implement a mempool for the sequencer

db/buckets.go

@@ -34,6 +34,10 @@ const (
 	Temporary // used temporarily for migrations
 	SchemaIntermediateState
 	L1HandlerTxnHashByMsgHash // maps l1 handler msg hash to l1 handler txn hash
+	MempoolHead               // key of the head node
+	MempoolTail               // key of the tail node
+	MempoolLength             // number of transactions
+	MempoolNode
 )
 
 // Key flattens a prefix and series of byte arrays into a single []byte.

mempool/db_utils.go

@@ -0,0 +1,63 @@
+package mempool
+
+import (
+	"errors"
+	"math/big"
+
+	"github.com/NethermindEth/juno/core/felt"
+	"github.com/NethermindEth/juno/db"
+	"github.com/NethermindEth/juno/encoder"
+)
+
+func headValue(txn db.Transaction, head *felt.Felt) error {
+	return txn.Get(db.MempoolHead.Key(), func(b []byte) error {
+		head.SetBytes(b)
+		return nil
+	})
+}
+
+func tailValue(txn db.Transaction, tail *felt.Felt) error {
+	return txn.Get(db.MempoolTail.Key(), func(b []byte) error {
+		tail.SetBytes(b)
+		return nil
+	})
+}
+
+func updateHead(txn db.Transaction, head *felt.Felt) error {
+	return txn.Set(db.MempoolHead.Key(), head.Marshal())
+}
+
+func updateTail(txn db.Transaction, tail *felt.Felt) error {
+	return txn.Set(db.MempoolTail.Key(), tail.Marshal())
+}
+
+func readTxn(txn db.Transaction, itemKey *felt.Felt) (dbPoolTxn, error) {
+	var item dbPoolTxn
+	keyBytes := itemKey.Bytes()
+	err := txn.Get(db.MempoolNode.Key(keyBytes[:]), func(b []byte) error {
+		return encoder.Unmarshal(b, &item)
+	})
+	return item, err
+}
+
+func setTxn(txn db.Transaction, item *dbPoolTxn) error {
+	itemBytes, err := encoder.Marshal(item)
+	if err != nil {
+		return err
+	}
+	keyBytes := item.Txn.Transaction.Hash().Bytes()
+	return txn.Set(db.MempoolNode.Key(keyBytes[:]), itemBytes)
+}
+
+func lenDB(txn db.Transaction) (int, error) {
+	var l int
+	err := txn.Get(db.MempoolLength.Key(), func(b []byte) error {
+		l = int(new(big.Int).SetBytes(b).Int64())
+		return nil
+	})
+
+	if err != nil && errors.Is(err, db.ErrKeyNotFound) {
+		return 0, nil
+	}
+	return l, err
+}

