fix: #8051 so that stale DNS entries are cleaned-up (#8053)

cmd/bucket-handlers.go

@@ -22,6 +22,7 @@ import (
 	"encoding/xml"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"net/url"
 	"path"
@@ -51,15 +52,27 @@ import (
 // -- If yes, check if the IP of entry matches local IP. This means entry is for this instance.
 // -- If IP of the entry doesn't match, this means entry is for another instance. Log an error to console.
 func initFederatorBackend(objLayer ObjectLayer) {
+	// Get buckets in the backend
 	b, err := objLayer.ListBuckets(context.Background())
 	if err != nil {
 		logger.LogIf(context.Background(), err)
 		return
 	}
 
+	// Get buckets in the DNS
+	dnsBuckets, err := globalDNSConfig.List()
+	if err != nil && err != dns.ErrNoEntriesFound {
+		logger.LogIf(context.Background(), err)
+		return
+	}
+
+	bucketSet := set.NewStringSet()
+
+	// Add buckets that are not registered with the DNS
 	g := errgroup.WithNErrs(len(b))
 	for index := range b {
 		index := index
+		bucketSet.Add(b[index].Name)
 		g.Go(func() error {
 			r, gerr := globalDNSConfig.Get(b[index].Name)
 			if gerr != nil {
@@ -79,7 +92,38 @@ func initFederatorBackend(objLayer ObjectLayer) {
 	for _, err := range g.Wait() {
 		if err != nil {
 			logger.LogIf(context.Background(), err)
-			return
+		}
+	}
+
+	g = errgroup.WithNErrs(len(dnsBuckets))
+	// Remove buckets that are in DNS for this server, but aren't local
+	for index := range dnsBuckets {
+		index := index
+
+		g.Go(func() error {
+			// This is a local bucket that exists, so we can continue
+			if bucketSet.Contains(dnsBuckets[index].Key) {
+				return nil
+			}
+
+			// This is not for our server, so we can continue
+			hostPort := net.JoinHostPort(dnsBuckets[index].Host, fmt.Sprintf("%d", dnsBuckets[index].Port))
+			if globalDomainIPs.Intersection(set.CreateStringSet(hostPort)).IsEmpty() {
+				return nil
+			}
+
+			// We go to here, so we know the bucket no longer exists, but is registered in DNS to this server
+			if err := globalDNSConfig.DeleteRecord(dnsBuckets[index]); err != nil {
+				return fmt.Errorf("Failed to remove DNS entry for %s due to %v", dnsBuckets[index].Key, err)
+			}
+
+			return nil
+		}, index)
+	}
+
+	for _, err := range g.Wait() {
+		if err != nil {
+			logger.LogIf(context.Background(), err)
 		}
 	}
 }

pkg/dns/etcd_dns.go

@@ -197,6 +197,21 @@ func (c *coreDNS) Delete(bucket string) error {
 	return nil
 }
 
+// Removes a specific DNS entry
+func (c *coreDNS) DeleteRecord(record SrvRecord) error {
+	for _, domainName := range c.domainNames {
+		key := msg.Path(fmt.Sprintf("%s.%s.", record.Key, domainName), defaultPrefixPath)
+
+		dctx, dcancel := context.WithTimeout(context.Background(), defaultContextTimeout)
+		if _, err := c.etcdClient.Delete(dctx, key+etcdPathSeparator+record.Host); err != nil {
+			dcancel()
+			return err
+		}
+		dcancel()
+	}
+	return nil
+}
+
 // CoreDNS - represents dns config for coredns server.
 type coreDNS struct {
 	domainNames []string

pkg/dns/types.go

@@ -62,4 +62,5 @@ type Config interface {
 	List() ([]SrvRecord, error)
 	Get(key string) ([]SrvRecord, error)
 	Delete(key string) error
+	DeleteRecord(record SrvRecord) error
 }