path: root/swarm/storage/ldbstore_test.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package storage

import (
    "bytes"
    "context"
    "encoding/binary"
    "fmt"
    "io/ioutil"
    "os"
    "strconv"
    "strings"
    "testing"
    "time"

    "github.com/dexon-foundation/dexon/common"
    ch "github.com/dexon-foundation/dexon/swarm/chunk"
    "github.com/dexon-foundation/dexon/swarm/log"
    "github.com/dexon-foundation/dexon/swarm/storage/mock/mem"
    ldberrors "github.com/syndtr/goleveldb/leveldb/errors"
)

type testDbStore struct {
    *LDBStore
    dir string
}

func newTestDbStore(mock bool, trusted bool) (*testDbStore, func(), error) {
    dir, err := ioutil.TempDir("", "bzz-storage-test")
    if err != nil {
        return nil, func() {}, err
    }

    var db *LDBStore
    storeparams := NewDefaultStoreParams()
    params := NewLDBStoreParams(storeparams, dir)
    params.Po = testPoFunc

    if mock {
        globalStore := mem.NewGlobalStore()
        addr := common.HexToAddress("0x5aaeb6053f3e94c9b9a09f33669435e7ef1beaed")
        mockStore := globalStore.NewNodeStore(addr)

        db, err = NewMockDbStore(params, mockStore)
    } else {
        db, err = NewLDBStore(params)
    }

    cleanup := func() {
        if db != nil {
            db.Close()
        }
        err = os.RemoveAll(dir)
        if err != nil {
            panic(fmt.Sprintf("db cleanup failed: %v", err))
        }
    }

    return &testDbStore{db, dir}, cleanup, err
}

func testPoFunc(k Address) (ret uint8) {
    basekey := make([]byte, 32)
    return uint8(Proximity(basekey, k[:]))
}

func testDbStoreRandom(n int, mock bool, t *testing.T) {
    db, cleanup, err := newTestDbStore(mock, true)
    defer cleanup()
    if err != nil {
        t.Fatalf("init dbStore failed: %v", err)
    }
    testStoreRandom(db, n, t)
}

func testDbStoreCorrect(n int, mock bool, t *testing.T) {
    db, cleanup, err := newTestDbStore(mock, false)
    defer cleanup()
    if err != nil {
        t.Fatalf("init dbStore failed: %v", err)
    }
    testStoreCorrect(db, n, t)
}

func TestMarkAccessed(t *testing.T) {
    db, cleanup, err := newTestDbStore(false, true)
    defer cleanup()
    if err != nil {
        t.Fatalf("init dbStore failed: %v", err)
    }

    h := GenerateRandomChunk(ch.DefaultSize)

    db.Put(context.Background(), h)

    var index dpaDBIndex
    addr := h.Address()
    idxk := getIndexKey(addr)

    idata, err := db.db.Get(idxk)
    if err != nil {
        t.Fatal(err)
    }
    decodeIndex(idata, &index)

    if index.Access != 0 {
        t.Fatalf("Expected the access index to be %d, but it is %d", 0, index.Access)
    }

    db.MarkAccessed(addr)
    db.writeCurrentBatch()

    idata, err = db.db.Get(idxk)
    if err != nil {
        t.Fatal(err)
    }
    decodeIndex(idata, &index)

    if index.Access != 1 {
        t.Fatalf("Expected the access index to be %d, but it is %d", 1, index.Access)
    }

}

func TestDbStoreRandom_1(t *testing.T) {
    testDbStoreRandom(1, false, t)
}

func TestDbStoreCorrect_1(t *testing.T) {
    testDbStoreCorrect(1, false, t)
}

func TestDbStoreRandom_1k(t *testing.T) {
    testDbStoreRandom(1000, false, t)
}

func TestDbStoreCorrect_1k(t *testing.T) {
    testDbStoreCorrect(1000, false, t)
}

func TestMockDbStoreRandom_1(t *testing.T) {
    testDbStoreRandom(1, true, t)
}

func TestMockDbStoreCorrect_1(t *testing.T) {
    testDbStoreCorrect(1, true, t)
}

func TestMockDbStoreRandom_1k(t *testing.T) {
    testDbStoreRandom(1000, true, t)
}

func TestMockDbStoreCorrect_1k(t *testing.T) {
    testDbStoreCorrect(1000, true, t)
}

func testDbStoreNotFound(t *testing.T, mock bool) {
    db, cleanup, err := newTestDbStore(mock, false)
    defer cleanup()
    if err != nil {
        t.Fatalf("init dbStore failed: %v", err)
    }

