Streams stderr from user functions and outputs a standard format for parsing. See #76.

api/runner/logger.go

@@ -0,0 +1,37 @@
+// This reads STDERR output from a container and outputs it in a parseable structured log format, see: https://github.com/iron-io/functions/issues/76
+package runner
+
+import (
+	"bufio"
+	"io"
+
+	"github.com/Sirupsen/logrus"
+)
+
+type FuncLogger struct {
+	r io.Reader
+	w io.Writer
+}
+
+func NewFuncLogger(appName, path, function, requestID string) io.Writer {
+	r, w := io.Pipe()
+	funcLogger := &FuncLogger{
+		r: r,
+		w: w,
+	}
+	log := logrus.WithFields(logrus.Fields{"app_name": appName, "path": path, "function": function, "request_id": requestID})
+	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 funcLogger
+}
+
+func (l *FuncLogger) Write(p []byte) (n int, err error) {
+	return l.w.Write(p)
+}