Make antiPastHashesBetween return blocks sorted in ghostdag-order (#1536)

* Make antiPastHashesBetween return blocks sorted in ghostdag-order

* Return sortedMergeSet instead of blueMergeSet

* Invert the order of parameters of IsAncestorOf

* Add RenderDAGToDot to TestConsensus

* Add HighHash explicitly, unless lowHash == highHash

* Use Equal instead of == when comparing hashes

* Fixed TestSyncManager_GetHashesBetween

* Fix tests

* findHighHashAccordingToMaxBlueScoreDifference: don't start looking if the whole thing fits

* Handle a missed error

* Remove redundant call to RenderToDot

* Fix bug in findHighHashAccordingToMaxBlueScoreDifference

app/rpc/rpchandlers/get_blocks_test.go

@@ -1,6 +1,10 @@
 package rpchandlers_test
 
 import (
+	"reflect"
+	"sort"
+	"testing"
+
 	"github.com/kaspanet/kaspad/app/appmessage"
 	"github.com/kaspanet/kaspad/app/rpc/rpccontext"
 	"github.com/kaspanet/kaspad/app/rpc/rpchandlers"
@@ -12,9 +16,6 @@ import (
 	"github.com/kaspanet/kaspad/domain/dagconfig"
 	"github.com/kaspanet/kaspad/domain/miningmanager"
 	"github.com/kaspanet/kaspad/infrastructure/config"
-	"reflect"
-	"sort"
-	"testing"
 )
 
 type fakeDomain struct {
@@ -65,66 +66,79 @@ func TestHandleGetBlocks(t *testing.T) {
 			return antipast
 		}
 
-		upBfsOrder := make([]*externalapi.DomainHash, 0, 30)
+		// Create a DAG with the following structure:
-		selectedParent := params.GenesisHash
+		//          merging block
-		upBfsOrder = append(upBfsOrder, selectedParent)
+		//         /      |      \
+		//      split1  split2   split3
+		//        \       |      /
+		//         merging block
+		//         /      |      \
+		//      split1  split2   split3
+		//        \       |      /
+		//               etc.
+		expectedOrder := make([]*externalapi.DomainHash, 0, 40)
+		mergingBlock := params.GenesisHash
 		for i := 0; i < 10; i++ {
-			parents := make([]*externalapi.DomainHash, 0, 3)
+			splitBlocks := make([]*externalapi.DomainHash, 0, 3)
-			for j := 0; j < 4; j++ {
+			for j := 0; j < 3; j++ {
-				blockHash, _, err := tc.AddBlock([]*externalapi.DomainHash{selectedParent}, nil, nil)
+				blockHash, _, err := tc.AddBlock([]*externalapi.DomainHash{mergingBlock}, nil, nil)
 				if err != nil {
 					t.Fatalf("Failed adding block: %v", err)
 				}
-				parents = append(parents, blockHash)
+				splitBlocks = append(splitBlocks, blockHash)
-				upBfsOrder = append(upBfsOrder, blockHash)
 			}
-			selectedParent, _, err = tc.AddBlock(parents, nil, nil)
+			sort.Sort(sort.Reverse(testutils.NewTestGhostDAGSorter(splitBlocks, tc, t)))
+			restOfSplitBlocks, selectedParent := splitBlocks[:len(splitBlocks)-1], splitBlocks[len(splitBlocks)-1]
+			expectedOrder = append(expectedOrder, selectedParent)
+			expectedOrder = append(expectedOrder, restOfSplitBlocks...)
+
+			mergingBlock, _, err = tc.AddBlock(splitBlocks, nil, nil)
 			if err != nil {
 				t.Fatalf("Failed adding block: %v", err)
 			}
-			upBfsOrder = append(upBfsOrder, selectedParent)
+			expectedOrder = append(expectedOrder, mergingBlock)
 		}
 
