Changes on function/metric loggers (#343)

* initial fix logger

* dix DefaultFuncLogger

* fix runner and tests

* reverting: sending async task stdout to func logger

api/runner/func_logger.go

@@ -0,0 +1,41 @@
+package runner
+
+import (
+	"bufio"
+	"io"
+
+	"context"
+	"github.com/Sirupsen/logrus"
+	"github.com/iron-io/runner/common"
+)
+
+type FuncLogger interface {
+	Writer(context.Context, string, string, string, string) io.Writer
+}
+
+// FuncLogger reads STDERR output from a container and outputs it in a parseable structured log format, see: https://github.com/iron-io/functions/issues/76
+type DefaultFuncLogger struct {
+}
+
+func NewFuncLogger() FuncLogger {
+	return &DefaultFuncLogger{}
+}
+
+func (l *DefaultFuncLogger) Writer(ctx context.Context, appName, path, image, reqID string) io.Writer {
+	r, w := io.Pipe()
+
+	log := common.Logger(ctx)
+	log = log.WithFields(logrus.Fields{"user_log": true, "app_name": appName, "path": path, "image": image, "call_id": reqID})
+
+	go func(reader io.Reader) {
+		scanner := bufio.NewScanner(reader)
+		for scanner.Scan() {
+			log.Println(scanner.Text())
+		}
+		if err := scanner.Err(); err != nil {
+			log.WithError(err).Println("There was an error with the scanner in attached container")
+		}
+	}(r)
+
+	return w
+}