swarm/storage: Add accessCnt for GC (#17845)

2 files changed, 358 insertions, 143 deletions

diff --git a/swarm/storage/ldbstore.go b/swarm/storage/ldbstore.go
index 2a7f51cb3..49508911f 100644
--- a/swarm/storage/ldbstore.go
+++ b/swarm/storage/ldbstore.go
@@ -32,7 +32,6 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
-	"sort"
 	"sync"
 
 	"github.com/ethereum/go-ethereum/metrics"
@@ -44,8 +43,13 @@ import (
 )
 
 const (
-	gcArrayFreeRatio = 0.1
-	maxGCitems       = 5000 // max number of items to be gc'd per call to collectGarbage()
+	defaultGCRatio    = 10
+	defaultMaxGCRound = 10000
+	defaultMaxGCBatch = 5000
+
+	wEntryCnt  = 1 << 0
+	wIndexCnt  = 1 << 1
+	wAccessCnt = 1 << 2
 )
 
 var (
@@ -61,6 +65,7 @@ var (
 	keyData        = byte(6)
 	keyDistanceCnt = byte(7)
 	keySchema      = []byte{8}
+	keyGCIdx       = byte(9) // access to chunk data index, used by garbage collection in ascending order from first entry
 )
 
 var (
@@ -68,7 +73,7 @@ var (
 )
 
 type gcItem struct {
-	idx    uint64
+	idx    *dpaDBIndex
 	value  uint64
 	idxKey []byte
 	po     uint8
@@ -89,6 +94,16 @@ func NewLDBStoreParams(storeparams *StoreParams, path string) *LDBStoreParams {
 	}
 }
 
+type garbage struct {
+	maxRound int           // maximum number of chunks to delete in one garbage collection round
+	maxBatch int           // maximum number of chunks to delete in one db request batch
+	ratio    int           // 1/x ratio to calculate the number of chunks to gc on a low capacity db
+	count    int           // number of chunks deleted in running round
+	target   int           // number of chunks to delete in running round
+	batch    *dbBatch      // the delete batch
+	runC     chan struct{} // struct in chan means gc is NOT running
+}
+
 type LDBStore struct {
 	db *LDBDatabase
 
@@ -102,12 +117,12 @@ type LDBStore struct {
 	hashfunc SwarmHasher
 	po       func(Address) uint8
 
-	batchC   chan bool
 	batchesC chan struct{}
 	closed   bool
 	batch    *dbBatch
 	lock     sync.RWMutex
 	quit     chan struct{}
+	gc       *garbage
 
 	// Functions encodeDataFunc is used to bypass
 	// the default functionality of DbStore with
@@ -166,9 +181,33 @@ func NewLDBStore(params *LDBStoreParams) (s *LDBStore, err error) {
 	data, _ = s.db.Get(keyDataIdx)
 	s.dataIdx = BytesToU64(data)
 
+	// set up garbage collection
+	s.gc = &garbage{
+		maxBatch: defaultMaxGCBatch,
+		maxRound: defaultMaxGCRound,
+		ratio:    defaultGCRatio,
+	}
+
+	s.gc.runC = make(chan struct{}, 1)
+	s.gc.runC <- struct{}{}
+
 	return s, nil
 }
 
+// initialize and set values for processing of gc round
+func (s *LDBStore) startGC(c int) {
+
+	s.gc.count = 0
+	// calculate the target number of deletions
+	if c >= s.gc.maxRound {
+		s.gc.target = s.gc.maxRound
+	} else {
+		s.gc.target = c / s.gc.ratio
+	}
+	s.gc.batch = newBatch()
+	log.Debug("startgc", "requested", c, "target", s.gc.target)
+}
+
 // NewMockDbStore creates a new instance of DbStore with
 // mockStore set to a provided value. If mockStore argument is nil,
 // this function behaves exactly as NewDbStore.
@@ -225,6 +264,31 @@ func getDataKey(idx uint64, po uint8) []byte {
 	return key
 }
 
