locksmithctl: add LOCKSMITHD_REBOOT_DELAY environment variable

README.md

@@ -138,6 +138,18 @@ function.
 
 [time.ParseDuration]: http://godoc.org/time#ParseDuration
 
+
+## Reboot delay
+Some systems might want to perform actions before a reboot occurs. These systems can watch the [semaphore](#semaphore) in `etcd` for changes to the `holders` and then do any tasks (e.g. pulling machines out of worker pools, load-balancers) necessary. Using `LOCKSMITHD_REBOOT_DELAY` environment variable grants the system time to perform these actions before the  machine reboots.
+
+Usage:
+```
+LOCKSMITHD_REBOOT_DELAY=300
+```
+
+This would cause the machine to wait 300 seconds (5 minutes) after getting the lock before rebooting.
+
+
 ## Implementation details 
 
 The following section describes how locksmith works under the hood.

locksmithctl/daemon.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"os"
 	"os/signal"
+	"strconv"
 	"sync"
 	"syscall"
 	"time"
@@ -107,7 +108,20 @@ func rebootAndSleep(lgn *login1.Conn) {
 	if 0 != lines {
 		dlog.Noticef("Logins detected, delaying reboot for %d minutes.", delaymins)
 		time.Sleep(loginsRebootDelay)
+	} else {
+		//Don't override delay when logins are found
+		rebootDelayEnv := os.Getenv("LOCKSMITHD_REBOOT_DELAY")
+		//ignore if not set
+		if rebootDelayEnv != "" {
+			specifiedRebootDelaySecs, err := strconv.Atoi(rebootDelayEnv)
+			if err != nil {
+				dlog.Warningf("Invalid value specified for LOCKSMITHD_REBOOT_DELAY: %v. Received %v expected int. Using 0.", err, rebootDelayEnv)
+			} else {
+				time.Sleep((time.Duration(int64(specifiedRebootDelaySecs))) * time.Second)
+			}
+		}
 	}
+
 	lgn.Reboot(false)
 	dlog.Info("Reboot sent. Going to sleep.")