mempool/mempool.go

@@ -0,0 +1,302 @@
+package mempool
+
+import (
+	"errors"
+	"fmt"
+	"math/big"
+	"sync"
+
+	"github.com/NethermindEth/juno/core"
+	"github.com/NethermindEth/juno/core/felt"
+	"github.com/NethermindEth/juno/db"
+	"github.com/NethermindEth/juno/utils"
+)
+
+var ErrTxnPoolFull = errors.New("transaction pool is full")
+
+type BroadcastedTransaction struct {
+	Transaction   core.Transaction
+	DeclaredClass core.Class
+}
+
+// runtime mempool txn
+type memPoolTxn struct {
+	Txn  BroadcastedTransaction
+	Next *memPoolTxn
+}
+
+// persistent db txn value
+type dbPoolTxn struct {
+	Txn      BroadcastedTransaction
+	NextHash *felt.Felt
+}
+
+// memTxnList represents a linked list of user transactions at runtime
+type memTxnList struct {
+	head *memPoolTxn
+	tail *memPoolTxn
+	len  int
+	mu   sync.Mutex
+}
+
+func (t *memTxnList) push(newNode *memPoolTxn) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.tail != nil {
+		t.tail.Next = newNode
+		t.tail = newNode
+	} else {
+		t.head = newNode
+		t.tail = newNode
+	}
+	t.len++
+}
+
+func (t *memTxnList) pop() (BroadcastedTransaction, error) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	if t.head == nil {
+		return BroadcastedTransaction{}, errors.New("transaction pool is empty")
+	}
+
+	headNode := t.head
+	t.head = headNode.Next
+	if t.head == nil {
+		t.tail = nil
+	}
+	t.len--
+	return headNode.Txn, nil
+}
+
+// Pool represents a blockchain mempool, managing transactions using both an
+// in-memory and persistent database.
+type Pool struct {
+	log         utils.SimpleLogger
+	state       core.StateReader
+	db          db.DB // to store the persistent mempool
+	txPushed    chan struct{}
+	memTxnList  *memTxnList
+	maxNumTxns  int
+	dbWriteChan chan *BroadcastedTransaction
+	wg          sync.WaitGroup
+}
+
+// New initialises the Pool and starts the database writer goroutine.
+// It is the responsibility of the caller to execute the closer function.
+func New(mainDB db.DB, state core.StateReader, maxNumTxns int, log utils.SimpleLogger) (*Pool, func() error) {
+	pool := &Pool{
+		log:         log,
+		state:       state,
+		db:          mainDB, // todo: txns should be deleted everytime a new block is stored (builder responsibility)
+		txPushed:    make(chan struct{}, 1),
+		memTxnList:  &memTxnList{},
+		maxNumTxns:  maxNumTxns,
+		dbWriteChan: make(chan *BroadcastedTransaction, maxNumTxns),
+	}
+	closer := func() error {
+		close(pool.dbWriteChan)
+		pool.wg.Wait()
+		if err := pool.db.Close(); err != nil {
+			return fmt.Errorf("failed to close mempool database: %v", err)
+		}
+		return nil
+	}
+	pool.dbWriter()
+	return pool, closer
+}
+
+func (p *Pool) dbWriter() {
+	p.wg.Add(1)
+	go func() {
+		defer p.wg.Done()
+		for txn := range p.dbWriteChan {
+			err := p.writeToDB(txn)
+			if err != nil {
+				p.log.Errorw("error in handling user transaction in persistent mempool", "err", err)
+			}
+		}
+	}()
+}
+
+// LoadFromDB restores the in-memory transaction pool from the database
+func (p *Pool) LoadFromDB() error {
+	return p.db.View(func(txn db.Transaction) error {
+		headVal := new(felt.Felt)
+		err := headValue(txn, headVal)
+		if err != nil {
+			if errors.Is(err, db.ErrKeyNotFound) {
+				return nil
+			}
+			return err
+		}
+		// loop through the persistent pool and push nodes to the in-memory pool
+		currentHash := headVal
+		for currentHash != nil {
+			curTxn, err := readTxn(txn, currentHash)
+			if err != nil {
+				return err
+			}
+			newMemPoolTxn := &memPoolTxn{
+				Txn: curTxn.Txn,
+			}
+			if curTxn.NextHash != nil {
+				nextDBTxn, err := readTxn(txn, curTxn.NextHash)
+				if err != nil {
+					return err
+				}
+				newMemPoolTxn.Next = &memPoolTxn{
+					Txn: nextDBTxn.Txn,
+				}
+			}
+			p.memTxnList.push(newMemPoolTxn)
+			currentHash = curTxn.NextHash
+		}
+		return nil
+	})
+}
+
+// writeToDB adds the transaction to the persistent pool db
+func (p *Pool) writeToDB(userTxn *BroadcastedTransaction) error {
+	return p.db.Update(func(dbTxn db.Transaction) error {
+		tailVal := new(felt.Felt)
+		if err := tailValue(dbTxn, tailVal); err != nil {
