[#191] engine: Allow to remove redundant object copies
RemoveDuplicates() removes all duplicate object copies stored on multiple shards. All shards are processed and the command tries to leave a copy on the best shard according to HRW. Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>
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4 changed files with 358 additions and 5 deletions
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@ -17,6 +17,8 @@ import (
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type StorageEngine struct {
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*cfg
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removeDuplicatesInProgress atomic.Bool
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mtx *sync.RWMutex
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shards map[string]hashedShard
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138
pkg/local_object_storage/engine/remove_copies.go
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138
pkg/local_object_storage/engine/remove_copies.go
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@ -0,0 +1,138 @@
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package engine
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import (
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"context"
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"errors"
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meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
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"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
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oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
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"git.frostfs.info/TrueCloudLab/hrw"
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"go.uber.org/zap"
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"golang.org/x/sync/errgroup"
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)
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// errRemoveDuplicatesInProgress is returned when another rebalancing is in progress.
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// We need it because `Rebalance` removes objects and executing it concurrently
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// on 2 shards can lead to data loss. In future this restriction could be relaxed.
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var errRemoveDuplicatesInProgress = errors.New("redundant copies removal is already in progress")
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const defaultRemoveDuplicatesConcurrency = 256
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type RemoveDuplicatesPrm struct {
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Concurrency int
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}
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// RemoveDuplicates iterates over all objects and removes duplicate object copies
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// from shards which are worse as defined by HRW sort.
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// Safety:
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// 1. Concurrent execution is prohibited, thus 1 object copy should always be left.
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// 2. If we delete an object from another thread, this is not a problem. Currently,
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// we have 2 thread that can remove "valid" (non-expired and logically non-removed) objects:
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// policer and rebalance. For rebalance see (1).
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// If policer removes something, we do not care if both copies are removed or one of them is left,
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// as the remaining copy will be removed during the next policer iteration.
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func (e *StorageEngine) RemoveDuplicates(ctx context.Context, prm RemoveDuplicatesPrm) error {
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if !e.removeDuplicatesInProgress.CompareAndSwap(false, true) {
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return errRemoveDuplicatesInProgress
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}
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defer e.removeDuplicatesInProgress.Store(false)
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if prm.Concurrency <= 0 {
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prm.Concurrency = defaultRemoveDuplicatesConcurrency
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}
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e.log.Info("starting removal of locally-redundant copies",
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zap.Int("concurrency", prm.Concurrency))
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// The mutext must be taken for the whole duration to avoid target shard being removed
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// concurrently: this can lead to data loss.
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e.mtx.RLock()
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defer e.mtx.RUnlock()
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// Iterate by shards to be sure that no objects from 2 different shards are removed simultaneously.
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// This is not currently the case, because `FreeSpace` metric used by weight sorting is always 0.
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// However we could change weights in future and easily forget this function.
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for _, sh := range e.shards {
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e.log.Debug("started duplicates removal routine", zap.String("shard_id", sh.ID().String()))
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ch := make(chan oid.Address)
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errG, ctx := errgroup.WithContext(ctx)
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errG.SetLimit(prm.Concurrency + 1) // +1 for the listing thread
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errG.Go(func() error {
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defer close(ch)
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var cursor *meta.Cursor
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for {
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var listPrm shard.ListWithCursorPrm
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listPrm.WithCount(uint32(prm.Concurrency))
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listPrm.WithCursor(cursor)
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res, err := sh.ListWithCursor(listPrm)
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if err != nil {
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if errors.Is(err, meta.ErrEndOfListing) {
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return nil
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}
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return err
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}
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for _, addr := range res.AddressList() {
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select {
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case <-ctx.Done():
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return ctx.Err()
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case ch <- addr.Address:
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}
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}
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cursor = res.Cursor()
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}
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})
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for i := 0; i < prm.Concurrency; i++ {
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errG.Go(func() error {
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return e.removeObjects(ctx, ch)
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})
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}
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if err := errG.Wait(); err != nil {
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e.log.Error("finished removal of locally-redundant copies", zap.Error(err))
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return err
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}
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}
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e.log.Info("finished removal of locally-redundant copies")
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return nil
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}
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// removeObjects reads addresses from ch and removes all objects from other shards, excluding excludeID.
