Merge pull request #1143 from tendermint/1091-race-condition

call FlushSync before calling CommitSync

mempool/mempool.go

@@ -159,6 +159,12 @@ func (mem *Mempool) Size() int {
 	return mem.txs.Len()
 }
 
+// Flushes the mempool connection to ensure async resCb calls are done e.g.
+// from CheckTx.
+func (mem *Mempool) FlushAppConn() error {
+	return mem.proxyAppConn.FlushSync()
+}
+
 // Flush removes all transactions from the mempool and cache
 func (mem *Mempool) Flush() {
 	mem.proxyMtx.Lock()
@@ -347,9 +353,6 @@ func (mem *Mempool) collectTxs(maxTxs int) types.Txs {
 // NOTE: this should be called *after* block is committed by consensus.
 // NOTE: unsafe; Lock/Unlock must be managed by caller
 func (mem *Mempool) Update(height int64, txs types.Txs) error {
-	if err := mem.proxyAppConn.FlushSync(); err != nil { // To flush async resCb calls e.g. from CheckTx
-		return err
-	}
 	// First, create a lookup map of txns in new txs.
 	txsMap := make(map[string]struct{})
 	for _, tx := range txs {

state/execution.go

@@ -127,6 +127,14 @@ func (blockExec *BlockExecutor) Commit(block *types.Block) ([]byte, error) {
 	blockExec.mempool.Lock()
 	defer blockExec.mempool.Unlock()
 
+	// while mempool is Locked, flush to ensure all async requests have completed
+	// in the ABCI app before Commit.
+	err := blockExec.mempool.FlushAppConn()
+	if err != nil {
+		blockExec.logger.Error("Client error during mempool.FlushAppConn", "err", err)
+		return nil, err
+	}
+
 	// Commit block, get hash back
 	res, err := blockExec.proxyApp.CommitSync()
 	if err != nil {

types/services.go

@@ -27,6 +27,7 @@ type Mempool interface {
 	Reap(int) Txs
 	Update(height int64, txs Txs) error
 	Flush()
+	FlushAppConn() error
 
 	TxsAvailable() <-chan int64
 	EnableTxsAvailable()
@@ -44,6 +45,7 @@ func (m MockMempool) CheckTx(tx Tx, cb func(*abci.Response)) error { return nil
 func (m MockMempool) Reap(n int) Txs                               { return Txs{} }
 func (m MockMempool) Update(height int64, txs Txs) error           { return nil }
 func (m MockMempool) Flush()                                       {}
+func (m MockMempool) FlushAppConn() error                          { return nil }
 func (m MockMempool) TxsAvailable() <-chan int64                   { return make(chan int64) }
 func (m MockMempool) EnableTxsAvailable()                          {}