agent: boilerplate

command/agent/agent.go

@@ -1,19 +1,81 @@
 package agent
 
-import "io"
+import (
+	"io"
+	"log"
+	"os"
+	"sync"
 
+	"github.com/hashicorp/nomad/nomad"
+)
+
+// Agent is a long running daemon that is used to run both
+// clients and servers. Servers are responsible for managing
+// state and making scheduling decisions. Clients can be
+// scheduled to, and are responsible for interfacing with
+// servers to run allocations.
 type Agent struct {
+	config    *Config
+	logger    *log.Logger
+	logOutput io.Writer
+
+	server *nomad.Server
+	client *nomad.Server // TODO
+
+	shutdown     bool
+	shutdownCh   chan struct{}
+	shutdownLock sync.Mutex
 }
 
+// NewAgent is used to create a new agent with the given configuration
 func NewAgent(config *Config, logOutput io.Writer) (*Agent, error) {
-	a := &Agent{}
+	// Ensure we have a log sink
+	if logOutput == nil {
+		logOutput = os.Stderr
+	}
+
+	a := &Agent{
+		config:     config,
+		logger:     log.New(logOutput, "", log.LstdFlags),
+		logOutput:  logOutput,
+		shutdownCh: make(chan struct{}),
+	}
 	return a, nil
 }
 
+// Leave is used gracefully exit. Clients will inform servers
+// of their departure so that allocations can be rescheduled.
 func (a *Agent) Leave() error {
 	return nil
 }
 
+// Shutdown is used to terminate the agent.
 func (a *Agent) Shutdown() error {
-	return nil
+	a.shutdownLock.Lock()
+	defer a.shutdownLock.Unlock()
+
+	if a.shutdown {
+		return nil
+	}
+
+	a.logger.Println("[INFO] agent: requesting shutdown")
+	var err error
+	if a.server != nil {
+		err = a.server.Shutdown()
+	} else {
+		err = a.client.Shutdown()
+	}
+
+	a.logger.Println("[INFO] agent: shutdown complete")
+	a.shutdown = true
+	close(a.shutdownCh)
+	return err
+}
+
+// RPC is used to make an RPC call to the Nomad servers
+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)
 }