexCh
worker := func() error {
var buf []byte
for fi := range ch {
debug.Log("worker got file %v", fi.ID.Str())
var err error
var idx *Index
oldFormat := false
buf, err = repo.LoadUnpacked(ctx, buf[:0], restic.IndexFile, fi.ID)
if err == nil {
idx, oldFormat, err = DecodeIndex(buf, fi.ID)
}
m.Lock()
err = fn(fi.ID, idx, oldFormat, err)
m.Unlock()
if err != nil {
return err
}
}
return nil
}
// run workers on ch
for i := 0; i < loadIndexParallelism; i++ {
wg.Go(worker)
}
return wg.Wait()
}