+func getGCIdxKey(index *dpaDBIndex) []byte {
+	key := make([]byte, 9)
+	key[0] = keyGCIdx
+	binary.BigEndian.PutUint64(key[1:], index.Access)
+	return key
+}
+
+func getGCIdxValue(index *dpaDBIndex, po uint8, addr Address) []byte {
+	val := make([]byte, 41) // po = 1, index.Index = 8, Address = 32
+	val[0] = po
+	binary.BigEndian.PutUint64(val[1:], index.Idx)
+	copy(val[9:], addr)
+	return val
+}
+
+func parseGCIdxEntry(accessCnt []byte, val []byte) (index *dpaDBIndex, po uint8, addr Address) {
+	index = &dpaDBIndex{
+		Idx:    binary.BigEndian.Uint64(val[1:]),
+		Access: binary.BigEndian.Uint64(accessCnt),
+	}
+	po = val[0]
+	addr = val[9:]
+	return
+}
+
 func encodeIndex(index *dpaDBIndex) []byte {
 	data, _ := rlp.EncodeToBytes(index)
 	return data
@@ -247,55 +311,70 @@ func decodeData(addr Address, data []byte) (*chunk, error) {
 	return NewChunk(addr, data[32:]), nil
 }
 
-func (s *LDBStore) collectGarbage(ratio float32) {
-	log.Trace("collectGarbage", "ratio", ratio)
+func (s *LDBStore) collectGarbage() error {
 
-	metrics.GetOrRegisterCounter("ldbstore.collectgarbage", nil).Inc(1)
+	// prevent duplicate gc from starting when one is already running
+	select {
+	case <-s.gc.runC:
+	default:
+		return nil
+	}
 
-	it := s.db.NewIterator()
-	defer it.Release()
+	s.lock.Lock()
+	entryCnt := s.entryCnt
+	s.lock.Unlock()
 
-	garbage := []*gcItem{}
-	gcnt := 0
+	metrics.GetOrRegisterCounter("ldbstore.collectgarbage", nil).Inc(1)
 
-	for ok := it.Seek([]byte{keyIndex}); ok && (gcnt < maxGCitems) && (uint64(gcnt) < s.entryCnt); ok = it.Next() {
-		itkey := it.Key()
+	// calculate the amount of chunks to collect and reset counter
+	s.startGC(int(entryCnt))
+	log.Debug("collectGarbage", "target", s.gc.target, "entryCnt", entryCnt)
 
-		if (itkey == nil) || (itkey[0] != keyIndex) {
-			break
-		}
+	var totalDeleted int
+	for s.gc.count < s.gc.target {
+		it := s.db.NewIterator()
+		ok := it.Seek([]byte{keyGCIdx})
+		var singleIterationCount int
 
-		// it.Key() contents change on next call to it.Next(), so we must copy it
-		key := make([]byte, len(it.Key()))
-		copy(key, it.Key())
+		// every batch needs a lock so we avoid entries changing accessidx in the meantime
+		s.lock.Lock()
+		for ; ok && (singleIterationCount < s.gc.maxBatch); ok = it.Next() {
 
-		val := it.Value()
+			// quit if no more access index keys
+			itkey := it.Key()
+			if (itkey == nil) || (itkey[0] != keyGCIdx) {
+				break
+			}
 
-		var index dpaDBIndex
+			// get chunk data entry from access index
+			val := it.Value()
+			index, po, hash := parseGCIdxEntry(itkey[1:], val)
+			keyIdx := make([]byte, 33)
+			keyIdx[0] = keyIndex
+			copy(keyIdx[1:], hash)
 
-		hash := key[1:]
-		decodeIndex(val, &index)
-		po := s.po(hash)
+			// add delete operation to batch
+			s.delete(s.gc.batch.Batch, index, keyIdx, po)
+			singleIterationCount++
+			s.gc.count++
 
-		gci := &gcItem{
-			idxKey: key,
-			idx:    index.Idx,
-			value:  index.Access, // the smaller, the more likely to be gc'd. see sort comparator below.
-			po:     po,
+			// break if target is not on max garbage batch boundary
+			if s.gc.count >= s.gc.target {
+				break
+			}
 		}
 
