Refactor metrics logger

example/config.yaml

@@ -14,20 +14,17 @@ startClock: 2019-01-01T00:00:00+09:00
 # Optional (default: same as tick)
 metricsTick: 60
 
-# Metrics of simulated kubernetes cluster is written to a file at this path.
+# Metrics of simulated kubernetes cluster is written
+# to a file at this path or standard out if not specified.
 # The metrics is formatted with the given formatter.
-# Optional (default: not writing metrics to a file)
-metricsFile:
+# Optional (default: not writing metrics)
+metricsLogger:
+- formatter: table
 - path: kubesim.log
   formatter: JSON
 - path: kubesim-hr.log
   formatter: humanReadable
 
-# Metrics is (also) written to stdout.
-# Optional (default: not writing metrics to stdout)
-metricsStdout:
-  formatter: table
-
 # Write configuration of each node.
 cluster:
 - metadata:

pkg/config/config.go

@@ -32,19 +32,16 @@ type Config struct {
 	Tick          int
 	StartClock    string
 	MetricsTick   int
-	MetricsFile   []MetricsFileConfig
-	MetricsStdout MetricsStdoutConfig
+	MetricsLogger []MetricsLoggerConfig
 	Cluster       []NodeConfig
 }
 
 // Made public to be parsed from YAML.
 
-type MetricsFileConfig struct {
-	Path      string
-	Formatter string
-}
-
-type MetricsStdoutConfig struct {
+type MetricsLoggerConfig struct {
+	// Path is a file path in which the metrics is written.
+	Path string
+	// Formetter is a type of metrics format.
 	Formatter string
 }
 
@@ -58,16 +55,12 @@ type NodeStatus struct {
 	Allocatable map[v1.ResourceName]string
 }
 
-// BuildMetricsFile builds metrics.FileWriter with the given MetricsFileConfig.
+// BuildMetricsLogger builds metrics.FileWriter with the given MetricsLoggerConfig.
 // Returns error if the config is invalid or failed to create a FileWriter.
-func BuildMetricsFile(conf []MetricsFileConfig) ([]*metrics.FileWriter, error) {
+func BuildMetricsLogger(conf []MetricsLoggerConfig) ([]*metrics.FileWriter, error) {
 	writers := make([]*metrics.FileWriter, 0, len(conf))
 
 	for _, conf := range conf {
-		if conf.Path == "" {
-			return nil, strongerrors.InvalidArgument(errors.New("empty metricsFile.Path"))
-		}
-
 		formatter, err := buildFormatter(conf.Formatter)
 		if err != nil {
 			return nil, err
@@ -84,22 +77,6 @@ func BuildMetricsFile(conf []MetricsFileConfig) ([]*metrics.FileWriter, error) {
 	return writers, nil
 }
 
-// BuildMetricsStdout builds a metrics.StdoutWriter with the given MetricsStdoutConfig.
-// Returns error if failed to parse.
-func BuildMetricsStdout(conf MetricsStdoutConfig) (*metrics.StdoutWriter, error) {
-	if conf.Formatter == "" {
-		return nil, nil
-	}
-
-	formatter, err := buildFormatter(conf.Formatter)
-	if err != nil {
-		return nil, err
-	}
-
-	w := metrics.NewStdoutWriter(formatter)
-	return &w, nil
-}
-
 func buildFormatter(conf string) (metrics.Formatter, error) {
 	switch conf {
 	case "JSON":

pkg/config/config_test.go

@@ -26,24 +26,24 @@ import (
 	"github.com/pfnet-research/k8s-cluster-simulator/pkg/metrics"
 )
 
-func TestBuildMetricsFile(t *testing.T) {
-	_, err := BuildMetricsFile([]MetricsFileConfig{MetricsFileConfig{
+func TestBuildMetricsLogger(t *testing.T) {
+	_, err := BuildMetricsLogger([]MetricsLoggerConfig{MetricsLoggerConfig{
 		Path:      "",
 		Formatter: "",
 	}})
 	if err == nil {
 		t.Error("nil error")
 	}
 
