From eecaa567fc7eda327ea9ff49bbef554c3cc97e9f Mon Sep 17 00:00:00 2001
From: Matthias Radestock <matthias.radestock@gmail.com>
Date: Mon, 22 Sep 2014 23:15:54 +0100
Subject: [PATCH] eliminate periodic 'tick' in connection_maker
 checkStateAndAttemptConnections already performs a full scan of all potential
 targets, from which we can easily determine the nearest future time (or,
 rather, its duration from now) on which an attempt is due.

We also need to kick the ConnectionMaker into action when we receive a
topology update containing new connections.
---
 connection_maker.go | 38 ++++++++++++++++++++++----------------
 peer_cache.go       |  4 ++++
 2 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/connection_maker.go b/connection_maker.go
index e52c413e..94064646 100644
--- a/connection_maker.go
+++ b/connection_maker.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"log"
+	"math"
 	"math/rand"
 	"net"
 	"time"
@@ -17,6 +18,7 @@ const (
 const (
 	CMInitiate   = iota
 	CMTerminated = iota
+	CMRefresh    = iota
 	CMStatus     = iota
 )
 
@@ -43,6 +45,11 @@ func (cm *ConnectionMaker) ConnectionTerminated(address string) {
 		address:     address}
 }
 
+func (cm *ConnectionMaker) Refresh() {
+	cm.queryChan <- &ConnectionMakerInteraction{
+		Interaction: Interaction{code: CMRefresh}}
+}
+
 func (cm *ConnectionMaker) String() string {
 	resultChan := make(chan interface{}, 0)
 	cm.queryChan <- &ConnectionMakerInteraction{
@@ -52,12 +59,8 @@ func (cm *ConnectionMaker) String() string {
 }
 
 func (cm *ConnectionMaker) queryLoop(queryChan <-chan *ConnectionMakerInteraction) {
-	var tick <-chan time.Time
-	maybeTick := func() {
-		if tick == nil {
-			tick = time.After(5 * time.Second)
-		}
-	}
+	timer := time.NewTimer(math.MaxInt64)
+	run := func() { timer.Reset(cm.checkStateAndAttemptConnections()) }
 	for {
 		select {
 		case query, ok := <-queryChan:
@@ -67,29 +70,27 @@ func (cm *ConnectionMaker) queryLoop(queryChan <-chan *ConnectionMakerInteractio
 			switch query.code {
 			case CMInitiate:
 				cm.cmdLineAddress[NormalisePeerAddr(query.address)] = true
-				cm.checkStateAndAttemptConnections()
-				maybeTick()
+				run()
 			case CMTerminated:
 				if target, found := cm.targets[query.address]; found {
 					target.attempting = false
 					target.tryAfter, target.tryInterval = tryAfter(target.tryInterval)
 				}
-				cm.checkStateAndAttemptConnections()
-				maybeTick()
+				run()
+			case CMRefresh:
+				run()
 			case CMStatus:
 				query.resultChan <- cm.status()
 			default:
 				log.Fatal("Unexpected connection maker query:", query)
 			}
-		case <-tick:
-			cm.checkStateAndAttemptConnections()
-			tick = nil
-			maybeTick()
+		case <-timer.C:
+			run()
 		}
 	}
 }
 
-func (cm *ConnectionMaker) checkStateAndAttemptConnections() {
+func (cm *ConnectionMaker) checkStateAndAttemptConnections() time.Duration {
 	ourself := cm.router.Ourself
 	validTarget := make(map[string]bool)
 
@@ -130,6 +131,7 @@ func (cm *ConnectionMaker) checkStateAndAttemptConnections() {
 	})
 
 	now := time.Now() // make sure we catch items just added
+	after := time.Duration(math.MaxInt64)
 	for address, target := range cm.targets {
 		if our_connected_targets[address] {
 			delete(cm.targets, address)
@@ -142,11 +144,15 @@ func (cm *ConnectionMaker) checkStateAndAttemptConnections() {
 			delete(cm.targets, address)
 			continue
 		}
-		if now.After(target.tryAfter) {
+		switch duration := target.tryAfter.Sub(now); {
+		case duration <= 0:
 			target.attempting = true
 			go cm.attemptConnection(address, cm.cmdLineAddress[address])
+		case duration < after:
+			after = duration
 		}
 	}
+	return after
 }
 
 func (cm *ConnectionMaker) addTarget(address string) {
diff --git a/peer_cache.go b/peer_cache.go
index a499d5ae..a5d9f956 100644
--- a/peer_cache.go
+++ b/peer_cache.go
@@ -77,6 +77,10 @@ func (cache *PeerCache) ApplyUpdate(update []byte, router *Router) ([]byte, erro
 	// Don't need to hold cache lock any longer
 	cache.Unlock()
 
+	if len(newUpdate) > 0 {
+		router.ConnectionMaker.Refresh()
+	}
+
 	return encodePeersMap(newUpdate), nil
 }