+			if !errors.Is(err, db.ErrKeyNotFound) {
+				return err
+			}
+			tailVal = nil
+		}
+		if err := setTxn(dbTxn, &dbPoolTxn{Txn: *userTxn}); err != nil {
+			return err
+		}
+		if tailVal != nil {
+			// Update old tail to point to the new item
+			var oldTailElem dbPoolTxn
+			oldTailElem, err := readTxn(dbTxn, tailVal)
+			if err != nil {
+				return err
+			}
+			oldTailElem.NextHash = userTxn.Transaction.Hash()
+			if err = setTxn(dbTxn, &oldTailElem); err != nil {
+				return err
+			}
+		} else {
+			// Empty list, make new item both the head and the tail
+			if err := updateHead(dbTxn, userTxn.Transaction.Hash()); err != nil {
+				return err
+			}
+		}
+		if err := updateTail(dbTxn, userTxn.Transaction.Hash()); err != nil {
+			return err
+		}
+		pLen, err := lenDB(dbTxn)
+		if err != nil {
+			return err
+		}
+		return dbTxn.Set(db.MempoolLength.Key(), new(big.Int).SetInt64(int64(pLen+1)).Bytes())
+	})
+}
+
+// Push queues a transaction to the pool
+func (p *Pool) Push(userTxn *BroadcastedTransaction) error {
+	err := p.validate(userTxn)
+	if err != nil {
+		return err
+	}
+
+	select {
+	case p.dbWriteChan <- userTxn:
+	default:
+		select {
+		case _, ok := <-p.dbWriteChan:
+			if !ok {
+				p.log.Errorw("cannot store user transasction in persistent pool, database write channel is closed")
+			}
+			p.log.Errorw("cannot store user transasction in persistent pool, database is full")
+		default:
+			p.log.Errorw("cannot store user transasction in persistent pool, database is full")
+		}
+	}
+
+	newNode := &memPoolTxn{Txn: *userTxn, Next: nil}
+	p.memTxnList.push(newNode)
+
+	select {
+	case p.txPushed <- struct{}{}:
+	default:
+	}
+
+	return nil
+}
+
+func (p *Pool) validate(userTxn *BroadcastedTransaction) error {
+	if p.memTxnList.len+1 >= p.maxNumTxns {
+		return ErrTxnPoolFull
+	}
+
+	switch t := userTxn.Transaction.(type) {
+	case *core.DeployTransaction:
+		return fmt.Errorf("deploy transactions are not supported")
+	case *core.DeployAccountTransaction:
+		if !t.Nonce.IsZero() {
+			return fmt.Errorf("validation failed, received non-zero nonce %s", t.Nonce)
+		}
+	case *core.DeclareTransaction:
+		nonce, err := p.state.ContractNonce(t.SenderAddress)
+		if err != nil {
+			return fmt.Errorf("validation failed, error when retrieving nonce, %v", err)
+		}
+		if nonce.Cmp(t.Nonce) > 0 {
+			return fmt.Errorf("validation failed, existing nonce %s, but received nonce %s", nonce, t.Nonce)
+		}
+	case *core.InvokeTransaction:
+		if t.TxVersion().Is(0) { // cant verify nonce since SenderAddress was only added in v1
+			return fmt.Errorf("invoke v0 transactions not supported")
+		}
+		nonce, err := p.state.ContractNonce(t.SenderAddress)
+		if err != nil {
+			return fmt.Errorf("validation failed, error when retrieving nonce, %v", err)
+		}
+		if nonce.Cmp(t.Nonce) > 0 {
+			return fmt.Errorf("validation failed, existing nonce %s, but received nonce %s", nonce, t.Nonce)
+		}
+	case *core.L1HandlerTransaction:
+		// todo: verification of the L1 handler nonce requires checking the
+		// message nonce on the L1 Core Contract.
+	}
+	return nil
+}
+
+// Pop returns the transaction with the highest priority from the in-memory pool
+func (p *Pool) Pop() (BroadcastedTransaction, error) {
+	return p.memTxnList.pop()
+}
+
+// Remove removes a set of transactions from the pool
+// todo: should be called by the builder to remove txns from the db everytime a new block is stored.
+// todo: in the consensus+p2p world, the txns should also be removed from the in-memory pool.
+func (p *Pool) Remove(hash ...*felt.Felt) error {
+	return errors.New("not implemented")
+}
+
+// Len returns the number of transactions in the in-memory pool
+func (p *Pool) Len() int {
+	return p.memTxnList.len
+}
+
+func (p *Pool) Wait() <-chan struct{} {
+	return p.txPushed
+}
+
+// Len returns the number of transactions in the persistent pool
+func (p *Pool) LenDB() (int, error) {
+	txn, err := p.db.NewTransaction(false)
+	if err != nil {
+		return 0, err
+	}
+	lenDB, err := lenDB(txn)
+	if err != nil {
+		return 0, err
+	}
+	return lenDB, txn.Discard()
+}