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func (e *StorageEngine) removeObjects(ctx context.Context, ch <-chan oid.Address) error {
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shards := make([]hashedShard, 0, len(e.shards))
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for _, sh := range e.shards {
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shards = append(shards, sh)
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}
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for addr := range ch {
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h := hrw.Hash([]byte(addr.EncodeToString()))
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shards := sortShardsByWeight(shards, h)
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found := false
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for i := range shards {
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var existsPrm shard.ExistsPrm
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existsPrm.SetAddress(addr)
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res, err := shards[i].Exists(existsPrm)
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if err != nil {
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return err
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} else if !res.Exists() {
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continue
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} else if !found {
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found = true
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continue
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}
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var deletePrm shard.DeletePrm
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deletePrm.SetAddresses(addr)
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_, err = shards[i].Delete(deletePrm)
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if err != nil {
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return err
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}
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}
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}
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return nil
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}
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208
pkg/local_object_storage/engine/remove_copies_test.go
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208
pkg/local_object_storage/engine/remove_copies_test.go
Normal file
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@ -0,0 +1,208 @@
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package engine
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import (
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"context"
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"sync"
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"testing"
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"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/object"
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"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
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"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/teststore"
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"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/testutil"
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"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
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cidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id/test"
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objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
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oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
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"github.com/stretchr/testify/require"
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)
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func TestRebalance(t *testing.T) {
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te := newEngineWithErrorThreshold(t, "", 0)
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const (
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objCount = 20
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copyCount = (objCount + 2) / 3
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)
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type objectWithShard struct {
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bestShard shard.ID
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worstShard shard.ID
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object *objectSDK.Object
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}
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objects := make([]objectWithShard, objCount)
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for i := range objects {
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obj := testutil.GenerateObjectWithCID(cidtest.ID())
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obj.SetPayload(make([]byte, errSmallSize))
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objects[i].object = obj
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shards := te.ng.sortShardsByWeight(object.AddressOf(obj))
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objects[i].bestShard = *shards[0].Shard.ID()
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objects[i].worstShard = *shards[1].Shard.ID()
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}
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for i := range objects {
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var prm shard.PutPrm
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prm.SetObject(objects[i].object)
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var err1, err2 error
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te.ng.mtx.RLock()
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// Every 3rd object (i%3 == 0) is put to both shards, others are distributed.
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if i%3 != 1 {
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_, err1 = te.ng.shards[te.shards[0].id.String()].Shard.Put(prm)
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}
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if i%3 != 2 {
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_, err2 = te.ng.shards[te.shards[1].id.String()].Shard.Put(prm)
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}
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te.ng.mtx.RUnlock()
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require.NoError(t, err1)
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require.NoError(t, err2)
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}
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var removedMtx sync.Mutex
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var removed []deleteEvent
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for _, shard := range te.shards {
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id := *shard.id
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shard.largeFileStorage.SetOption(teststore.WithDelete(func(prm common.DeletePrm) (common.DeleteRes, error) {
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removedMtx.Lock()
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removed = append(removed, deleteEvent{shardID: id, addr: prm.Address})
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removedMtx.Unlock()
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return common.DeleteRes{}, nil
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}))
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}
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err := te.ng.RemoveDuplicates(context.Background(), RemoveDuplicatesPrm{})
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require.NoError(t, err)
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require.Equal(t, copyCount, len(removed))
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removedMask := make([]bool, len(objects))
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loop:
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for i := range removed {
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for j := range objects {
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if removed[i].addr == object.AddressOf(objects[j].object) {
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require.Equal(t, objects[j].worstShard, removed[i].shardID,
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"object %d was expected to be removed from another shard", j)
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removedMask[j] = true
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continue loop
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}
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}
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require.FailNow(t, "unexpected object was removed", removed[i].addr)
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}
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for i := 0; i < copyCount; i++ {
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if i%3 == 0 {
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require.True(t, removedMask[i], "object %d was expected to be removed", i)
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} else {
