Implement reload signal debouncing

child/child.go

@@ -13,6 +13,7 @@ import (
 	"os/exec"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"syscall"
 	"time"
 
@@ -52,6 +53,7 @@ type Child struct {
 	timeout time.Duration
 
 	reloadSignal os.Signal
+	reloading    uint32
 
 	killSignal  os.Signal
 	killTimeout time.Duration
@@ -400,7 +402,7 @@ func (c *Child) signal(s os.Signal) error {
 		// kill takes negative pid to indicate that you want to use gpid
 		pid = -(pid)
 	}
-	// cross platform way to signal process/process group
+	// cross-platform way to signal process/process group
 	if p, err := os.FindProcess(pid); err != nil {
 		return err
 	} else {
@@ -409,6 +411,15 @@ func (c *Child) signal(s os.Signal) error {
 }
 
 func (c *Child) reload() error {
+	if !atomic.CompareAndSwapUint32(&c.reloading, 0, 1) {
+		c.logger.Printf("[INFO] (child) reload already in progress")
+		return nil
+	}
+	defer func() {
+		c.logger.Printf("[INFO] (child) reload completed")
+		atomic.StoreUint32(&c.reloading, 0)
+	}()
+
 	select {
 	case <-c.stopCh:
 	case <-c.randomSplay():
@@ -480,8 +491,9 @@ func (c *Child) randomSplay() <-chan time.Time {
 		return time.After(0)
 	}
 
-	ns := c.splay.Nanoseconds()
-	offset := rand.Int63n(ns)
+	max := c.splay.Nanoseconds()
+	min := c.splay.Nanoseconds() / 2
+	offset := rand.Int63n(max-min+1) + min
 	t := time.Duration(offset)
 
 	c.logger.Printf("[DEBUG] (child) waiting %.2fs for random splay", t.Seconds())

cli.go

@@ -170,15 +170,15 @@ func (cli *CLI) Run(args []string) int {
 				return ExitCodeInterrupt
 			default:
 				// Propagate the signal to the child process
-				runner.Signal(s)
+				go runner.Signal(s)
 			}
 		case <-cli.stopCh:
 			return ExitCodeOK
 		}
 	}
 }
 
-// stop is used internally to shutdown a running CLI
+// stop is used internally to shut down a running CLI
 func (cli *CLI) stop() {
 	cli.Lock()
 	defer cli.Unlock()