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archiver: fix race condition during worker startup
When the tomb is created with a canceled context, then the workers started via `t.Go` exist nearly immediately. Once for the first time all started goroutines have been stopped, it is not allowed to issue further calls to `t.Go`. This is a problem when the started goroutines exit immediately, as for example the first goroutine might already have stopped before starting the second one, which is not allowed as once the first goroutines has stopped no goroutines were running. To fix this race condition the startup and main task of the archiver now also run within a `t.Go` function. This also allows unifying the error handling as it is no longer necessary to distinguish between errors returned by the workers or the saveTree processing. The tomb now just returns the first error encountered, which should also be the most descriptive one.
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b2efa0af39
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debc4a3a99
1 changed files with 15 additions and 17 deletions
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@ -784,33 +784,31 @@ func (arch *Archiver) Snapshot(ctx context.Context, targets []string, opts Snaps
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var t tomb.Tomb
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wctx := t.Context(ctx)
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arch.runWorkers(wctx, &t)
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start := time.Now()
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debug.Log("starting snapshot")
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rootTreeID, stats, err := func() (restic.ID, ItemStats, error) {
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var rootTreeID restic.ID
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var stats ItemStats
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t.Go(func() error {
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arch.runWorkers(wctx, &t)
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debug.Log("starting snapshot")
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tree, err := arch.SaveTree(wctx, "/", atree, arch.loadParentTree(wctx, opts.ParentSnapshot))
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if err != nil {
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return restic.ID{}, ItemStats{}, err
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return err
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}
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if len(tree.Nodes) == 0 {
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return restic.ID{}, ItemStats{}, errors.New("snapshot is empty")
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return errors.New("snapshot is empty")
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}
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return arch.saveTree(wctx, tree)
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}()
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debug.Log("saved tree, error: %v", err)
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rootTreeID, stats, err = arch.saveTree(wctx, tree)
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// trigger shutdown but don't set an error
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t.Kill(nil)
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return err
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})
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t.Kill(nil)
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werr := t.Wait()
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debug.Log("err is %v, werr is %v", err, werr)
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// Use werr when it might contain a more specific error than "context canceled"
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if err == nil || (errors.Cause(err) == context.Canceled && werr != nil) {
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err = werr
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}
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err = t.Wait()
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debug.Log("err is %v", err)
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if err != nil {
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debug.Log("error while saving tree: %v", err)
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