path: root/core/tx_list.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 core

import (
    "container/heap"
    "math"
    "math/big"
    "sort"

    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/core/types"
    "github.com/dexon-foundation/dexon/log"
)

// nonceHeap is a heap.Interface implementation over 64bit unsigned integers for
// retrieving sorted transactions from the possibly gapped future queue.
type nonceHeap []uint64

func (h nonceHeap) Len() int           { return len(h) }
func (h nonceHeap) Less(i, j int) bool { return h[i] < h[j] }
func (h nonceHeap) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }

func (h *nonceHeap) Push(x interface{}) {
    *h = append(*h, x.(uint64))
}

func (h *nonceHeap) Pop() interface{} {
    old := *h
    n := len(old)
    x := old[n-1]
    *h = old[0 : n-1]
    return x
}

// txSortedMap is a nonce->transaction hash map with a heap based index to allow
// iterating over the contents in a nonce-incrementing way.
type txSortedMap struct {
    items map[uint64]*types.Transaction // Hash map storing the transaction data
    index *nonceHeap                    // Heap of nonces of all the stored transactions (non-strict mode)
    cache types.Transactions            // Cache of the transactions already sorted
}

// newTxSortedMap creates a new nonce-sorted transaction map.
func newTxSortedMap() *txSortedMap {
    return &txSortedMap{
        items: make(map[uint64]*types.Transaction),
        index: new(nonceHeap),
    }
}

// Get retrieves the current transactions associated with the given nonce.
func (m *txSortedMap) Get(nonce uint64) *types.Transaction {
    return m.items[nonce]
}

// Put inserts a new transaction into the map, also updating the map's nonce
// index. If a transaction already exists with the same nonce, it's overwritten.
func (m *txSortedMap) Put(tx *types.Transaction) {
    nonce := tx.Nonce()
    if m.items[nonce] == nil {
        heap.Push(m.index, nonce)
    }
    m.items[nonce], m.cache = tx, nil
}

// Forward removes all transactions from the map with a nonce lower than the
// provided threshold. Every removed transaction is returned for any post-removal
// maintenance.
func (m *txSortedMap) Forward(threshold uint64) types.Transactions {
    var removed types.Transactions

    // Pop off heap items until the threshold is reached
    for m.index.Len() > 0 && (*m.index)[0] < threshold {
        nonce := heap.Pop(m.index).(uint64)
        removed = append(removed, m.items[nonce])
        delete(m.items, nonce)
    }
    // If we had a cached order, shift the front
    if m.cache != nil {
        m.cache = m.cache[len(removed):]
    }
    return removed
}

// Filter iterates over the list of transactions and removes all of them for which
// the specified function evaluates to true.
func (m *txSortedMap) Filter(filter func(*types.Transaction) bool) types.Transactions {
    var removed types.Transactions

    // Collect all the transactions to filter out
    for nonce, tx := range m.items {
        if filter(tx) {
            removed = append(removed, tx)
            delete(m.items, nonce)
        }
    }
    // If transactions were removed, the heap and cache are ruined
    if len(removed) > 0 {
        *m.index = make([]uint64, 0, len(m.items))
        for nonce := range m.items {
            *m.index = append(*m.index, nonce)
        }
        heap.Init(m.index)

        m.cache = nil
    }
    return removed
}

// Cap places a hard limit on the number of items, returning all transactions
// exceeding that limit.
func (m *txSortedMap) Cap(threshold int) types.Transactions {
    // Short circuit if the number of items is under the limit
    if len(m.items) <= threshold {
        return nil
    }
    // Otherwise gather and drop the highest nonce'd transactions
    var drops types.Transactions

    sort.Sort(*m.index)
    for size := len(m.items); size > threshold; size-- {
        drops = append(drops, m.items[(*m.index)[size-1]])
        delete(m.items, (*m.index)[size-1])
    }
    *m.index = (*m.index)[:threshold]
    heap.Init(m.index)

    // If we had a cache, shift the back
    if m.cache != nil {
        m.cache = m.cache[:len(m.cache)-len(drops)]
    }
    return drops
}

