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226 lines
6.4 KiB
226 lines
6.4 KiB
package mempool
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import (
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"bytes"
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"sync"
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"sync/atomic"
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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 proxyAppCtx.
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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 AppendTx()
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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. AppendTx() 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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*/
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type Mempool struct {
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proxyMtx sync.Mutex
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proxyAppCtx proxy.AppContext
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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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expected *clist.CElement // pointer to .txs for next response
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}
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func NewMempool(proxyAppCtx proxy.AppContext) *Mempool {
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mempool := &Mempool{
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proxyAppCtx: proxyAppCtx,
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txs: clist.New(),
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counter: 0,
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height: 0,
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expected: nil,
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}
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proxyAppCtx.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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func (mem *Mempool) AppendTx(tx types.Tx) (err error) {
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mem.proxyMtx.Lock()
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defer mem.proxyMtx.Unlock()
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if err = mem.proxyAppCtx.Error(); err != nil {
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return err
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}
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mem.proxyAppCtx.AppendTxAsync(tx)
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return nil
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}
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// TMSP callback function
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// CONTRACT: No other goroutines mutate mem.expected concurrently.
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func (mem *Mempool) resCb(req tmsp.Request, res tmsp.Response) {
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switch res := res.(type) {
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case tmsp.ResponseAppendTx:
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reqAppendTx := req.(tmsp.RequestAppendTx)
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if mem.expected == nil { // Normal operation
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if res.RetCode == tmsp.RetCodeOK {
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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: reqAppendTx.TxBytes,
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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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} else { // During Update()
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// TODO Log sane warning if mem.expected is nil.
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memTx := mem.expected.Value.(*mempoolTx)
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if !bytes.Equal(reqAppendTx.TxBytes, memTx.tx) {
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PanicSanity("Unexpected tx response from proxy")
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}
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if res.RetCode == tmsp.RetCodeOK {
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// Good, nothing to do.
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} else {
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// TODO: handle other retcodes
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// Tx became invalidated due to newly committed block.
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// NOTE: Concurrent traversal of mem.txs via CElement.Next() still works.
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mem.txs.Remove(mem.expected)
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mem.expected.DetachPrev()
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}
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mem.expected = mem.expected.Next()
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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 run so far, and the hash of
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// the application state that results from those transactions.
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func (mem *Mempool) Reap() ([]types.Tx, []byte, error) {
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mem.proxyMtx.Lock()
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defer mem.proxyMtx.Unlock()
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// First, get the hash of txs run so far
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hash, err := mem.proxyAppCtx.GetHashSync()
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if err != nil {
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return nil, nil, err
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}
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// And collect all the transactions.
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txs := mem.collectTxs()
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return txs, hash, nil
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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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// "block" is the new block that was committed.
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// Txs that are present in "block" are discarded from mempool.
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// NOTE: this should be called *after* block is committed by consensus.
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// CONTRACT: block is valid and next in sequence.
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func (mem *Mempool) Update(block *types.Block) error {
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mem.proxyMtx.Lock()
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defer mem.proxyMtx.Unlock()
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// Rollback mempool synchronously
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// TODO: test that proxyAppCtx's state matches the block's
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err := mem.proxyAppCtx.RollbackSync()
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if err != nil {
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return err
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}
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// First, create a lookup map of txns in new block.
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blockTxsMap := make(map[string]struct{})
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for _, tx := range block.Data.Txs {
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blockTxsMap[string(tx)] = struct{}{}
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}
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// Remove transactions that are already in block.
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// Return the remaining potentially good txs.
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goodTxs := mem.filterTxs(block.Height, blockTxsMap)
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// Set height and expected
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mem.height = block.Height
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mem.expected = mem.txs.Front()
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// Push good txs to proxyAppCtx
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// NOTE: resCb() may be called concurrently.
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for _, tx := range goodTxs {
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mem.proxyAppCtx.AppendTxAsync(tx)
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if err := mem.proxyAppCtx.Error(); err != nil {
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return err
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}
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}
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// NOTE: Even though we return immediately without e.g.
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// calling mem.proxyAppCtx.FlushSync(),
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// New mempool txs will still have to wait until
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// all goodTxs are re-processed.
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// So we could make synchronous calls here to proxyAppCtx.
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return nil
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}
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func (mem *Mempool) filterTxs(height int, 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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atomic.StoreInt64(&memTx.height, int64(height))
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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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//--------------------------------------------------------------------------------
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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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