 		virtualSelectedParent, err := tc.GetVirtualSelectedParent()
 		if err != nil {
 			t.Fatalf("Failed getting SelectedParent: %v", err)
 		}
-		if !virtualSelectedParent.Equal(upBfsOrder[len(upBfsOrder)-1]) {
+		if !virtualSelectedParent.Equal(expectedOrder[len(expectedOrder)-1]) {
-			t.Fatalf("Expected %s to be selectedParent, instead found: %s", upBfsOrder[len(upBfsOrder)-1], virtualSelectedParent)
+			t.Fatalf("Expected %s to be selectedParent, instead found: %s", expectedOrder[len(expectedOrder)-1], virtualSelectedParent)
 		}
 
 		requestSelectedParent := getBlocks(virtualSelectedParent)
 		if !reflect.DeepEqual(requestSelectedParent.BlockHashes, hashes.ToStrings([]*externalapi.DomainHash{virtualSelectedParent})) {
-			t.Fatalf("TestSyncManager_GetHashesBetween expected %v\n == \n%v", requestSelectedParent.BlockHashes, virtualSelectedParent)
+			t.Fatalf("TestHandleGetBlocks expected:\n%v\nactual:\n%v", virtualSelectedParent, requestSelectedParent.BlockHashes)
 		}
 
-		for i, blockHash := range upBfsOrder {
+		for i, blockHash := range expectedOrder {
-			expectedBlocks := filterAntiPast(blockHash, upBfsOrder)
+			expectedBlocks := filterAntiPast(blockHash, expectedOrder)
-			// sort the slice in the order GetBlocks is returning them
-			sort.Sort(sort.Reverse(testutils.NewTestGhostDAGSorter(expectedBlocks, tc, t)))
 			expectedBlocks = append([]*externalapi.DomainHash{blockHash}, expectedBlocks...)
 
-			blocks := getBlocks(blockHash)
+			actualBlocks := getBlocks(blockHash)
-			if !reflect.DeepEqual(blocks.BlockHashes, hashes.ToStrings(expectedBlocks)) {
+			if !reflect.DeepEqual(actualBlocks.BlockHashes, hashes.ToStrings(expectedBlocks)) {
-				t.Fatalf("TestSyncManager_GetHashesBetween %d expected %s\n == \n%s", i, blocks.BlockHashes, hashes.ToStrings(expectedBlocks))
+				t.Fatalf("TestHandleGetBlocks %d \nexpected: \n%v\nactual:\n%v", i,
+					hashes.ToStrings(expectedBlocks), actualBlocks.BlockHashes)
 			}
 		}
 
-		// Make explitly sure that if lowHash==highHash we get a slice with a single hash.
+		// Make explicitly sure that if lowHash==highHash we get a slice with a single hash.
-		blocks := getBlocks(virtualSelectedParent)
+		actualBlocks := getBlocks(virtualSelectedParent)
-		if !reflect.DeepEqual(blocks.BlockHashes, []string{virtualSelectedParent.String()}) {
+		if !reflect.DeepEqual(actualBlocks.BlockHashes, []string{virtualSelectedParent.String()}) {
-			t.Fatalf("TestSyncManager_GetHashesBetween expected blocks to contain just '%s', instead got: \n%s", virtualSelectedParent, blocks.BlockHashes)
+			t.Fatalf("TestHandleGetBlocks expected blocks to contain just '%s', instead got: \n%v",
+				virtualSelectedParent, actualBlocks.BlockHashes)
 		}
 
-		sort.Sort(sort.Reverse(testutils.NewTestGhostDAGSorter(upBfsOrder, tc, t)))
+		expectedOrder = append([]*externalapi.DomainHash{params.GenesisHash}, expectedOrder...)
-		requestAllViaNil := getBlocks(nil)
+		actualOrder := getBlocks(nil)
-		if !reflect.DeepEqual(requestAllViaNil.BlockHashes, hashes.ToStrings(upBfsOrder)) {
+		if !reflect.DeepEqual(actualOrder.BlockHashes, hashes.ToStrings(expectedOrder)) {
-			t.Fatalf("TestSyncManager_GetHashesBetween expected %v\n == \n%v", requestAllViaNil.BlockHashes, upBfsOrder)
+			t.Fatalf("TestHandleGetBlocks \nexpected: %v \nactual:\n%v", expectedOrder, actualOrder.BlockHashes)
 		}
 
