Allow to set daemon and server configurations in a file.

Read configuration after flags making this the priority:

1- Apply configuration from file.
2- Apply configuration from flags.

Reload configuration when a signal is received, USR2 in Linux:

- Reload router if the debug configuration changes.
- Reload daemon labels.
- Reload cluster discovery.

Signed-off-by: David Calavera <david.calavera@gmail.com>

utils/debug.go

@@ -0,0 +1,26 @@
+package utils
+
+import (
+	"os"
+
+	"github.com/Sirupsen/logrus"
+)
+
+// EnableDebug sets the DEBUG env var to true
+// and makes the logger to log at debug level.
+func EnableDebug() {
+	os.Setenv("DEBUG", "1")
+	logrus.SetLevel(logrus.DebugLevel)
+}
+
+// DisableDebug sets the DEBUG env var to false
+// and makes the logger to log at info level.
+func DisableDebug() {
+	os.Setenv("DEBUG", "")
+	logrus.SetLevel(logrus.InfoLevel)
+}
+
+// IsDebugEnabled checks whether the debug flag is set or not.
+func IsDebugEnabled() bool {
+	return os.Getenv("DEBUG") != ""
+}