package mempool import ( "container/list" "sync" "sync/atomic" "github.com/tendermint/go-clist" . "github.com/tendermint/go-common" "github.com/tendermint/tendermint/proxy" "github.com/tendermint/tendermint/types" tmsp "github.com/tendermint/tmsp/types" ) /* The mempool pushes new txs onto the proxyAppConn. It gets a stream of (req, res) tuples from the proxy. The memool stores good txs in a concurrent linked-list. Multiple concurrent go-routines can traverse this linked-list safely by calling .NextWait() on each element. So we have several go-routines: 1. Consensus calling Update() and Reap() synchronously 2. Many mempool reactor's peer routines calling CheckTx() 3. Many mempool reactor's peer routines traversing the txs linked list 4. Another goroutine calling GarbageCollectTxs() periodically To manage these goroutines, there are three methods of locking. 1. Mutations to the linked-list is protected by an internal mtx (CList is goroutine-safe) 2. Mutations to the linked-list elements are atomic 3. CheckTx() calls can be paused upon Update() and Reap(), protected by .proxyMtx Garbage collection of old elements from mempool.txs is handlde via the DetachPrev() call, which makes old elements not reachable by peer broadcastTxRoutine() automatically garbage collected. */ const cacheSize = 100000 type Mempool struct { proxyMtx sync.Mutex proxyAppConn proxy.AppConn txs *clist.CList // concurrent linked-list of good txs counter int64 // simple incrementing counter height int // the last block Update()'d to // Keep a cache of already-seen txs. // This reduces the pressure on the proxyApp. cacheMap map[string]struct{} cacheList *list.List } func NewMempool(proxyAppConn proxy.AppConn) *Mempool { mempool := &Mempool{ proxyAppConn: proxyAppConn, txs: clist.New(), counter: 0, height: 0, cacheMap: make(map[string]struct{}, cacheSize), cacheList: list.New(), } proxyAppConn.SetResponseCallback(mempool.resCb) return mempool } // Return the first element of mem.txs for peer goroutines to call .NextWait() on. // Blocks until txs has elements. func (mem *Mempool) TxsFrontWait() *clist.CElement { return mem.txs.FrontWait() } // Try a new transaction in the mempool. // Potentially blocking if we're blocking on Update() or Reap(). func (mem *Mempool) CheckTx(tx types.Tx) (err error) { mem.proxyMtx.Lock() defer mem.proxyMtx.Unlock() // CACHE if _, exists := mem.cacheMap[string(tx)]; exists { return nil } if mem.cacheList.Len() >= cacheSize { popped := mem.cacheList.Front() poppedTx := popped.Value.(types.Tx) delete(mem.cacheMap, string(poppedTx)) mem.cacheList.Remove(popped) } mem.cacheMap[string(tx)] = struct{}{} mem.cacheList.PushBack(tx) // END CACHE if err = mem.proxyAppConn.Error(); err != nil { return err } mem.proxyAppConn.CheckTxAsync(tx) return nil } // TMSP callback function func (mem *Mempool) resCb(req tmsp.Request, res tmsp.Response) { switch res := res.(type) { case tmsp.ResponseCheckTx: reqCheckTx := req.(tmsp.RequestCheckTx) if res.RetCode == tmsp.RetCodeOK { mem.counter++ memTx := &mempoolTx{ counter: mem.counter, height: int64(mem.height), tx: reqCheckTx.TxBytes, } mem.txs.PushBack(memTx) } else { // ignore bad transaction // TODO: handle other retcodes } default: // ignore other messages } } // Get the valid transactions remaining func (mem *Mempool) Reap() ([]types.Tx, error) { mem.proxyMtx.Lock() defer mem.proxyMtx.Unlock() txs := mem.collectTxs() return txs, nil } func (mem *Mempool) collectTxs() []types.Tx { txs := make([]types.Tx, 0, mem.txs.Len()) for e := mem.txs.Front(); e != nil; e = e.Next() { memTx := e.Value.(*mempoolTx) txs = append(txs, memTx.tx) } return txs } // Tell mempool that these txs were committed. // Mempool will discard these txs. // NOTE: this should be called *after* block is committed by consensus. func (mem *Mempool) Update(height int, txs []types.Tx) error { mem.proxyMtx.Lock() defer mem.proxyMtx.Unlock() // First, create a lookup map of txns in new txs. txsMap := make(map[string]struct{}) for _, tx := range txs { txsMap[string(tx)] = struct{}{} } // Set height mem.height = height // Remove transactions that are already in txs. mem.filterTxs(txsMap) return nil } func (mem *Mempool) filterTxs(blockTxsMap map[string]struct{}) []types.Tx { goodTxs := make([]types.Tx, 0, mem.txs.Len()) for e := mem.txs.Front(); e != nil; e = e.Next() { memTx := e.Value.(*mempoolTx) if _, ok := blockTxsMap[string(memTx.tx)]; ok { // Remove the tx since already in block. mem.txs.Remove(e) e.DetachPrev() continue } // Good tx! goodTxs = append(goodTxs, memTx.tx) } return goodTxs } //-------------------------------------------------------------------------------- // A transaction that successfully ran type mempoolTx struct { counter int64 // a simple incrementing counter height int64 // height that this tx had been validated in tx types.Tx // } func (memTx *mempoolTx) Height() int { return int(atomic.LoadInt64(&memTx.height)) }