-		garbage = append(garbage, gci)
-		gcnt++
+		s.writeBatch(s.gc.batch, wEntryCnt)
+		s.lock.Unlock()
+		it.Release()
+		log.Trace("garbage collect batch done", "batch", singleIterationCount, "total", s.gc.count)
 	}
 
-	sort.Slice(garbage[:gcnt], func(i, j int) bool { return garbage[i].value < garbage[j].value })
-
-	cutoff := int(float32(gcnt) * ratio)
-	metrics.GetOrRegisterCounter("ldbstore.collectgarbage.delete", nil).Inc(int64(cutoff))
+	s.gc.runC <- struct{}{}
+	log.Debug("garbage collect done", "c", s.gc.count)
 
-	for i := 0; i < cutoff; i++ {
-		s.delete(garbage[i].idx, garbage[i].idxKey, garbage[i].po)
-	}
+	metrics.GetOrRegisterCounter("ldbstore.collectgarbage.delete", nil).Inc(int64(totalDeleted))
+	return nil
 }
 
 // Export writes all chunks from the store to a tar archive, returning the
@@ -474,7 +553,7 @@ func (s *LDBStore) Cleanup(f func(*chunk) bool) {
 		// if chunk is to be removed
 		if f(c) {
 			log.Warn("chunk for cleanup", "key", fmt.Sprintf("%x", key), "ck", fmt.Sprintf("%x", ck), "dkey", fmt.Sprintf("%x", datakey), "dataidx", index.Idx, "po", po, "len data", len(data), "len sdata", len(c.sdata), "size", cs)
-			s.delete(index.Idx, getIndexKey(key[1:]), po)
+			s.deleteNow(&index, getIndexKey(key[1:]), po)
 			removed++
 			errorsFound++
 		}
@@ -526,24 +605,43 @@ func (s *LDBStore) ReIndex() {
 	log.Warn(fmt.Sprintf("Found %v errors out of %v entries", errorsFound, total))
 }
 
-func (s *LDBStore) Delete(addr Address) {
+// Delete is removes a chunk and updates indices.
+// Is thread safe
+func (s *LDBStore) Delete(addr Address) error {
 	s.lock.Lock()
 	defer s.lock.Unlock()
 
 	ikey := getIndexKey(addr)
 
-	var indx dpaDBIndex
-	s.tryAccessIdx(ikey, &indx)
+	idata, err := s.db.Get(ikey)
+	if err != nil {
+		return err
+	}
 
-	s.delete(indx.Idx, ikey, s.po(addr))
+	var idx dpaDBIndex
+	decodeIndex(idata, &idx)
+	proximity := s.po(addr)
+	return s.deleteNow(&idx, ikey, proximity)
 }
 
-func (s *LDBStore) delete(idx uint64, idxKey []byte, po uint8) {
+// executes one delete operation immediately
+// see *LDBStore.delete
+func (s *LDBStore) deleteNow(idx *dpaDBIndex, idxKey []byte, po uint8) error {
+	batch := new(leveldb.Batch)
+	s.delete(batch, idx, idxKey, po)
+	return s.db.Write(batch)
+}
+
+// adds a delete chunk operation to the provided batch
+// if called directly, decrements entrycount regardless if the chunk exists upon deletion. Risk of wrap to max uint64
+func (s *LDBStore) delete(batch *leveldb.Batch, idx *dpaDBIndex, idxKey []byte, po uint8) {
 	metrics.GetOrRegisterCounter("ldbstore.delete", nil).Inc(1)
 
-	batch := new(leveldb.Batch)
+	gcIdxKey := getGCIdxKey(idx)
+	batch.Delete(gcIdxKey)
+	dataKey := getDataKey(idx.Idx, po)
+	batch.Delete(dataKey)
 	batch.Delete(idxKey)
-	batch.Delete(getDataKey(idx, po))
 	s.entryCnt--
 	dbEntryCount.Dec(1)
 	cntKey := make([]byte, 2)
@@ -551,7 +649,6 @@ func (s *LDBStore) delete(idx uint64, idxKey []byte, po uint8) {
 	cntKey[1] = po
 	batch.Put(keyEntryCnt, U64ToBytes(s.entryCnt))
 	batch.Put(cntKey, U64ToBytes(s.bucketCnt[po]))
-	s.db.Write(batch)
 }
 
 func (s *LDBStore) BinIndex(po uint8) uint64 {
@@ -572,6 +669,9 @@ func (s *LDBStore) CurrentStorageIndex() uint64 {
 	return s.dataIdx
 }
 
