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500 lines
14 KiB
500 lines
14 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/pkg/errors"
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abci "github.com/tendermint/abci/types"
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auto "github.com/tendermint/tmlibs/autofile"
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"github.com/tendermint/tmlibs/clist"
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cmn "github.com/tendermint/tmlibs/common"
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"github.com/tendermint/tmlibs/log"
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cfg "github.com/tendermint/tendermint/config"
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"github.com/tendermint/tendermint/proxy"
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"github.com/tendermint/tendermint/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 mempool 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 abci client errors. (make it automatically handle connection errors)
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*/
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var ErrTxInCache = errors.New("Tx already exists in cache")
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// Mempool is an ordered in-memory pool for transactions before they are proposed in a consensus
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// round. Transaction validity is checked using the CheckTx abci message before the transaction is
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// added to the pool. The Mempool uses a concurrent list structure for storing transactions that
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// can be efficiently accessed by multiple concurrent readers.
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type Mempool struct {
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config *cfg.MempoolConfig
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proxyMtx sync.Mutex
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proxyAppConn proxy.AppConnMempool
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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 int64 // 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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notifiedTxsAvailable bool // true if fired on txsAvailable for this height
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txsAvailable chan int64 // fires the next height once for each height, when the mempool is not empty
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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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cache *txCache
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// A log of mempool txs
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wal *auto.AutoFile
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logger log.Logger
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}
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// NewMempool returns a new Mempool with the given configuration and connection to an application.
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// TODO: Extract logger into arguments.
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func NewMempool(config *cfg.MempoolConfig, proxyAppConn proxy.AppConnMempool, height int64) *Mempool {
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mempool := &Mempool{
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config: config,
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proxyAppConn: proxyAppConn,
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txs: clist.New(),
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counter: 0,
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height: height,
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rechecking: 0,
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recheckCursor: nil,
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recheckEnd: nil,
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logger: log.NewNopLogger(),
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cache: newTxCache(config.CacheSize),
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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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// EnableTxsAvailable initializes the TxsAvailable channel,
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// ensuring it will trigger once every height when transactions are available.
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// NOTE: not thread safe - should only be called once, on startup
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func (mem *Mempool) EnableTxsAvailable() {
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mem.txsAvailable = make(chan int64, 1)
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}
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// SetLogger sets the Logger.
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func (mem *Mempool) SetLogger(l log.Logger) {
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mem.logger = l
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}
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// CloseWAL closes and discards the underlying WAL file.
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// Any further writes will not be relayed to disk.
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func (mem *Mempool) CloseWAL() bool {
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if mem == nil {
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return false
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}
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mem.proxyMtx.Lock()
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defer mem.proxyMtx.Unlock()
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if mem.wal == nil {
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return false
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}
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if err := mem.wal.Close(); err != nil && mem.logger != nil {
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mem.logger.Error("Mempool.CloseWAL", "err", err)
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}
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mem.wal = nil
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return true
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}
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func (mem *Mempool) InitWAL() {
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walDir := mem.config.WalDir()
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if walDir != "" {
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err := cmn.EnsureDir(walDir, 0700)
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if err != nil {
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cmn.PanicSanity(errors.Wrap(err, "Error ensuring Mempool wal dir"))
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}
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af, err := auto.OpenAutoFile(walDir + "/wal")
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if err != nil {
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cmn.PanicSanity(errors.Wrap(err, "Error opening Mempool wal file"))
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}
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mem.wal = af
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}
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}
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// Lock locks the mempool. The consensus must be able to hold lock to safely update.
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func (mem *Mempool) Lock() {
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mem.proxyMtx.Lock()
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}
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// Unlock unlocks the mempool.
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func (mem *Mempool) Unlock() {
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mem.proxyMtx.Unlock()
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}
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// Size returns the number of transactions in the mempool.
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func (mem *Mempool) Size() int {
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return mem.txs.Len()
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}
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// Flushes the mempool connection to ensure async resCb calls are done e.g.
