agent: Warn on dns-incompatible characters during service registration. Fixes #683.

command/agent/agent.go

@@ -8,6 +8,7 @@ import (
 	"net"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strconv"
 	"strings"
 	"sync"
@@ -35,6 +36,11 @@ const (
 		"service, but no reason was provided. This is a default message."
 )
 
+var (
+	// serviceNameRe checks if a service name is compatible with DNS.
+	serviceNameRe = regexp.MustCompile(`^[a-zA-Z0-9\-]+$`)
+)
+
 /*
  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
@@ -595,6 +601,12 @@ func (a *Agent) AddService(service *structs.NodeService, chkTypes CheckTypes, pe
 		}
 	}
 
+	// Warn if the service name is incompatible with DNS
+	if !serviceNameRe.MatchString(service.Service) {
+		a.logger.Printf("[WARN] Service name %q will not be discoverable "+
+			"via DNS due to invalid characters", service.Service)
+	}
+
 	// Add the service
 	a.state.AddService(service)