    _, err = db.Get(context.TODO(), ZeroAddr)
    if err != ErrChunkNotFound {
        t.Errorf("Expected ErrChunkNotFound, got %v", err)
    }
}

func TestDbStoreNotFound(t *testing.T) {
    testDbStoreNotFound(t, false)
}
func TestMockDbStoreNotFound(t *testing.T) {
    testDbStoreNotFound(t, true)
}

func testIterator(t *testing.T, mock bool) {
    var chunkcount int = 32
    var i int
    var poc uint
    chunkkeys := NewAddressCollection(chunkcount)
    chunkkeys_results := NewAddressCollection(chunkcount)

    db, cleanup, err := newTestDbStore(mock, false)
    defer cleanup()
    if err != nil {
        t.Fatalf("init dbStore failed: %v", err)
    }

    chunks := GenerateRandomChunks(ch.DefaultSize, chunkcount)

    for i = 0; i < len(chunks); i++ {
        chunkkeys[i] = chunks[i].Address()
        err := db.Put(context.TODO(), chunks[i])
        if err != nil {
            t.Fatalf("dbStore.Put failed: %v", err)
        }
    }

    for i = 0; i < len(chunkkeys); i++ {
        log.Trace(fmt.Sprintf("Chunk array pos %d/%d: '%v'", i, chunkcount, chunkkeys[i]))
    }
    i = 0
    for poc = 0; poc <= 255; poc++ {
        err := db.SyncIterator(0, uint64(chunkkeys.Len()), uint8(poc), func(k Address, n uint64) bool {
            log.Trace(fmt.Sprintf("Got key %v number %d poc %d", k, n, uint8(poc)))
            chunkkeys_results[n] = k
            i++
            return true
        })
        if err != nil {
            t.Fatalf("Iterator call failed: %v", err)
        }
    }

    for i = 0; i < chunkcount; i++ {
        if !bytes.Equal(chunkkeys[i], chunkkeys_results[i]) {
            t.Fatalf("Chunk put #%d key '%v' does not match iterator's key '%v'", i, chunkkeys[i], chunkkeys_results[i])
        }
    }

}

func TestIterator(t *testing.T) {
    testIterator(t, false)
}
func TestMockIterator(t *testing.T) {
    testIterator(t, true)
}

func benchmarkDbStorePut(n int, mock bool, b *testing.B) {
    db, cleanup, err := newTestDbStore(mock, true)
    defer cleanup()
    if err != nil {
        b.Fatalf("init dbStore failed: %v", err)
    }
    benchmarkStorePut(db, n, b)
}

func benchmarkDbStoreGet(n int, mock bool, b *testing.B) {
    db, cleanup, err := newTestDbStore(mock, true)
    defer cleanup()
    if err != nil {
        b.Fatalf("init dbStore failed: %v", err)
    }
    benchmarkStoreGet(db, n, b)
}

func BenchmarkDbStorePut_500(b *testing.B) {
    benchmarkDbStorePut(500, false, b)
}

func BenchmarkDbStoreGet_500(b *testing.B) {
    benchmarkDbStoreGet(500, false, b)
}

func BenchmarkMockDbStorePut_500(b *testing.B) {
    benchmarkDbStorePut(500, true, b)
}

func BenchmarkMockDbStoreGet_500(b *testing.B) {
    benchmarkDbStoreGet(500, true, b)
}

// TestLDBStoreWithoutCollectGarbage tests that we can put a number of random chunks in the LevelDB store, and
// retrieve them, provided we don't hit the garbage collection
func TestLDBStoreWithoutCollectGarbage(t *testing.T) {
    capacity := 50
    n := 10

    ldb, cleanup := newLDBStore(t)
    ldb.setCapacity(uint64(capacity))
    defer cleanup()

    chunks, err := mputRandomChunks(ldb, n)
    if err != nil {
        t.Fatal(err.Error())
    }

    log.Info("ldbstore", "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt)

    for _, ch := range chunks {
        ret, err := ldb.Get(context.TODO(), ch.Address())
        if err != nil {
            t.Fatal(err)
        }

        if !bytes.Equal(ret.Data(), ch.Data()) {
            t.Fatal("expected to get the same data back, but got smth else")
        }
    }

    if ldb.entryCnt != uint64(n) {
        t.Fatalf("expected entryCnt to be equal to %v, but got %v", n, ldb.entryCnt)
    }

    if ldb.accessCnt != uint64(2*n) {
        t.Fatalf("expected accessCnt to be equal to %v, but got %v", 2*n, ldb.accessCnt)
    }
}

// TestLDBStoreCollectGarbage tests that we can put more chunks than LevelDB's capacity, and
// 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) {

    // below max ronud
    initialCap := defaultMaxGCRound / 100
    cap := initialCap / 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 = initialCap
    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 = initialCap + 500
    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()

    // 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)
        if err != nil {
            t.Fatal(err.Error())
        }
        allChunks = append(allChunks, chunks...)
        log.Debug("ldbstore", "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt, "cap", capacity, "n", n)