+// Put adds a chunk to the database, adding indices and incrementing global counters.
+// If it already exists, it merely increments the access count of the existing entry.
+// Is thread safe
 func (s *LDBStore) Put(ctx context.Context, chunk Chunk) error {
 	metrics.GetOrRegisterCounter("ldbstore.put", nil).Inc(1)
 	log.Trace("ldbstore.put", "key", chunk.Address())
@@ -594,7 +694,7 @@ func (s *LDBStore) Put(ctx context.Context, chunk Chunk) error {
 	if err != nil {
 		s.doPut(chunk, &index, po)
 	} else {
-		log.Trace("ldbstore.put: chunk already exists, only update access", "key", chunk.Address)
+		log.Debug("ldbstore.put: chunk already exists, only update access", "key", chunk.Address(), "po", po)
 		decodeIndex(idata, &index)
 	}
 	index.Access = s.accessCnt
@@ -602,6 +702,10 @@ func (s *LDBStore) Put(ctx context.Context, chunk Chunk) error {
 	idata = encodeIndex(&index)
 	s.batch.Put(ikey, idata)
 
+	// add the access-chunkindex index for garbage collection
+	gcIdxKey := getGCIdxKey(&index)
+	gcIdxData := getGCIdxValue(&index, po, chunk.Address())
+	s.batch.Put(gcIdxKey, gcIdxData)
 	s.lock.Unlock()
 
 	select {
@@ -617,7 +721,7 @@ func (s *LDBStore) Put(ctx context.Context, chunk Chunk) error {
 	}
 }
 
-// force putting into db, does not check access index
+// force putting into db, does not check or update necessary indices
 func (s *LDBStore) doPut(chunk Chunk, index *dpaDBIndex, po uint8) {
 	data := s.encodeDataFunc(chunk)
 	dkey := getDataKey(s.dataIdx, po)
@@ -659,38 +763,26 @@ func (s *LDBStore) writeCurrentBatch() error {
 	if l == 0 {
 		return nil
 	}
-	e := s.entryCnt
-	d := s.dataIdx
-	a := s.accessCnt
 	s.batch = newBatch()
-	b.err = s.writeBatch(b, e, d, a)
+	b.err = s.writeBatch(b, wEntryCnt|wAccessCnt|wIndexCnt)
 	close(b.c)
-	for e > s.capacity {
-		log.Trace("for >", "e", e, "s.capacity", s.capacity)
-		// Collect garbage in a separate goroutine
-		// to be able to interrupt this loop by s.quit.
-		done := make(chan struct{})
-		go func() {
-			s.collectGarbage(gcArrayFreeRatio)
-			log.Trace("collectGarbage closing done")
-			close(done)
-		}()
-
-		select {
-		case <-s.quit:
-			return errors.New("CollectGarbage terminated due to quit")
-		case <-done:
-		}
-		e = s.entryCnt
+	if s.entryCnt >= s.capacity {
+		go s.collectGarbage()
 	}
 	return nil
 }
 
 // must be called non concurrently
-func (s *LDBStore) writeBatch(b *dbBatch, entryCnt, dataIdx, accessCnt uint64) error {
-	b.Put(keyEntryCnt, U64ToBytes(entryCnt))
-	b.Put(keyDataIdx, U64ToBytes(dataIdx))
-	b.Put(keyAccessCnt, U64ToBytes(accessCnt))
+func (s *LDBStore) writeBatch(b *dbBatch, wFlag uint8) error {
+	if wFlag&wEntryCnt > 0 {
+		b.Put(keyEntryCnt, U64ToBytes(s.entryCnt))
+	}
+	if wFlag&wIndexCnt > 0 {
+		b.Put(keyDataIdx, U64ToBytes(s.dataIdx))
+	}
+	if wFlag&wAccessCnt > 0 {
+		b.Put(keyAccessCnt, U64ToBytes(s.accessCnt))
+	}
 	l := b.Len()
 	if err := s.db.Write(b.Batch); err != nil {
 		return fmt.Errorf("unable to write batch: %v", err)
@@ -713,17 +805,22 @@ func newMockEncodeDataFunc(mockStore *mock.NodeStore) func(chunk Chunk) []byte {
 }
 