 		requestAllExplictly := getBlocks(params.GenesisHash)
-		if !reflect.DeepEqual(requestAllExplictly.BlockHashes, hashes.ToStrings(upBfsOrder)) {
+		if !reflect.DeepEqual(requestAllExplictly.BlockHashes, hashes.ToStrings(expectedOrder)) {
-			t.Fatalf("TestSyncManager_GetHashesBetween expected %v\n == \n%v", requestAllExplictly.BlockHashes, upBfsOrder)
+			t.Fatalf("TestHandleGetBlocks \nexpected: \n%v\n. actual:\n%v", expectedOrder, requestAllExplictly.BlockHashes)
 		}
 	})
 }

domain/consensus/log.go

@@ -2,6 +2,8 @@ package consensus
 
 import (
 	"github.com/kaspanet/kaspad/infrastructure/logger"
+	"github.com/kaspanet/kaspad/util/panics"
 )
 
 var log, _ = logger.Get(logger.SubsystemTags.BDAG)
+var spawn = panics.GoroutineWrapperFunc(log)

domain/consensus/model/testapi/test_consensus.go

@@ -1,11 +1,12 @@
 package testapi
 
 import (
+	"io"
+
 	"github.com/kaspanet/kaspad/domain/consensus/model"
 	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
 	"github.com/kaspanet/kaspad/domain/dagconfig"
 	"github.com/kaspanet/kaspad/infrastructure/db/database"
-	"io"
 )
 
 // MineJSONBlockType indicates which type of blocks MineJSON mines
@@ -50,6 +51,8 @@ type TestConsensus interface {
 	MineJSON(r io.Reader, blockType MineJSONBlockType) (tips []*externalapi.DomainHash, err error)
 	DiscardAllStores()
 
+	RenderDAGToDot(filename string) error
+
 	AcceptanceDataStore() model.AcceptanceDataStore
 	BlockHeaderStore() model.BlockHeaderStore
 	BlockRelationStore() model.BlockRelationStore

domain/consensus/processes/syncmanager/antipast.go

@@ -1,14 +1,15 @@
 package syncmanager
 
 import (
+	"github.com/kaspanet/kaspad/domain/consensus/model"
 	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
-	"github.com/kaspanet/kaspad/domain/consensus/utils/hashset"
 	"github.com/pkg/errors"
 )
 
 // antiPastHashesBetween returns the hashes of the blocks between the
 // lowHash's antiPast and highHash's antiPast, or up to
 // `maxBlueScoreDifference`, if non-zero.
+// The result excludes lowHash and includes highHash. If lowHash == highHash, returns nothing.
 func (sm *syncManager) antiPastHashesBetween(lowHash, highHash *externalapi.DomainHash,
 	maxBlueScoreDifference uint64) ([]*externalapi.DomainHash, error) {
 
@@ -17,19 +18,10 @@ func (sm *syncManager) antiPastHashesBetween(lowHash, highHash *externalapi.Doma
 	// highHash's selectedParentChain.
 	// We keep originalLowHash to filter out blocks in it's past later down the road
 	originalLowHash := lowHash
-	for {
+	var err error
-		isInSelectedParentChain, err := sm.dagTopologyManager.IsInSelectedParentChainOf(lowHash, highHash)
+	lowHash, err = sm.findLowHashInHighHashSelectedParentChain(lowHash, highHash)
-		if err != nil {
+	if err != nil {
-			return nil, err
+		return nil, err
-		}
-		if isInSelectedParentChain {
-			break
-		}
-		lowBlockGHOSTDAGData, err := sm.ghostdagDataStore.Get(sm.databaseContext, lowHash)
-		if err != nil {
-			return nil, err
-		}
-		lowHash = lowBlockGHOSTDAGData.SelectedParent()
 	}
 
