consul: Adding protocol version numbers

consul/client.go

@@ -63,6 +63,11 @@ type Client struct {
 // NewClient is used to construct a new Consul client from the
 // configuration, potentially returning an error
 func NewClient(config *Config) (*Client, error) {
+	// Check the protocol version
+	if err := config.CheckVersion(); err != nil {
+		return nil, err
+	}
+
 	// Check for a data directory!
 	if config.DataDir == "" {
 		return nil, fmt.Errorf("Config must provide a DataDir")
@@ -109,7 +114,7 @@ func (c *Client) setupSerf(conf *serf.Config, ch chan serf.Event, path string) (
 	conf.LogOutput = c.config.LogOutput
 	conf.EventCh = ch
 	conf.SnapshotPath = filepath.Join(c.config.DataDir, path)
-	conf.ProtocolVersion = 3 // TODO: Support version 4
+	conf.ProtocolVersion = protocolVersionMap[c.config.ProtocolVersion]
 	if err := ensurePath(conf.SnapshotPath, false); err != nil {
 		return nil, err
 	}

consul/config.go

@@ -1,6 +1,7 @@
 package consul
 
 import (
+	"fmt"
 	"github.com/hashicorp/memberlist"
 	"github.com/hashicorp/raft"
 	"github.com/hashicorp/serf/serf"
@@ -20,6 +21,17 @@ var (
 	DefaultRPCAddr = &net.TCPAddr{IP: net.ParseIP("0.0.0.0"), Port: 8300}
 )
 
+// ProtocolVersionMap is the mapping of Consul protocol versions
+// to Serf protocol versions. We mask the Serf protocols using
+// our own protocol version.
+var protocolVersionMap map[uint8]uint8
+
+func init() {
+	protocolVersionMap = map[uint8]uint8{
+		1: 4,
+	}
+}
+
 // Config is used to configure the server
 type Config struct {
 	// Bootstrap mode is used to bring up the first Consul server.
@@ -65,11 +77,27 @@ type Config struct {
 	// logs will go to stderr.
 	LogOutput io.Writer
 
+	// ProtocolVersion is the protocol version to speak. This must be between
+	// ProtocolVersionMin and ProtocolVersionMax.
+	ProtocolVersion uint8
+
 	// ServerUp callback can be used to trigger a notification that
 	// a Consul server is now up and known about.
 	ServerUp func()
 }
 
+// CheckVersion is used to check if the ProtocolVersion is valid
+func (c *Config) CheckVersion() error {
+	if c.ProtocolVersion < ProtocolVersionMin {
+		return fmt.Errorf("Protocol version '%d' too low. Must be in range: [%d, %d]",
+			c.ProtocolVersion, ProtocolVersionMin, ProtocolVersionMax)
+	} else if c.ProtocolVersion > ProtocolVersionMax {
+		return fmt.Errorf("Protocol version '%d' too high. Must be in range: [%d, %d]",
+			c.ProtocolVersion, ProtocolVersionMin, ProtocolVersionMax)
+	}
+	return nil
+}
+
 // DefaultConfig is used to return a sane default configuration
 func DefaultConfig() *Config {
 	hostname, err := os.Hostname()
@@ -85,6 +113,7 @@ func DefaultConfig() *Config {
 		SerfLANConfig:     serf.DefaultConfig(),
 		SerfWANConfig:     serf.DefaultConfig(),
 		ReconcileInterval: 60 * time.Second,
+		ProtocolVersion:   ProtocolVersionMax,
 	}
 
 	// WAN Serf should use the WAN timing, since we are using it

consul/server.go

@@ -14,6 +14,14 @@ import (
 	"time"
 )
 
+// These are the protocol versions that Consul can _understand_. These are
+// Consul-level protocol versions, that are used to configure the Serf
+// protocol versions.
+const (
+	ProtocolVersionMin uint8 = 1
+	ProtocolVersionMax       = 1
+)
+
 const (
 	serfLANSnapshot   = "serf/local.snapshot"
 	serfWANSnapshot   = "serf/remote.snapshot"
@@ -97,6 +105,11 @@ type endpoints struct {
 // NewServer is used to construct a new Consul server from the
 // configuration, potentially returning an error
 func NewServer(config *Config) (*Server, error) {
+	// Check the protocol version
+	if err := config.CheckVersion(); err != nil {
+		return nil, err
+	}
+
 	// Check for a data directory!
 	if config.DataDir == "" {
 		return nil, fmt.Errorf("Config must provide a DataDir")
@@ -175,7 +188,7 @@ func (s *Server) setupSerf(conf *serf.Config, ch chan serf.Event, path string) (
 	conf.LogOutput = s.config.LogOutput
 	conf.EventCh = ch
 	conf.SnapshotPath = filepath.Join(s.config.DataDir, path)
-	conf.ProtocolVersion = 3 // TODO: Support version 4
+	conf.ProtocolVersion = protocolVersionMap[s.config.ProtocolVersion]
 	if err := ensurePath(conf.SnapshotPath, false); err != nil {
 		return nil, err
 	}