spec/reactors/mempool: batch txs per peer (#155)

* spec/reactors/mempool: batch txs per peer

Refs https://github.com/tendermint/tendermint/issues/625

* update

spec/reactors/mempool/messages.md

@@ -2,25 +2,16 @@
 
 ## P2P Messages
 
-There is currently only one message that Mempool broadcasts
-and receives over the p2p gossip network (via the reactor):
-`TxMessage`
+There is currently only one message that Mempool broadcasts and receives over
+the p2p gossip network (via the reactor): `TxsMessage`
 
 ```go
-// TxMessage is a MempoolMessage containing a transaction.
-type TxMessage struct {
-    Tx types.Tx
+// TxsMessage is a MempoolMessage containing a list of transactions.
+type TxsMessage struct {
+    Txs []types.Tx
 }
 ```
 
-TxMessage is go-amino encoded and prepended with `0x1` as a
-"type byte". This is followed by a go-amino encoded byte-slice.
-Prefix of 40=0x28 byte tx is: `0x010128...` followed by
-the actual 40-byte tx. Prefix of 350=0x015e byte tx is:
-`0x0102015e...` followed by the actual 350 byte tx.
-
-(Please see the [go-amino repo](https://github.com/tendermint/go-amino#an-interface-example) for more information)
-
 ## RPC Messages
 
 Mempool exposes `CheckTx([]byte)` over the RPC interface.

spec/reactors/mempool/reactor.md

@@ -13,6 +13,11 @@ for details.
 Sending incorrectly encoded data or data exceeding `maxMsgSize` will result
 in stopping the peer.
 
+`maxMsgSize` equals `MaxBatchBytes` (10MB) + 4 (proto overhead).
+`MaxBatchBytes` is a mempool config parameter -> defined locally. The reactor
+sends transactions to the connected peers in batches. The maximum size of one
+batch is `MaxBatchBytes`.
+
 The mempool will not send a tx back to any peer which it received it from.
 
 The reactor assigns an `uint16` number for each peer and maintains a map from