Docker auto-scale and asleep motd status (#488)

README.md

@@ -14,7 +14,8 @@ Some other features included:
 - Rate limits incoming connections to reduce DDoS attacks.
 - Can be configured to allow/deny IP addresses or ranges
 - Includes a webhook integration for notifying other systems when a player connects and disconnects from a server.
-- Can auto-scale (between zero and one) backend servers deployed as Kubernetes StatefulSets.
+- Can auto-scale (between zero and one) backend servers deployed as Kubernetes StatefulSets
+- or start and stop backend servers running as docker containers.
 - Built-in ngrok integration where mc-router acts as an agent
 - Exports/exposes metrics for various Prometheus and InfluxDB. If enabled, includes player login metrics.
 
@@ -25,12 +26,14 @@ Some other features included:
     	The host:port bound for servicing API requests (env API_BINDING)
   -auto-scale-allow-deny string
     	Path to config for server allowlists and denylists. If a global/server entry is specified, only players allowed to connect to the server will be able to trigger a scale up when -auto-scale-up is enabled or cancel active down scalers when -auto-scale-down is enabled (env AUTO_SCALE_ALLOW_DENY)
+  -auto-scale-asleep-motd string
+      MOTD to display when auto-scaled down servers are accessed; if empty, no status will be served (env AUTO_SCALE_ASLEEP_MOTD)
   -auto-scale-down
-    	Decrease Kubernetes StatefulSet Replicas (only) from 1 to 0 on respective backend servers after there are no connections (env AUTO_SCALE_DOWN)
+    	Scale to zero after idle. For Kubernetes, decreases StatefulSet replicas from 1 to 0. For Docker, gracefully stops the container when there are no connections (env AUTO_SCALE_DOWN)
   -auto-scale-down-after string
     	Server scale down delay after there are no connections (env AUTO_SCALE_DOWN_AFTER) (default "10m")
   -auto-scale-up
-    	Increase Kubernetes StatefulSet Replicas (only) from 0 to 1 on respective backend servers when accessed (env AUTO_SCALE_UP)
+    	Scale from zero on access. For Kubernetes, increases StatefulSet replicas from 0 to 1. For Docker, starts or unpauses the container when accessed (env AUTO_SCALE_UP)
   -clients-to-allow value
     	Zero or more client IP addresses or CIDRs to allow. Takes precedence over deny. (env CLIENTS_TO_ALLOW)
   -clients-to-deny value
@@ -169,6 +172,35 @@ These are the labels scanned:
 - `mc-router.port`: This value must be set to the port the Minecraft server is listening on. The default value is 25565.
 - `mc-router.default`: Set this to a truthy value to make this server the default backend. Please note that `mc-router.host` is still required to be set.
 - `mc-router.network`: Specify the network you are using for the router if multiple are present in the container/service. You can either use the network ID, it's full name or an alias.
+- `mc-router.auto-scale-up`: Per-container override to enable/disable auto scale up for Docker. When true (or left unspecified and the global `-auto-scale-up` flag is enabled), mc-router will start or unpause this container when a client connects to the declared hostname(s).
+- `mc-router.auto-scale-down`: Per-container override to enable/disable auto scale down for Docker. When true (or left unspecified and the global `-auto-scale-down` flag is enabled), mc-router will stop this container after it has been idle for the configured `-auto-scale-down-after` duration.
+- `mc-router.auto-scale-asleep-motd`: Per-container override for MOTD to show when container is scaled to zero. If empty or not set the host will
+appear unresponsive.
+
+#### Docker Auto Scale Up/Down
+
+To use scale-to-zero with Docker containers:
+
+- Start mc-router with Docker discovery and scaling enabled, for example:
+
+  ```bash
+  docker run --rm \
+    -p 25565:25565 \
+    -v /var/run/docker.sock:/var/run/docker.sock:ro \
+    itzg/mc-router \
+    -in-docker -auto-scale-up -auto-scale-down -auto-scale-down-after=10m
+  ```
+
+- Label each Minecraft container with at least `mc-router.host`. You can also set per-container autoscale overrides using `mc-router.auto-scale-up` and `mc-router.auto-scale-down` labels.
+
+For usage with docker compose refer to the [examples/docker-autoscale/compose.yml](examples/docker-autoscale/compose.yml) or [examples/docker-autoscale/compose-minimal.yml](examples/docker-autoscale/compose-minimal.yml) examples.
+
+Behavior:
+
+- When a client connects to a labeled hostname and the container is stopped or paused, mc-router will start/unpause it and wait until it becomes reachable (up to ~60s).
+- When no clients remain connected and the idle timer elapses (`-auto-scale-down-after`), mc-router gracefully stops the container.
+
+Note: Docker Swarm discovery is supported; however, auto scale up/down is not yet supported for Swarm services.
 
 #### Example Docker deployment
 

examples/docker-autoscale/compose-minimal.yml

@@ -0,0 +1,27 @@
+services:
+  router:
+    image: itzg/mc-router
+    environment:
+      IN_DOCKER: true
+      AUTO_SCALE_DOWN: true
+      AUTO_SCALE_UP: true
+      AUTO_SCALE_DOWN_AFTER: 2h
+      AUTO_SCALE_ASLEEP_MOTD: "Server is asleep. Join again to wake it up!"
+    ports:
+      - "25565:25565"
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+  vanilla:
+    image: itzg/minecraft-server
+    environment:
+      EULA: "TRUE"
+    labels:
+      mc-router.host: "vanilla.example.com"
+  paper:
+    image: itzg/minecraft-server
+    environment:
+      EULA: "TRUE"
+      TYPE: PAPER
+    labels:
+      mc-router.host: "paper.example.com"
+

examples/docker-autoscale/compose.yml

@@ -0,0 +1,50 @@
+# This is a verbose example with comments and explanations for configuring auto-scaling behavior
+# for Docker backend servers. See compose-minimal.yml for a simple minimal example.
+services:
+  router:
+    image: itzg/mc-router
+    environment:
+      IN_DOCKER: true
+      # Global auto-scaling settings for all docker-backend servers
+      # Settings can be overridden per-backend using labels
+      # as shown in the backend services below (except for AUTO_SCALE_DOWN_AFTER which is global only)
+      # Enable auto-scaling down after inactivity for all backends by default
+      AUTO_SCALE_DOWN: true
+      # Enable auto-scaling up after player join for all backends by default
+      AUTO_SCALE_UP: true
+      # Time of inactivity after which to scale down (default: 10m) - Global only setting
+      AUTO_SCALE_DOWN_AFTER: 2h
+      # MOTD to show when server is asleep (default: empty string - don't show MOTD, show server offline instead)
+      AUTO_SCALE_ASLEEP_MOTD: "Server is asleep. Join again to wake it up!"
+    ports:
+      - "25565:25565"
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+  vanilla:
+    image: itzg/minecraft-server
+    environment:
+      EULA: "TRUE"
+    labels:
+      # If global auto scaling settings are enabled, this backend will
+      # auto-scale without any additional auto-scale related configuration
+      mc-router.host: "vanilla.example.com"
+  fabric:
+    image: itzg/minecraft-server
+    environment:
+      EULA: "TRUE"
+      TYPE: FABRIC
+    labels:
+      mc-router.host: "fabric.example.com"
+      # Disable auto-scaling for this backend specifically
+      mc-router.auto-scale-up: false
+      mc-router.auto-scale-down: false
+  paper:
+    image: itzg/minecraft-server
+    environment:
+      EULA: "TRUE"
+      TYPE: PAPER
+    labels:
+      mc-router.host: "paper.example.com"
+      # Override asleep MOTD for this backend
+      mc-router.auto-scale-asleep-motd: "Paper is folded. Join to unfold!"
+

mcproto/read.go

@@ -58,7 +58,29 @@ func ReadPacket(reader *bufio.Reader, addr net.Addr, state State) (*Packet, erro
 		return nil, err
 	}
 
-	packet.Data = remainder.Bytes()
+	// For status state, decode based on packet ID:
+	// - 0x00 Status Request: no payload
+	// - 0x01 Ping: 8-byte long payload
+	if state == StateStatus {
+		switch packet.PacketID {
+		case PacketIdStatusRequest:
+			// no payload
+			packet.Data = nil
+		case PacketIdPingRequest:
+			timestamp, err := ReadLong(remainder)
+			if err != nil {
+				return nil, err
+			}
+			packet.Data = &PingPayload{
+				Timestamp: timestamp,
+			}
+		default:
+			// unknown in status state; keep raw
+			packet.Data = remainder.Bytes()
+		}
+	} else {
+		packet.Data = remainder.Bytes()
+	}
 
 	logrus.
 		WithField("client", addr).

mcproto/types.go

@@ -79,6 +79,13 @@ const (
 	PacketIdHandshake            = 0x00
 	PacketIdLogin                = 0x00 // during StateLogin
 	PacketIdLegacyServerListPing = 0xFE
+	PacketIdStatusRequest        = 0x00
+	PacketIdPingRequest          = 0x01
+)
+
+const (
+	PacketIdStatusResponse = 0x00
+	PackedIdPongResponse   = 0x01
 )
 
 type Handshake struct {
@@ -106,6 +113,30 @@ type LegacyServerListPing struct {
 	ServerPort      uint16
 }
 