 // try to find index; if found, update access cnt and return true
-func (s *LDBStore) tryAccessIdx(ikey []byte, index *dpaDBIndex) bool {
+func (s *LDBStore) tryAccessIdx(ikey []byte, po uint8, index *dpaDBIndex) bool {
 	idata, err := s.db.Get(ikey)
 	if err != nil {
 		return false
 	}
 	decodeIndex(idata, index)
+	oldGCIdxKey := getGCIdxKey(index)
 	s.batch.Put(keyAccessCnt, U64ToBytes(s.accessCnt))
 	s.accessCnt++
 	index.Access = s.accessCnt
 	idata = encodeIndex(index)
 	s.batch.Put(ikey, idata)
+	newGCIdxKey := getGCIdxKey(index)
+	newGCIdxData := getGCIdxValue(index, po, ikey)
+	s.batch.Delete(oldGCIdxKey)
+	s.batch.Put(newGCIdxKey, newGCIdxData)
 	select {
 	case s.batchesC <- struct{}{}:
 	default:
@@ -755,6 +852,9 @@ func (s *LDBStore) PutSchema(schema string) error {
 	return s.db.Put(keySchema, []byte(schema))
 }
 
+// Get retrieves the chunk matching the provided key from the database.
+// If the chunk entry does not exist, it returns an error
+// Updates access count and is thread safe
 func (s *LDBStore) Get(_ context.Context, addr Address) (chunk Chunk, err error) {
 	metrics.GetOrRegisterCounter("ldbstore.get", nil).Inc(1)
 	log.Trace("ldbstore.get", "key", addr)
@@ -764,12 +864,14 @@ func (s *LDBStore) Get(_ context.Context, addr Address) (chunk Chunk, err error)
 	return s.get(addr)
 }
 
+// TODO: To conform with other private methods of this object indices should not be updated
 func (s *LDBStore) get(addr Address) (chunk *chunk, err error) {
 	var indx dpaDBIndex
 	if s.closed {
 		return nil, ErrDBClosed
 	}
-	if s.tryAccessIdx(getIndexKey(addr), &indx) {
+	proximity := s.po(addr)
+	if s.tryAccessIdx(getIndexKey(addr), proximity, &indx) {
 		var data []byte
 		if s.getDataFunc != nil {
 			// if getDataFunc is defined, use it to retrieve the chunk data
@@ -780,13 +882,12 @@ func (s *LDBStore) get(addr Address) (chunk *chunk, err error) {
 			}
 		} else {
 			// default DbStore functionality to retrieve chunk data
-			proximity := s.po(addr)
 			datakey := getDataKey(indx.Idx, proximity)
 			data, err = s.db.Get(datakey)
 			log.Trace("ldbstore.get retrieve", "key", addr, "indexkey", indx.Idx, "datakey", fmt.Sprintf("%x", datakey), "proximity", proximity)
 			if err != nil {
 				log.Trace("ldbstore.get chunk found but could not be accessed", "key", addr, "err", err)
-				s.delete(indx.Idx, getIndexKey(addr), s.po(addr))
+				s.deleteNow(&indx, getIndexKey(addr), s.po(addr))
 				return
 			}
 		}
@@ -813,33 +914,14 @@ func newMockGetDataFunc(mockStore *mock.NodeStore) func(addr Address) (data []by
 	}
 }
 