// Remove deletes a transaction from the maintained map, returning whether the
// transaction was found.
func (m *txSortedMap) Remove(nonce uint64) bool {
    // Short circuit if no transaction is present
    _, ok := m.items[nonce]
    if !ok {
        return false
    }
    // Otherwise delete the transaction and fix the heap index
    for i := 0; i < m.index.Len(); i++ {
        if (*m.index)[i] == nonce {
            heap.Remove(m.index, i)
            break
        }
    }
    delete(m.items, nonce)
    m.cache = nil

    return true
}

// Ready retrieves a sequentially increasing list of transactions starting at the
// provided nonce that is ready for processing. The returned transactions will be
// removed from the list.
//
// Note, all transactions with nonces lower than start will also be returned to
// prevent getting into and invalid state. This is not something that should ever
// happen but better to be self correcting than failing!
func (m *txSortedMap) Ready(start uint64) types.Transactions {
    // Short circuit if no transactions are available
    if m.index.Len() == 0 || (*m.index)[0] > start {
        return nil
    }
    // Otherwise start accumulating incremental transactions
    var ready types.Transactions
    for next := (*m.index)[0]; m.index.Len() > 0 && (*m.index)[0] == next; next++ {
        ready = append(ready, m.items[next])
        delete(m.items, next)
        heap.Pop(m.index)
    }
    m.cache = nil

    return ready
}

// Len returns the length of the transaction map.
func (m *txSortedMap) Len() int {
    return len(m.items)
}

// Flatten creates a nonce-sorted slice of transactions based on the loosely
// sorted internal representation. The result of the sorting is cached in case
// it's requested again before any modifications are made to the contents.
func (m *txSortedMap) Flatten() types.Transactions {
    // If the sorting was not cached yet, create and cache it
    if m.cache == nil {
        m.cache = make(types.Transactions, 0, len(m.items))
        for _, tx := range m.items {
            m.cache = append(m.cache, tx)
        }
        sort.Sort(types.TxByNonce(m.cache))
    }
    // Copy the cache to prevent accidental modifications
    txs := make(types.Transactions, len(m.cache))
    copy(txs, m.cache)
    return txs
}

// txList is a "list" of transactions belonging to an account, sorted by account
// nonce. The same type can be used both for storing contiguous transactions for
// the executable/pending queue; and for storing gapped transactions for the non-
// executable/future queue, with minor behavioral changes.
type txList struct {
    strict bool         // Whether nonces are strictly continuous or not
    txs    *txSortedMap // Heap indexed sorted hash map of the transactions

    costcap *big.Int // Price of the highest costing transaction (reset only if exceeds balance)
    gascap  uint64   // Gas limit of the highest spending transaction (reset only if exceeds block limit)
}

// newTxList create a new transaction list for maintaining nonce-indexable fast,
// gapped, sortable transaction lists.
func newTxList(strict bool) *txList {
    return &txList{
        strict:  strict,
        txs:     newTxSortedMap(),
        costcap: new(big.Int),
    }
}

// Overlaps returns whether the transaction specified has the same nonce as one
// already contained within the list.
func (l *txList) Overlaps(tx *types.Transaction) bool {
    return l.txs.Get(tx.Nonce()) != nil
}

// Add tries to insert a new transaction into the list, returning whether the
// transaction was accepted, and if yes, any previous transaction it replaced.
//
// If the new transaction is accepted into the list, the lists' cost and gas
// thresholds are also potentially updated.
func (l *txList) Add(tx *types.Transaction, priceBump uint64) (bool, *types.Transaction) {
    // If there's an older better transaction, abort
    old := l.txs.Get(tx.Nonce())
    if old != nil {
        threshold := new(big.Int).Div(new(big.Int).Mul(old.GasPrice(), big.NewInt(100+int64(priceBump))), big.NewInt(100))
        // Have to ensure that the new gas price is higher than the old gas
        // price as well as checking the percentage threshold to ensure that
        // this is accurate for low (Wei-level) gas price replacements
        if old.GasPrice().Cmp(tx.GasPrice()) >= 0 || threshold.Cmp(tx.GasPrice()) > 0 {
            return false, nil
        }
    }
    // Otherwise overwrite the old transaction with the current one
    l.txs.Put(tx)
    if cost := tx.Cost(); l.costcap.Cmp(cost) < 0 {
        l.costcap = cost
    }
    if gas := tx.Gas(); l.gascap < gas {
        l.gascap = gas
    }
    return true, old
}

