mempool no gossip back

CHANGELOG_PENDING.md

@@ -20,6 +20,8 @@
 
 ### IMPROVEMENTS:
 
+- [mempool] \#2778 No longer send txs back to peers who sent it to you
+
 ### BUG FIXES:
 
 - [blockchain] \#2699 update the maxHeight when a peer is removed

docs/spec/reactors/mempool/reactor.md

@@ -12,3 +12,5 @@ for details.
 
 Sending incorrectly encoded data or data exceeding `maxMsgSize` will result
 in stopping the peer.
+
+The mempool will not send a tx back to any peer which it received it from.

mempool/bench_test.go

@@ -26,6 +26,19 @@ func BenchmarkReap(b *testing.B) {
 	}
 }
 
+func BenchmarkCheckTx(b *testing.B) {
+	app := kvstore.NewKVStoreApplication()
+	cc := proxy.NewLocalClientCreator(app)
+	mempool, cleanup := newMempoolWithApp(cc)
+	defer cleanup()
+
+	for i := 0; i < b.N; i++ {
+		tx := make([]byte, 8)
+		binary.BigEndian.PutUint64(tx, uint64(i))
+		mempool.CheckTx(tx, nil)
+	}
+}
+
 func BenchmarkCacheInsertTime(b *testing.B) {
 	cache := newMapTxCache(b.N)
 	txs := make([][]byte, b.N)

mempool/cache_test.go

@@ -0,0 +1,101 @@
+package mempool
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/tendermint/tendermint/abci/example/kvstore"
+	"github.com/tendermint/tendermint/proxy"
+	"github.com/tendermint/tendermint/types"
+)
+
+func TestCacheRemove(t *testing.T) {
+	cache := newMapTxCache(100)
+	numTxs := 10
+	txs := make([][]byte, numTxs)
+	for i := 0; i < numTxs; i++ {
+		// probability of collision is 2**-256
+		txBytes := make([]byte, 32)
+		rand.Read(txBytes)
+		txs[i] = txBytes
+		cache.Push(txBytes)
+		// make sure its added to both the linked list and the map
+		require.Equal(t, i+1, len(cache.map_))
+		require.Equal(t, i+1, cache.list.Len())
+	}
+	for i := 0; i < numTxs; i++ {
+		cache.Remove(txs[i])
+		// make sure its removed from both the map and the linked list
+		require.Equal(t, numTxs-(i+1), len(cache.map_))
+		require.Equal(t, numTxs-(i+1), cache.list.Len())
+	}
+}
+
+func TestCacheAfterUpdate(t *testing.T) {
+	app := kvstore.NewKVStoreApplication()
+	cc := proxy.NewLocalClientCreator(app)
+	mempool, cleanup := newMempoolWithApp(cc)
+	defer cleanup()
+
+	// reAddIndices & txsInCache can have elements > numTxsToCreate
+	// also assumes max index is 255 for convenience
+	// txs in cache also checks order of elements
+	tests := []struct {
+		numTxsToCreate int
+		updateIndices  []int
+		reAddIndices   []int
+		txsInCache     []int
+	}{
+		{1, []int{}, []int{1}, []int{1, 0}},    // adding new txs works
+		{2, []int{1}, []int{}, []int{1, 0}},    // update doesn't remove tx from cache
+		{2, []int{2}, []int{}, []int{2, 1, 0}}, // update adds new tx to cache
+		{2, []int{1}, []int{1}, []int{1, 0}},   // re-adding after update doesn't make dupe
+	}
+	for tcIndex, tc := range tests {
+		for i := 0; i < tc.numTxsToCreate; i++ {
+			tx := types.Tx{byte(i)}
+			err := mempool.CheckTx(tx, nil)
+			require.NoError(t, err)
+		}
+
+		updateTxs := []types.Tx{}
+		for _, v := range tc.updateIndices {
+			tx := types.Tx{byte(v)}
+			updateTxs = append(updateTxs, tx)
+		}
+		mempool.Update(int64(tcIndex), updateTxs, nil, nil)
+
+		for _, v := range tc.reAddIndices {
+			tx := types.Tx{byte(v)}
+			_ = mempool.CheckTx(tx, nil)
+		}
+
+		cache := mempool.cache.(*mapTxCache)
+		node := cache.list.Front()
+		counter := 0
+		for node != nil {
+			require.NotEqual(t, len(tc.txsInCache), counter,
+				"cache larger than expected on testcase %d", tcIndex)
+
+			nodeVal := node.Value.([sha256.Size]byte)
+			expectedBz := sha256.Sum256([]byte{byte(tc.txsInCache[len(tc.txsInCache)-counter-1])})
+			// Reference for reading the errors:
+			// >>> sha256('\x00').hexdigest()
+			// '6e340b9cffb37a989ca544e6bb780a2c78901d3fb33738768511a30617afa01d'
+			// >>> sha256('\x01').hexdigest()
+			// '4bf5122f344554c53bde2ebb8cd2b7e3d1600ad631c385a5d7cce23c7785459a'
+			// >>> sha256('\x02').hexdigest()
+			// 'dbc1b4c900ffe48d575b5da5c638040125f65db0fe3e24494b76ea986457d986'
+
+			require.Equal(t, expectedBz, nodeVal, "Equality failed on index %d, tc %d", counter, tcIndex)
+			counter++
+			node = node.Next()
+		}
+		require.Equal(t, len(tc.txsInCache), counter,
+			"cache smaller than expected on testcase %d", tcIndex)
+		mempool.Flush()
+	}
+}