shim logger improvements

plugins/common/shim/config.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"log"
 	"os"
 
 	"github.com/BurntSushi/toml"
@@ -152,14 +153,17 @@ func DefaultImportedPlugins() (config, error) {
 		Outputs:    map[string][]toml.Primitive{},
 	}
 	for name := range inputs.Inputs {
+		log.Println("No config found. Loading default config for plugin", name)
 		conf.Inputs[name] = []toml.Primitive{}
 		return conf, nil
 	}
 	for name := range processors.Processors {
+		log.Println("No config found. Loading default config for plugin", name)
 		conf.Processors[name] = []toml.Primitive{}
 		return conf, nil
 	}
 	for name := range outputs.Outputs {
+		log.Println("No config found. Loading default config for plugin", name)
 		conf.Outputs[name] = []toml.Primitive{}
 		return conf, nil
 	}

plugins/common/shim/input.go

@@ -13,6 +13,7 @@ import (
 
 // AddInput adds the input to the shim. Later calls to Run() will run this input.
 func (s *Shim) AddInput(input telegraf.Input) error {
+	setLoggerOnPlugin(input, NewLogger())
 	if p, ok := input.(telegraf.Initializer); ok {
 		err := p.Init()
 		if err != nil {
@@ -57,13 +58,16 @@ func (s *Shim) RunInput(pollInterval time.Duration) error {
 		wg.Done()
 	}()
 
-	scanner := bufio.NewScanner(s.stdin)
-	for scanner.Scan() {
-		// push a non-blocking message to trigger metric collection.
-		s.pushCollectMetricsRequest()
-	}
+	go func() {
+		scanner := bufio.NewScanner(s.stdin)
+		for scanner.Scan() {
+			// push a non-blocking message to trigger metric collection.
+			s.pushCollectMetricsRequest()
+		}
+
+		cancel() // cancel gracefully stops gathering
+	}()
 
-	cancel()  // cancel gracefully stops gathering
 	wg.Wait() // wait for writing to stdout to finish
 	return nil
 }

plugins/common/shim/logger.go

@@ -0,0 +1,87 @@
+package shim
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"reflect"
+
+	"github.com/influxdata/telegraf"
+)
+
+func init() {
+	log.SetOutput(os.Stderr)
+}
+
+// Logger defines a logging structure for plugins.
+// external plugins can only ever write to stderr and writing to stdout
+// would interfere with input/processor writing out of metrics.
+type Logger struct{}
+
+// NewLogger creates a new logger instance
+func NewLogger() *Logger {
+	return &Logger{}
+}
+
+// Errorf logs an error message, patterned after log.Printf.
+func (l *Logger) Errorf(format string, args ...interface{}) {
+	log.Printf("E! "+format, args...)
+}
+
+// Error logs an error message, patterned after log.Print.
+func (l *Logger) Error(args ...interface{}) {
+	log.Print("E! ", fmt.Sprint(args...))
+}
+
+// Debugf logs a debug message, patterned after log.Printf.
+func (l *Logger) Debugf(format string, args ...interface{}) {
+	log.Printf("D! "+format, args...)
+}
+
+// Debug logs a debug message, patterned after log.Print.
+func (l *Logger) Debug(args ...interface{}) {
+	log.Print("D! ", fmt.Sprint(args...))
+}
+
+// Warnf logs a warning message, patterned after log.Printf.
+func (l *Logger) Warnf(format string, args ...interface{}) {
+	log.Printf("W! "+format, args...)
+}
+
+// Warn logs a warning message, patterned after log.Print.
+func (l *Logger) Warn(args ...interface{}) {
+	log.Print("W! ", fmt.Sprint(args...))
+}
+
+// Infof logs an information message, patterned after log.Printf.
+func (l *Logger) Infof(format string, args ...interface{}) {
+	log.Printf("I! "+format, args...)
+}
+
+// Info logs an information message, patterned after log.Print.
+func (l *Logger) Info(args ...interface{}) {
+	log.Print("I! ", fmt.Sprint(args...))
+}
+
+// setLoggerOnPlugin used to be called setLogIfExist
+func setLoggerOnPlugin(i interface{}, log telegraf.Logger) {
+	valI := reflect.ValueOf(i)
+
+	if valI.Type().Kind() != reflect.Ptr {
+		valI = reflect.New(reflect.TypeOf(i))
+	}
+
+	field := valI.Elem().FieldByName("Log")
+	if !field.IsValid() {
+		return
+	}
+
+	switch field.Type().String() {
+	case "telegraf.Logger":
+		if field.CanSet() {
+			field.Set(reflect.ValueOf(log))
+		}
+	}
+
+	return
+}

plugins/common/shim/output.go

@@ -10,6 +10,7 @@ import (
 
 // AddOutput adds the input to the shim. Later calls to Run() will run this.
 func (s *Shim) AddOutput(output telegraf.Output) error {
+	setLoggerOnPlugin(output, NewLogger())
 	if p, ok := output.(telegraf.Initializer); ok {
 		err := p.Init()
 		if err != nil {

plugins/common/shim/processor.go

@@ -14,12 +14,14 @@ import (
 
 // AddProcessor adds the processor to the shim. Later calls to Run() will run this.
 func (s *Shim) AddProcessor(processor telegraf.Processor) error {
+	setLoggerOnPlugin(processor, NewLogger())
 	p := processors.NewStreamingProcessorFromProcessor(processor)
 	return s.AddStreamingProcessor(p)
 }
 
 // AddStreamingProcessor adds the processor to the shim. Later calls to Run() will run this.
 func (s *Shim) AddStreamingProcessor(processor telegraf.StreamingProcessor) error {
+	setLoggerOnPlugin(processor, NewLogger())
 	if p, ok := processor.(telegraf.Initializer); ok {
 		err := p.Init()
 		if err != nil {

plugins/inputs/execd/shim/goshim.go

@@ -49,8 +49,15 @@ type Shim struct {
 	stderr io.Writer
 }
 
+var (
+	oldpkg = "github.com/influxdata/telegraf/plugins/inputs/execd/shim"
+	newpkg = "github.com/influxdata/telegraf/plugins/common/shim"
+)
+
 // New creates a new shim interface
 func New() *Shim {
+	fmt.Fprintf(os.Stderr, "%s is deprecated; please change your import to %s\n",
+		oldpkg, newpkg)
 	return &Shim{
 		stdin:  os.Stdin,
 		stdout: os.Stdout,