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278 lines
7.5 KiB
278 lines
7.5 KiB
package mempool
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import (
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"bytes"
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"container/list"
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"sync"
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"sync/atomic"
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"time"
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"github.com/tendermint/go-clist"
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. "github.com/tendermint/go-common"
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"github.com/tendermint/tendermint/proxy"
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"github.com/tendermint/tendermint/types"
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tmsp "github.com/tendermint/tmsp/types"
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)
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/*
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The mempool pushes new txs onto the proxyAppConn.
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It gets a stream of (req, res) tuples from the proxy.
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The memool stores good txs in a concurrent linked-list.
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Multiple concurrent go-routines can traverse this linked-list
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safely by calling .NextWait() on each element.
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So we have several go-routines:
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1. Consensus calling Update() and Reap() synchronously
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2. Many mempool reactor's peer routines calling CheckTx()
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3. Many mempool reactor's peer routines traversing the txs linked list
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4. Another goroutine calling GarbageCollectTxs() periodically
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To manage these goroutines, there are three methods of locking.
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1. Mutations to the linked-list is protected by an internal mtx (CList is goroutine-safe)
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2. Mutations to the linked-list elements are atomic
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3. CheckTx() calls can be paused upon Update() and Reap(), protected by .proxyMtx
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Garbage collection of old elements from mempool.txs is handlde via
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the DetachPrev() call, which makes old elements not reachable by
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peer broadcastTxRoutine() automatically garbage collected.
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TODO: Better handle tmsp client errors. (make it automatically handle connection errors)
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*/
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const cacheSize = 100000
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type Mempool struct {
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proxyMtx sync.Mutex
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proxyAppConn proxy.AppConn
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txs *clist.CList // concurrent linked-list of good txs
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counter int64 // simple incrementing counter
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height int // the last block Update()'d to
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rechecking int32 // for re-checking filtered txs on Update()
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recheckCursor *clist.CElement // next expected response
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recheckEnd *clist.CElement // re-checking stops here
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// Keep a cache of already-seen txs.
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// This reduces the pressure on the proxyApp.
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cacheMap map[string]struct{}
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cacheList *list.List
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}
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func NewMempool(proxyAppConn proxy.AppConn) *Mempool {
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mempool := &Mempool{
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proxyAppConn: proxyAppConn,
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txs: clist.New(),
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counter: 0,
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height: 0,
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rechecking: 0,
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recheckCursor: nil,
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recheckEnd: nil,
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cacheMap: make(map[string]struct{}, cacheSize),
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cacheList: list.New(),
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}
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proxyAppConn.SetResponseCallback(mempool.resCb)
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return mempool
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}
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// Return the first element of mem.txs for peer goroutines to call .NextWait() on.
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// Blocks until txs has elements.
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func (mem *Mempool) TxsFrontWait() *clist.CElement {
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return mem.txs.FrontWait()
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}
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// Try a new transaction in the mempool.
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// Potentially blocking if we're blocking on Update() or Reap().
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// cb: A callback from the CheckTx command.
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// It gets called from another goroutine.
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// CONTRACT: Either cb will get called, or err returned.
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func (mem *Mempool) CheckTx(tx types.Tx, cb func(*tmsp.Response)) (err error) {
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mem.proxyMtx.Lock()
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defer mem.proxyMtx.Unlock()
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// CACHE
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if _, exists := mem.cacheMap[string(tx)]; exists {
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if cb != nil {
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cb(&tmsp.Response{
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Code: tmsp.CodeType_BadNonce, // TODO or duplicate tx
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Log: "Duplicate transaction (ignored)",
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})
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}
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return nil
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}
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if mem.cacheList.Len() >= cacheSize {
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popped := mem.cacheList.Front()
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poppedTx := popped.Value.(types.Tx)
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delete(mem.cacheMap, string(poppedTx))
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mem.cacheList.Remove(popped)
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}
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mem.cacheMap[string(tx)] = struct{}{}
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mem.cacheList.PushBack(tx)
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// END CACHE
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// NOTE: proxyAppConn may error if tx buffer is full
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if err = mem.proxyAppConn.Error(); err != nil {
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return err
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}
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reqRes := mem.proxyAppConn.CheckTxAsync(tx)
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if cb != nil {
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reqRes.SetCallback(cb)
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}
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return nil
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}
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// TMSP callback function
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func (mem *Mempool) resCb(req *tmsp.Request, res *tmsp.Response) {
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if mem.recheckCursor == nil {
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mem.resCbNormal(req, res)
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} else {
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mem.resCbRecheck(req, res)
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}
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}
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func (mem *Mempool) resCbNormal(req *tmsp.Request, res *tmsp.Response) {
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switch res.Type {
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case tmsp.MessageType_CheckTx:
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if res.Code == tmsp.CodeType_OK {
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mem.counter++
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memTx := &mempoolTx{
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counter: mem.counter,
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height: int64(mem.height),
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tx: req.Data,
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}
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mem.txs.PushBack(memTx)
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} else {
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// ignore bad transaction
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// TODO: handle other retcodes
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}
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default:
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// ignore other messages
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}
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}
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func (mem *Mempool) resCbRecheck(req *tmsp.Request, res *tmsp.Response) {
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switch res.Type {
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case tmsp.MessageType_CheckTx:
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memTx := mem.recheckCursor.Value.(*mempoolTx)
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if !bytes.Equal(req.Data, memTx.tx) {
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PanicSanity(Fmt("Unexpected tx response from proxy during recheck\n"+
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"Expected %X, got %X", req.Data, memTx.tx))
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}
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if res.Code == tmsp.CodeType_OK {
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// Good, nothing to do.