 	lowBlockGHOSTDAGData, err := sm.ghostdagDataStore.Get(sm.databaseContext, lowHash)
@@ -55,78 +47,138 @@ func (sm *syncManager) antiPastHashesBetween(lowHash, highHash *externalapi.Doma
 		// Using blueScore as an approximation is considered to be
 		// fairly accurate because we presume that most DAG blocks are
 		// blue.
-		iterator, err := sm.dagTraversalManager.SelectedChildIterator(highHash, lowHash)
+		highHash, err = sm.findHighHashAccordingToMaxBlueScoreDifference(lowHash, highHash, maxBlueScoreDifference, highBlockGHOSTDAGData, lowBlockGHOSTDAGData)
 		if err != nil {
 			return nil, err
 		}
-		for ok := iterator.First(); ok; ok = iterator.Next() {
-			highHash, err = iterator.Get()
-			if err != nil {
-				return nil, err
-			}
-			highBlockGHOSTDAGData, err = sm.ghostdagDataStore.Get(sm.databaseContext, highHash)
-			if err != nil {
-				return nil, err
-			}
-			if highBlockGHOSTDAGData.BlueScore()-lowBlockGHOSTDAGData.BlueScore()+1 > maxBlueScoreDifference {
-				break
-			}
-		}
 	}
 
-	// Collect every node in highHash's past (including itself) but
+	// Collect all hashes by concatenating the merge-sets of all blocks between highHash and lowHash
-	// NOT in the lowHash's past (excluding itself) into an up-heap
+	blockHashes := []*externalapi.DomainHash{}
-	// (a heap sorted by blueScore from lowest to greatest).
+	iterator, err := sm.dagTraversalManager.SelectedChildIterator(highHash, lowHash)
-	visited := hashset.New()
-	hashesUpHeap := sm.dagTraversalManager.NewUpHeap()
-	queue := sm.dagTraversalManager.NewDownHeap()
-	err = queue.Push(highHash)
 	if err != nil {
 		return nil, err
 	}
-	for queue.Len() > 0 {
+	for ok := iterator.First(); ok; ok = iterator.Next() {
-		current := queue.Pop()
+		current, err := iterator.Get()
-		if visited.Contains(current) {
-			continue
-		}
-		visited.Add(current)
-		var isCurrentAncestorOfLowHash bool
-		if current == lowHash {
-			isCurrentAncestorOfLowHash = false
-		} else {
-			var err error
-			isCurrentAncestorOfLowHash, err = sm.dagTopologyManager.IsAncestorOf(current, lowHash)
-			if err != nil {
-				return nil, err
-			}
-		}
-		if isCurrentAncestorOfLowHash {
-			continue
-		}
-		// Push current to hashesUpHeap if it's not in the past of originalLowHash
-		isInPastOfOriginalLowHash, err := sm.dagTopologyManager.IsAncestorOf(current, originalLowHash)
 		if err != nil {
 			return nil, err
 		}
-		if !isInPastOfOriginalLowHash {
+		// Both blue and red merge sets are topologically sorted, but not the concatenation of the two.
-			err = hashesUpHeap.Push(current)
+		// We require the blocks to be topologically sorted. In addition,  for optimal performance,
-			if err != nil {
+		// we want the selectedParent to be first.
-				return nil, err
+		// Since the rest of the merge set is in the anticone of selectedParent, it's position in the list does not
-			}
+		// matter, even though it's blue score is the highest, we can arbitrarily decide it comes first.
-		}
+		// Therefore we first append the selectedParent, then the rest of blocks in ghostdag order.
-		parents, err := sm.dagTopologyManager.Parents(current)
+		sortedMergeSet, err := sm.getSortedMergeSet(current)
 		if err != nil {
 			return nil, err
 		}
-		for _, parent := range parents {
+
-			err := queue.Push(parent)
+		// append to blockHashes all blocks in sortedMergeSet which are not in the past of originalLowHash
+		for _, blockHash := range sortedMergeSet {
+			isInPastOfOriginalLowHash, err := sm.dagTopologyManager.IsAncestorOf(blockHash, originalLowHash)
 			if err != nil {
 				return nil, err
 			}
+			if isInPastOfOriginalLowHash {
+				continue
+			}
+			blockHashes = append(blockHashes, blockHash)
 		}
 	}
 