+// StatusResponse is a minimal structure for the status JSON
+type StatusResponse struct {
+	Version struct {
+		Name     string `json:"name"`
+		Protocol int    `json:"protocol"`
+	} `json:"version"`
+	Players struct {
+		Max    int `json:"max"`
+		Online int `json:"online"`
+		Sample []struct {
+			Name string `json:"name"`
+			ID   string `json:"id"`
+		} `json:"sample,omitempty"`
+	} `json:"players"`
+	Description        map[string]interface{} `json:"description"`
+	Favicon            string                 `json:"favicon,omitempty"`
+	EnforcesSecureChat *bool                  `json:"enforcesSecureChat,omitempty"`
+}
+
+// PingPayload represents the status ping payload (packet 0x01)
+type PingPayload struct {
+	Timestamp int64
+}
+
 type ByteReader interface {
 	ReadByte() (byte, error)
 }

mcproto/write.go

@@ -0,0 +1,148 @@
+package mcproto
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/binary"
+	"encoding/json"
+	"io"
+	"unicode/utf16"
+)
+
+// WriteVarInt writes a VarInt (Minecraft format) to w
+func WriteVarInt(w io.Writer, value int32) error {
+	var buf [5]byte
+	i := 0
+	v := uint32(value)
+	for {
+		temp := byte(v & 0x7F)
+		v >>= 7
+		if v != 0 {
+			temp |= 0x80
+		}
+		buf[i] = temp
+		i++
+		if v == 0 {
+			break
+		}
+	}
+	_, err := w.Write(buf[:i])
+	return err
+}
+
+// WriteString writes a Minecraft length-prefixed string
+func WriteString(w io.Writer, s string) error {
+	if err := WriteVarInt(w, int32(len(s))); err != nil {
+		return err
+	}
+	_, err := io.WriteString(w, s)
+	return err
+}
+
+// buildPacket builds a framed packet: [length VarInt][packetId VarInt][payload]
+func buildPacket(packetID int32, payload []byte) []byte {
+	var b bytes.Buffer
+	_ = WriteVarInt(&b, packetID)
+	b.Write(payload)
+
+	var framed bytes.Buffer
+	_ = WriteVarInt(&framed, int32(b.Len()))
+	framed.Write(b.Bytes())
+	return framed.Bytes()
+}
+
+// WriteStatusJSONPacket writes a Status Response (packet 0x00) with the provided JSON string
+func WriteStatusJSONPacket(w io.Writer, jsonString string) error {
+	// payload is the JSON as a Minecraft string
+	var payload bytes.Buffer
+	if err := WriteString(&payload, jsonString); err != nil {
+		return err
+	}
+	pkt := buildPacket(PacketIdStatusResponse, payload.Bytes())
+	_, err := w.Write(pkt)
+	return err
+}
+
+// WriteStatusFromStruct writes a Status Response from a struct
+func WriteStatusFromStruct(w io.Writer, status StatusResponse) error {
+	b, err := json.Marshal(status)
+	if err != nil {
+		return err
+	}
+	return WriteStatusJSONPacket(w, string(b))
+}
+
+// WritePongPacket writes Pong (packet 0x01) with the same payload
+func WritePongPacket(w io.Writer, timestamp int64) error {
+	var pl bytes.Buffer
+	// payload is a signed long (64-bit)
+	var buf [8]byte
+	binary.BigEndian.PutUint64(buf[:], uint64(timestamp))
+	pl.Write(buf[:])
+	pkt := buildPacket(PackedIdPongResponse, pl.Bytes())
+	_, err := w.Write(pkt)
+	return err
+}
+
+// WriteLegacySLPResponse writes the 1.6-compatible legacy response packet (0xFF)
+// Format: FF, [length short], UTF16BE string beginning with "\u00A7\u0031\u0000" then null-delimited fields
+// fields: protocol, version, motd, online, max
+func WriteLegacySLPResponse(w io.Writer, protocol int, version string, motd string, online int, max int) error {
+	// Build the string with null separators
+	s := "\u00A7\u0031\u0000" +
+		intToString(protocol) + "\u0000" +
+		version + "\u0000" +
+		motd + "\u0000" +
+		intToString(online) + "\u0000" +
+		intToString(max)
+
+	// Encode UTF-16BE
+	runes := []rune(s)
+	encoded := utf16.Encode(runes)
+	var be bytes.Buffer
+	for _, v := range encoded {
+		var tmp [2]byte
+		binary.BigEndian.PutUint16(tmp[:], v)
+		be.Write(tmp[:])
+	}
+
+	bw := bufio.NewWriter(w)
+	// 0xFF
+	if _, err := bw.Write([]byte{0xFF}); err != nil {
+		return err
+	}
+	// length short in code units
+	var lenBuf [2]byte
+	binary.BigEndian.PutUint16(lenBuf[:], uint16(len(encoded)))
+	if _, err := bw.Write(lenBuf[:]); err != nil {
+		return err
+	}
+	if _, err := bw.Write(be.Bytes()); err != nil {
+		return err
+	}
+	return bw.Flush()
+}
+
+// helpers
+func intToString(i int) string {
+	if i == 0 {
+		return "0"
+	}
+	neg := false
+	if i < 0 {
+		neg = true
+		i = -i
+	}
+	var buf [20]byte
+	pos := len(buf)
+	for i > 0 {
+		pos--
+		buf[pos] = byte('0' + (i % 10))
+		i /= 10
+	}
+	if neg {
+		pos--
+		buf[pos] = '-'
+	}
+	return string(buf[pos:])
+}

server/api_server.go

@@ -81,7 +81,7 @@ func routesCreateHandler(writer http.ResponseWriter, request *http.Request) {
 		return
 	}
 
-	Routes.CreateMapping(definition.ServerAddress, definition.Backend, EmptyScalerFunc, EmptyScalerFunc)
+	Routes.CreateMapping(definition.ServerAddress, definition.Backend, nil, nil, "")
 	RoutesConfigLoader.SaveRoutes()
 	writer.WriteHeader(http.StatusCreated)
 }
@@ -102,7 +102,7 @@ func routesSetDefault(writer http.ResponseWriter, request *http.Request) {
 		return
 	}
 
-	Routes.SetDefaultRoute(body.Backend)
+	Routes.SetDefaultRoute(body.Backend, nil, nil, "")
 	RoutesConfigLoader.SaveRoutes()
 	writer.WriteHeader(http.StatusOK)
 }

server/configs.go

@@ -6,10 +6,11 @@ type WebhookConfig struct {
 }
 
 type AutoScale struct {
-	Up        bool   `usage:"Increase Kubernetes StatefulSet Replicas (only) from 0 to 1 on respective backend servers when accessed"`
+	Up         bool   `usage:"Scale from zero on access. For Kubernetes, increases StatefulSet replicas from 0 to 1. For Docker, starts or unpauses the container when accessed"`
-	Down      bool   `default:"false" usage:"Decrease Kubernetes StatefulSet Replicas (only) from 1 to 0 on respective backend servers after there are no connections"`
+	Down       bool   `default:"false" usage:"Scale to zero after idle. For Kubernetes, decreases StatefulSet replicas from 1 to 0. For Docker, gracefully stops the container when there are no connections"`
-	DownAfter string `default:"10m" usage:"Server scale down delay after there are no connections"`
+	DownAfter  string `default:"10m" usage:"Server scale down delay after there are no connections"`
-	AllowDeny string `usage:"Path to config for server allowlists and denylists. If a global/server entry is specified, only players allowed to connect to the server will be able to trigger a scale up when -auto-scale-up is enabled or cancel active down scalers when -auto-scale-down is enabled"`
+	AllowDeny  string `usage:"Path to config for server allowlists and denylists. If a global/server entry is specified, only players allowed to connect to the server will be able to trigger a scale up when -auto-scale-up is enabled or cancel active down scalers when -auto-scale-down is enabled"`
+	AsleepMOTD string `usage:"MOTD to display when auto-scaled down servers are accessed; if empty, no status will be served"`
 }
 
 type RoutesConfig struct {

server/connector.go

@@ -38,30 +38,30 @@ func NewActiveConnections() *ActiveConnections {
 	}
 }
 
-func (sm *ActiveConnections) Increment(serverAddress string) {
+func (sm *ActiveConnections) Increment(backendAddress string) {
 	sm.Lock()
 	defer sm.Unlock()
-	if _, ok := sm.activeConnections[serverAddress]; !ok {
+	if _, ok := sm.activeConnections[backendAddress]; !ok {
-		sm.activeConnections[serverAddress] = 1
+		sm.activeConnections[backendAddress] = 1
 		return
 	}
-	sm.activeConnections[serverAddress] += 1
+	sm.activeConnections[backendAddress] += 1
 }
 
-func (sm *ActiveConnections) Decrement(serverAddress string) {
+func (sm *ActiveConnections) Decrement(backendAddress string) {
 	sm.Lock()
 	defer sm.Unlock()
-	if activeConnections, ok := sm.activeConnections[serverAddress]; ok && activeConnections <= 0 {
+	if activeConnections, ok := sm.activeConnections[backendAddress]; ok && activeConnections <= 0 {
-		sm.activeConnections[serverAddress] = 0
+		sm.activeConnections[backendAddress] = 0
 		return
 	}
-	sm.activeConnections[serverAddress] -= 1
+	sm.activeConnections[backendAddress] -= 1
 }
 
-func (sm *ActiveConnections) GetCount(serverAddress string) int {
+func (sm *ActiveConnections) GetCount(backendAddress string) int {
 	sm.Lock()
 	defer sm.Unlock()
-	if activeConnections, ok := sm.activeConnections[serverAddress]; ok {
+	if activeConnections, ok := sm.activeConnections[backendAddress]; ok {
 		return activeConnections
 	}
 	return 0
@@ -100,6 +100,7 @@ type Connector struct {
 	clientFilter               *ClientFilter
 	autoScaleUpAllowDenyConfig *AllowDenyConfig
 	connectionNotifier         ConnectionNotifier
+	asleepMOTD                 string
 }
 
 func (c *Connector) UseConnectionNotifier(notifier ConnectionNotifier) {
@@ -312,7 +313,7 @@ func (c *Connector) HandleConnection(frontendConn net.Conn) {
 				Debug("Got user info")
 		}
 