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// from CheckTx.
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func (mem *Mempool) FlushAppConn() error {
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return mem.proxyAppConn.FlushSync()
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}
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// Flush removes all transactions from the mempool and cache
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func (mem *Mempool) Flush() {
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mem.proxyMtx.Lock()
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defer mem.proxyMtx.Unlock()
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mem.cache.Reset()
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for e := mem.txs.Front(); e != nil; e = e.Next() {
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mem.txs.Remove(e)
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e.DetachPrev()
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}
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}
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// TxsFront returns the first transaction in the ordered list for peer
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// goroutines to call .NextWait() on.
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func (mem *Mempool) TxsFront() *clist.CElement {
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return mem.txs.Front()
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}
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// TxsWaitChan returns a channel to wait on transactions. It will be closed
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// once the mempool is not empty (ie. the internal `mem.txs` has at least one
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// element)
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func (mem *Mempool) TxsWaitChan() <-chan struct{} {
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return mem.txs.WaitChan()
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}
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// CheckTx executes a new transaction against the application to determine its validity
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// and whether it should be added to the mempool.
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// It blocks if we're waiting 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(*abci.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 mem.cache.Exists(tx) {
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return ErrTxInCache
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}
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mem.cache.Push(tx)
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// END CACHE
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// WAL
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if mem.wal != nil {
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// TODO: Notify administrators when WAL fails
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_, err := mem.wal.Write([]byte(tx))
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if err != nil {
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mem.logger.Error("Error writing to WAL", "err", err)
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}
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_, err = mem.wal.Write([]byte("\n"))
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if err != nil {
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mem.logger.Error("Error writing to WAL", "err", err)
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}
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}
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// END WAL
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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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// ABCI callback function
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func (mem *Mempool) resCb(req *abci.Request, res *abci.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 *abci.Request, res *abci.Response) {
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switch r := res.Value.(type) {
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case *abci.Response_CheckTx:
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tx := req.GetCheckTx().Tx
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if r.CheckTx.Code == abci.CodeTypeOK {
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mem.counter++
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memTx := &mempoolTx{
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counter: mem.counter,
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height: mem.height,
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tx: tx,
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}
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mem.txs.PushBack(memTx)
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mem.logger.Info("Added good transaction", "tx", tx, "res", r)
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mem.notifyTxsAvailable()
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} else {
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// ignore bad transaction
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mem.logger.Info("Rejected bad transaction", "tx", tx, "res", r)
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// remove from cache (it might be good later)
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mem.cache.Remove(tx)
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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 *abci.Request, res *abci.Response) {
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switch r := res.Value.(type) {
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case *abci.Response_CheckTx:
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memTx := mem.recheckCursor.Value.(*mempoolTx)
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if !bytes.Equal(req.GetCheckTx().Tx, memTx.tx) {
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cmn.PanicSanity(cmn.Fmt("Unexpected tx response from proxy during recheck\n"+
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"Expected %X, got %X", r.CheckTx.Data, memTx.tx))
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}
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if r.CheckTx.Code == abci.CodeTypeOK {
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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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// remove from cache (it might be good later)
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mem.cache.Remove(req.GetCheckTx().Tx)
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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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mem.logger.Info("Done rechecking txs")
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// incase the recheck removed all txs
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if mem.Size() > 0 {
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mem.notifyTxsAvailable()
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}
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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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// TxsAvailable returns a channel which fires once for every height,
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// and only when transactions are available in the mempool.
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// NOTE: the returned channel may be nil if EnableTxsAvailable was not called.
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func (mem *Mempool) TxsAvailable() <-chan int64 {
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return mem.txsAvailable
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}
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func (mem *Mempool) notifyTxsAvailable() {
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if mem.Size() == 0 {
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panic("notified txs available but mempool is empty!")
