fixes #252 Add logging to ease debugging connection reattempts

AUTHORS

@@ -11,3 +11,4 @@ wenfang <[email protected]>
 Anner van Hardenbroek <[email protected]>
 Gerrit Renker <[email protected]>
 Rene Kaufmann <[email protected]>
+Ben Krieger <[email protected]>

core.go

@@ -636,6 +636,7 @@ func (d *dialer) dialer() {
 		case <-d.sock.closeq: // exit if parent socket closed
 			return
 		case <-time.After(rtime):
+			log.Debug(err)
 			if rtmax > 0 {
 				rtime *= 2
 				if rtime > rtmax {

log.go

@@ -0,0 +1,71 @@
+package mangos
+
+import "strings"
+
+// Logger is an interface that describes a very basic logger.
+// It only needs INFO and DEBUG levels, because errors are
+// returned by the library code and warnings are just ignored
+// errors (which is a bad idea). See:
+// http://dave.cheney.net/2015/11/05/lets-talk-about-logging
+type Logger interface {
+	Infof(string, ...interface{})
+	Debugf(string, ...interface{})
+}
+
+type loggers struct {
+	logs  []Logger
+	level int
+}
+
+var log loggers
+
+// RegisterLogger appends a new logger to the list of loggers.
+// The same logger can be registered multiple times, but will
+// then be used multiple times.
+func RegisterLogger(l Logger) {
+	log.logs = append(log.logs, l)
+}
+
+// SetLogLevel understands the following levels:
+// 0 - No output
+// 1 - Only INFO level
+// 2 - Both INFO and DEBUG level
+func SetLogLevel(i int) {
+	log.level = i
+}
+
+// Infof calls Infof on all registered loggers if the log level
+// is set to 1 or greater
+func (l *loggers) Infof(fmt string, v ...interface{}) {
+	if l.level < 1 {
+		return
+	}
+	for _, log := range l.logs {
+		log.Infof(fmt, v...)
+	}
+}
+
+// Info logs the values space-separated on all registered
+// loggers if the log level is set to 1 or greater
+func (l *loggers) Info(v ...interface{}) {
+	fmt := strings.Repeat(" %v", len(v))
+	l.Infof(fmt[1:], v...)
+}
+
+// Debugf calls Debugf on all registered loggers if the log level
+// is set to 2 or greater
+func (l *loggers) Debugf(fmt string, v ...interface{}) {
+	if l.level < 2 {
+		return
+	}
+	for _, log := range l.logs {
+		log.Debugf(fmt, v...)
+	}
+}
+
+// Debug logs the values space-separated on all registered
+// loggers if the log level is set to 2 or greater
+func (l *loggers) Debug(v ...interface{}) {
+	fmt := strings.Repeat(" %v", len(v))
+	l.Debugf(fmt[1:], v...)
+}

log/log.go

@@ -0,0 +1,21 @@
+package log
+
+import (
+	"log"
+
+	"github.com/go-mangos/mangos"
+)
+
+func init() {
+	mangos.RegisterLogger(&logger{})
+}
+
+type logger struct{}
+
+func (l *logger) Infof(fmt string, v ...interface{}) {
+	log.Printf("[INFO] "+fmt, v...)
+}
+
+func (l *logger) Debugf(fmt string, v ...interface{}) {
+	log.Printf("[DEBUG] "+fmt, v...)
+}