-		c.findAndConnectBackend(frontendConn, clientAddr, inspectionBuffer, handshake.ServerAddress, playerInfo, handshake.NextState)
+		c.findAndConnectBackend(frontendConn, clientAddr, inspectionBuffer, handshake.ServerAddress, playerInfo, handshake.NextState, false, int(handshake.ProtocolVersion))
 
 	} else if packet.PacketID == mcproto.PacketIdLegacyServerListPing {
 		handshake, ok := packet.Data.(*mcproto.LegacyServerListPing)
@@ -332,7 +333,7 @@ func (c *Connector) HandleConnection(frontendConn net.Conn) {
 
 		serverAddress := handshake.ServerAddress
 
-		c.findAndConnectBackend(frontendConn, clientAddr, inspectionBuffer, serverAddress, nil, mcproto.StateStatus)
+		c.findAndConnectBackend(frontendConn, clientAddr, inspectionBuffer, serverAddress, nil, mcproto.StateStatus, true, 0)
 	} else {
 		logrus.
 			WithField("client", clientAddr).
@@ -343,6 +344,110 @@ func (c *Connector) HandleConnection(frontendConn net.Conn) {
 	}
 }
 
+// serveStatus writes a predefined status JSON and optionally handles ping/pong
+func (c *Connector) serveStatus(frontendConn net.Conn, reader *bufio.Reader, serverAddress string, clientProtocol int) {
+	motd := Routes.GetAsleepMOTD(serverAddress)
+	if motd == "" {
+		motd = c.asleepMOTD
+	}
+	if motd == "" {
+		return
+	}
+
+	// Consume Status Request (0x00) if present; some clients may send Ping (0x01) directly
+	_ = frontendConn.SetReadDeadline(time.Now().Add(3 * time.Second))
+	firstPkt, err := mcproto.ReadPacket(reader, frontendConn.RemoteAddr(), mcproto.StateStatus)
+	var pingPending bool
+	var pingVal int64
+	if err == nil && firstPkt != nil {
+		if firstPkt.PacketID == mcproto.PacketIdPingRequest {
+			if payload, ok := firstPkt.Data.(mcproto.PingPayload); ok {
+				pingPending = true
+				pingVal = payload.Timestamp
+				logrus.WithFields(logrus.Fields{
+					"client":   frontendConn.RemoteAddr(),
+					"ping_val": pingVal,
+				}).Debug("Predefined status: received immediate ping")
+			}
+		}
+		// else 0x00 is the normal status request; proceed to write response
+	} else if err != nil {
+		logrus.WithFields(logrus.Fields{
+			"client": frontendConn.RemoteAddr(),
+			"error":  err,
+		}).Warn("Predefined status: error reading initial status packet")
+	}
+
+	// Build and write Status Response
+	viName, viProto := c.getVersionInfo(serverAddress, clientProtocol)
+	var status mcproto.StatusResponse
+	status.Version.Name = viName
+	status.Version.Protocol = viProto
+	status.Players.Max = 1
+	status.Players.Online = 0
+	status.Description = map[string]interface{}{"text": motd}
+
+	// Write Status Response
+	_ = frontendConn.SetWriteDeadline(time.Now().Add(handshakeTimeout))
+	if err := mcproto.WriteStatusFromStruct(frontendConn, status); err != nil {
+		logrus.WithError(err).Warn("Failed to write predefined status response")
+		return
+	}
+
+	// If we didn't already get a ping, briefly wait for one
+	if !pingPending {
+		_ = frontendConn.SetReadDeadline(time.Now().Add(2 * time.Second))
+		if nextPkt, err2 := mcproto.ReadPacket(reader, frontendConn.RemoteAddr(), mcproto.StateStatus); err2 == nil && nextPkt != nil {
+			if nextPkt.PacketID == mcproto.PacketIdPingRequest {
+				if payload, ok := nextPkt.Data.(mcproto.PingPayload); ok {
+					pingPending = true
+					pingVal = payload.Timestamp
+					logrus.WithFields(logrus.Fields{
+						"client":   frontendConn.RemoteAddr(),
+						"ping_val": pingVal,
+					}).Debug("Predefined status: received ping after status")
+				}
+			}
+		} else if err2 != nil {
+			logrus.WithFields(logrus.Fields{
+				"client": frontendConn.RemoteAddr(),
+				"error":  err2,
+			}).Debug("Predefined status: error/timeout reading ping after status")
+		}
+	}
+	if pingPending {
+		if err := mcproto.WritePongPacket(frontendConn, pingVal); err != nil {
+			logrus.WithFields(logrus.Fields{
+				"client": frontendConn.RemoteAddr(),
+				"error":  err,
+			}).Warn("Predefined status: failed to write pong")
+		} else {
+			logrus.WithFields(logrus.Fields{
+				"client":   frontendConn.RemoteAddr(),
+				"ping_val": pingVal,
+			}).Debug("Predefined status: wrote pong")
+		}
+	} else {
+		logrus.WithFields(logrus.Fields{
+			"client": frontendConn.RemoteAddr(),
+		}).Debug("Predefined status: no ping received, closing")
+	}
+}
+
+// serveLegacyStatus writes a simple legacy SLP response and closes the connection
+func (c *Connector) serveLegacyStatus(frontendConn net.Conn) {
+	motd := c.asleepMOTD
+	if motd == "" {
+		return
+	}
+	_ = frontendConn.SetWriteDeadline(time.Now().Add(handshakeTimeout))
+	// 127 protocol for legacy response per spec; version name and motd from predefined JSON if available
+	// write a basic response: protocol=127, version="1.7+", motd, online=0, max=1
+	if err := mcproto.WriteLegacySLPResponse(frontendConn, 127, "1.7+", motd, 0, 1); err != nil {
+		logrus.WithError(err).Warn("Failed to write legacy SLP response")
+	}
+}
+
 func (c *Connector) readPlayerInfo(protocolVersion mcproto.ProtocolVersion, bufferedReader *bufio.Reader, clientAddr net.Addr, state mcproto.State) (*PlayerInfo, error) {
 	loginPacket, err := mcproto.ReadPacket(bufferedReader, clientAddr, state)
 	if err != nil {
@@ -375,10 +480,10 @@ func (c *Connector) cleanupBackendConnection(clientAddr net.Addr, serverAddress
 		c.metrics.ActiveConnections.Set(float64(
 			atomic.AddInt32(&c.totalActiveConnections, -1)))
 
-		c.activeConnections.Decrement(serverAddress)
+		c.activeConnections.Decrement(backendHostPort)
 		c.metrics.ServerActiveConnections.
 			With("server_address", serverAddress).
-			Set(float64(c.activeConnections.GetCount(serverAddress)))
+			Set(float64(c.activeConnections.GetCount(backendHostPort)))
 
 		if c.recordLogins && playerInfo != nil {
 			c.metrics.ServerActivePlayer.
@@ -388,14 +493,19 @@ func (c *Connector) cleanupBackendConnection(clientAddr net.Addr, serverAddress
 				Set(0)
 		}
 	}
-	if checkScaleDown && c.activeConnections.GetCount(serverAddress) <= 0 {
+	logrus.
-		DownScaler.Begin(serverAddress)
+		WithField("client", clientAddr).
+		WithField("backendHostPort", backendHostPort).
+		WithField("connectionCount", c.activeConnections.GetCount(backendHostPort)).
+		Info("Closed connection to backend")
+	if checkScaleDown && c.activeConnections.GetCount(backendHostPort) <= 0 {
+		DownScaler.Begin(backendHostPort)
 	}
 	c.connectionsCond.Signal()
 }
 
 func (c *Connector) findAndConnectBackend(frontendConn net.Conn,
-	clientAddr net.Addr, preReadContent io.Reader, serverAddress string, playerInfo *PlayerInfo, nextState mcproto.State) {
+	clientAddr net.Addr, preReadContent io.Reader, serverAddress string, playerInfo *PlayerInfo, nextState mcproto.State, isLegacy bool, clientProtocol int) {
 
 	backendHostPort, resolvedHost, waker, _ := Routes.FindBackendForServerAddress(c.ctx, serverAddress)
 	cleanupMetrics := false
@@ -415,13 +525,29 @@ func (c *Connector) findAndConnectBackend(frontendConn net.Conn,
 			Debug("checked if player is allowed to wake up the server")
 		if serverAllowsPlayer {
 			// Cancel down scaler if active before scale up
-			DownScaler.Cancel(serverAddress)
+			if backendHostPort != "" {
+				DownScaler.Cancel(backendHostPort)
+			}
 			cleanupCheckScaleDown = true
-			if err := waker(c.ctx); err != nil {
+			logrus.WithField("serverAddress", serverAddress).Info("Waking up backend server")
+			newBackendHostPort, err := waker(c.ctx)
+			if err != nil {
 				logrus.WithFields(logrus.Fields{"serverAddress": serverAddress}).WithError(err).Error("failed to wake up backend")
 				c.metrics.Errors.With("type", "wakeup_failed").Add(1)
 				return
 			}
+			if newBackendHostPort == "" {
+				logrus.WithFields(logrus.Fields{"serverAddress": serverAddress}).Warn("waker did not return a backend address")
+				c.metrics.Errors.With("type", "wakeup_no_address").Add(1)
+				return
+			}
+			// Cancel again in case any routes were changed during wake up
+			DownScaler.Cancel(newBackendHostPort)
+			backendHostPort = newBackendHostPort
+			logrus.WithFields(logrus.Fields{
+				"serverAddress":   serverAddress,
+				"backendHostPort": backendHostPort,
+			}).Info("Woke up backend server")
 		}
 	}
 