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require.False(t, removedMask[i], "object %d was not expected to be removed", i)
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}
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}
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}
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func TestRebalanceSingleThread(t *testing.T) {
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te := newEngineWithErrorThreshold(t, "", 0)
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obj := testutil.GenerateObjectWithCID(cidtest.ID())
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obj.SetPayload(make([]byte, errSmallSize))
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var prm shard.PutPrm
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prm.SetObject(obj)
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te.ng.mtx.RLock()
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_, err1 := te.ng.shards[te.shards[0].id.String()].Shard.Put(prm)
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_, err2 := te.ng.shards[te.shards[1].id.String()].Shard.Put(prm)
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te.ng.mtx.RUnlock()
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require.NoError(t, err1)
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require.NoError(t, err2)
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signal := make(chan struct{}) // unblock rebalance
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started := make(chan struct{}) // make sure rebalance is started
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for _, shard := range te.shards {
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shard.largeFileStorage.SetOption(teststore.WithDelete(func(common.DeletePrm) (common.DeleteRes, error) {
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close(started)
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<-signal
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return common.DeleteRes{}, nil
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}))
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}
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var firstErr error
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var wg sync.WaitGroup
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wg.Add(1)
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go func() {
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defer wg.Done()
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firstErr = te.ng.RemoveDuplicates(context.Background(), RemoveDuplicatesPrm{})
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}()
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<-started
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secondErr := te.ng.RemoveDuplicates(context.Background(), RemoveDuplicatesPrm{})
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require.ErrorIs(t, secondErr, errRemoveDuplicatesInProgress)
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close(signal)
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wg.Wait()
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require.NoError(t, firstErr)
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}
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type deleteEvent struct {
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shardID shard.ID
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addr oid.Address
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}
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func TestRebalanceExitByContext(t *testing.T) {
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te := newEngineWithErrorThreshold(t, "", 0)
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objects := make([]*objectSDK.Object, 4)
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for i := range objects {
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obj := testutil.GenerateObjectWithCID(cidtest.ID())
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obj.SetPayload(make([]byte, errSmallSize))
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objects[i] = obj
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}
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for i := range objects {
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var prm shard.PutPrm
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prm.SetObject(objects[i])
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te.ng.mtx.RLock()
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_, err1 := te.ng.shards[te.shards[0].id.String()].Shard.Put(prm)
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_, err2 := te.ng.shards[te.shards[1].id.String()].Shard.Put(prm)
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te.ng.mtx.RUnlock()
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require.NoError(t, err1)
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require.NoError(t, err2)
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}
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var removed []deleteEvent
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deleteCh := make(chan struct{})
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signal := make(chan struct{})
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for _, shard := range te.shards {
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id := *shard.id
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shard.largeFileStorage.SetOption(teststore.WithDelete(func(prm common.DeletePrm) (common.DeleteRes, error) {
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deleteCh <- struct{}{}
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<-signal
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removed = append(removed, deleteEvent{shardID: id, addr: prm.Address})
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return common.DeleteRes{}, nil
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}))
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}
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ctx, cancel := context.WithCancel(context.Background())
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var rebalanceErr error
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var wg sync.WaitGroup
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wg.Add(1)
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go func() {
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defer wg.Done()
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rebalanceErr = te.ng.RemoveDuplicates(ctx, RemoveDuplicatesPrm{Concurrency: 1})
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}()
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const removeCount = 3
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for i := 0; i < removeCount-1; i++ {
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<-deleteCh
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signal <- struct{}{}
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}
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<-deleteCh
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cancel()
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close(signal)
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wg.Wait()
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require.ErrorIs(t, rebalanceErr, context.Canceled)
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require.Equal(t, removeCount, len(removed))
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}
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@ -208,16 +208,21 @@ func (e *StorageEngine) sortShardsByWeight(objAddr interface{ EncodeToString() s
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e.mtx.RLock()
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defer e.mtx.RUnlock()
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h := hrw.Hash([]byte(objAddr.EncodeToString()))
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shards := make([]hashedShard, 0, len(e.shards))
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weights := make([]float64, 0, len(e.shards))
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for _, sh := range e.shards {
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shards = append(shards, hashedShard(sh))
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weights = append(weights, e.shardWeight(sh.Shard))
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}
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return sortShardsByWeight(shards, h)
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}
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func sortShardsByWeight(shards []hashedShard, h uint64) []hashedShard {
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weights := make([]float64, 0, len(shards))
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for _, sh := range shards {
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weights = append(weights, float64(sh.Shard.WeightValues().FreeSpace))
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}
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hrw.SortHasherSliceByWeightValue(shards, weights, hrw.Hash([]byte(objAddr.EncodeToString())))
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hrw.SortHasherSliceByWeightValue(shards, weights, h)
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return shards
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}
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