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connection_maker.go
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connection_maker.go
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package router
import (
"bytes"
"fmt"
"log"
"math/rand"
"net"
"time"
)
const (
InitialInterval = 5 * time.Second
MaxInterval = 10 * time.Minute
)
const (
CMInitiate = iota
CMTerminated = iota
CMRefresh = iota
CMStatus = iota
)
type ConnectionMaker struct {
ourself *LocalPeer
peers *Peers
targets map[string]*Target
cmdLineAddress map[string]bool
queryChan chan<- *ConnectionMakerInteraction
}
// Information about an address where we may find a peer
type Target struct {
attempting bool // are we currently attempting to connect there?
tryAfter time.Time // next time to try this address
tryInterval time.Duration // backoff time on next failure
}
type ConnectionMakerInteraction struct {
Interaction
address string
}
func StartConnectionMaker(ourself *LocalPeer, peers *Peers) *ConnectionMaker {
queryChan := make(chan *ConnectionMakerInteraction, ChannelSize)
state := &ConnectionMaker{
ourself: ourself,
peers: peers,
queryChan: queryChan,
cmdLineAddress: make(map[string]bool),
targets: make(map[string]*Target)}
go state.queryLoop(queryChan)
return state
}
func (cm *ConnectionMaker) InitiateConnection(address string) {
cm.queryChan <- &ConnectionMakerInteraction{
Interaction: Interaction{code: CMInitiate},
address: address}
}
func (cm *ConnectionMaker) ConnectionTerminated(address string) {
cm.queryChan <- &ConnectionMakerInteraction{
Interaction: Interaction{code: CMTerminated},
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{
Interaction: Interaction{code: CMStatus, resultChan: resultChan}}
result := <-resultChan
return result.(string)
}
func (cm *ConnectionMaker) queryLoop(queryChan <-chan *ConnectionMakerInteraction) {
timer := time.NewTimer(MaxDuration)
run := func() { timer.Reset(cm.checkStateAndAttemptConnections()) }
for {
select {
case query, ok := <-queryChan:
if !ok {
return
}
switch query.code {
case CMInitiate:
cm.cmdLineAddress[NormalisePeerAddr(query.address)] = true
run()
case CMTerminated:
if target, found := cm.targets[query.address]; found {
target.attempting = false
target.tryAfter, target.tryInterval = tryAfter(target.tryInterval)
}
run()
case CMRefresh:
run()
case CMStatus:
run()
query.resultChan <- cm.status()
default:
log.Fatal("Unexpected connection maker query:", query)
}
case <-timer.C:
run()
}
}
}
func (cm *ConnectionMaker) checkStateAndAttemptConnections() time.Duration {
validTarget := make(map[string]bool)
// copy the set of things we are connected to, so we can access them without locking
our_connected_peers := make(map[PeerName]bool)
our_connected_targets := make(map[string]bool)
cm.ourself.ForEachConnection(func(peer PeerName, conn Connection) {
our_connected_peers[peer] = true
our_connected_targets[conn.RemoteTCPAddr()] = true
})
addTarget := func(address string) {
if !our_connected_targets[address] {
validTarget[address] = true
cm.addTarget(address)
}
}
// Add command-line targets that are not connected
for address, _ := range cm.cmdLineAddress {
addTarget(address)
}
// Add targets for peers that someone else is connected to, but we
// aren't
cm.peers.ForEach(func(name PeerName, peer *Peer) {
peer.ForEachConnection(func(otherPeer PeerName, conn Connection) {
if otherPeer == cm.ourself.Name || our_connected_peers[otherPeer] {
return
}
address := conn.RemoteTCPAddr()
// try both portnumber of connection and standard port
addTarget(address)
if host, _, err := net.SplitHostPort(address); err == nil {
addTarget(NormalisePeerAddr(host))
}
})
})
now := time.Now() // make sure we catch items just added
after := MaxDuration
for address, target := range cm.targets {
if our_connected_targets[address] {
delete(cm.targets, address)
continue
}
if target.attempting {
continue
}
if !validTarget[address] {
delete(cm.targets, address)
continue
}
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) {
if _, found := cm.targets[address]; !found {
target := &Target{}
target.tryAfter, target.tryInterval = tryImmediately()
cm.targets[address] = target
}
}
func (cm *ConnectionMaker) status() string {
var buf bytes.Buffer
for address, target := range cm.targets {
var fmtStr string
if target.attempting {
fmtStr = "%s (trying since %v)\n"
} else {
fmtStr = "%s (next try at %v)\n"
}
buf.WriteString(fmt.Sprintf(fmtStr, address, target.tryAfter))
}
return buf.String()
}
func (cm *ConnectionMaker) attemptConnection(address string, acceptNewPeer bool) {
log.Println("Attempting connection to", address)
if err := cm.ourself.CreateConnection(address, acceptNewPeer); err != nil {
log.Println(err)
cm.ConnectionTerminated(address)
}
}
func tryImmediately() (time.Time, time.Duration) {
interval := time.Duration(rand.Int63n(int64(InitialInterval)))
return time.Now(), interval
}
func tryAfter(interval time.Duration) (time.Time, time.Duration) {
interval += time.Duration(rand.Int63n(int64(interval)))
if interval > MaxInterval {
interval = MaxInterval
}
return time.Now().Add(interval), interval
}