@@ -440,6 +566,22 @@ func (c *Connector) findAndConnectBackend(frontendConn net.Conn,
 			}
 		}
 
+		// If status request and configured, serve predefined response
+		if nextState == mcproto.StateStatus && Routes.HasRoute(serverAddress) {
+			logrus.WithFields(logrus.Fields{
+				"client":   clientAddr,
+				"server":   serverAddress,
+				"isLegacy": isLegacy,
+			}).Debug("Missing backend: serving predefined status response")
+
+			// Read Status Request and Ping directly from the client connection
+			br := bufio.NewReader(frontendConn)
+			if isLegacy {
+				c.serveLegacyStatus(frontendConn)
+			} else {
+				c.serveStatus(frontendConn, br, serverAddress, clientProtocol)
+			}
+		}
 		return
 	}
 
@@ -483,10 +625,10 @@ func (c *Connector) findAndConnectBackend(frontendConn net.Conn,
 	c.metrics.ActiveConnections.Set(float64(
 		atomic.AddInt32(&c.totalActiveConnections, 1)))
 
-	c.activeConnections.Increment(serverAddress)
+	c.activeConnections.Increment(backendHostPort)
 	c.metrics.ServerActiveConnections.
 		With("server_address", serverAddress).
-		Set(float64(c.activeConnections.GetCount(serverAddress)))
+		Set(float64(c.activeConnections.GetCount(backendHostPort)))
 
 	if c.recordLogins && playerInfo != nil {
 		logrus.
@@ -624,3 +766,24 @@ func (c *Connector) UseReceiveProxyProto(trustedProxyNets []*net.IPNet) {
 	c.trustedProxyNets = trustedProxyNets
 	c.receiveProxyProto = true
 }
+
+// UseAsleepMOTD configures a predefined MOTD to serve when backends are asleep
+func (c *Connector) UseAsleepMOTD(motd string) {
+	c.asleepMOTD = motd
+}
+
+// getVersionInfo falls back to client protocol and a derived name but in future
+// could be extended to cache server-reported versions
+func (c *Connector) getVersionInfo(_ string, clientProtocol int) (string, int) {
+	// no cache; use client protocol
+	return protocolToName(clientProtocol), clientProtocol
+}
+
+// protocolToName maps protocol numbers to a friendly name; falls back to "1.7+"
+func protocolToName(proto int) string {
+	switch proto {
+	// TODO: expand this mapping as needed
+	default:
+		return "1.7+"
+	}
+}

server/docker.go

@@ -3,12 +3,12 @@ package server
 import (
 	"context"
 	"fmt"
+	"net"
 	"strconv"
 	"strings"
 	"sync"
 	"time"
 
-	dockertypes "github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/container"
 	"github.com/docker/docker/client"
 	"github.com/sirupsen/logrus"
@@ -19,10 +19,13 @@ type IDockerWatcher interface {
 }
 
 const (
-	DockerRouterLabelHost    = "mc-router.host"
+	DockerRouterLabelHost                = "mc-router.host"
-	DockerRouterLabelPort    = "mc-router.port"
+	DockerRouterLabelPort                = "mc-router.port"
-	DockerRouterLabelDefault = "mc-router.default"
+	DockerRouterLabelDefault             = "mc-router.default"
-	DockerRouterLabelNetwork = "mc-router.network"
+	DockerRouterLabelNetwork             = "mc-router.network"
+	DockerRouterLabelAutoScaleUp         = "mc-router.auto-scale-up"
+	DockerRouterLabelAutoScaleDown       = "mc-router.auto-scale-down"
+	DockerRouterLabelAutoScaleAsleepMOTD = "mc-router.auto-scale-asleep-motd"
 )
 
 type dockerWatcherConfig struct {
@@ -63,22 +66,94 @@ type dockerWatcherImpl struct {
 	client *client.Client
 }
 
-func (w *dockerWatcherImpl) makeWakerFunc(_ *routableContainer) ScalerFunc {
+func (w *dockerWatcherImpl) makeWakerFunc(rc *routableContainer) WakerFunc {
-	if !w.config.autoScaleUp {
+	if rc == nil || !rc.autoScaleUp {
 		return nil
 	}
-	return func(ctx context.Context) error {
+	return func(ctx context.Context) (string, error) {
-		logrus.Fatal("Auto scale up is not yet supported for docker")
+		containerID := rc.containerID
-		return nil
+		if containerID == "" {
+			return "", fmt.Errorf("missing container id for wake")
+		}
+		inspect, err := w.client.ContainerInspect(ctx, containerID)
+		if err != nil {
+			return "", err
+		}
+		if inspect.State == nil {
+			return "", fmt.Errorf("unable to determine container state")
+		}
+		// If paused, unpause; if not running, start; otherwise no-op
+		if inspect.State.Paused {
+			logrus.WithFields(logrus.Fields{"containerID": containerID}).Debug("Unpausing container for wake")
+			if err := w.client.ContainerUnpause(ctx, containerID); err != nil {
+				return "", err
+			}
+		} else if !inspect.State.Running {
+			logrus.WithFields(logrus.Fields{"containerID": containerID}).Debug("Starting container for wake")
+			if err := w.client.ContainerStart(ctx, containerID, container.StartOptions{}); err != nil {
+				return "", err
+			}
+		}
+
+		inspect, err = w.client.ContainerInspect(ctx, containerID)
+		if err != nil {
+			return "", err
+		}
+		data, ok := w.parseContainerData(&inspect)
+		if !ok {
+			return "", fmt.Errorf("failed to parse container data after starting")
+		}
+		if data.ip == "" {
+			return "", fmt.Errorf("container has no accessible IP after starting")
+		}
+		endpoint := net.JoinHostPort(data.ip, strconv.Itoa(int(data.port)))
+
+		// Wait until the container is reachable
+		deadline := time.Now().Add(60 * time.Second)
+		for {
+			conn, err := net.DialTimeout("tcp", endpoint, 1*time.Second)
+			if err == nil {
+				_ = conn.Close()
+				break
+			}
+			if ctx.Err() != nil {
+				return endpoint, ctx.Err()
+			}
+			if time.Now().After(deadline) {
+				return endpoint, fmt.Errorf("timeout waiting for container to become reachable at %s", endpoint)
+			}
+			select {
+			case <-ctx.Done():
+				return endpoint, ctx.Err()
+			case <-time.After(500 * time.Millisecond):
+			}
+		}
+
+		return endpoint, nil
 	}
 }
 
-func (w *dockerWatcherImpl) makeSleeperFunc(_ *routableContainer) ScalerFunc {
+func (w *dockerWatcherImpl) makeSleeperFunc(rc *routableContainer) SleeperFunc {
-	if !w.config.autoScaleDown {
+	if rc == nil || !rc.autoScaleDown {
 		return nil
 	}
 	return func(ctx context.Context) error {
-		logrus.Fatal("Auto scale down is not yet supported for docker")
+		containerID := rc.containerID
+		if containerID == "" {
+			return fmt.Errorf("missing container id for sleep")
+		}
+		inspect, err := w.client.ContainerInspect(ctx, containerID)
+		if err != nil {
+			return err
+		}
+		if inspect.State != nil && inspect.State.Running {
+			// Graceful stop with 60s timeout
+			timeout := 60
+			logrus.WithFields(logrus.Fields{"containerID": containerID}).Debug("Stopping container for sleep")
+			if err := w.client.ContainerStop(ctx, containerID, container.StopOptions{Timeout: &timeout}); err != nil {
+				return err
+			}
+		}
 		return nil
 	}
 }
@@ -104,7 +179,6 @@ func (w *dockerWatcherImpl) Start(ctx context.Context) error {
 	}
 
 	ticker := time.NewTicker(refreshInterval)
-	containerMap := map[string]*routableContainer{}
 
 	logrus.Trace("Performing initial listing of Docker containers")
 	initialContainers, err := w.listContainers(ctx)
@@ -112,12 +186,15 @@ func (w *dockerWatcherImpl) Start(ctx context.Context) error {
 		return err
 	}
 
+	containerMap := map[string]*routableContainer{}
 	for _, c := range initialContainers {
 		containerMap[c.externalContainerName] = c
+		wakerFunc := w.makeWakerFunc(c)
+		sleeperFunc := w.makeSleeperFunc(c)
 		if c.externalContainerName != "" {
-			Routes.CreateMapping(c.externalContainerName, c.containerEndpoint, w.makeWakerFunc(c), w.makeSleeperFunc(c))
+			Routes.CreateMapping(c.externalContainerName, c.containerEndpoint, wakerFunc, sleeperFunc, c.autoScaleAsleepMOTD)
 		} else {
-			Routes.SetDefaultRoute(c.containerEndpoint)
+			Routes.SetDefaultRoute(c.containerEndpoint, wakerFunc, sleeperFunc, c.autoScaleAsleepMOTD)
 		}
 	}
 