-func (s *LDBStore) updateAccessCnt(addr Address) {
-
-	s.lock.Lock()
-	defer s.lock.Unlock()
-
-	var index dpaDBIndex
-	s.tryAccessIdx(getIndexKey(addr), &index) // result_chn == nil, only update access cnt
-
-}
-
 func (s *LDBStore) setCapacity(c uint64) {
 	s.lock.Lock()
 	defer s.lock.Unlock()
 
 	s.capacity = c
 
-	if s.entryCnt > c {
-		ratio := float32(1.01) - float32(c)/float32(s.entryCnt)
-		if ratio < gcArrayFreeRatio {
-			ratio = gcArrayFreeRatio
-		}
-		if ratio > 1 {
-			ratio = 1
-		}
-		for s.entryCnt > c {
-			s.collectGarbage(ratio)
-		}
+	for s.entryCnt > c {
+		s.collectGarbage()
 	}
 }
 
diff --git a/swarm/storage/ldbstore_test.go b/swarm/storage/ldbstore_test.go
index 14a42b5e3..48af8c57c 100644
--- a/swarm/storage/ldbstore_test.go
+++ b/swarm/storage/ldbstore_test.go
@@ -22,6 +22,8 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -297,27 +299,73 @@ func TestLDBStoreWithoutCollectGarbage(t *testing.T) {
 }
 
 // TestLDBStoreCollectGarbage tests that we can put more chunks than LevelDB's capacity, and
-// retrieve only some of them, because garbage collection must have cleared some of them
+// retrieve only some of them, because garbage collection must have partially cleared the store
+// Also tests that we can delete chunks and that we can trigger garbage collection
 func TestLDBStoreCollectGarbage(t *testing.T) {
-	capacity := 500
-	n := 2000
+
+	// below max ronud
+	cap := defaultMaxGCRound / 2
+	t.Run(fmt.Sprintf("A/%d/%d", cap, cap*4), testLDBStoreCollectGarbage)
+	t.Run(fmt.Sprintf("B/%d/%d", cap, cap*4), testLDBStoreRemoveThenCollectGarbage)
+
+	// at max round
+	cap = defaultMaxGCRound
+	t.Run(fmt.Sprintf("A/%d/%d", cap, cap*4), testLDBStoreCollectGarbage)
+	t.Run(fmt.Sprintf("B/%d/%d", cap, cap*4), testLDBStoreRemoveThenCollectGarbage)
+
+	// more than max around, not on threshold
+	cap = defaultMaxGCRound * 1.1
+	t.Run(fmt.Sprintf("A/%d/%d", cap, cap*4), testLDBStoreCollectGarbage)
+	t.Run(fmt.Sprintf("B/%d/%d", cap, cap*4), testLDBStoreRemoveThenCollectGarbage)
+
+}
+
+func testLDBStoreCollectGarbage(t *testing.T) {
+	params := strings.Split(t.Name(), "/")
+	capacity, err := strconv.Atoi(params[2])
+	if err != nil {
+		t.Fatal(err)
+	}
+	n, err := strconv.Atoi(params[3])
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	ldb, cleanup := newLDBStore(t)
 	ldb.setCapacity(uint64(capacity))
 	defer cleanup()
 
-	chunks, err := mputRandomChunks(ldb, n, int64(ch.DefaultSize))
-	if err != nil {
-		t.Fatal(err.Error())
-	}
-	log.Info("ldbstore", "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt)
+	// retrieve the gc round target count for the db capacity
+	ldb.startGC(capacity)
+	roundTarget := ldb.gc.target
+
+	// split put counts to gc target count threshold, and wait for gc to finish in between
+	var allChunks []Chunk
+	remaining := n
+	for remaining > 0 {
+		var putCount int
+		if remaining < roundTarget {
+			putCount = remaining
+		} else {
+			putCount = roundTarget
+		}
+		remaining -= putCount
+		chunks, err := mputRandomChunks(ldb, putCount, int64(ch.DefaultSize))
+		if err != nil {
+			t.Fatal(err.Error())
+		}
+		allChunks = append(allChunks, chunks...)
+		log.Debug("ldbstore", "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt, "cap", capacity, "n", n)
 
-	// wait for garbage collection to kick in on the responsible actor
-	time.Sleep(1 * time.Second)
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+		defer cancel()
+		waitGc(ctx, ldb)
+	}
 