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} else {
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// Tx became invalidated due to newly committed block.
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mem.txs.Remove(mem.recheckCursor)
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mem.recheckCursor.DetachPrev()
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}
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if mem.recheckCursor == mem.recheckEnd {
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mem.recheckCursor = nil
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} else {
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mem.recheckCursor = mem.recheckCursor.Next()
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}
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if mem.recheckCursor == nil {
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// Done!
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atomic.StoreInt32(&mem.rechecking, 0)
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}
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default:
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// ignore other messages
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}
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}
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// Get the valid transactions remaining
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func (mem *Mempool) Reap() []types.Tx {
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mem.proxyMtx.Lock()
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defer mem.proxyMtx.Unlock()
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for atomic.LoadInt32(&mem.rechecking) > 0 {
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// TODO: Something better?
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time.Sleep(time.Millisecond * 10)
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}
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txs := mem.collectTxs()
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return txs
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}
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func (mem *Mempool) collectTxs() []types.Tx {
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txs := make([]types.Tx, 0, mem.txs.Len())
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for e := mem.txs.Front(); e != nil; e = e.Next() {
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memTx := e.Value.(*mempoolTx)
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txs = append(txs, memTx.tx)
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}
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return txs
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}
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// Tell mempool that these txs were committed.
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// Mempool will discard these txs.
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// NOTE: this should be called *after* block is committed by consensus.
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func (mem *Mempool) Update(height int, txs []types.Tx) {
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mem.proxyMtx.Lock()
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defer mem.proxyMtx.Unlock()
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// First, create a lookup map of txns in new txs.
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txsMap := make(map[string]struct{})
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for _, tx := range txs {
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txsMap[string(tx)] = struct{}{}
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}
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// Set height
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mem.height = height
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// Remove transactions that are already in txs.
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goodTxs := mem.filterTxs(txsMap)
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// Recheck mempool txs
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// TODO: make optional
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mem.recheckTxs(goodTxs)
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// At this point, mem.txs are being rechecked.
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// mem.recheckCursor re-scans mem.txs and possibly removes some txs.
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// Before mem.Reap(), we should wait for mem.recheckCursor to be nil.
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}
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func (mem *Mempool) filterTxs(blockTxsMap map[string]struct{}) []types.Tx {
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goodTxs := make([]types.Tx, 0, mem.txs.Len())
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for e := mem.txs.Front(); e != nil; e = e.Next() {
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memTx := e.Value.(*mempoolTx)
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if _, ok := blockTxsMap[string(memTx.tx)]; ok {
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// Remove the tx since already in block.
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mem.txs.Remove(e)
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e.DetachPrev()
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continue
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}
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// Good tx!
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goodTxs = append(goodTxs, memTx.tx)
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}
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return goodTxs
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}
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// NOTE: pass in goodTxs because mem.txs can mutate concurrently.
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func (mem *Mempool) recheckTxs(goodTxs []types.Tx) {
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if len(goodTxs) == 0 {
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return
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}
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atomic.StoreInt32(&mem.rechecking, 1)
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mem.recheckCursor = mem.txs.Front()
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mem.recheckEnd = mem.txs.Back()
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// Push txs to proxyAppConn
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// NOTE: resCb() may be called concurrently.
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for _, tx := range goodTxs {
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mem.proxyAppConn.CheckTxAsync(tx)
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}
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mem.proxyAppConn.FlushAsync()
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}
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//--------------------------------------------------------------------------------
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// A transaction that successfully ran
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type mempoolTx struct {
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counter int64 // a simple incrementing counter
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height int64 // height that this tx had been validated in
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tx types.Tx //
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}
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func (memTx *mempoolTx) Height() int {
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return int(atomic.LoadInt64(&memTx.height))
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}
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