@@ -137,18 +214,26 @@ func (w *dockerWatcherImpl) Start(ctx context.Context) error {
 					if oldRs, ok := containerMap[rs.externalContainerName]; !ok {
 						containerMap[rs.externalContainerName] = rs
 						logrus.WithField("routableContainer", rs).Debug("ADD")
+						wakerFunc := w.makeWakerFunc(rs)
+						sleeperFunc := w.makeSleeperFunc(rs)
 						if rs.externalContainerName != "" {
-							Routes.CreateMapping(rs.externalContainerName, rs.containerEndpoint, w.makeWakerFunc(rs), w.makeSleeperFunc(rs))
+							Routes.CreateMapping(rs.externalContainerName, rs.containerEndpoint, wakerFunc, sleeperFunc, rs.autoScaleAsleepMOTD)
 						} else {
-							Routes.SetDefaultRoute(rs.containerEndpoint)
+							Routes.SetDefaultRoute(rs.containerEndpoint, wakerFunc, sleeperFunc, rs.autoScaleAsleepMOTD)
 						}
-					} else if oldRs.containerEndpoint != rs.containerEndpoint {
+					} else if oldRs.containerEndpoint != rs.containerEndpoint ||
+						oldRs.containerID != rs.containerID ||
+						oldRs.autoScaleUp != rs.autoScaleUp ||
+						oldRs.autoScaleDown != rs.autoScaleDown ||
+						oldRs.autoScaleAsleepMOTD != rs.autoScaleAsleepMOTD {
 						containerMap[rs.externalContainerName] = rs
+						wakerFunc := w.makeWakerFunc(rs)
+						sleeperFunc := w.makeSleeperFunc(rs)
 						if rs.externalContainerName != "" {
 							Routes.DeleteMapping(rs.externalContainerName)
-							Routes.CreateMapping(rs.externalContainerName, rs.containerEndpoint, w.makeWakerFunc(rs), w.makeSleeperFunc(rs))
+							Routes.CreateMapping(rs.externalContainerName, rs.containerEndpoint, wakerFunc, sleeperFunc, rs.autoScaleAsleepMOTD)
 						} else {
-							Routes.SetDefaultRoute(rs.containerEndpoint)
+							Routes.SetDefaultRoute(rs.containerEndpoint, wakerFunc, sleeperFunc, rs.autoScaleAsleepMOTD)
 						}
 						logrus.WithFields(logrus.Fields{"old": oldRs, "new": rs}).Debug("UPDATE")
 					}
@@ -160,7 +245,7 @@ func (w *dockerWatcherImpl) Start(ctx context.Context) error {
 						if rs.externalContainerName != "" {
 							Routes.DeleteMapping(rs.externalContainerName)
 						} else {
-							Routes.SetDefaultRoute("")
+							Routes.SetDefaultRoute("", nil, nil, "")
 						}
 						logrus.WithField("routableContainer", rs).Debug("DELETE")
 					}
@@ -179,28 +264,46 @@ func (w *dockerWatcherImpl) Start(ctx context.Context) error {
 }
 
 func (w *dockerWatcherImpl) listContainers(ctx context.Context) ([]*routableContainer, error) {
-	containers, err := w.client.ContainerList(ctx, container.ListOptions{})
+	containers, err := w.client.ContainerList(ctx, container.ListOptions{All: true})
 	if err != nil {
 		return nil, err
 	}
 
 	var result []*routableContainer
 	for _, container := range containers {
-		data, ok := w.parseContainerData(&container)
+		inspect, err := w.client.ContainerInspect(ctx, container.ID)
+		if err != nil {
+			logrus.WithFields(logrus.Fields{"containerID": container.ID}).WithError(err).Error("Failed to inspect Docker container")
+			continue
+		}
+		data, ok := w.parseContainerData(&inspect)
 		if !ok {
 			continue
 		}
 
+		endpoint := ""
+		if !data.notRunning {
+			endpoint = fmt.Sprintf("%s:%d", data.ip, data.port)
+		}
+
 		for _, host := range data.hosts {
 			result = append(result, &routableContainer{
-				containerEndpoint:     fmt.Sprintf("%s:%d", data.ip, data.port),
+				containerEndpoint:     endpoint,
 				externalContainerName: host,
+				containerID:           container.ID,
+				autoScaleUp:           data.autoScaleUp,
+				autoScaleDown:         data.autoScaleDown,
+				autoScaleAsleepMOTD:   data.autoScaleAsleepMOTD,
 			})
 		}
 		if data.def != nil && *data.def {
 			result = append(result, &routableContainer{
-				containerEndpoint:     fmt.Sprintf("%s:%d", data.ip, data.port),
+				containerEndpoint:     endpoint,
 				externalContainerName: "",
+				containerID:           container.ID,
+				autoScaleUp:           data.autoScaleUp,
+				autoScaleDown:         data.autoScaleDown,
+				autoScaleAsleepMOTD:   data.autoScaleAsleepMOTD,
 			})
 		}
 	}
@@ -209,18 +312,24 @@ func (w *dockerWatcherImpl) listContainers(ctx context.Context) ([]*routableCont
 }
 
 type parsedDockerContainerData struct {
-	hosts   []string
+	hosts               []string
-	port    uint64
+	port                uint64
-	def     *bool
+	def                 *bool
-	network *string
+	network             *string
-	ip      string
+	ip                  string
+	autoScaleDown       bool
+	autoScaleUp         bool
+	autoScaleAsleepMOTD string
+	notRunning          bool
 }
 
-func (w *dockerWatcherImpl) parseContainerData(container *dockertypes.Container) (data parsedDockerContainerData, ok bool) {
+func (w *dockerWatcherImpl) parseContainerData(container *container.InspectResponse) (data parsedDockerContainerData, ok bool) {
-	for key, value := range container.Labels {
+	data.autoScaleUp = w.config.autoScaleUp
+	data.autoScaleDown = w.config.autoScaleDown
+	for key, value := range container.Config.Labels {
 		if key == DockerRouterLabelHost {
 			if data.hosts != nil {
-				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Names}).
+				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
 					Warnf("ignoring container with duplicate %s label", DockerRouterLabelHost)
 				return
 			}
@@ -229,14 +338,14 @@ func (w *dockerWatcherImpl) parseContainerData(container *dockertypes.Container)
 
 		if key == DockerRouterLabelPort {
 			if data.port != 0 {
-				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Names}).
+				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
 					Warnf("ignoring container with duplicate %s label", DockerRouterLabelPort)
 				return
 			}
 			var err error
 			data.port, err = strconv.ParseUint(value, 10, 32)
 			if err != nil {
-				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Names}).
+				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
 					WithError(err).
 					Warnf("ignoring container with invalid %s label", DockerRouterLabelPort)
 				return
@@ -244,24 +353,51 @@ func (w *dockerWatcherImpl) parseContainerData(container *dockertypes.Container)
 		}
 		if key == DockerRouterLabelDefault {
 			if data.def != nil {
-				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Names}).
+				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
 					Warnf("ignoring container with duplicate %s label", DockerRouterLabelDefault)
 				return
 			}
-			data.def = new(bool)
+			defaultValue, err := strconv.ParseBool(strings.TrimSpace(value))
-
+			if err != nil {
-			lowerValue := strings.TrimSpace(strings.ToLower(value))
+				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
-			*data.def = lowerValue != "" && lowerValue != "0" && lowerValue != "false" && lowerValue != "no"
+					WithError(err).
+					Warnf("ignoring container with invalid value for %s label", DockerRouterLabelDefault)
+				return
+			}
+			data.def = &defaultValue
 		}
 		if key == DockerRouterLabelNetwork {
 			if data.network != nil {
-				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Names}).
+				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
 					Warnf("ignoring container with duplicate %s label", DockerRouterLabelNetwork)
 				return
 			}
 			data.network = new(string)
 			*data.network = value
 		}
+		if key == DockerRouterLabelAutoScaleUp {
+			autoScaleUp, err := strconv.ParseBool(strings.TrimSpace(value))
+			if err != nil {
+				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
+					WithError(err).
+					Warnf("ignoring container with invalid value for %s label", DockerRouterLabelAutoScaleUp)
+				return
+			}
+			data.autoScaleUp = autoScaleUp
+		}
+		if key == DockerRouterLabelAutoScaleDown {
+			autoScaleDown, err := strconv.ParseBool(strings.TrimSpace(value))
+			if err != nil {
+				logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
+					WithError(err).
+					Warnf("ignoring container with invalid value for %s label", DockerRouterLabelAutoScaleDown)
+				return
+			}
+			data.autoScaleDown = autoScaleDown
+		}
+		if key == DockerRouterLabelAutoScaleAsleepMOTD {
+			data.autoScaleAsleepMOTD = value
+		}
 	}
 
 	// probably not minecraft related
@@ -270,7 +406,7 @@ func (w *dockerWatcherImpl) parseContainerData(container *dockertypes.Container)
 	}
 
 	if len(container.NetworkSettings.Networks) == 0 {
-		logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Names}).
+		logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
 			Warnf("ignoring container, no networks found")
 		return
 	}
@@ -304,7 +440,7 @@ func (w *dockerWatcherImpl) parseContainerData(container *dockertypes.Container)
 		// if there's more than one network on this container, we should require that the user specifies a network to avoid
 		// weird problems.
 		if len(container.NetworkSettings.Networks) > 1 {
-			logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Names}).
+			logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
 				Warnf("ignoring container, multiple networks found and none specified using label %s", DockerRouterLabelNetwork)
 			return
 		}
@@ -315,12 +451,21 @@ func (w *dockerWatcherImpl) parseContainerData(container *dockertypes.Container)
 		}
 	}
 
-	if data.ip == "" {
+	if data.ip == "" && container.State != nil && container.State.Running {
-		logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Names}).
+		logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
 			Warnf("ignoring container, unable to find accessible ip address")
 		return
 	}
 