+	// attempt gets on all put chunks
 	var missing int
-	for _, ch := range chunks {
-		ret, err := ldb.Get(context.Background(), ch.Address())
+	for _, ch := range allChunks {
+		ret, err := ldb.Get(context.TODO(), ch.Address())
 		if err == ErrChunkNotFound || err == ldberrors.ErrNotFound {
 			missing++
 			continue
@@ -333,8 +381,10 @@ func TestLDBStoreCollectGarbage(t *testing.T) {
 		log.Trace("got back chunk", "chunk", ret)
 	}
 
-	if missing < n-capacity {
-		t.Fatalf("gc failure: expected to miss %v chunks, but only %v are actually missing", n-capacity, missing)
+	// all surplus chunks should be missing
+	expectMissing := roundTarget + (((n - capacity) / roundTarget) * roundTarget)
+	if missing != expectMissing {
+		t.Fatalf("gc failure: expected to miss %v chunks, but only %v are actually missing", expectMissing, missing)
 	}
 
 	log.Info("ldbstore", "total", n, "missing", missing, "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt)
@@ -367,7 +417,6 @@ func TestLDBStoreAddRemove(t *testing.T) {
 		if i%2 == 0 {
 			// expect even chunks to be missing
 			if err == nil {
-				// if err != ErrChunkNotFound {
 				t.Fatal("expected chunk to be missing, but got no error")
 			}
 		} else {
@@ -383,30 +432,48 @@ func TestLDBStoreAddRemove(t *testing.T) {
 	}
 }
 
-// TestLDBStoreRemoveThenCollectGarbage tests that we can delete chunks and that we can trigger garbage collection
-func TestLDBStoreRemoveThenCollectGarbage(t *testing.T) {
-	capacity := 11
-	surplus := 4
+func testLDBStoreRemoveThenCollectGarbage(t *testing.T) {
+
+	params := strings.Split(t.Name(), "/")
+	capacity, err := strconv.Atoi(params[2])
+	if err != nil {
+		t.Fatal(err)
+	}
+	n, err := strconv.Atoi(params[3])
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	ldb, cleanup := newLDBStore(t)
+	defer cleanup()
 	ldb.setCapacity(uint64(capacity))
 
-	n := capacity
-
-	chunks := []Chunk{}
-	for i := 0; i < n+surplus; i++ {
+	// put capacity count number of chunks
+	chunks := make([]Chunk, n)
+	for i := 0; i < n; i++ {
 		c := GenerateRandomChunk(ch.DefaultSize)
-		chunks = append(chunks, c)
+		chunks[i] = c
 		log.Trace("generate random chunk", "idx", i, "chunk", c)
 	}
 
 	for i := 0; i < n; i++ {
-		ldb.Put(context.TODO(), chunks[i])
+		err := ldb.Put(context.TODO(), chunks[i])
+		if err != nil {
+			t.Fatal(err)
+		}
 	}
 
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+	defer cancel()
+	waitGc(ctx, ldb)
+
 	// delete all chunks
+	// (only count the ones actually deleted, the rest will have been gc'd)
+	deletes := 0
 	for i := 0; i < n; i++ {
-		ldb.Delete(chunks[i].Address())
+		if ldb.Delete(chunks[i].Address()) == nil {
+			deletes++
+		}
 	}
 
 	log.Info("ldbstore", "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt)
@@ -415,37 +482,49 @@ func TestLDBStoreRemoveThenCollectGarbage(t *testing.T) {
 		t.Fatalf("ldb.entrCnt expected 0 got %v", ldb.entryCnt)
 	}
 
-	expAccessCnt := uint64(n * 2)
+	// the manual deletes will have increased accesscnt, so we need to add this when we verify the current count
+	expAccessCnt := uint64(n)
 	if ldb.accessCnt != expAccessCnt {
-		t.Fatalf("ldb.accessCnt expected %v got %v", expAccessCnt, ldb.entryCnt)
+		t.Fatalf("ldb.accessCnt expected %v got %v", expAccessCnt, ldb.accessCnt)
 	}
 
