frostfs-node/pkg/local_object_storage/engine/remove_copies.go

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package engine
import (
"context"
"errors"
meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
"git.frostfs.info/TrueCloudLab/hrw"
"go.uber.org/zap"
"golang.org/x/sync/errgroup"
)
// errRemoveDuplicatesInProgress is returned when another rebalancing is in progress.
// We need it because `Rebalance` removes objects and executing it concurrently
// on 2 shards can lead to data loss. In future this restriction could be relaxed.
var errRemoveDuplicatesInProgress = errors.New("redundant copies removal is already in progress")
const defaultRemoveDuplicatesConcurrency = 256
type RemoveDuplicatesPrm struct {
Concurrency int
}
// RemoveDuplicates iterates over all objects and removes duplicate object copies
// from shards which are worse as defined by HRW sort.
// Safety:
// 1. Concurrent execution is prohibited, thus 1 object copy should always be left.
// 2. If we delete an object from another thread, this is not a problem. Currently,
// we have 2 thread that can remove "valid" (non-expired and logically non-removed) objects:
// policer and rebalance. For rebalance see (1).
// If policer removes something, we do not care if both copies are removed or one of them is left,
// as the remaining copy will be removed during the next policer iteration.
func (e *StorageEngine) RemoveDuplicates(ctx context.Context, prm RemoveDuplicatesPrm) error {
if !e.removeDuplicatesInProgress.CompareAndSwap(false, true) {
return errRemoveDuplicatesInProgress
}
defer e.removeDuplicatesInProgress.Store(false)
if prm.Concurrency <= 0 {
prm.Concurrency = defaultRemoveDuplicatesConcurrency
}
e.log.Info("starting removal of locally-redundant copies",
zap.Int("concurrency", prm.Concurrency))
// The mutext must be taken for the whole duration to avoid target shard being removed
// concurrently: this can lead to data loss.
e.mtx.RLock()
defer e.mtx.RUnlock()
// Iterate by shards to be sure that no objects from 2 different shards are removed simultaneously.
// This is not currently the case, because `FreeSpace` metric used by weight sorting is always 0.
// However we could change weights in future and easily forget this function.
for _, sh := range e.shards {
e.log.Debug("started duplicates removal routine", zap.String("shard_id", sh.ID().String()))
ch := make(chan oid.Address)
errG, ctx := errgroup.WithContext(ctx)
errG.SetLimit(prm.Concurrency + 1) // +1 for the listing thread
errG.Go(func() error {
defer close(ch)
var cursor *meta.Cursor
for {
var listPrm shard.ListWithCursorPrm
listPrm.WithCount(uint32(prm.Concurrency))
listPrm.WithCursor(cursor)
res, err := sh.ListWithCursor(listPrm)
if err != nil {
if errors.Is(err, meta.ErrEndOfListing) {
return nil
}
return err
}
for _, addr := range res.AddressList() {
select {
case <-ctx.Done():
return ctx.Err()
case ch <- addr.Address:
}
}
cursor = res.Cursor()
}
})
for i := 0; i < prm.Concurrency; i++ {
errG.Go(func() error {
return e.removeObjects(ctx, ch)
})
}
if err := errG.Wait(); err != nil {
e.log.Error("finished removal of locally-redundant copies", zap.Error(err))
return err
}
}
e.log.Info("finished removal of locally-redundant copies")
return nil
}
// removeObjects reads addresses from ch and removes all objects from other shards, excluding excludeID.
func (e *StorageEngine) removeObjects(ctx context.Context, ch <-chan oid.Address) error {
shards := make([]hashedShard, 0, len(e.shards))
for _, sh := range e.shards {
shards = append(shards, sh)
}
for addr := range ch {
h := hrw.Hash([]byte(addr.EncodeToString()))
shards := sortShardsByWeight(shards, h)
found := false
for i := range shards {
var existsPrm shard.ExistsPrm
existsPrm.SetAddress(addr)
res, err := shards[i].Exists(ctx, existsPrm)
if err != nil {
return err
} else if !res.Exists() {
continue
} else if !found {
found = true
continue
}
var deletePrm shard.DeletePrm
deletePrm.SetAddresses(addr)
_, err = shards[i].Delete(deletePrm)
if err != nil {
return err
}
}
}
return nil
}