+	if container.State != nil && !container.State.Running {
+		if !w.config.autoScaleUp {
+			logrus.WithFields(logrus.Fields{"containerId": container.ID, "containerNames": container.Name}).
+				Warnf("ignoring container, not running and auto scale up is disabled")
+			return
+		}
+		data.notRunning = true
+	}
+
 	ok = true
 
 	return
@@ -329,4 +474,8 @@ func (w *dockerWatcherImpl) parseContainerData(container *dockertypes.Container)
 type routableContainer struct {
 	externalContainerName string
 	containerEndpoint     string
+	containerID           string
+	autoScaleUp           bool
+	autoScaleDown         bool
+	autoScaleAsleepMOTD   string
 }

server/docker_swarm.go

@@ -38,17 +38,17 @@ type dockerSwarmWatcherImpl struct {
 	client *client.Client
 }
 
-func (w *dockerSwarmWatcherImpl) makeWakerFunc(_ *routableService) ScalerFunc {
+func (w *dockerSwarmWatcherImpl) makeWakerFunc(_ *routableService) WakerFunc {
 	if !w.config.autoScaleUp {
 		return nil
 	}
-	return func(ctx context.Context) error {
+	return func(ctx context.Context) (string, error) {
 		logrus.Fatal("Auto scale up is not yet supported for docker swarm")
-		return nil
+		return "", nil
 	}
 }
 
-func (w *dockerSwarmWatcherImpl) makeSleeperFunc(_ *routableService) ScalerFunc {
+func (w *dockerSwarmWatcherImpl) makeSleeperFunc(_ *routableService) SleeperFunc {
 	if !w.config.autoScaleDown {
 		return nil
 	}
@@ -89,10 +89,12 @@ func (w *dockerSwarmWatcherImpl) Start(ctx context.Context) error {
 
 	for _, s := range initialServices {
 		serviceMap[s.externalServiceName] = s
+		wakerFunc := w.makeWakerFunc(s)
+		sleeperFunc := w.makeSleeperFunc(s)
 		if s.externalServiceName != "" {
-			Routes.CreateMapping(s.externalServiceName, s.containerEndpoint, w.makeWakerFunc(s), w.makeSleeperFunc(s))
+			Routes.CreateMapping(s.externalServiceName, s.containerEndpoint, wakerFunc, sleeperFunc, "")
 		} else {
-			Routes.SetDefaultRoute(s.containerEndpoint)
+			Routes.SetDefaultRoute(s.containerEndpoint, wakerFunc, sleeperFunc, "")
 		}
 	}
 
@@ -111,18 +113,22 @@ func (w *dockerSwarmWatcherImpl) Start(ctx context.Context) error {
 					if oldRs, ok := serviceMap[rs.externalServiceName]; !ok {
 						serviceMap[rs.externalServiceName] = rs
 						logrus.WithField("routableService", rs).Debug("ADD")
+						wakerFunc := w.makeWakerFunc(rs)
+						sleeperFunc := w.makeSleeperFunc(rs)
 						if rs.externalServiceName != "" {
-							Routes.CreateMapping(rs.externalServiceName, rs.containerEndpoint, w.makeWakerFunc(rs), w.makeSleeperFunc(rs))
+							Routes.CreateMapping(rs.externalServiceName, rs.containerEndpoint, wakerFunc, sleeperFunc, "")
 						} else {
-							Routes.SetDefaultRoute(rs.containerEndpoint)
+							Routes.SetDefaultRoute(rs.containerEndpoint, wakerFunc, sleeperFunc, "")
 						}
 					} else if oldRs.containerEndpoint != rs.containerEndpoint {
 						serviceMap[rs.externalServiceName] = rs
+						wakerFunc := w.makeWakerFunc(rs)
+						sleeperFunc := w.makeSleeperFunc(rs)
 						if rs.externalServiceName != "" {
 							Routes.DeleteMapping(rs.externalServiceName)
-							Routes.CreateMapping(rs.externalServiceName, rs.containerEndpoint, w.makeWakerFunc(rs), w.makeSleeperFunc(rs))
+							Routes.CreateMapping(rs.externalServiceName, rs.containerEndpoint, wakerFunc, sleeperFunc, "")
 						} else {
-							Routes.SetDefaultRoute(rs.containerEndpoint)
+							Routes.SetDefaultRoute(rs.containerEndpoint, wakerFunc, sleeperFunc, "")
 						}
 						logrus.WithFields(logrus.Fields{"old": oldRs, "new": rs}).Debug("UPDATE")
 					}
@@ -134,7 +140,7 @@ func (w *dockerSwarmWatcherImpl) Start(ctx context.Context) error {
 						if rs.externalServiceName != "" {
 							Routes.DeleteMapping(rs.externalServiceName)
 						} else {
-							Routes.SetDefaultRoute("")
+							Routes.SetDefaultRoute("", nil, nil, "")
 						}
 						logrus.WithField("routableService", rs).Debug("DELETE")
 					}

server/down_scaler.go

@@ -10,17 +10,17 @@ import (
 
 type IDownScaler interface {
 	Reset()
-	Begin(serverAddress string)
+	Begin(backendEndpoint string)
-	Cancel(serverAddress string)
+	Cancel(backendEndpoint string)
 }
 
 var DownScaler IDownScaler
 
 func NewDownScaler(ctx context.Context, enabled bool, delay time.Duration) IDownScaler {
 	ds := &downScalerImpl{
-		enabled: enabled,
+		enabled:              enabled,
-		delay: delay,
+		delay:                delay,
-		parentContext: ctx,
+		parentContext:        ctx,
 		contextCancellations: make(map[string]context.CancelFunc),
 	}
 
@@ -43,7 +43,7 @@ func (ds *downScalerImpl) Reset() {
 	ds.contextCancellations = make(map[string]context.CancelFunc)
 }
 
-func (ds *downScalerImpl) Begin(serverAddress string) {
+func (ds *downScalerImpl) Begin(backendEndpoint string) {
 	ds.Lock()
 	defer ds.Unlock()
 
@@ -52,17 +52,17 @@ func (ds *downScalerImpl) Begin(serverAddress string) {
 	}
 
 	// If an existing scale down routine exists, cancel it
-	if scaleDownCancel, ok := ds.contextCancellations[serverAddress]; ok {
+	if scaleDownCancel, ok := ds.contextCancellations[backendEndpoint]; ok {
 		scaleDownCancel()
 	}
-	
+
-	logrus.WithField("serverAddress", serverAddress).Debug("Beginning scale down")
+	logrus.WithField("backendEndpoint", backendEndpoint).Debug("Beginning scale down")
 	scaleDownContext, scaleDownContextCancellation := context.WithCancel(ds.parentContext)
-	ds.contextCancellations[serverAddress] = scaleDownContextCancellation
+	ds.contextCancellations[backendEndpoint] = scaleDownContextCancellation
-	go ds.scaleDown(scaleDownContext, serverAddress)
+	go ds.scaleDown(scaleDownContext, backendEndpoint)
 }
 
-func (ds *downScalerImpl) Cancel(serverAddress string) {
+func (ds *downScalerImpl) Cancel(backendEndpoint string) {
 	ds.Lock()
 	defer ds.Unlock()
 
@@ -70,27 +70,34 @@ func (ds *downScalerImpl) Cancel(serverAddress string) {
 		return
 	}
 
-	if scaleDownContextCancellation, ok := ds.contextCancellations[serverAddress]; ok {
+	if scaleDownContextCancellation, ok := ds.contextCancellations[backendEndpoint]; ok {
-		logrus.WithField("serverAddress", serverAddress).Debug("Canceling scale down")
+		logrus.WithField("backendEndpoint", backendEndpoint).Debug("Canceling scale down")
 		scaleDownContextCancellation()
-		delete(ds.contextCancellations, serverAddress)
+		delete(ds.contextCancellations, backendEndpoint)
 	}
 }
 
-func (ds *downScalerImpl) scaleDown(ctx context.Context, serverAddress string) {
+func (ds *downScalerImpl) scaleDown(ctx context.Context, backendEndpoint string) {
 	for {
 		select {
-			case <-ctx.Done():
+		case <-ctx.Done():
-				return
+			return
-			case <-time.After(ds.delay):
+		case <-time.After(ds.delay):
-				_, _, _, sleeper := Routes.FindBackendForServerAddress(ctx, serverAddress)
+			sleepers := Routes.GetSleepers(backendEndpoint)
-				if sleeper == nil {
+			if len(sleepers) == 0 {
-					return
-				}
-				if err := sleeper(ctx); err != nil {
-					logrus.WithField("serverAddress", serverAddress).WithError(err).Error("failed to scale down backend")
-				}
 				return
+			}
+			for _, sleeper := range sleepers {
+				go func(s SleeperFunc) {
+					err := s(ctx)
+					if err != nil {
+						logrus.WithError(err).
+							WithField("backendEndpoint", backendEndpoint).
+							Error("Error while executing sleeper function")
+					}
+				}(sleeper)
+			}
+			return
 		}
 	}
 }

server/k8s.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net"
 	"strconv"
+	"strings"
 	"sync"
 
