Filling in Agent basics

command/agent/agent.go

@@ -1,5 +1,10 @@
 package agent
 
+import (
+	"fmt"
+	"github.com/hashicorp/consul/consul"
+)
+
 /*
  The agent is the long running process that is run on every machine.
  It exposes an RPC interface that is used by the CLI to control the
@@ -10,6 +15,11 @@ package agent
 */
 type Agent struct {
 	config *Config
+
+	// We have one of a client or a server, depending
+	// on our configuration
+	server *consul.Server
+	client *consul.Client
 }
 
 // Create is used to create a new Agent. Returns
@@ -18,16 +28,102 @@ func Create(config *Config) (*Agent, error) {
 	agent := &Agent{
 		config: config,
 	}
+
+	// Setup either the client or the server
+	var err error
+	if config.Server {
+		err = agent.setupServer()
+	} else {
+		err = agent.setupClient()
+	}
+	if err != nil {
+		return nil, err
+	}
+
 	return agent, nil
 }
 
+// consulConfig is used to return a consul configuration
+func (a *Agent) consulConfig() *consul.Config {
+	// Start with the provided config or default config
+	var base *consul.Config
+	if a.config.ConsulConfig != nil {
+		base = a.config.ConsulConfig
+	} else {
+		base = consul.DefaultConfig()
+	}
+
+	// Override with our config
+	if a.config.Datacenter != "" {
+		base.Datacenter = a.config.Datacenter
+	}
+	if a.config.DataDir != "" {
+		base.DataDir = a.config.DataDir
+	}
+	if a.config.NodeName != "" {
+		base.NodeName = a.config.NodeName
+	}
+	if a.config.SerfBindAddr != "" {
+		base.SerfLANConfig.MemberlistConfig.BindAddr = a.config.SerfBindAddr
+		base.SerfWANConfig.MemberlistConfig.BindAddr = a.config.SerfBindAddr
+	}
+	if a.config.SerfLanPort != 0 {
+		base.SerfLANConfig.MemberlistConfig.Port = a.config.SerfLanPort
+	}
+	if a.config.SerfWanPort != 0 {
+		base.SerfWANConfig.MemberlistConfig.Port = a.config.SerfWanPort
+	}
+	if a.config.ServerRPCAddr != "" {
+		base.RPCAddr = a.config.ServerRPCAddr
+	}
+
+	return base
+}
+
+// setupServer is used to initialize the Consul server
+func (a *Agent) setupServer() error {
+	server, err := consul.NewServer(a.consulConfig())
+	if err != nil {
+		return fmt.Errorf("Failed to start Consul server: %v", err)
+	}
+	a.server = server
+	return nil
+}
+
+// setupClient is used to initialize the Consul client
+func (a *Agent) setupClient() error {
+	client, err := consul.NewClient(a.consulConfig())
+	if err != nil {
+		return fmt.Errorf("Failed to start Consul client: %v", err)
+	}
+	a.client = client
+	return nil
+}
+
+// RPC is used to make an RPC call to the Consul servers
+// This allows the agent to implement the Consul.Interface
+func (a *Agent) RPC(method string, args interface{}, reply interface{}) error {
+	if a.server != nil {
+		return a.server.RPC(method, args, reply)
+	}
+	return a.client.RPC(method, args, reply)
+}
+
 // Leave prepares the agent for a graceful shutdown
 func (a *Agent) Leave() error {
-	return nil
+	if a.server != nil {
+		return a.server.Leave()
+	} else {
+		return a.client.Leave()
+	}
 }
 
 // Shutdown is used to hard stop the agent. Should be preceeded
 // by a call to Leave to do it gracefully.
 func (a *Agent) Shutdown() error {
-	return nil
+	if a.server != nil {
+		return a.server.Shutdown()
+	} else {
+		return a.client.Shutdown()
+	}
 }

command/agent/config.go

@@ -1,12 +1,62 @@
 package agent
 
+import (
+	"github.com/hashicorp/consul/consul"
+)
+
+// This is the default port we use for co
+const DefaultBindPort int = 8300
+
 // Config is the configuration that can be set for an Agent.
 // Some of this is configurable as CLI flags, but most must
 // be set using a configuration file.
 type Config struct {
+	// Datacenter is the datacenter this node is in. Defaults to dc1
+	Datacenter string
+
+	// DataDir is the directory to store our state in
+	DataDir string
+
+	// LogLevel is the level of the logs to putout
+	LogLevel string
+
+	// Node name is the name we use to advertise. Defaults to hostname.
+	NodeName string
+
+	// RPCAddr is the address and port to listen on for the
+	// agent's RPC interface.
+	RPCAddr string
+
+	// BindAddr is the address that Consul's RPC and Serf's will
+	// bind to. This address should be routable by all other hosts.
+	SerfBindAddr string
+
+	// SerfLanPort is the port we use for the lan-local serf cluster
+	// This is used for all nodes.
+	SerfLanPort int
+
+	// SerfWanPort is the port we use for the wan serf cluster.
+	// This is only for the Consul servers
+	SerfWanPort int
+
+	// ServerRPCAddr is the address we use for Consul server communication.
+	// Defaults to 0.0.0.0:8300
+	ServerRPCAddr string
+
+	// Server controls if this agent acts like a Consul server,
+	// or merely as a client. Servers have more state, take part
+	// in leader election, etc.
+	Server bool
+
+	// ConsulConfig can either be provided or a default one created
+	ConsulConfig *consul.Config
 }
 
 // DefaultConfig is used to return a sane default configuration
 func DefaultConfig() *Config {
-	return &Config{}
+	return &Config{
+		LogLevel: "INFO",
+		RPCAddr:  "127.0.0.1:8400",
+		Server:   false,
+	}
 }

consul/config.go

@@ -9,7 +9,9 @@ import (
 )
 
 const (
+	DefaultDC          = "dc1"
 	DefaultRPCAddr     = "0.0.0.0:8300"
+	DefaultRPCPort     = 8000
 	DefaultLANSerfPort = 8301
 	DefaultWANSerfPort = 8302
 )
@@ -51,7 +53,7 @@ func DefaultConfig() *Config {
 	}
 
 	conf := &Config{
-		Datacenter:    "dc1",
+		Datacenter:    DefaultDC,
 		NodeName:      hostname,
 		RPCAddr:       DefaultRPCAddr,
 		RaftConfig:    raft.DefaultConfig(),