fix aggressive expiration detection (#11446)

for some flaky networks this may be too fast of a value
choose a defensive value, and let this be addressed
properly in a new refactor of dsync with renewal logic.

Also enable faster fallback delay to cater for misconfigured
IPv6 servers

refer
 - https://golang.org/pkg/net/#Dialer
 - https://tools.ietf.org/html/rfc6555

cmd/http/dial_dnscache.go

@@ -44,7 +44,9 @@ func DialContextWithDNSCache(cache *DNSCache, baseDialCtx DialContext) DialConte
 		baseDialCtx = (&net.Dialer{
 			Timeout:   30 * time.Second,
 			KeepAlive: 30 * time.Second,
-			DualStack: true,
+			// If zero, Go defaults to '300ms', we will default to 100ms instead.
+			// https://tools.ietf.org/html/rfc6555
+			FallbackDelay: 100 * time.Millisecond,
 		}).DialContext
 	}
 	return func(ctx context.Context, network, host string) (net.Conn, error) {

cmd/http/dial_linux.go

@@ -68,6 +68,9 @@ func NewInternodeDialContext(dialTimeout time.Duration) DialContext {
 	return func(ctx context.Context, network, addr string) (net.Conn, error) {
 		dialer := &net.Dialer{
 			Timeout: dialTimeout,
+			// If zero, Go defaults to '300ms', we will default to 100ms instead.
+			// https://tools.ietf.org/html/rfc6555
+			FallbackDelay: 100 * time.Millisecond,
 			Control: func(network, address string, c syscall.RawConn) error {
 				return setInternalTCPParameters(c)
 			},
@@ -81,6 +84,9 @@ func NewCustomDialContext(dialTimeout time.Duration) DialContext {
 	return func(ctx context.Context, network, addr string) (net.Conn, error) {
 		dialer := &net.Dialer{
 			Timeout: dialTimeout,
+			// If zero, Go defaults to '300ms', we will default to 100ms instead.
+			// https://tools.ietf.org/html/rfc6555
+			FallbackDelay: 100 * time.Millisecond,
 			Control: func(network, address string, c syscall.RawConn) error {
 				return c.Control(func(fdPtr uintptr) {
 					// got socket file descriptor to set parameters.

cmd/local-locker.go

@@ -258,7 +258,7 @@ func (l *localLocker) Expired(ctx context.Context, args dsync.LockArgs) (expired
 				ep := globalRemoteEndpoints[args.Owner]
 				if !ep.IsLocal {
 					// check if the owner is online
-					return isServerResolvable(ep, 250*time.Millisecond) != nil, nil
+					return isServerResolvable(ep, 1*time.Second) != nil, nil
 				}
 				return false, nil
 			}

cmd/lock-rest-server.go

@@ -302,7 +302,7 @@ func lockMaintenance(ctx context.Context, interval time.Duration) error {
 		for _, c := range lockers {
 			go func(lrip lockRequesterInfo, c dsync.NetLocker) {
 				defer wg.Done()
-				ctx, cancel := context.WithTimeout(GlobalContext, 3*time.Second)
+				ctx, cancel := context.WithTimeout(GlobalContext, 5*time.Second)
 
 				// Call back to all participating servers, verify
 				// if each of those servers think lock is still

pkg/madmin/transport.go

@@ -30,8 +30,9 @@ var DefaultTransport = func(secure bool) http.RoundTripper {
 	tr := &http.Transport{
 		Proxy: http.ProxyFromEnvironment,
 		DialContext: (&net.Dialer{
-			Timeout:   5 * time.Second,
+			Timeout:       5 * time.Second,
-			KeepAlive: 15 * time.Second,
+			KeepAlive:     15 * time.Second,
+			FallbackDelay: 100 * time.Millisecond,
 		}).DialContext,
 		MaxIdleConns:          1024,
 		MaxIdleConnsPerHost:   1024,