 	"github.com/pkg/errors"
@@ -183,9 +184,9 @@ func (w *K8sWatcher) handleUpdate(oldObj interface{}, newObj interface{}) {
 			"new": newRoutableService,
 		}).Debug("UPDATE")
 		if newRoutableService.externalServiceName != "" {
-			w.routesHandler.CreateMapping(newRoutableService.externalServiceName, newRoutableService.containerEndpoint, newRoutableService.autoScaleUp, newRoutableService.autoScaleDown)
+			w.routesHandler.CreateMapping(newRoutableService.externalServiceName, newRoutableService.containerEndpoint, newRoutableService.autoScaleUp, newRoutableService.autoScaleDown, "")
 		} else {
-			w.routesHandler.SetDefaultRoute(newRoutableService.containerEndpoint)
+			w.routesHandler.SetDefaultRoute(newRoutableService.containerEndpoint, newRoutableService.autoScaleUp, newRoutableService.autoScaleDown, "")
 		}
 	}
 }
@@ -200,7 +201,7 @@ func (w *K8sWatcher) handleDelete(obj interface{}) {
 			if routableService.externalServiceName != "" {
 				w.routesHandler.DeleteMapping(routableService.externalServiceName)
 			} else {
-				w.routesHandler.SetDefaultRoute("")
+				w.routesHandler.SetDefaultRoute("", nil, nil, "")
 			}
 		}
 	}
@@ -214,9 +215,9 @@ func (w *K8sWatcher) handleAdd(obj interface{}) {
 			logrus.WithField("routableService", routableService).Debug("ADD")
 
 			if routableService.externalServiceName != "" {
-				w.routesHandler.CreateMapping(routableService.externalServiceName, routableService.containerEndpoint, routableService.autoScaleUp, routableService.autoScaleDown)
+				w.routesHandler.CreateMapping(routableService.externalServiceName, routableService.containerEndpoint, routableService.autoScaleUp, routableService.autoScaleDown, "")
 			} else {
-				w.routesHandler.SetDefaultRoute(routableService.containerEndpoint)
+				w.routesHandler.SetDefaultRoute(routableService.containerEndpoint, routableService.autoScaleUp, routableService.autoScaleDown, "")
 			}
 		}
 	}
@@ -225,8 +226,8 @@ func (w *K8sWatcher) handleAdd(obj interface{}) {
 type routableService struct {
 	externalServiceName string
 	containerEndpoint   string
-	autoScaleUp         ScalerFunc
+	autoScaleUp         WakerFunc
-	autoScaleDown       ScalerFunc
+	autoScaleDown       SleeperFunc
 }
 
 // obj is expected to be a *v1.Service
@@ -271,22 +272,37 @@ func (w *K8sWatcher) buildDetails(service *core.Service, externalServiceName str
 	} else if len(mcPort) > 0 {
 		port = mcPort
 	}
+	endpoint := net.JoinHostPort(clusterIp, port)
+	wakerFunc := w.buildScaleFunction(service, 0, 1)
 	rs := &routableService{
 		externalServiceName: externalServiceName,
-		containerEndpoint:   net.JoinHostPort(clusterIp, port),
+		containerEndpoint:   endpoint,
-		autoScaleUp:         w.buildScaleFunction(service, 0, 1),
+		autoScaleUp: func(ctx context.Context) (string, error) {
-		autoScaleDown:       w.buildScaleFunction(service, 1, 0),
+			if err := wakerFunc(ctx); err != nil {
+				return "", err
+			}
+			return endpoint, nil
+		},
+		autoScaleDown: w.buildScaleFunction(service, 1, 0),
 	}
 	return rs
 }
 
-func (w *K8sWatcher) buildScaleFunction(service *core.Service, from int32, to int32) ScalerFunc {
+func (w *K8sWatcher) buildScaleFunction(service *core.Service, from int32, to int32) SleeperFunc {
 	// Currently, annotations can only be used to opt-out of auto-scaling.
-	// However, this logic is prepared also for opt-in, as it returns a `ScalerFunc` when flags are false but annotations are set to `enabled`.
+	// However, this logic is prepared also for opt-in, as it returns a `SleeperFunc` when flags are false but annotations are set to `enabled`.
 	if from <= to {
 		enabled, exists := service.Annotations[AnnotationAutoScaleUp]
 		if exists {
-			if enabled == "false" {
+			enabledBool, err := strconv.ParseBool(strings.TrimSpace(enabled))
+			if err != nil {
+				logrus.WithFields(logrus.Fields{"service": service.Name}).
+					WithError(err).
+					Warnf("invalid value for %s annotation - disabling service auto-scale-up", AnnotationAutoScaleUp)
+				return nil
+			}
+
+			if !enabledBool {
 				return nil
 			}
 		} else {
@@ -298,7 +314,15 @@ func (w *K8sWatcher) buildScaleFunction(service *core.Service, from int32, to in
 	if from >= to {
 		enabled, exists := service.Annotations[AnnotationAutoScaleDown]
 		if exists {
-			if enabled == "false" {
+			enabledBool, err := strconv.ParseBool(strings.TrimSpace(enabled))
+			if err != nil {
+				logrus.WithFields(logrus.Fields{"service": service.Name}).
+					WithError(err).
+					Warnf("invalid value for %s annotation - disabling service auto-scale-down", AnnotationAutoScaleDown)
+				return nil
+			}
+
+			if !enabledBool {
 				return nil
 			}
 		} else {

server/k8s_test.go

@@ -3,10 +3,11 @@ package server
 import (
 	"context"
 	"encoding/json"
-	"github.com/stretchr/testify/mock"
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/mock"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	v1 "k8s.io/api/core/v1"
@@ -27,22 +28,27 @@ func (m *MockedRoutesHandler) GetBackendForServer(server string) string {
 	}
 }
 
-func (m *MockedRoutesHandler) CreateMapping(serverAddress string, backend string, waker ScalerFunc, sleeper ScalerFunc) {
+func (m *MockedRoutesHandler) CreateMapping(serverAddress string, backend string, waker WakerFunc, sleeper SleeperFunc, asleepMOTD string) {
-	m.MethodCalled("CreateMapping", serverAddress, backend, waker, sleeper)
+	m.MethodCalled("CreateMapping", serverAddress, backend, waker, sleeper, asleepMOTD)
 	if m.routes == nil {
 		m.routes = make(map[string]string)
 	}
 	m.routes[serverAddress] = backend
 }
 
-func (m *MockedRoutesHandler) SetDefaultRoute(backend string) {
+func (m *MockedRoutesHandler) SetDefaultRoute(backend string, waker WakerFunc, sleeper SleeperFunc, asleepMOTD string) {
-	m.MethodCalled("SetDefaultRoute", backend)
+	m.MethodCalled("SetDefaultRoute", backend, waker, sleeper, asleepMOTD)
 	if m.routes == nil {
 		m.routes = make(map[string]string)
 	}
 	m.defaultBackend = backend
 }
 
+func (m *MockedRoutesHandler) GetAsleepMOTD(serverAddress string) string {
+	args := m.MethodCalled("GetAsleepMOTD", serverAddress)
+	return args.String(0)
+}
+
 func (m *MockedRoutesHandler) DeleteMapping(serverAddress string) bool {
 	args := m.MethodCalled("DeleteMapping", serverAddress)
 	if m.routes == nil {
@@ -177,7 +183,9 @@ func TestK8sWatcherImpl_handleAddThenUpdate(t *testing.T) {
 			DownScaler = NewDownScaler(context.Background(), false, 1*time.Second)
 
 			routesHandler := new(MockedRoutesHandler)
-			routesHandler.On("CreateMapping", mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return()
+			routesHandler.On("CreateMapping", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return()
+			routesHandler.On("SetDefaultRoute", mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return()
+			routesHandler.On("GetAsleepMOTD", mock.Anything).Return("")
 			routesHandler.On("DeleteMapping", mock.Anything).Return(true)
 
 			watcher := &K8sWatcher{
@@ -256,7 +264,9 @@ func TestK8sWatcherImpl_handleAddThenDelete(t *testing.T) {
 			DownScaler = NewDownScaler(context.Background(), false, 1*time.Second)
 
 			routesHandler := new(MockedRoutesHandler)
-			routesHandler.On("CreateMapping", mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return()
+			routesHandler.On("CreateMapping", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return()
+			routesHandler.On("SetDefaultRoute", mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return()
+			routesHandler.On("GetAsleepMOTD", mock.Anything).Return("")
 			routesHandler.On("DeleteMapping", mock.Anything).Return(true)
 
 			watcher := &K8sWatcher{
@@ -353,7 +363,9 @@ func TestK8s_externalName(t *testing.T) {
 			DownScaler = NewDownScaler(context.Background(), false, 1*time.Second)
 
 			routesHandler := new(MockedRoutesHandler)
-			routesHandler.On("CreateMapping", mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return()
+			routesHandler.On("CreateMapping", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return()
+			routesHandler.On("SetDefaultRoute", mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return()
+			routesHandler.On("GetAsleepMOTD", mock.Anything).Return("")
 			routesHandler.On("DeleteMapping", mock.Anything).Return(true)
 
 			watcher := &K8sWatcher{

server/routes.go

@@ -9,9 +9,11 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
-type ScalerFunc func(ctx context.Context) error
+// WakerFunc is a function that wakes up a server and returns its address.
+type WakerFunc func(ctx context.Context) (string, error)
 
-var EmptyScalerFunc = func(ctx context.Context) error { return nil }
+// SleeperFunc is a function that puts a server to sleep.
+type SleeperFunc func(ctx context.Context) error
 
 var tcpShieldPattern = regexp.MustCompile("///.*")
 
@@ -22,8 +24,8 @@ type RouteFinder interface {
 }
 
 type RoutesHandler interface {
-	CreateMapping(serverAddress string, backend string, waker ScalerFunc, sleeper ScalerFunc)
+	CreateMapping(serverAddress string, backend string, waker WakerFunc, sleeper SleeperFunc, asleepMOTD string)
-	SetDefaultRoute(backend string)
+	SetDefaultRoute(backend string, waker WakerFunc, sleeper SleeperFunc, asleepMOTD string)
 	// DeleteMapping requests that the serverAddress be removed from routes.
 	// Returns true if the route existed.
 	DeleteMapping(serverAddress string) bool
@@ -38,9 +40,12 @@ type IRoutes interface {
 	// Otherwise, an empty string is returned. Also returns the normalized version of the given serverAddress.
 	// The 3rd value returned is an (optional) "waker" function which a caller must invoke to wake up serverAddress.
 	// The 4th value returned is an (optional) "sleeper" function which a caller must invoke to shut down serverAddress.
-	FindBackendForServerAddress(ctx context.Context, serverAddress string) (string, string, ScalerFunc, ScalerFunc)
+	HasRoute(serverAddress string) bool
+	FindBackendForServerAddress(ctx context.Context, serverAddress string) (string, string, WakerFunc, SleeperFunc)
+	GetSleepers(backend string) []SleeperFunc
 	GetMappings() map[string]string
-	GetDefaultRoute() string
+	GetDefaultRoute() (string, WakerFunc, SleeperFunc)
+	GetAsleepMOTD(serverAddress string) string
 	SimplifySRV(srvEnabled bool)
 }
 
