Add fd output to debug metrics

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

util/fds.go

@@ -0,0 +1,16 @@
+package util
+
+import (
+	"io/ioutil"
+	"path/filepath"
+	"strconv"
+)
+
+// GetOpenFds returns the number of open fds for the process provided by pid
+func GetOpenFds(pid int) (int, error) {
+	dirs, err := ioutil.ReadDir(filepath.Join("/proc", strconv.Itoa(pid), "fd"))
+	if err != nil {
+		return -1, err
+	}
+	return len(dirs), nil
+}