Better "sample config" implementation

Three changes:

- Sample configuration is no longer a dump of a string constant. It's
  generated using the same data structure used for configuration
  parsing. This guarantees that 'teleport configure' will always dump a
  valid sample config file.

- Added a unit test which validates sample configuration and  verifies
  its correctness

- MakeSampleConfig() does not return an error anymore. It will
  default   to 'localhost' with error logged instead of failing. It
  makes no sense to fail when generating an example. Also this makes
  code cleaner.

Makefile

@@ -47,6 +47,8 @@ production: clean
 #
 test: 
 	go test -v github.com/gravitational/teleport/lib/... -cover
+	go test -v github.com/gravitational/teleport/tool/teleport... -cover
+
 
 test-with-etcd: install
 	${ETCD_FLAGS} go test -v -test.parallel=0 $(shell go list ./... | grep -v /vendor/) -cover

lib/config/config_test.go

@@ -22,6 +22,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/gravitational/teleport/lib/defaults"
 	"gopkg.in/check.v1"
 )
 
@@ -71,6 +72,25 @@ func (s *ConfigTestSuite) TearDownSuite(c *check.C) {
 	os.RemoveAll(s.tempDir)
 }
 
+func (s *ConfigTestSuite) TestSampleConfig(c *check.C) {
+	// generate sample config and write it into a temp file:
+	sfc := MakeSampleFileConfig()
+	c.Assert(sfc, check.NotNil)
+	fn := filepath.Join(c.MkDir(), "default-config.yaml")
+	err := ioutil.WriteFile(fn, []byte(sfc.DebugDumpToYAML()), 0660)
+	c.Assert(err, check.IsNil)
+
+	// make sure it could be parsed:
+	fc, err := ReadFromFile(fn)
+	c.Assert(err, check.IsNil)
+
+	// validate a couple of values:
+	c.Assert(fc.Limits.MaxUsers, check.Equals, defaults.LimiterMaxConcurrentUsers)
+	c.Assert(fc.Global.Storage.DirName, check.Equals, defaults.DataDir)
+	c.Assert(fc.Logger.Severity, check.Equals, "INFO")
+
+}
+
 func (s *ConfigTestSuite) TestConfigReading(c *check.C) {
 	// invalid config file type:
 	conf, err := ReadFromFile("/bin/true")

lib/config/fileconf.go

@@ -24,6 +24,8 @@ import (
 
 	"gopkg.in/yaml.v2"
 
+	"github.com/gravitational/teleport/lib/defaults"
+	"github.com/gravitational/teleport/lib/service"
 	"github.com/gravitational/trace"
 )
 
@@ -117,6 +119,66 @@ func ReadFromFile(fp string) (fc *FileConfig, err error) {
 	return fc, nil
 }
 
+// makeSampleFileConfig returns a sample config structure populated by defaults,
+// useful to generate sample configuration files
+func MakeSampleFileConfig() (fc *FileConfig) {
+	conf := service.MakeDefaultConfig()
+
+	// sample global config:
+	var g Global
+	g.NodeName = conf.Hostname
+	g.AuthToken = "xxxx-token-xxxx"
+	g.Logger.Output = "stderr"
+	g.Logger.Severity = "INFO"
+	g.AuthServers = defaults.AuthListenAddr().Addr
+	g.Limits.MaxConnections = defaults.LimiterMaxConnections
+	g.Limits.MaxUsers = defaults.LimiterMaxConcurrentUsers
+	g.Storage.DirName = defaults.DataDir
+	g.Storage.Type = conf.Auth.RecordsBackend.Type
+
+	// sample SSH config:
+	var s SSH
+	s.EnabledFlag = "yes"
+	s.ListenAddress = conf.SSH.Addr.Addr
+	s.Commands = []CommandLabel{
+		{
+			Name:    "hostname",
+			Command: []string{"/usr/bin/hostname"},
+			Period:  time.Minute,
+		},
+		{
+			Name:    "arch",
+			Command: []string{"/usr/bin/uname", "-p"},
+			Period:  time.Hour,
+		},
+	}
+	s.Labels = map[string]string{
+		"db_type": "postgres",
+		"db_role": "master",
+	}
+
+	// sample Auth config:
+	var a Auth
+	a.ListenAddress = conf.Auth.SSHAddr.Addr
+	a.EnabledFlag = "yes"
+
+	// sample proxy config:
+	var p Proxy
+	p.EnabledFlag = "yes"
+	p.ListenAddress = conf.Proxy.SSHAddr.Addr
+	p.WebAddr = conf.Proxy.WebAddr.Addr
+	p.CertFile = "/etc/teleport/teleport.crt"
+	p.KeyFile = "/etc/teleport/teleport.key"
+
+	fc = &FileConfig{
+		Global: g,
+		Proxy:  p,
+		SSH:    s,
+		Auth:   a,
+	}
+	return fc
+}
+
 // DebugDump allows for quick YAML dumping of the config
 func (conf *FileConfig) DebugDumpToYAML() string {
 	bytes, err := yaml.Marshal(&conf)
@@ -204,7 +266,7 @@ type SSH struct {
 // `command` section of `ssh_service` in the config file
 type CommandLabel struct {
 	Name    string        `yaml:"name"`
-	Command []string      `yaml:"command"`
+	Command []string      `yaml:"command,flow"`
 	Period  time.Duration `yaml:"period"`
 }
 

lib/service/cfg.go

@@ -23,6 +23,7 @@ import (
 
 	"io"
 
+	log "github.com/Sirupsen/logrus"
 	"gopkg.in/yaml.v2"
 