-	return hashesUpHeap.ToSlice(), nil
+	// The process above doesn't return highHash, so include it explicitly, unless highHash == lowHash
+	if !lowHash.Equal(highHash) {
+		blockHashes = append(blockHashes, highHash)
+	}
+
+	return blockHashes, nil
+}
+
+func (sm *syncManager) getSortedMergeSet(current *externalapi.DomainHash) ([]*externalapi.DomainHash, error) {
+	currentGhostdagData, err := sm.ghostdagDataStore.Get(sm.databaseContext, current)
+	if err != nil {
+		return nil, err
+	}
+
+	blueMergeSet := currentGhostdagData.MergeSetBlues()
+	redMergeSet := currentGhostdagData.MergeSetReds()
+	sortedMergeSet := make([]*externalapi.DomainHash, 0, len(blueMergeSet)+len(redMergeSet))
+	selectedParent, blueMergeSet := blueMergeSet[0], blueMergeSet[1:]
+	sortedMergeSet = append(sortedMergeSet, selectedParent)
+	i, j := 0, 0
+	for i < len(blueMergeSet) && j < len(redMergeSet) {
+		currentBlue := blueMergeSet[i]
+		currentBlueGhostdagData, err := sm.ghostdagDataStore.Get(sm.databaseContext, currentBlue)
+		if err != nil {
+			return nil, err
+		}
+		currentRed := redMergeSet[j]
+		currentRedGhostdagData, err := sm.ghostdagDataStore.Get(sm.databaseContext, currentRed)
+		if err != nil {
+			return nil, err
+		}
+		if sm.ghostdagManager.Less(currentBlue, currentBlueGhostdagData, currentRed, currentRedGhostdagData) {
+			sortedMergeSet = append(sortedMergeSet, currentBlue)
+			i++
+		} else {
+			sortedMergeSet = append(sortedMergeSet, currentRed)
+			j++
+		}
+	}
+	sortedMergeSet = append(sortedMergeSet, blueMergeSet[i:]...)
+	sortedMergeSet = append(sortedMergeSet, redMergeSet[j:]...)
+
+	return sortedMergeSet, nil
+}
+
+func (sm *syncManager) findHighHashAccordingToMaxBlueScoreDifference(lowHash *externalapi.DomainHash,
+	highHash *externalapi.DomainHash, maxBlueScoreDifference uint64, highBlockGHOSTDAGData *model.BlockGHOSTDAGData,
+	lowBlockGHOSTDAGData *model.BlockGHOSTDAGData) (*externalapi.DomainHash, error) {
+
+	if highBlockGHOSTDAGData.BlueScore()-lowBlockGHOSTDAGData.BlueScore() <= maxBlueScoreDifference {
+		return highHash, nil
+	}
+
+	iterator, err := sm.dagTraversalManager.SelectedChildIterator(highHash, lowHash)
+	if err != nil {
+		return nil, err
+	}
+	for ok := iterator.First(); ok; ok = iterator.Next() {
+		highHashCandidate, err := iterator.Get()
+		if err != nil {
+			return nil, err
+		}
+		highBlockGHOSTDAGData, err = sm.ghostdagDataStore.Get(sm.databaseContext, highHashCandidate)
+		if err != nil {
+			return nil, err
+		}
+		if highBlockGHOSTDAGData.BlueScore()-lowBlockGHOSTDAGData.BlueScore() > maxBlueScoreDifference {
+			break
+		}
+		highHash = highHashCandidate
+	}
+	return highHash, nil
+}
+
+func (sm *syncManager) findLowHashInHighHashSelectedParentChain(
+	lowHash *externalapi.DomainHash, highHash *externalapi.DomainHash) (*externalapi.DomainHash, error) {
+	for {
+		isInSelectedParentChain, err := sm.dagTopologyManager.IsInSelectedParentChainOf(lowHash, highHash)
+		if err != nil {
+			return nil, err
+		}
+		if isInSelectedParentChain {
+			break
+		}
+		lowBlockGHOSTDAGData, err := sm.ghostdagDataStore.Get(sm.databaseContext, lowHash)
+		if err != nil {
+			return nil, err
+		}
+		lowHash = lowBlockGHOSTDAGData.SelectedParent()
+	}
+	return lowHash, nil
 }
 