-	_, err = BuildMetricsFile([]MetricsFileConfig{MetricsFileConfig{
+	_, err = BuildMetricsLogger([]MetricsLoggerConfig{MetricsLoggerConfig{
 		Path:      "",
 		Formatter: "foo",
 	}})
 	if err == nil {
 		t.Error("nil error")
 	}
 
-	_, err = BuildMetricsFile([]MetricsFileConfig{MetricsFileConfig{
+	_, err = BuildMetricsLogger([]MetricsLoggerConfig{MetricsLoggerConfig{
 		Path:      "foo",
 		Formatter: "",
 	}})
@@ -52,29 +52,6 @@ func TestBuildMetricsFile(t *testing.T) {
 	}
 }
 
-func TestBuildMetricsStdout(t *testing.T) {
-	actual, err := BuildMetricsStdout(MetricsStdoutConfig{
-		Formatter: "",
-	})
-	if actual != nil || err != nil {
-		t.Errorf("got: (%+v, %+v)\nwant: (nil, nil)", actual, err)
-	}
-
-	_, err = BuildMetricsStdout(MetricsStdoutConfig{
-		Formatter: "foo",
-	})
-	if err == nil {
-		t.Error("nil error")
-	}
-
-	_, err = BuildMetricsStdout(MetricsStdoutConfig{
-		Formatter: "JSON",
-	})
-	if err != nil {
-		t.Errorf("error %s", err.Error())
-	}
-}
-
 func TestBuildFormatter(t *testing.T) {
 	actual0, _ := buildFormatter("JSON")
 	expected0 := &metrics.JSONFormatter{}

pkg/kubesim.go

@@ -259,7 +259,7 @@ func buildCluster(conf *config.Config) (map[string]*node.Node, error) {
 func buildMetricsWriters(conf *config.Config) ([]metrics.Writer, error) {
 	writers := []metrics.Writer{}
 
-	fileWriters, err := config.BuildMetricsFile(conf.MetricsFile)
+	fileWriters, err := config.BuildMetricsLogger(conf.MetricsLogger)
 	if err != nil {
 		return []metrics.Writer{}, err
 	}
@@ -269,15 +269,6 @@ func buildMetricsWriters(conf *config.Config) ([]metrics.Writer, error) {
 		writers = append(writers, writer)
 	}
 
-	stdoutWriter, err := config.BuildMetricsStdout(conf.MetricsStdout)
-	if err != nil {
-		return []metrics.Writer{}, err
-	}
-	if stdoutWriter != nil {
-		log.L.Info("Metrics and log written to Stdout")
-		writers = append(writers, stdoutWriter)
-	}
-
 	return writers, nil
 }
 

pkg/metrics/file_writer.go

@@ -25,13 +25,23 @@ type FileWriter struct {
 }
 
 // NewFileWriter creates a new FileWriter with a file at the given path, and the formatter that
-// formats metrics to a string.
-// If the file exists, it will be truncaed.
+// formats metrics to a string
+// If /dev/stdout or empty string is given, the standard out is set.
+// If /dev/stderr is given, the standard error is set.
+// Otherwise, the file of a given path is set and it will be truncated if it exists.
 // Returns error if failed to create a file.
 func NewFileWriter(path string, formatter Formatter) (*FileWriter, error) {
-	file, err := os.Create(path)
-	if err != nil {
-		return nil, err
+	var file *os.File
+	if path == "/dev/stdout" || path == "stdout" || path == "" {
+		file = os.Stdout
+	} else if path == "/dev/stderr" || path == "stderr" {
+		file = os.Stderr
+	} else {
+		f, err := os.Create(path)
+		if err != nil {
+			return nil, err
+		}
+		file = f
 	}
 
 	return &FileWriter{