-	cleanup()
+	// retrieve the gc round target count for the db capacity
+	ldb.startGC(capacity)
+	roundTarget := ldb.gc.target
 
-	ldb, cleanup = newLDBStore(t)
-	capacity = 10
-	ldb.setCapacity(uint64(capacity))
-	defer cleanup()
-
-	n = capacity + surplus
+	remaining := n
+	var puts int
+	for remaining > 0 {
+		var putCount int
+		if remaining < roundTarget {
+			putCount = remaining
+		} else {
+			putCount = roundTarget
+		}
+		remaining -= putCount
+		for putCount > 0 {
+			ldb.Put(context.TODO(), chunks[puts])
+			log.Debug("ldbstore", "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt, "cap", capacity, "n", n, "puts", puts, "remaining", remaining, "roundtarget", roundTarget)
+			puts++
+			putCount--
+		}
 
-	for i := 0; i < n; i++ {
-		ldb.Put(context.TODO(), chunks[i])
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+		defer cancel()
+		waitGc(ctx, ldb)
 	}
 
-	// wait for garbage collection
-	time.Sleep(1 * time.Second)
-
 	// expect first surplus chunks to be missing, because they have the smallest access value
-	for i := 0; i < surplus; i++ {
+	expectMissing := roundTarget + (((n - capacity) / roundTarget) * roundTarget)
+	for i := 0; i < expectMissing; i++ {
 		_, err := ldb.Get(context.TODO(), chunks[i].Address())
 		if err == nil {
-			t.Fatal("expected surplus chunk to be missing, but got no error")
+			t.Fatalf("expected surplus chunk %d to be missing, but got no error", i)
 		}
 	}
 
 	// expect last chunks to be present, as they have the largest access value
-	for i := surplus; i < surplus+capacity; i++ {
+	for i := expectMissing; i < n; i++ {
 		ret, err := ldb.Get(context.TODO(), chunks[i].Address())
 		if err != nil {
 			t.Fatalf("chunk %v: expected no error, but got %s", i, err)
@@ -455,3 +534,57 @@ func TestLDBStoreRemoveThenCollectGarbage(t *testing.T) {
 		}
 	}
 }
+
+// TestLDBStoreCollectGarbageAccessUnlikeIndex tests garbage collection where accesscount differs from indexcount
+func TestLDBStoreCollectGarbageAccessUnlikeIndex(t *testing.T) {
+
+	capacity := defaultMaxGCRound * 2
+	n := capacity - 1
+
+	ldb, cleanup := newLDBStore(t)
+	ldb.setCapacity(uint64(capacity))
+	defer cleanup()
+
+	chunks, err := mputRandomChunks(ldb, n, int64(ch.DefaultSize))
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+	log.Info("ldbstore", "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt)
+
+	// set first added capacity/2 chunks to highest accesscount
+	for i := 0; i < capacity/2; i++ {
+		_, err := ldb.Get(context.TODO(), chunks[i].Address())
+		if err != nil {
+			t.Fatalf("fail add chunk #%d - %s: %v", i, chunks[i].Address(), err)
+		}
+	}
+	_, err = mputRandomChunks(ldb, 2, int64(ch.DefaultSize))
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+
+	// wait for garbage collection to kick in on the responsible actor
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
+	defer cancel()
+	waitGc(ctx, ldb)
+
+	var missing int
+	for i, ch := range chunks[2 : capacity/2] {
+		ret, err := ldb.Get(context.TODO(), ch.Address())
+		if err == ErrChunkNotFound || err == ldberrors.ErrNotFound {
+			t.Fatalf("fail find chunk #%d - %s: %v", i, ch.Address(), err)
+		}
+
+		if !bytes.Equal(ret.Data(), ch.Data()) {
+			t.Fatal("expected to get the same data back, but got smth else")
+		}
+		log.Trace("got back chunk", "chunk", ret)
+	}
+
+	log.Info("ldbstore", "total", n, "missing", missing, "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt)
+}
+
+func waitGc(ctx context.Context, ldb *LDBStore) {
+	<-ldb.gc.runC
+	ldb.gc.runC <- struct{}{}
+}