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repository: Reduce repack workers to prevent deadlock

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As repack streams packs these occupy one backend connection. Uploading a
new pack also requires a backend connection. To prevent a deadlock
during repack when reaching the backend connections limit, simply limit
the repackWorker count to always leave one connection for uploading.
This commit is contained in:
Michael Eischer 2022-04-23 11:28:18 +02:00
parent ee627cd832
commit e597b99b55
1 changed files with 10 additions and 1 deletions
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11
internal/repository/repack.go
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@ -5,6 +5,7 @@ import (
"sync"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/errors"
"github.com/restic/restic/internal/restic"
"github.com/restic/restic/internal/ui/progress"
@ -23,6 +24,10 @@ const numRepackWorkers = 8
func Repack(ctx context.Context, repo restic.Repository, dstRepo restic.Repository, packs restic.IDSet, keepBlobs restic.BlobSet, p *progress.Counter) (obsoletePacks restic.IDSet, err error) {
debug.Log("repacking %d packs while keeping %d blobs", len(packs), len(keepBlobs))
if repo == dstRepo && dstRepo.Backend().Connections() < 2 {
return nil, errors.Fatal("repack step requires a backend connection limit of at least two")
}
var keepMutex sync.Mutex
wg, wgCtx := errgroup.WithContext(ctx)
@ -86,7 +91,11 @@ func Repack(ctx context.Context, repo restic.Repository, dstRepo restic.Reposito
return nil
}
for i := 0; i < numRepackWorkers; i++ {
connectionLimit := dstRepo.Backend().Connections() - 1
if connectionLimit > numRepackWorkers {
connectionLimit = numRepackWorkers
}
for i := 0; i < int(connectionLimit); i++ {
wg.Go(worker)
}