        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 allChunks {
        ret, err := ldb.Get(context.TODO(), ch.Address())
        if err == ErrChunkNotFound || err == ldberrors.ErrNotFound {
            missing++
            continue
        }
        if err != nil {
            t.Fatal(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)
    }

    // 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)
}

// TestLDBStoreAddRemove tests that we can put and then delete a given chunk
func TestLDBStoreAddRemove(t *testing.T) {
    ldb, cleanup := newLDBStore(t)
    ldb.setCapacity(200)
    defer cleanup()

    n := 100
    chunks, err := mputRandomChunks(ldb, n)
    if err != nil {
        t.Fatalf(err.Error())
    }

    for i := 0; i < n; i++ {
        // delete all even index chunks
        if i%2 == 0 {
            ldb.Delete(chunks[i].Address())
        }
    }

    log.Info("ldbstore", "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt)

    for i := 0; i < n; i++ {
        ret, err := ldb.Get(context.TODO(), chunks[i].Address())

        if i%2 == 0 {
            // expect even chunks to be missing
            if err == nil {
                t.Fatal("expected chunk to be missing, but got no error")
            }
        } else {
            // expect odd chunks to be retrieved successfully
            if err != nil {
                t.Fatalf("expected no error, but got %s", err)
            }

            if !bytes.Equal(ret.Data(), chunks[i].Data()) {
                t.Fatal("expected to get the same data back, but got smth else")
            }
        }
    }
}

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))

    // put capacity count number of chunks
    chunks := make([]Chunk, n)
    for i := 0; i < n; i++ {
        c := GenerateRandomChunk(ch.DefaultSize)
        chunks[i] = c
        log.Trace("generate random chunk", "idx", i, "chunk", c)
    }

    for i := 0; i < n; 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++ {
        if ldb.Delete(chunks[i].Address()) == nil {
            deletes++
        }
    }

    log.Info("ldbstore", "entrycnt", ldb.entryCnt, "accesscnt", ldb.accessCnt)

    if ldb.entryCnt != 0 {
        t.Fatalf("ldb.entrCnt expected 0 got %v", ldb.entryCnt)
    }

    // 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.accessCnt)
    }

    // retrieve the gc round target count for the db capacity
    ldb.startGC(capacity)
    roundTarget := ldb.gc.target

    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--
        }

        ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
        defer cancel()
        waitGc(ctx, ldb)
    }

    // expect first surplus chunks to be missing, because they have the smallest access value
    expectMissing := roundTarget + (((n - capacity) / roundTarget) * roundTarget)
    for i := 0; i < expectMissing; i++ {
        _, err := ldb.Get(context.TODO(), chunks[i].Address())
        if err == nil {
            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 := 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)
        }
        if !bytes.Equal(ret.Data(), chunks[i].Data()) {
            t.Fatal("expected to get the same data back, but got smth else")
        }
    }
}

// TestLDBStoreCollectGarbageAccessUnlikeIndex tests garbage collection where accesscount differs from indexcount
func TestLDBStoreCollectGarbageAccessUnlikeIndex(t *testing.T) {

    capacity := defaultMaxGCRound / 100 * 2
    n := capacity - 1

    ldb, cleanup := newLDBStore(t)
    ldb.setCapacity(uint64(capacity))
    defer cleanup()

    chunks, err := mputRandomChunks(ldb, n)
    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)
    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 TestCleanIndex(t *testing.T) {
    capacity := 5000
    n := 3

    ldb, cleanup := newLDBStore(t)
    ldb.setCapacity(uint64(capacity))
    defer cleanup()

    chunks, err := mputRandomChunks(ldb, n)
    if err != nil {
        t.Fatal(err)
    }

    // remove the data of the first chunk
    po := ldb.po(chunks[0].Address()[:])
    dataKey := make([]byte, 10)
    dataKey[0] = keyData
    dataKey[1] = byte(po)
    // dataKey[2:10] = first chunk has storageIdx 0 on [2:10]
    if _, err := ldb.db.Get(dataKey); err != nil {
        t.Fatal(err)
    }
    if err := ldb.db.Delete(dataKey); err != nil {
        t.Fatal(err)
    }

    // remove the gc index row for the first chunk
    gcFirstCorrectKey := make([]byte, 9)
    gcFirstCorrectKey[0] = keyGCIdx
    if err := ldb.db.Delete(gcFirstCorrectKey); err != nil {
        t.Fatal(err)
    }

