From 642a24dc9c4fe8f44035a753e4213c9554151e08 Mon Sep 17 00:00:00 2001
From: Jae Kwon <jae@tendermint.com>
Date: Mon, 17 Oct 2016 16:54:51 -0700
Subject: [PATCH] Mempool WAL

---
 config/tendermint/config.go      |  1 +
 config/tendermint_test/config.go |  1 +
 mempool/mempool.go               | 23 +++++++++++++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/config/tendermint/config.go b/config/tendermint/config.go
index 4d2323ab3..465297ba3 100644
--- a/config/tendermint/config.go
+++ b/config/tendermint/config.go
@@ -84,6 +84,7 @@ func GetConfig(rootDir string) cfg.Config {
 	mapConfig.SetDefault("mempool_recheck", true)
 	mapConfig.SetDefault("mempool_recheck_empty", true)
 	mapConfig.SetDefault("mempool_broadcast", true)
+	mapConfig.SetDefault("mempool_wal", rootDir+"/data/mempool_wal")
 
 	return mapConfig
 }
diff --git a/config/tendermint_test/config.go b/config/tendermint_test/config.go
index 120079858..6f3217475 100644
--- a/config/tendermint_test/config.go
+++ b/config/tendermint_test/config.go
@@ -97,6 +97,7 @@ func ResetConfig(localPath string) cfg.Config {
 	mapConfig.SetDefault("mempool_recheck", true)
 	mapConfig.SetDefault("mempool_recheck_empty", true)
 	mapConfig.SetDefault("mempool_broadcast", true)
+	mapConfig.SetDefault("mempool_wal", "")
 
 	return mapConfig
 }
diff --git a/mempool/mempool.go b/mempool/mempool.go
index 2b7be1ddb..c3c9a5f06 100644
--- a/mempool/mempool.go
+++ b/mempool/mempool.go
@@ -60,6 +60,9 @@ type Mempool struct {
 	// Keep a cache of already-seen txs.
 	// This reduces the pressure on the proxyApp.
 	cache *txCache
+
+	// A log of mempool txs
+	wal *AutoFile
 }
 
 func NewMempool(config cfg.Config, proxyAppConn proxy.AppConnMempool) *Mempool {
@@ -75,10 +78,22 @@ func NewMempool(config cfg.Config, proxyAppConn proxy.AppConnMempool) *Mempool {
 
 		cache: newTxCache(cacheSize),
 	}
+	mempool.initWAL()
 	proxyAppConn.SetResponseCallback(mempool.resCb)
 	return mempool
 }
 
+func (mem *Mempool) initWAL() {
+	walFileName := mem.config.GetString("mempool_wal")
+	if walFileName != "" {
+		af, err := OpenAutoFile(walFileName)
+		if err != nil {
+			PanicSanity(err)
+		}
+		mem.wal = af
+	}
+}
+
 // consensus must be able to hold lock to safely update
 func (mem *Mempool) Lock() {
 	mem.proxyMtx.Lock()
@@ -138,6 +153,14 @@ func (mem *Mempool) CheckTx(tx types.Tx, cb func(*tmsp.Response)) (err error) {
 	mem.cache.Push(tx)
 	// END CACHE
 
+	// WAL
+	if mem.wal != nil {
+		// TODO: Notify administrators when WAL fails
+		mem.wal.Write([]byte(tx))
+		mem.wal.Write([]byte("\n"))
+	}
+	// END WAL
+
 	// NOTE: proxyAppConn may error if tx buffer is full
 	if err = mem.proxyAppConn.Error(); err != nil {
 		return err