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archiver: Fix intermediate index upload 

A user discovered[1] that when the backup finishes during the upload of
an intermediate index, the upload is cancelled and the index never fully
saved, but the snapshot is saved and the backup finalizes without an
error. This lead to a situation where a snapshot references data that is
contained in the repo, but not referenced in any index, leading to
strange error messages.

This commit uses a dedicated context to signal the intermediate index
uploading routine to terminate after the last index has been uploaded.
This way, an upload running when the backup finishes is completed before
the routine terminates and the snapshot is saved.

[1] https://forum.restic.net/t/error-loading-tree-check-prune-and-forget-gives-error-b2-backend/406
This commit is contained in:
Alexander Neumann 2018-01-26 19:49:43 +01:00
parent cccb2fc7e7
commit f99c95c766
1 changed files with 8 additions and 6 deletions
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14
internal/archiver/archiver.go
View File

@ -620,7 +620,7 @@ func (j archiveJob) Copy() pipe.Job {
const saveIndexTime = 30 * time.Second
// saveIndexes regularly queries the master index for full indexes and saves them.
func (arch *Archiver) saveIndexes(ctx context.Context, wg *sync.WaitGroup) {
func (arch *Archiver) saveIndexes(saveCtx, shutdownCtx context.Context, wg *sync.WaitGroup) {
defer wg.Done()
ticker := time.NewTicker(saveIndexTime)
@ -628,11 +628,13 @@ func (arch *Archiver) saveIndexes(ctx context.Context, wg *sync.WaitGroup) {
for {
select {
case <-ctx.Done():
case <-saveCtx.Done():
return
case <-shutdownCtx.Done():
return
case <-ticker.C:
debug.Log("saving full indexes")
err := arch.repo.SaveFullIndex(ctx)
err := arch.repo.SaveFullIndex(saveCtx)
if err != nil {
debug.Log("save indexes returned an error: %v", err)
fmt.Fprintf(os.Stderr, "error saving preliminary index: %v\n", err)
@ -748,16 +750,16 @@ func (arch *Archiver) Snapshot(ctx context.Context, p *restic.Progress, paths, t
// run index saver
var wgIndexSaver sync.WaitGroup
indexCtx, indexCancel := context.WithCancel(ctx)
shutdownCtx, indexShutdown := context.WithCancel(ctx)
wgIndexSaver.Add(1)
go arch.saveIndexes(indexCtx, &wgIndexSaver)
go arch.saveIndexes(ctx, shutdownCtx, &wgIndexSaver)
// wait for all workers to terminate
debug.Log("wait for workers")
wg.Wait()
// stop index saver
indexCancel()
indexShutdown()
wgIndexSaver.Wait()
debug.Log("workers terminated")