From 7a38f7642e8349661aeede3945437bf74979b487 Mon Sep 17 00:00:00 2001
From: vyzo <vyzo@hackzen.org>
Date: Thu, 25 Apr 2019 21:28:13 +0300
Subject: [PATCH] validation pipeline front-end for handling signature
 validation synchronously

---
 pubsub.go | 66 ++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 53 insertions(+), 13 deletions(-)

diff --git a/pubsub.go b/pubsub.go
index c8a0e91..a9fe375 100644
--- a/pubsub.go
+++ b/pubsub.go
@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"math/rand"
+	"runtime"
 	"sync/atomic"
 	"time"
 
@@ -92,6 +93,9 @@ type PubSub struct {
 	// topicVals tracks per topic validators
 	topicVals map[string]*topicVal
 
+	// validateQ is the front-end to the validation pipeline
+	validateQ chan *validateReq
+
 	// validateThrottle limits the number of active validation goroutines
 	validateThrottle chan struct{}
 
@@ -184,6 +188,7 @@ func NewPubSub(ctx context.Context, h host.Host, rt PubSubRouter, opts ...Option
 		topics:           make(map[string]map[peer.ID]struct{}),
 		peers:            make(map[peer.ID]chan *RPC),
 		topicVals:        make(map[string]*topicVal),
+		validateQ:        make(chan *validateReq, 32),
 		blacklist:        NewMapBlacklist(),
 		blacklistPeer:    make(chan peer.ID),
 		seenMessages:     timecache.NewTimeCache(TimeCacheDuration),
@@ -210,6 +215,11 @@ func NewPubSub(ctx context.Context, h host.Host, rt PubSubRouter, opts ...Option
 
 	go ps.processLoop(ctx)
 
+	numcpu := runtime.NumCPU()
+	for i := 0; i < numcpu; i++ {
+		go ps.validateWorker()
+	}
+
 	return ps, nil
 }
 
@@ -631,16 +641,8 @@ func (p *PubSub) pushMsg(vals []*topicVal, src peer.ID, msg *Message) {
 	}
 
 	if len(vals) > 0 || msg.Signature != nil {
-		// validation is asynchronous and globally throttled with the throttleValidate semaphore.
-		// the purpose of the global throttle is to bound the goncurrency possible from incoming
-		// network traffic; each validator also has an individual throttle to preclude
-		// slow (or faulty) validators from starving other topics; see validate below.
 		select {
-		case p.validateThrottle <- struct{}{}:
-			go func() {
-				p.validate(vals, src, msg)
-				<-p.validateThrottle
-			}()
+		case p.validateQ <- &validateReq{vals, src, msg}:
 		default:
 			log.Warningf("message validation throttled; dropping message from %s", src)
 		}
@@ -650,7 +652,20 @@ func (p *PubSub) pushMsg(vals []*topicVal, src peer.ID, msg *Message) {
 	p.publishMessage(src, msg.Message)
 }
 
+func (p *PubSub) validateWorker() {
+	for {
+		select {
+		case req := <-p.validateQ:
+			p.validate(req.vals, req.src, req.msg)
+		case <-p.ctx.Done():
+			return
+		}
+	}
+}
+
 // validate performs validation and only sends the message if all validators succeed
+// signature validation is performed synchronously, while user validators are invoked
+// asynchronously, throttled by the global validation throttle.
 func (p *PubSub) validate(vals []*topicVal, src peer.ID, msg *Message) {
 	if msg.Signature != nil {
 		if !p.validateSignature(msg) {
@@ -660,13 +675,19 @@ func (p *PubSub) validate(vals []*topicVal, src peer.ID, msg *Message) {
 	}
 
 	if len(vals) > 0 {
-		if !p.validateTopic(vals, src, msg) {
-			log.Warningf("message validation failed; dropping message from %s", src)
-			return
+		select {
+		case p.validateThrottle <- struct{}{}:
+			go func() {
+				p.doValidateTopic(vals, src, msg)
+				<-p.validateThrottle
+			}()
+		default:
+			log.Warningf("message validation throttled; dropping message from %s", src)
 		}
+		return
 	}
 
-	// all validators were successful, send the message
+	// no user validators and the signature was valid, send the message
 	p.sendMsg <- &sendReq{
 		from: src,
 		msg:  msg,
@@ -683,6 +704,18 @@ func (p *PubSub) validateSignature(msg *Message) bool {
 	return true
 }
 
+func (p *PubSub) doValidateTopic(vals []*topicVal, src peer.ID, msg *Message) {
+	if !p.validateTopic(vals, src, msg) {
+		log.Warningf("message validation failed; dropping message from %s", src)
+		return
+	}
+
+	p.sendMsg <- &sendReq{
+		from: src,
+		msg:  msg,
+	}
+}
+
 func (p *PubSub) validateTopic(vals []*topicVal, src peer.ID, msg *Message) bool {
 	if len(vals) == 1 {
 		return p.validateSingleTopic(vals[0], src, msg)
@@ -883,6 +916,13 @@ func (p *PubSub) BlacklistPeer(pid peer.ID) {
 	p.blacklistPeer <- pid
 }
 
+// validation requests
+type validateReq struct {
+	vals []*topicVal
+	src  peer.ID
+	msg  *Message
+}
+
 // per topic validators
 type addValReq struct {
 	topic    string