agent: simplify signal handling

command/agent/command.go

@@ -28,9 +28,6 @@ import (
 	"github.com/mitchellh/cli"
 )
 
-// gracefulTimeout controls how long we wait before forcefully terminating
-var gracefulTimeout = 5 * time.Second
-
 // validDatacenter is used to validate a datacenter
 var validDatacenter = regexp.MustCompile("^[a-zA-Z0-9_-]+$")
 
@@ -732,8 +729,7 @@ func (cmd *Command) wait(agent *Agent, cfg *Config) int {
 	signal.Notify(signalCh, os.Interrupt, syscall.SIGTERM, syscall.SIGHUP)
 	signal.Notify(signalCh, os.Interrupt, syscall.SIGTERM, syscall.SIGHUP, syscall.SIGPIPE)
 
-	// Wait for a signal
-WAIT:
+	for {
 		var sig os.Signal
 		var reloadErrCh chan error
 		select {
@@ -748,19 +744,17 @@ WAIT:
 			cmd.UI.Error(err.Error())
 			return 1
 		case <-agent.ShutdownCh():
-		// Agent is already shutdown!
+			// Agent is already down!
 			return 0
 		}
 
-	// Skip SIGPIPE signals and skip logging whenever such signal is received as well
-	if sig == syscall.SIGPIPE {
-		goto WAIT
-	}
+		switch sig {
+		case syscall.SIGPIPE:
+			continue
 
+		case syscall.SIGHUP:
 			cmd.UI.Output(fmt.Sprintf("Caught signal: %v", sig))
 
-	// Check if this is a SIGHUP
-	if sig == syscall.SIGHUP {
 			conf, err := cmd.handleReload(agent, cfg)
 			if conf != nil {
 				cfg = conf
@@ -772,25 +766,17 @@ WAIT:
 			if reloadErrCh != nil {
 				reloadErrCh <- err
 			}
-		goto WAIT
-	}
 
-	// Check if we should do a graceful leave
-	graceful := false
-	if sig == os.Interrupt && !(*cfg.SkipLeaveOnInt) {
-		graceful = true
-	} else if sig == syscall.SIGTERM && (*cfg.LeaveOnTerm) {
-		graceful = true
-	}
+		default:
+			cmd.UI.Output(fmt.Sprintf("Caught signal: %v", sig))
 
-	// Bail fast if not doing a graceful leave
+			graceful := (sig == os.Interrupt && !(*cfg.SkipLeaveOnInt)) || (sig == syscall.SIGTERM && (*cfg.LeaveOnTerm))
 			if !graceful {
 				return 1
 			}
 
-	// Attempt a graceful leave
-	gracefulCh := make(chan struct{})
 			cmd.UI.Output("Gracefully shutting down agent...")
+			gracefulCh := make(chan struct{})
 			go func() {
 				if err := agent.Leave(); err != nil {
 					cmd.UI.Error(fmt.Sprintf("Error: %s", err))
@@ -799,7 +785,7 @@ WAIT:
 				close(gracefulCh)
 			}()
 
-	// Wait for leave or another signal
+			gracefulTimeout := 5 * time.Second
 			select {
 			case <-signalCh:
 				return 1
@@ -808,6 +794,8 @@ WAIT:
 			case <-gracefulCh:
 				return 0
 			}
+		}
+	}
 }
 
 // handleReload is invoked when we should reload our configs, e.g. SIGHUP