// Forward removes all transactions from the list with a nonce lower than the
// provided threshold. Every removed transaction is returned for any post-removal
// maintenance.
func (l *txList) Forward(threshold uint64) types.Transactions {
    return l.txs.Forward(threshold)
}

// Filter removes all transactions from the list with a cost or gas limit higher
// than the provided thresholds. Every removed transaction is returned for any
// post-removal maintenance. Strict-mode invalidated transactions are also
// returned.
//
// This method uses the cached costcap and gascap to quickly decide if there's even
// a point in calculating all the costs or if the balance covers all. If the threshold
// is lower than the costgas cap, the caps will be reset to a new high after removing
// the newly invalidated transactions.
func (l *txList) Filter(costLimit *big.Int, gasLimit uint64) (types.Transactions, types.Transactions) {
    // If all transactions are below the threshold, short circuit
    if l.costcap.Cmp(costLimit) <= 0 && l.gascap <= gasLimit {
        return nil, nil
    }
    l.costcap = new(big.Int).Set(costLimit) // Lower the caps to the thresholds
    l.gascap = gasLimit

    // Filter out all the transactions above the account's funds
    removed := l.txs.Filter(func(tx *types.Transaction) bool { return tx.Cost().Cmp(costLimit) > 0 || tx.Gas() > gasLimit })

    // If the list was strict, filter anything above the lowest nonce
    var invalids types.Transactions

    if l.strict && len(removed) > 0 {
        lowest := uint64(math.MaxUint64)
        for _, tx := range removed {
            if nonce := tx.Nonce(); lowest > nonce {
                lowest = nonce
            }
        }
        invalids = l.txs.Filter(func(tx *types.Transaction) bool { return tx.Nonce() > lowest })
    }
    return removed, invalids
}

// Cap places a hard limit on the number of items, returning all transactions
// exceeding that limit.
func (l *txList) Cap(threshold int) types.Transactions {
    return l.txs.Cap(threshold)
}

// Remove deletes a transaction from the maintained list, returning whether the
// transaction was found, and also returning any transaction invalidated due to
// the deletion (strict mode only).
func (l *txList) Remove(tx *types.Transaction) (bool, types.Transactions) {
    // Remove the transaction from the set
    nonce := tx.Nonce()
    if removed := l.txs.Remove(nonce); !removed {
        return false, nil
    }
    // In strict mode, filter out non-executable transactions
    if l.strict {
        return true, l.txs.Filter(func(tx *types.Transaction) bool { return tx.Nonce() > nonce })
    }
    return true, nil
}

// Ready retrieves a sequentially increasing list of transactions starting at the
// provided nonce that is ready for processing. The returned transactions will be
// removed from the list.
//
// Note, all transactions with nonces lower than start will also be returned to
// prevent getting into and invalid state. This is not something that should ever
// happen but better to be self correcting than failing!
func (l *txList) Ready(start uint64) types.Transactions {
    return l.txs.Ready(start)
}

// Len returns the length of the transaction list.
func (l *txList) Len() int {
    return l.txs.Len()
}

// Empty returns whether the list of transactions is empty or not.
func (l *txList) Empty() bool {
    return l.Len() == 0
}

// Flatten creates a nonce-sorted slice of transactions based on the loosely
// sorted internal representation. The result of the sorting is cached in case
// it's requested again before any modifications are made to the contents.
func (l *txList) Flatten() types.Transactions {
    return l.txs.Flatten()
}

// priceHeap is a heap.Interface implementation over transactions for retrieving
// price-sorted transactions to discard when the pool fills up.
type priceHeap []*types.Transaction

func (h priceHeap) Len() int      { return len(h) }
func (h priceHeap) Swap(i, j int) { h[i], h[j] = h[j], h[i] }

func (h priceHeap) Less(i, j int) bool {
    // Sort primarily by price, returning the cheaper one
    switch h[i].GasPrice().Cmp(h[j].GasPrice()) {
    case -1:
        return true
    case 1:
        return false
    }
    // If the prices match, stabilize via nonces (high nonce is worse)
    return h[i].Nonce() > h[j].Nonce()
}

func (h *priceHeap) Push(x interface{}) {
    *h = append(*h, x.(*types.Transaction))
}

func (h *priceHeap) Pop() interface{} {
    old := *h
    n := len(old)
    x := old[n-1]
    *h = old[0 : n-1]
    return x
}

