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

@@ -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) {

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
 }