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}
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if mem.txsAvailable != nil && !mem.notifiedTxsAvailable {
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mem.notifiedTxsAvailable = true
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mem.txsAvailable <- mem.height + 1
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}
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}
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// Reap returns a list of transactions currently in the mempool.
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// If maxTxs is -1, there is no cap on the number of returned transactions.
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func (mem *Mempool) Reap(maxTxs int) types.Txs {
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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(maxTxs)
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return txs
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}
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// maxTxs: -1 means uncapped, 0 means none
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func (mem *Mempool) collectTxs(maxTxs int) types.Txs {
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if maxTxs == 0 {
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return []types.Tx{}
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} else if maxTxs < 0 {
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maxTxs = mem.txs.Len()
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}
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txs := make([]types.Tx, 0, cmn.MinInt(mem.txs.Len(), maxTxs))
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for e := mem.txs.Front(); e != nil && len(txs) < maxTxs; 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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// Update informs the mempool that the given txs were committed and can be discarded.
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// NOTE: this should be called *after* block is committed by consensus.
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// NOTE: unsafe; Lock/Unlock must be managed by caller
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func (mem *Mempool) Update(height int64, txs types.Txs) error {
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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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mem.notifiedTxsAvailable = false
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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 if any txs were committed in the block
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// NOTE/XXX: in some apps a tx could be invalidated due to EndBlock,
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// so we really still do need to recheck, but this is for debugging
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if mem.config.Recheck && (mem.config.RecheckEmpty || len(txs) > 0) {
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mem.logger.Info("Recheck txs", "numtxs", len(goodTxs), "height", height)
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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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return 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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// Remove the tx if it's alredy in a block.
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if _, ok := blockTxsMap[string(memTx.tx)]; ok {
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// remove from clist
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mem.txs.Remove(e)
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e.DetachPrev()
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// NOTE: we don't remove committed txs from the cache.
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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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// mempoolTx is 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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// Height returns the height for this transaction
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func (memTx *mempoolTx) Height() int64 {
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return atomic.LoadInt64(&memTx.height)
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}
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//--------------------------------------------------------------------------------
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// txCache maintains a cache of transactions.
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type txCache struct {
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mtx sync.Mutex
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size int
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map_ map[string]struct{}
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list *list.List // to remove oldest tx when cache gets too big
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}
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// newTxCache returns a new txCache.
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func newTxCache(cacheSize int) *txCache {
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return &txCache{
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size: cacheSize,
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map_: make(map[string]struct{}, cacheSize),
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list: list.New(),
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}
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}
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// Reset resets the txCache to empty.
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func (cache *txCache) Reset() {
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cache.mtx.Lock()
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cache.map_ = make(map[string]struct{}, cache.size)
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cache.list.Init()
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cache.mtx.Unlock()
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}
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// Exists returns true if the given tx is cached.
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func (cache *txCache) Exists(tx types.Tx) bool {
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cache.mtx.Lock()
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_, exists := cache.map_[string(tx)]
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cache.mtx.Unlock()
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return exists
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}
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// Push adds the given tx to the txCache. It returns false if tx is already in the cache.
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func (cache *txCache) Push(tx types.Tx) bool {
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cache.mtx.Lock()
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defer cache.mtx.Unlock()
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if _, exists := cache.map_[string(tx)]; exists {
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return false
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}
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if cache.list.Len() >= cache.size {
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popped := cache.list.Front()
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poppedTx := popped.Value.(types.Tx)
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// NOTE: the tx may have already been removed from the map
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// but deleting a non-existent element is fine
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delete(cache.map_, string(poppedTx))
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cache.list.Remove(popped)
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}
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cache.map_[string(tx)] = struct{}{}
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cache.list.PushBack(tx)
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return true
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}
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// Remove removes the given tx from the cache.
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func (cache *txCache) Remove(tx types.Tx) {
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cache.mtx.Lock()
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delete(cache.map_, string(tx))
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cache.mtx.Unlock()
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}
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