 func (sm *syncManager) missingBlockBodyHashes(highHash *externalapi.DomainHash) ([]*externalapi.DomainHash, error) {

domain/consensus/processes/syncmanager/syncmanager_test.go

@@ -1,14 +1,15 @@
 package syncmanager_test
 
 import (
-	"github.com/kaspanet/kaspad/domain/consensus"
-	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
-	"github.com/kaspanet/kaspad/domain/consensus/utils/testutils"
-	"github.com/kaspanet/kaspad/domain/dagconfig"
 	"math"
 	"reflect"
 	"sort"
 	"testing"
+
+	"github.com/kaspanet/kaspad/domain/consensus"
+	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
+	"github.com/kaspanet/kaspad/domain/consensus/utils/testutils"
+	"github.com/kaspanet/kaspad/domain/dagconfig"
 )
 
 func TestSyncManager_GetHashesBetween(t *testing.T) {
@@ -20,27 +21,40 @@ func TestSyncManager_GetHashesBetween(t *testing.T) {
 		}
 		defer teardown(false)
 
-		upBfsOrder := make([]*externalapi.DomainHash, 0, 30)
+		// Create a DAG with the following structure:
-		selectedParent := params.GenesisHash
+		//          merging block
-		upBfsOrder = append(upBfsOrder, selectedParent)
+		//         /      |      \
+		//      split1  split2   split3
+		//        \       |      /
+		//         merging block
+		//         /      |      \
+		//      split1  split2   split3
+		//        \       |      /
+		//               etc.
+		expectedOrder := make([]*externalapi.DomainHash, 0, 40)
+		mergingBlock := params.GenesisHash
 		for i := 0; i < 10; i++ {
-			parents := make([]*externalapi.DomainHash, 0, 3)
+			splitBlocks := make([]*externalapi.DomainHash, 0, 3)
-			for j := 0; j < 4; j++ {
+			for j := 0; j < 3; j++ {
-				blockHash, _, err := tc.AddBlock([]*externalapi.DomainHash{selectedParent}, nil, nil)
+				splitBlock, _, err := tc.AddBlock([]*externalapi.DomainHash{mergingBlock}, nil, nil)
 				if err != nil {
 					t.Fatalf("Failed adding block: %v", err)
 				}
-				parents = append(parents, blockHash)
+				splitBlocks = append(splitBlocks, splitBlock)
-				upBfsOrder = append(upBfsOrder, blockHash)
 			}
-			selectedParent, _, err = tc.AddBlock(parents, nil, nil)
+			sort.Sort(sort.Reverse(testutils.NewTestGhostDAGSorter(splitBlocks, tc, t)))
+			restOfSplitBlocks, selectedParent := splitBlocks[:len(splitBlocks)-1], splitBlocks[len(splitBlocks)-1]
+			expectedOrder = append(expectedOrder, selectedParent)
+			expectedOrder = append(expectedOrder, restOfSplitBlocks...)
+
+			mergingBlock, _, err = tc.AddBlock(splitBlocks, nil, nil)
 			if err != nil {
 				t.Fatalf("Failed adding block: %v", err)
 			}
-			upBfsOrder = append(upBfsOrder, selectedParent)
+			expectedOrder = append(expectedOrder, mergingBlock)
 		}
 
-		for i, blockHash := range upBfsOrder {
+		for i, blockHash := range expectedOrder {
 			empty, err := tc.SyncManager().GetHashesBetween(blockHash, blockHash, math.MaxUint64)
 			if err != nil {
 				t.Fatalf("TestSyncManager_GetHashesBetween failed returning 0 hashes on the %d'th block: %v", i, err)
@@ -50,15 +64,13 @@ func TestSyncManager_GetHashesBetween(t *testing.T) {
 			}
 		}
 
-		allHashes, err := tc.SyncManager().GetHashesBetween(upBfsOrder[0], upBfsOrder[len(upBfsOrder)-1], math.MaxUint64)
+		actualOrder, err := tc.SyncManager().GetHashesBetween(params.GenesisHash, expectedOrder[len(expectedOrder)-1], math.MaxUint64)
 		if err != nil {
-			t.Fatalf("TestSyncManager_GetHashesBetween failed returning allHashes: %v", err)
+			t.Fatalf("TestSyncManager_GetHashesBetween failed returning actualOrder: %v", err)
 		}
 
