Merge pull request go-kit#157 from go-kit/levels-api

Make levels API more composable.

log/levels/levels.go

@@ -62,29 +62,29 @@ func (l Levels) With(keyvals ...interface{}) Levels {
 	}
 }
 
-// Debug logs a debug event along with keyvals.
-func (l Levels) Debug(keyvals ...interface{}) error {
-	return l.ctx.WithPrefix(l.levelKey, l.debugValue).Log(keyvals...)
+// Debug returns a debug level logger.
+func (l Levels) Debug(keyvals ...interface{}) log.Logger {
+	return l.ctx.WithPrefix(l.levelKey, l.debugValue)
 }
 
-// Info logs an info event along with keyvals.
-func (l Levels) Info(keyvals ...interface{}) error {
-	return l.ctx.WithPrefix(l.levelKey, l.infoValue).Log(keyvals...)
+// Info returns an info level logger.
+func (l Levels) Info(keyvals ...interface{}) log.Logger {
+	return l.ctx.WithPrefix(l.levelKey, l.infoValue)
 }
 
-// Warn logs a warn event along with keyvals.
-func (l Levels) Warn(keyvals ...interface{}) error {
-	return l.ctx.WithPrefix(l.levelKey, l.warnValue).Log(keyvals...)
+// Warn returns a warning level logger.
+func (l Levels) Warn(keyvals ...interface{}) log.Logger {
+	return l.ctx.WithPrefix(l.levelKey, l.warnValue)
 }
 
-// Error logs an error event along with keyvals.
-func (l Levels) Error(keyvals ...interface{}) error {
-	return l.ctx.WithPrefix(l.levelKey, l.errorValue).Log(keyvals...)
+// Error returns an error level logger.
+func (l Levels) Error(keyvals ...interface{}) log.Logger {
+	return l.ctx.WithPrefix(l.levelKey, l.errorValue)
 }
 
-// Crit logs a crit event along with keyvals.
-func (l Levels) Crit(keyvals ...interface{}) error {
-	return l.ctx.WithPrefix(l.levelKey, l.critValue).Log(keyvals...)
+// Crit returns a critical level logger.
+func (l Levels) Crit(keyvals ...interface{}) log.Logger {
+	return l.ctx.WithPrefix(l.levelKey, l.critValue)
 }
 
 // Option sets a parameter for leveled loggers.

log/levels/levels_test.go

@@ -13,25 +13,25 @@ func TestDefaultLevels(t *testing.T) {
 	buf := bytes.Buffer{}
 	logger := levels.New(log.NewLogfmtLogger(&buf))
 
-	logger.Debug("msg", "résumé") // of course you'd want to do this
+	logger.Debug().Log("msg", "résumé") // of course you'd want to do this
 	if want, have := "level=debug msg=résumé\n", buf.String(); want != have {
 		t.Errorf("want %#v, have %#v", want, have)
 	}
 
 	buf.Reset()
-	logger.Info("msg", "Åhus")
+	logger.Info().Log("msg", "Åhus")
 	if want, have := "level=info msg=Åhus\n", buf.String(); want != have {
 		t.Errorf("want %#v, have %#v", want, have)
 	}
 
 	buf.Reset()
-	logger.Error("msg", "© violation")
+	logger.Error().Log("msg", "© violation")
 	if want, have := "level=error msg=\"© violation\"\n", buf.String(); want != have {
 		t.Errorf("want %#v, have %#v", want, have)
 	}
 
 	buf.Reset()
-	logger.Crit("msg", "	")
+	logger.Crit().Log("msg", "	")
 	if want, have := "level=crit msg=\"\\t\"\n", buf.String(); want != have {
 		t.Errorf("want %#v, have %#v", want, have)
 	}
@@ -48,16 +48,16 @@ func TestModifiedLevels(t *testing.T) {
 		levels.ErrorValue("err"),
 		levels.CritValue("crt"),
 	)
-	logger.With("easter_island", "176°").Debug("msg", "moai")
+	logger.With("easter_island", "176°").Debug().Log("msg", "moai")
 	if want, have := `{"easter_island":"176°","l":"dbg","msg":"moai"}`+"\n", buf.String(); want != have {
 		t.Errorf("want %#v, have %#v", want, have)
 	}
 }
 
 func ExampleLevels() {
 	logger := levels.New(log.NewLogfmtLogger(os.Stdout))
-	logger.Debug("msg", "hello")
-	logger.With("context", "foo").Warn("err", "error")
+	logger.Debug().Log("msg", "hello")
+	logger.With("context", "foo").Warn().Log("err", "error")
 
 	// Output:
 	// level=debug msg=hello