fix(process): keep signal zero as liveness probe

Co-Authored-By: Virgil <virgil@lethean.io>

process.go

@@ -269,6 +269,10 @@ func (p *ManagedProcess) Signal(sig os.Signal) error {
 		return cmd.Process.Signal(sig)
 	}
 
+	if sysSig == 0 {
+		return syscall.Kill(-cmd.Process.Pid, 0)
+	}
+
 	if err := syscall.Kill(-cmd.Process.Pid, sysSig); err != nil {
 		return err
 	}

process_test.go

@@ -3,6 +3,7 @@ package process
 import (
 	"context"
 	"os"
+	"syscall"
 	"testing"
 	"time"
 
@@ -300,6 +301,33 @@ func TestProcess_Signal(t *testing.T) {
 			t.Fatal("process group should have been terminated by signal")
 		}
 	})
+
+	t.Run("signal zero only probes process group liveness", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		proc, err := svc.StartWithOptions(context.Background(), RunOptions{
+			Command:   "sh",
+			Args:      []string{"-c", "sleep 60 & wait"},
+			Detach:    true,
+			KillGroup: true,
+		})
+		require.NoError(t, err)
+
+		err = proc.Signal(syscall.Signal(0))
+		assert.NoError(t, err)
+
+		time.Sleep(300 * time.Millisecond)
+		assert.True(t, proc.IsRunning())
+
+		err = proc.Kill()
+		assert.NoError(t, err)
+
+		select {
+		case <-proc.Done():
+		case <-time.After(5 * time.Second):
+			t.Fatal("process group should have been killed for cleanup")
+		}
+	})
 }
 
 func TestProcess_CloseStdin(t *testing.T) {

service_test.go

@@ -927,6 +927,34 @@ func TestService_OnStartup(t *testing.T) {
 		<-proc.Done()
 	})
 
+	t.Run("signal zero does not kill process groups", func(t *testing.T) {
+		svc, c := newTestService(t)
+
+		err := svc.OnStartup(context.Background())
+		require.NoError(t, err)
+
+		proc, err := svc.StartWithOptions(context.Background(), RunOptions{
+			Command:   "sh",
+			Args:      []string{"-c", "sleep 60 & wait"},
+			Detach:    true,
+			KillGroup: true,
+		})
+		require.NoError(t, err)
+
+		result := c.PERFORM(TaskProcessSignal{
+			ID:     proc.ID,
+			Signal: syscall.Signal(0),
+		})
+		require.True(t, result.OK)
+
+		time.Sleep(300 * time.Millisecond)
+		assert.True(t, proc.IsRunning())
+
+		err = proc.Kill()
+		require.NoError(t, err)
+		<-proc.Done()
+	})
+
 	t.Run("registers process.wait task", func(t *testing.T) {
 		svc, c := newTestService(t)