    // warp the gc data of the second chunk
    // this data should be correct again after the clean
    gcSecondCorrectKey := make([]byte, 9)
    gcSecondCorrectKey[0] = keyGCIdx
    binary.BigEndian.PutUint64(gcSecondCorrectKey[1:], uint64(1))
    gcSecondCorrectVal, err := ldb.db.Get(gcSecondCorrectKey)
    if err != nil {
        t.Fatal(err)
    }
    warpedGCVal := make([]byte, len(gcSecondCorrectVal)+1)
    copy(warpedGCVal[1:], gcSecondCorrectVal)
    if err := ldb.db.Delete(gcSecondCorrectKey); err != nil {
        t.Fatal(err)
    }
    if err := ldb.db.Put(gcSecondCorrectKey, warpedGCVal); err != nil {
        t.Fatal(err)
    }

    if err := ldb.CleanGCIndex(); err != nil {
        t.Fatal(err)
    }

    // the index without corresponding data should have been deleted
    idxKey := make([]byte, 33)
    idxKey[0] = keyIndex
    copy(idxKey[1:], chunks[0].Address())
    if _, err := ldb.db.Get(idxKey); err == nil {
        t.Fatalf("expected chunk 0 idx to be pruned: %v", idxKey)
    }

    // the two other indices should be present
    copy(idxKey[1:], chunks[1].Address())
    if _, err := ldb.db.Get(idxKey); err != nil {
        t.Fatalf("expected chunk 1 idx to be present: %v", idxKey)
    }

    copy(idxKey[1:], chunks[2].Address())
    if _, err := ldb.db.Get(idxKey); err != nil {
        t.Fatalf("expected chunk 2 idx to be present: %v", idxKey)
    }

    // first gc index should still be gone
    if _, err := ldb.db.Get(gcFirstCorrectKey); err == nil {
        t.Fatalf("expected gc 0 idx to be pruned: %v", idxKey)
    }

    // second gc index should still be fixed
    if _, err := ldb.db.Get(gcSecondCorrectKey); err != nil {
        t.Fatalf("expected gc 1 idx to be present: %v", idxKey)
    }

    // third gc index should be unchanged
    binary.BigEndian.PutUint64(gcSecondCorrectKey[1:], uint64(2))
    if _, err := ldb.db.Get(gcSecondCorrectKey); err != nil {
        t.Fatalf("expected gc 2 idx to be present: %v", idxKey)
    }

    c, err := ldb.db.Get(keyEntryCnt)
    if err != nil {
        t.Fatalf("expected gc 2 idx to be present: %v", idxKey)
    }

    // entrycount should now be one less
    entryCount := binary.BigEndian.Uint64(c)
    if entryCount != 2 {
        t.Fatalf("expected entrycnt to be 2, was %d", c)
    }

    // the chunks might accidentally be in the same bin
    // if so that bin counter will now be 2 - the highest added index.
    // if not, the total of them will be 3
    poBins := []uint8{ldb.po(chunks[1].Address()), ldb.po(chunks[2].Address())}
    if poBins[0] == poBins[1] {
        poBins = poBins[:1]
    }

    var binTotal uint64
    var currentBin [2]byte
    currentBin[0] = keyDistanceCnt
    if len(poBins) == 1 {
        currentBin[1] = poBins[0]
        c, err := ldb.db.Get(currentBin[:])
        if err != nil {
            t.Fatalf("expected gc 2 idx to be present: %v", idxKey)
        }
        binCount := binary.BigEndian.Uint64(c)
        if binCount != 2 {
            t.Fatalf("expected entrycnt to be 2, was %d", binCount)
        }
    } else {
        for _, bin := range poBins {
            currentBin[1] = bin
            c, err := ldb.db.Get(currentBin[:])
            if err != nil {
                t.Fatalf("expected gc 2 idx to be present: %v", idxKey)
            }
            binCount := binary.BigEndian.Uint64(c)
            binTotal += binCount

        }
        if binTotal != 3 {
            t.Fatalf("expected sum of bin indices to be 3, was %d", binTotal)
        }
    }

    // check that the iterator quits properly
    chunks, err = mputRandomChunks(ldb, 4100)
    if err != nil {
        t.Fatal(err)
    }

    po = ldb.po(chunks[4099].Address()[:])
    dataKey = make([]byte, 10)
    dataKey[0] = keyData
    dataKey[1] = byte(po)
    binary.BigEndian.PutUint64(dataKey[2:], 4099+3)
    if _, err := ldb.db.Get(dataKey); err != nil {
        t.Fatal(err)
    }
    if err := ldb.db.Delete(dataKey); err != nil {
        t.Fatal(err)
    }

    if err := ldb.CleanGCIndex(); err != nil {
        t.Fatal(err)
    }

    // entrycount should now be one less of added chunks
    c, err = ldb.db.Get(keyEntryCnt)
    if err != nil {
        t.Fatalf("expected gc 2 idx to be present: %v", idxKey)
    }
    entryCount = binary.BigEndian.Uint64(c)
    if entryCount != 4099+2 {
        t.Fatalf("expected entrycnt to be 2, was %d", c)
    }
}

func waitGc(ctx context.Context, ldb *LDBStore) {
    <-ldb.gc.runC
    ldb.gc.runC <- struct{}{}
}