@@ -56,20 +61,21 @@ func NewRoutes() IRoutes {
 
 func (r *routesImpl) RegisterAll(mappings map[string]string) {
 	for k, v := range mappings {
-		r.CreateMapping(k, v, EmptyScalerFunc, EmptyScalerFunc)
+		r.CreateMapping(k, v, nil, nil, "")
 	}
 }
 
 type mapping struct {
-	backend string
+	backend    string
-	waker   ScalerFunc
+	waker      WakerFunc
-	sleeper ScalerFunc
+	sleeper    SleeperFunc
+	asleepMOTD string
 }
 
 type routesImpl struct {
 	sync.RWMutex
 	mappings     map[string]mapping
-	defaultRoute string
+	defaultRoute mapping
 	simplifySRV  bool
 }
 
@@ -78,23 +84,45 @@ func (r *routesImpl) Reset() {
 	DownScaler.Reset()
 }
 
-func (r *routesImpl) SetDefaultRoute(backend string) {
+func (r *routesImpl) SetDefaultRoute(backend string, waker WakerFunc, sleeper SleeperFunc, asleepMOTD string) {
-	r.defaultRoute = backend
+	r.defaultRoute = mapping{backend: backend, waker: waker, sleeper: sleeper, asleepMOTD: asleepMOTD}
 
 	logrus.WithFields(logrus.Fields{
 		"backend": backend,
 	}).Info("Using default route")
 }
 
-func (r *routesImpl) GetDefaultRoute() string {
+func (r *routesImpl) GetDefaultRoute() (string, WakerFunc, SleeperFunc) {
-	return r.defaultRoute
+	return r.defaultRoute.backend, r.defaultRoute.waker, r.defaultRoute.sleeper
+}
+
+func (r *routesImpl) GetAsleepMOTD(serverAddress string) string {
+	r.RLock()
+	defer r.RUnlock()
+
+	if serverAddress == "" {
+		return r.defaultRoute.asleepMOTD
+	}
+
+	if m, ok := r.mappings[serverAddress]; ok {
+		return m.asleepMOTD
+	}
+	return ""
 }
 
 func (r *routesImpl) SimplifySRV(srvEnabled bool) {
 	r.simplifySRV = srvEnabled
 }
 
-func (r *routesImpl) FindBackendForServerAddress(_ context.Context, serverAddress string) (string, string, ScalerFunc, ScalerFunc) {
+func (r *routesImpl) HasRoute(serverAddress string) bool {
+	r.RLock()
+	defer r.RUnlock()
+
+	_, exists := r.mappings[serverAddress]
+	return exists
+}
+
+func (r *routesImpl) FindBackendForServerAddress(_ context.Context, serverAddress string) (string, string, WakerFunc, SleeperFunc) {
 	r.RLock()
 	defer r.RUnlock()
 
@@ -136,7 +164,23 @@ func (r *routesImpl) FindBackendForServerAddress(_ context.Context, serverAddres
 			return mapping.backend, serverAddress, mapping.waker, mapping.sleeper
 		}
 	}
-	return r.defaultRoute, serverAddress, nil, nil
+	return r.defaultRoute.backend, serverAddress, r.defaultRoute.waker, r.defaultRoute.sleeper
+}
+
+func (r *routesImpl) GetSleepers(backend string) []SleeperFunc {
+	r.RLock()
+	defer r.RUnlock()
+
+	var sleepers []SleeperFunc
+	for _, m := range r.mappings {
+		if m.backend == backend && m.sleeper != nil {
+			sleepers = append(sleepers, m.sleeper)
+		}
+	}
+	if r.defaultRoute.backend == backend && r.defaultRoute.sleeper != nil {
+		sleepers = append(sleepers, r.defaultRoute.sleeper)
+	}
+	return sleepers
 }
 
 func (r *routesImpl) GetMappings() map[string]string {
@@ -155,9 +199,8 @@ func (r *routesImpl) DeleteMapping(serverAddress string) bool {
 	defer r.Unlock()
 	logrus.WithField("serverAddress", serverAddress).Info("Deleting route")
 
-	DownScaler.Cancel(serverAddress)
+	if m, ok := r.mappings[serverAddress]; ok {
-
+		DownScaler.Cancel(m.backend)
-	if _, ok := r.mappings[serverAddress]; ok {
 		delete(r.mappings, serverAddress)
 		return true
 	} else {
@@ -165,7 +208,7 @@ func (r *routesImpl) DeleteMapping(serverAddress string) bool {
 	}
 }
 
-func (r *routesImpl) CreateMapping(serverAddress string, backend string, waker ScalerFunc, sleeper ScalerFunc) {
+func (r *routesImpl) CreateMapping(serverAddress string, backend string, waker WakerFunc, sleeper SleeperFunc, asleepMOTD string) {
 	r.Lock()
 	defer r.Unlock()
 
@@ -175,8 +218,10 @@ func (r *routesImpl) CreateMapping(serverAddress string, backend string, waker S
 		"serverAddress": serverAddress,
 		"backend":       backend,
 	}).Info("Created route mapping")
-	r.mappings[serverAddress] = mapping{backend: backend, waker: waker, sleeper: sleeper}
+	r.mappings[serverAddress] = mapping{backend: backend, waker: waker, sleeper: sleeper, asleepMOTD: asleepMOTD}
 
 	// Trigger auto scale down when mapping is created to ensure servers are shut down if router restarts
-	DownScaler.Begin(serverAddress)
+	if DownScaler != nil && backend != "" {
+		DownScaler.Begin(backend)
+	}
 }

server/routes_config_loader.go

@@ -44,7 +44,7 @@ func (r *routesConfigLoader) Load(routesConfigFileName string) error {
 	}
 
 	Routes.RegisterAll(config.Mappings)
-	Routes.SetDefaultRoute(config.DefaultServer)
+	Routes.SetDefaultRoute(config.DefaultServer, nil, nil, "")
 	return nil
 }
 
@@ -62,7 +62,7 @@ func (r *routesConfigLoader) Reload() error {
 	logrus.WithField("routesConfig", r.fileName).Info("Re-loading routes config file")
 	Routes.Reset()
 	Routes.RegisterAll(config.Mappings)
-	Routes.SetDefaultRoute(config.DefaultServer)
+	Routes.SetDefaultRoute(config.DefaultServer, nil, nil, "")
 
 	return nil
 }
@@ -135,8 +135,9 @@ func (r *routesConfigLoader) SaveRoutes() {
 		return
 	}
 
+	server, _, _ := Routes.GetDefaultRoute()
 	err := r.writeFile(&RoutesConfigSchema{
-		DefaultServer: Routes.GetDefaultRoute(),
+		DefaultServer: server,
 		Mappings:      Routes.GetMappings(),
 	})
 	if err != nil {

server/routes_test.go

@@ -66,7 +66,7 @@ func Test_routesImpl_FindBackendForServerAddress(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			r := NewRoutes()
 
-			r.CreateMapping(tt.mapping.serverAddress, tt.mapping.backend, EmptyScalerFunc, EmptyScalerFunc)
+			r.CreateMapping(tt.mapping.serverAddress, tt.mapping.backend, nil, nil, "")
 
 			if got, server, _, _ := r.FindBackendForServerAddress(context.Background(), tt.args.serverAddress); got != tt.want {
 				t.Errorf("routesImpl.FindBackendForServerAddress() = %v, want %v", got, tt.want)

server/server.go

@@ -49,7 +49,7 @@ func NewServer(ctx context.Context, config *Config) (*Server, error) {
 
 	metricsBuilder := NewMetricsBuilder(config.MetricsBackend, &config.MetricsBackendConfig)
 
-	downScalerEnabled := config.AutoScale.Down && (config.InKubeCluster || config.KubeConfig != "")
+	downScalerEnabled := config.AutoScale.Down && (config.InKubeCluster || config.KubeConfig != "" || config.InDocker)
 	downScalerDelay, err := time.ParseDuration(config.AutoScale.DownAfter)
 	if err != nil {
 		return nil, fmt.Errorf("could not parse auto-scale-down-after duration: %w", err)
@@ -73,7 +73,7 @@ func NewServer(ctx context.Context, config *Config) (*Server, error) {
 
 	Routes.RegisterAll(config.Mapping)
 	if config.Default != "" {
-		Routes.SetDefaultRoute(config.Default)
+		Routes.SetDefaultRoute(config.Default, nil, nil, "")
 	}
 
 	if config.ConnectionRateLimit < 1 {
@@ -86,6 +86,8 @@ func NewServer(ctx context.Context, config *Config) (*Server, error) {
 		config.RecordLogins,
 		autoScaleAllowDenyConfig)
 
+	connector.UseAsleepMOTD(config.AutoScale.AsleepMOTD)
+
 	clientFilter, err := NewClientFilter(config.ClientsToAllow, config.ClientsToDeny)
 	if err != nil {
 		return nil, fmt.Errorf("could not create client filter: %w", err)