-		sort.Sort(sort.Reverse(testutils.NewTestGhostDAGSorter(upBfsOrder, tc, t)))
+		if !reflect.DeepEqual(actualOrder, expectedOrder) {
-		upBfsOrderExcludingGenesis := upBfsOrder[1:]
+			t.Fatalf("TestSyncManager_GetHashesBetween expected: \n%s\nactual:\n%s\n", expectedOrder, actualOrder)
-		if !reflect.DeepEqual(allHashes, upBfsOrderExcludingGenesis) {
-			t.Fatalf("TestSyncManager_GetHashesBetween expected %v\n == \n%v", allHashes, upBfsOrder)
 		}
 	})
 }

domain/consensus/test_consensus.go

@@ -2,6 +2,8 @@ package consensus
 
 import (
 	"encoding/json"
+	"io"
+
 	"github.com/kaspanet/kaspad/domain/consensus/model"
 	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"
 	"github.com/kaspanet/kaspad/domain/consensus/model/testapi"
@@ -9,7 +11,6 @@ import (
 	"github.com/kaspanet/kaspad/domain/dagconfig"
 	"github.com/kaspanet/kaspad/infrastructure/db/database"
 	"github.com/pkg/errors"
-	"io"
 )
 
 type testConsensus struct {

domain/consensus/test_consensus_render_to_dot.go

@@ -0,0 +1,79 @@
+package consensus
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os/exec"
+	"strings"
+)
+
+// RenderDAGToDot is a helper function for debugging tests.
+// It requires graphviz installed.
+func (tc *testConsensus) RenderDAGToDot(filename string) error {
+	dotScript, _ := tc.convertToDot()
+	return renderDotScript(dotScript, filename)
+}
+
+func (tc *testConsensus) convertToDot() (string, error) {
+	var dotScriptBuilder strings.Builder
+	dotScriptBuilder.WriteString("digraph {\n\trankdir = TB; \n")
+
+	edges := []string{}
+
+	blocksIterator, err := tc.blockStore.AllBlockHashesIterator(tc.databaseContext)
+	if err != nil {
+		return "", err
+	}
+
+	for ok := blocksIterator.First(); ok; ok = blocksIterator.Next() {
+		hash, err := blocksIterator.Get()
+		if err != nil {
+			return "", err
+		}
+		dotScriptBuilder.WriteString(fmt.Sprintf("\t\"%s\";\n", hash))
+
+		parents, err := tc.dagTopologyManager.Parents(hash)
+		if err != nil {
+			return "", err
+		}
+
+		for _, parentHash := range parents {
+			edges = append(edges, fmt.Sprintf("\t\"%s\" -> \"%s\";", hash, parentHash))
+		}
+	}
+
+	dotScriptBuilder.WriteString("\n")
+
+	dotScriptBuilder.WriteString(strings.Join(edges, "\n"))
+
+	dotScriptBuilder.WriteString("\n}")
+
+	return dotScriptBuilder.String(), nil
+}
+
+func renderDotScript(dotScript string, filename string) error {
+	command := exec.Command("dot", "-Tsvg")
+	stdin, err := command.StdinPipe()
+	if err != nil {
+		return fmt.Errorf("Error creating stdin pipe: %s", err)
+	}
+	spawn("renderDotScript", func() {
+		defer stdin.Close()
+
+		_, err = io.WriteString(stdin, dotScript)
+		if err != nil {
+			panic(fmt.Errorf("Error writing dotScript into stdin pipe: %s", err))
+		}
+	})
+
+	var stderr bytes.Buffer
+	command.Stderr = &stderr
+	svg, err := command.Output()
+	if err != nil {
+		return fmt.Errorf("Error getting output of dot: %s\nstderr:\n%s", err, stderr.String())
+	}
+
+	return ioutil.WriteFile(filename, svg, 0600)
+}