 	"github.com/gravitational/teleport/lib/defaults"
@@ -307,19 +308,18 @@ func (c *LocalCertificateAuthority) CA() (*services.CertAuthority, error) {
 }
 
 // MakeDefaultConfig() creates a new Config structure and populates it with defaults
-func MakeDefaultConfig() (config *Config, err error) {
+func MakeDefaultConfig() (config *Config) {
 	config = &Config{}
-	if err = ApplyDefaults(config); err != nil {
-		return nil, trace.Wrap(err)
-	}
-	return config, nil
+	ApplyDefaults(config)
+	return config
 }
 
 // ApplyDefaults applies default values to the existing config structure
-func ApplyDefaults(cfg *Config) error {
+func ApplyDefaults(cfg *Config) {
 	hostname, err := os.Hostname()
 	if err != nil {
-		return trace.Wrap(err)
+		hostname = "localhost"
+		log.Errorf("Failed to determine hostname: %v", err)
 	}
 
 	// defaults for the auth service:
@@ -358,7 +358,6 @@ func ApplyDefaults(cfg *Config) error {
 		cfg.AuthServers = []utils.NetAddr{cfg.Auth.SSHAddr}
 	}
 	cfg.Console = os.Stdout
-	return nil
 }
 
 // Generates a string accepted by the BoltDB driver, like this:

lib/service/cfg_test.go

@@ -36,8 +36,7 @@ func (s *ConfigSuite) SetUpSuite(c *C) {
 }
 
 func (s *ConfigSuite) TestDefaultConfig(c *C) {
-	config, err := MakeDefaultConfig()
-	c.Assert(err, IsNil)
+	config := MakeDefaultConfig()
 	c.Assert(config, NotNil)
 
 	// all 3 services should be enabled by default

tool/tctl/main.go

@@ -56,10 +56,7 @@ func main() {
 	app := utils.InitCLIParser("tctl", GlobalHelpString)
 
 	// generate default tctl configuration:
-	cfg, err := service.MakeDefaultConfig()
-	if err != nil {
-		utils.FatalError(err)
-	}
+	cfg := service.MakeDefaultConfig()
 	cmdUsers := UserCommand{config: cfg}
 	cmdNodes := NodeCommand{config: cfg}
 

tool/teleport/configuration.go

@@ -243,10 +243,7 @@ func applyString(src string, target *string) bool {
 // with CLI commands taking precedence
 func configure(clf *CommandLineFlags) (cfg *service.Config, err error) {
 	// create the default configuration:
-	cfg, err = service.MakeDefaultConfig()
-	if err != nil {
-		return cfg, trace.Wrap(err)
-	}
+	cfg = service.MakeDefaultConfig()
 
 	// load /etc/teleport.yaml and apply it's values:
 	fileConf, err := readConfigFile(clf.ConfigFile)

tool/teleport/main.go

@@ -20,6 +20,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/gravitational/teleport/lib/config"
 	"github.com/gravitational/teleport/lib/defaults"
 	"github.com/gravitational/teleport/lib/service"
 	"github.com/gravitational/teleport/lib/utils"
@@ -102,7 +103,7 @@ func run(cmdlineArgs []string, testRun bool) (executedCommand string, appliedCon
 		case status.FullCommand():
 			err = onStatus(config)
 		case dump.FullCommand():
-			err = onConfigDump()
+			onConfigDump()
 		case ver.FullCommand():
 			onVersion()
 		}
@@ -134,9 +135,9 @@ func onStatus(config *service.Config) error {
 }
 
 // onConfigDump is the handler for "configure" CLI command
-func onConfigDump() error {
-	fmt.Println(sampleConfig)
-	return nil
+func onConfigDump() {
+	sfc := config.MakeSampleFileConfig()
+	fmt.Printf("%s\n%s\n", sampleConfComment, sfc.DebugDumpToYAML())
 }
 
 // onVersion is the handler for "version"

tool/teleport/usage.go

@@ -24,55 +24,7 @@ Examples:
       Starts this SSH node named 'database' running in SSH server mode and 
       authenticating connections via the auth server running on 10.5.0.2`
 
-	sampleConfig = `##
-## This is the example of a Teleport configuration file with all settings
-## set to their default value. Uncomment & customize as needed.
-##
-#global:
-#    hostname:localhost
-#    listen_interface:0.0.0.0
-#    advertize_interface:auto
-#    proxy_addr: 127.0.0.1:3023
-#    proxy_token: ""
-#    auth_servers: ["tcp://127.0.0.1:3024"]
-#    connection_limits:
-#    max: 100
-#    rates:
-#      - period: 10s
-#        average: 5
-#        burst: 10
-#    storage:
-#        type: bolt
-#        params: { path: "/var/lib/teleport" }
-#    log:
-#        output: stderr  
-#        severity: INFO  
-#
-#auth_service:
-#   enabled: yes
-#   listen_addr: tcp://127.0.0.1:3024
-#
-#
-#ssh_service:
-#   enabled: yes
-#   token: “”
-#   proxy_addr: tcp://127.0.0.1:3023
-#   labels:
-#       name:value
-#       name2:value2
-#   label-commands:
-#       os:
-#           period: 1m
-#           command: ["uname", "-r"]
-#
-#proxy_service:
-#   enabled: yes
-#   https_only: true
-#   insecure_http_addr: tcp://0.0.0.0:3080
-#   https_addr: tcp://0.0.0.0:3081
-#   https_key_file: ""
-#   https_crt_file: ""
-#   ssh_addr: tcp://0.0.0.0:3023
-#   auth_token: ""
-`
+	sampleConfComment = `#
+# Sample Teleport configuration file.
+#`
 )