// txPricedList is a price-sorted heap to allow operating on transactions pool
// contents in a price-incrementing way.
type txPricedList struct {
    all    *txLookup  // Pointer to the map of all transactions
    items  *priceHeap // Heap of prices of all the stored transactions
    stales int        // Number of stale price points to (re-heap trigger)
}

// newTxPricedList creates a new price-sorted transaction heap.
func newTxPricedList(all *txLookup) *txPricedList {
    return &txPricedList{
        all:   all,
        items: new(priceHeap),
    }
}

// Put inserts a new transaction into the heap.
func (l *txPricedList) Put(tx *types.Transaction) {
    heap.Push(l.items, tx)
}

// Removed notifies the prices transaction list that an old transaction dropped
// from the pool. The list will just keep a counter of stale objects and update
// the heap if a large enough ratio of transactions go stale.
func (l *txPricedList) Removed() {
    // Bump the stale counter, but exit if still too low (< 25%)
    l.stales++
    if l.stales <= len(*l.items)/4 {
        return
    }
    // Seems we've reached a critical number of stale transactions, reheap
    reheap := make(priceHeap, 0, l.all.Count())

    l.stales, l.items = 0, &reheap
    l.all.Range(func(hash common.Hash, tx *types.Transaction) bool {
        *l.items = append(*l.items, tx)
        return true
    })
    heap.Init(l.items)
}

// Cap finds all the transactions below the given price threshold, drops them
// from the priced list and returns them for further removal from the entire pool.
func (l *txPricedList) Cap(threshold *big.Int, local *accountSet) types.Transactions {
    drop := make(types.Transactions, 0, 128) // Remote underpriced transactions to drop
    save := make(types.Transactions, 0, 64)  // Local underpriced transactions to keep

    for len(*l.items) > 0 {
        // Discard stale transactions if found during cleanup
        tx := heap.Pop(l.items).(*types.Transaction)
        if l.all.Get(tx.Hash()) == nil {
            l.stales--
            continue
        }
        // Stop the discards if we've reached the threshold
        if tx.GasPrice().Cmp(threshold) >= 0 {
            save = append(save, tx)
            break
        }
        // Non stale transaction found, discard unless local
        if local.containsTx(tx) {
            save = append(save, tx)
        } else {
            drop = append(drop, tx)
        }
    }
    for _, tx := range save {
        heap.Push(l.items, tx)
    }
    return drop
}

// Underpriced checks whether a transaction is cheaper than (or as cheap as) the
// lowest priced transaction currently being tracked.
func (l *txPricedList) Underpriced(tx *types.Transaction, local *accountSet) bool {
    // Local transactions cannot be underpriced
    if local.containsTx(tx) {
        return false
    }
    // Discard stale price points if found at the heap start
    for len(*l.items) > 0 {
        head := []*types.Transaction(*l.items)[0]
        if l.all.Get(head.Hash()) == nil {
            l.stales--
            heap.Pop(l.items)
            continue
        }
        break
    }
    // Check if the transaction is underpriced or not
    if len(*l.items) == 0 {
        log.Error("Pricing query for empty pool") // This cannot happen, print to catch programming errors
        return false
    }
    cheapest := []*types.Transaction(*l.items)[0]
    return cheapest.GasPrice().Cmp(tx.GasPrice()) >= 0
}

// Discard finds a number of most underpriced transactions, removes them from the
// priced list and returns them for further removal from the entire pool.
func (l *txPricedList) Discard(count int, local *accountSet) types.Transactions {
    drop := make(types.Transactions, 0, count) // Remote underpriced transactions to drop
    save := make(types.Transactions, 0, 64)    // Local underpriced transactions to keep

    for len(*l.items) > 0 && count > 0 {
        // Discard stale transactions if found during cleanup
        tx := heap.Pop(l.items).(*types.Transaction)
        if l.all.Get(tx.Hash()) == nil {
            l.stales--
            continue
        }
        // Non stale transaction found, discard unless local
        if local.containsTx(tx) {
            save = append(save, tx)
        } else {
            drop = append(drop, tx)
            count--
        }
    }
    for _, tx := range save {
        heap.Push(l.items, tx)
    }
    return drop
}