docs: warn developers about calling blocking funcs in Receive (#5679)

Refs #2888

blockchain/v0/reactor.go

@@ -204,6 +204,8 @@ func (bcR *BlockchainReactor) respondToPeer(msg *bcproto.BlockRequest,
 }
 
 // Receive implements Reactor by handling 4 types of messages (look below).
+// XXX: do not call any methods that can block or incur heavy processing.
+// https://github.com/tendermint/tendermint/issues/2888
 func (bcR *BlockchainReactor) Receive(chID byte, src p2p.Peer, msgBytes []byte) {
 	msg, err := bc.DecodeMsg(msgBytes)
 	if err != nil {

blockchain/v1/reactor.go

@@ -250,6 +250,8 @@ func (bcR *BlockchainReactor) RemovePeer(peer p2p.Peer, reason interface{}) {
 }
 
 // Receive implements Reactor by handling 4 types of messages (look below).
+// XXX: do not call any methods that can block or incur heavy processing.
+// https://github.com/tendermint/tendermint/issues/2888
 func (bcR *BlockchainReactor) Receive(chID byte, src p2p.Peer, msgBytes []byte) {
 	msg, err := bc.DecodeMsg(msgBytes)
 	if err != nil {

blockchain/v2/reactor.go

@@ -455,6 +455,8 @@ func (r *BlockchainReactor) Stop() error {
 }
 
 // Receive implements Reactor by handling different message types.
+// XXX: do not call any methods that can block or incur heavy processing.
+// https://github.com/tendermint/tendermint/issues/2888
 func (r *BlockchainReactor) Receive(chID byte, src p2p.Peer, msgBytes []byte) {
 	msg, err := bc.DecodeMsg(msgBytes)
 	if err != nil {

consensus/reactor.go

@@ -220,6 +220,8 @@ func (conR *Reactor) RemovePeer(peer p2p.Peer, reason interface{}) {
 // Peer state updates can happen in parallel, but processing of
 // proposals, block parts, and votes are ordered by the receiveRoutine
 // NOTE: blocks on consensus state for proposals, block parts, and votes
+// XXX: do not call any methods that can block or incur heavy processing.
+// https://github.com/tendermint/tendermint/issues/2888
 func (conR *Reactor) Receive(chID byte, src p2p.Peer, msgBytes []byte) {
 	if !conR.IsRunning() {
 		conR.Logger.Debug("Receive", "src", src, "chId", chID, "bytes", msgBytes)

evidence/reactor.go

@@ -66,6 +66,8 @@ func (evR *Reactor) AddPeer(peer p2p.Peer) {
 
 // Receive implements Reactor.
 // It adds any received evidence to the evpool.
+// XXX: do not call any methods that can block or incur heavy processing.
+// https://github.com/tendermint/tendermint/issues/2888
 func (evR *Reactor) Receive(chID byte, src p2p.Peer, msgBytes []byte) {
 	evis, err := decodeMsg(msgBytes)
 	if err != nil {

mempool/reactor.go

@@ -160,6 +160,8 @@ func (memR *Reactor) RemovePeer(peer p2p.Peer, reason interface{}) {
 
 // Receive implements Reactor.
 // It adds any received transactions to the mempool.
+// XXX: do not call any methods that can block or incur heavy processing.
+// https://github.com/tendermint/tendermint/issues/2888
 func (memR *Reactor) Receive(chID byte, src p2p.Peer, msgBytes []byte) {
 	msg, err := memR.decodeMsg(msgBytes)
 	if err != nil {

p2p/base_reactor.go

@@ -44,6 +44,9 @@ type Reactor interface {
 	// copying.
 	//
 	// CONTRACT: msgBytes are not nil.
+	//
+	// XXX: do not call any methods that can block or incur heavy processing.
+	// https://github.com/tendermint/tendermint/issues/2888
 	Receive(chID byte, peer Peer, msgBytes []byte)
 }
 

p2p/pex/pex_reactor.go

@@ -236,6 +236,8 @@ func (r *Reactor) logErrAddrBook(err error) {
 }
 
 // Receive implements Reactor by handling incoming PEX messages.
+// XXX: do not call any methods that can block or incur heavy processing.
+// https://github.com/tendermint/tendermint/issues/2888
 func (r *Reactor) Receive(chID byte, src Peer, msgBytes []byte) {
 	msg, err := decodeMsg(msgBytes)
 	if err != nil {

statesync/reactor.go

@@ -90,6 +90,8 @@ func (r *Reactor) RemovePeer(peer p2p.Peer, reason interface{}) {
 }
 
 // Receive implements p2p.Reactor.
+// XXX: do not call any methods that can block or incur heavy processing.
+// https://github.com/tendermint/tendermint/issues/2888
 func (r *Reactor) Receive(chID byte, src p2p.Peer, msgBytes []byte) {
 	if !r.IsRunning() {
 		return