Merge pull request #663 from strukturag/improve-dnsmonitor

Minor improvements to DNS monitor

dns_monitor.go

@@ -43,8 +43,7 @@ const (
 type DnsMonitorCallback = func(entry *DnsMonitorEntry, all []net.IP, add []net.IP, keep []net.IP, remove []net.IP)
 
 type DnsMonitorEntry struct {
-	removing atomic.Bool
+	entry    atomic.Pointer[dnsMonitorEntry]
-	entry    *dnsMonitorEntry
 	url      string
 	callback DnsMonitorCallback
 }
@@ -145,6 +144,7 @@ type DnsMonitor struct {
 
 	stopCtx  context.Context
 	stopFunc func()
+	stopped  chan struct{}
 
 	mu        sync.RWMutex
 	cond      *sync.Cond
@@ -167,6 +167,7 @@ func NewDnsMonitor(interval time.Duration) (*DnsMonitor, error) {
 
 		stopCtx:  stopCtx,
 		stopFunc: stopFunc,
+		stopped:  make(chan struct{}),
 
 		hostnames: make(map[string]*dnsMonitorEntry),
 	}
@@ -183,6 +184,7 @@ func (m *DnsMonitor) Start() error {
 func (m *DnsMonitor) Stop() {
 	m.stopFunc()
 	m.cond.Signal()
+	<-m.stopped
 }
 
 func (m *DnsMonitor) Add(target string, callback DnsMonitorCallback) (*DnsMonitorEntry, error) {
@@ -219,14 +221,15 @@ func (m *DnsMonitor) Add(target string, callback DnsMonitorCallback) (*DnsMonito
 		}
 		m.hostnames[hostname] = entry
 	}
-	e.entry = entry
+	e.entry.Store(entry)
 	entry.addEntry(e)
 	m.cond.Signal()
 	return e, nil
 }
 
 func (m *DnsMonitor) Remove(entry *DnsMonitorEntry) {
-	if !entry.removing.CompareAndSwap(false, true) {
+	oldEntry := entry.entry.Swap(nil)
+	if oldEntry == nil {
 		// Already removed.
 		return
 	}
@@ -244,16 +247,11 @@ func (m *DnsMonitor) Remove(entry *DnsMonitorEntry) {
 	}
 	defer m.mu.Unlock()
 
-	if entry.entry == nil {
+	e, found := m.hostnames[oldEntry.hostname]
-		return
-	}
-
-	e, found := m.hostnames[entry.entry.hostname]
 	if !found {
 		return
 	}
 
-	entry.entry = nil
 	if e.removeEntry(entry) {
 		delete(m.hostnames, e.hostname)
 	}
@@ -270,7 +268,7 @@ func (m *DnsMonitor) clearRemoved() {
 	for hostname, entry := range m.hostnames {
 		deleted := false
 		for e := range entry.entries {
-			if e.removing.Load() {
+			if e.entry.Load() == nil {
 				delete(entry.entries, e)
 				deleted = true
 			}
@@ -296,6 +294,7 @@ func (m *DnsMonitor) waitForEntries() (waited bool) {
 func (m *DnsMonitor) run() {
 	ticker := time.NewTicker(m.interval)
 	defer ticker.Stop()
+	defer close(m.stopped)
 
 	for {
 		if m.waitForEntries() {

proxy_config_static.go

@@ -151,6 +151,10 @@ func (p *proxyConfigStatic) Start() error {
 
 	if p.dnsDiscovery {
 		for u, ips := range p.connectionsMap {
+			if ips.entry != nil {
+				continue
+			}
+
 			entry, err := p.dnsMonitor.Add(u, p.onLookup)
 			if err != nil {
 				return err
@@ -170,6 +174,19 @@ func (p *proxyConfigStatic) Start() error {
 }
 
 func (p *proxyConfigStatic) Stop() {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	if p.dnsDiscovery {
+		for _, ips := range p.connectionsMap {
+			if ips.entry == nil {
+				continue
+			}
+
+			p.dnsMonitor.Remove(ips.entry)
+			ips.entry = nil
+		}
+	}
 }
 
 func (p *proxyConfigStatic) Reload(config *goconf.ConfigFile) error {