From a95d80b14c57d801db6b699505ee93297f94179c Mon Sep 17 00:00:00 2001
From: Bernhard Tittelbach <xro@realraum.at>
Date: Mon, 25 Nov 2013 02:24:49 +0000
Subject: [PATCH] serial reconnect with exponential backoff

---
 go/uc_sensor_node_zmq/main.go |   36 +++++++++++++++++++++++++++++-------
 1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/go/uc_sensor_node_zmq/main.go b/go/uc_sensor_node_zmq/main.go
index bd55297..2e3c0de 100644
--- a/go/uc_sensor_node_zmq/main.go
+++ b/go/uc_sensor_node_zmq/main.go
@@ -4,6 +4,8 @@ package main
 
 import (
     "flag"
+    "time"
+    zmq "github.com/vaughan0/go-zmq"
 )
 
 
@@ -16,6 +18,8 @@ var (
     enable_debug_ bool    
 )
 
+const exponential_backof_activation_threshold int64 = 4
+
 func init() {
     flag.StringVar(&pub_addr, "brokeraddr", "tcp://torwaechter.realraum.at:4243", "zmq address to send stuff to")
     flag.StringVar(&tty_dev_, "ttydev", "/dev/ttyACM0", "path do tty uc device")
@@ -24,6 +28,21 @@ func init() {
     flag.Parse()
 }
 
+func ConnectSerialToZMQ(pub_sock *zmq.Socket) {
+    defer func() {
+        if x:= recover(); x != nil { Syslog_.Println(x) }
+    }()
+
+    serial_wr, serial_rd, err := OpenAndHandleSerial(tty_dev_)
+    if err != nil { panic(err) }
+    defer close(serial_wr)
+
+    for incoming_ser_line := range(serial_rd) {
+        Syslog_.Printf("%s",incoming_ser_line)
+        if err := pub_sock.Send(incoming_ser_line); err != nil { Syslog_.Println(err.Error()) }
+    }
+}
+
 func main() {
     zmqctx, pub_sock := ZmqsInit(pub_addr)
     if pub_sock == nil { panic("zmq socket creation failed") }
@@ -37,12 +56,15 @@ func main() {
         Syslog_.Print("started")
     }
 
-    serial_wr, serial_rd, err := OpenAndHandleSerial(tty_dev_)
-    if err != nil { panic(err) }    
-    defer close(serial_wr)
-    
-    for incoming_ser_line := range(serial_rd) {
-        Syslog_.Printf("%s",incoming_ser_line)
-        if err := pub_sock.Send(incoming_ser_line); err != nil { panic(err) }
+    var backoff_exp uint32 = 0
+    for {
+        start_time := time.Now().Unix()
+        ConnectSerialToZMQ(pub_sock)
+        run_time := time.Now().Unix() - start_time
+        if run_time > exponential_backof_activation_threshold {
+            backoff_exp = 0
+        }
+        time.Sleep(150*(1 << backoff_exp) * time.Millisecond)
+        if backoff_exp < 12 { backoff_exp++ }
     }
 }
-- 
1.7.10.4