fix(host-cleanup): auto host cleanup doesn't work on linux

Signed-off-by: Alexandr Zaytsev <alexandr.zaytsev@flant.com>

Author: nervgh

Diff for: pkg/host_cleaning/host_cleanup.go

@@ -4,14 +4,12 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"os"
-	"os/exec"
-	"strings"
 
 	"github.com/werf/logboek"
 	"github.com/werf/werf/v2/pkg/container_backend"
 	"github.com/werf/werf/v2/pkg/git_repo/gitdata"
 	"github.com/werf/werf/v2/pkg/tmp_manager"
+	"github.com/werf/werf/v2/pkg/werf/exec"
 )
 
 const (
@@ -86,37 +84,7 @@ func RunAutoHostCleanup(ctx context.Context, backend container_backend.Container
 		args = append(args, "--backend-storage-path", *options.BackendStoragePath)
 	}
 
-	executableName := os.Getenv("WERF_ORIGINAL_EXECUTABLE")
-	if executableName == "" {
-		executableName = os.Args[0]
-	}
-
-	cmd := exec.Command(executableName, args...)
-
-	var env []string
-	for _, spec := range os.Environ() {
-		k := strings.SplitN(spec, "=", 2)[0]
-		if k == "WERF_ENABLE_PROCESS_EXTERMINATOR" {
-			continue
-		}
-
-		env = append(env, spec)
-	}
-	env = append(env, "_WERF_BACKGROUND_MODE_ENABLED=1")
-
-	cmd.Env = env
-
-	if err := cmd.Start(); err != nil {
-		logboek.Context(ctx).Warn().LogF("WARNING: unable to start background auto host cleanup process: %s\n", err)
-		return nil
-	}
-
-	if err := cmd.Process.Release(); err != nil {
-		logboek.Context(ctx).Warn().LogF("WARNING: unable to detach background auto host cleanup process: %s\n", err)
-		return nil
-	}
-
-	return nil
+	return exec.Detach(ctx, args)
 }
 
 func RunHostCleanup(ctx context.Context, backend container_backend.ContainerBackend, options HostCleanupOptions) error {

Diff for: pkg/util/exec/unix.go

@@ -0,0 +1,26 @@
+//go:build linux || darwin
+
+package exec
+
+import (
+	"os/exec"
+	"syscall"
+
+	"github.com/werf/werf/v2/pkg/util/option"
+)
+
+// MakeDetachable ensures command could start a detachable process.
+// Detachable process is a group leader process which has not controlling terminal.
+func MakeDetachable(cmd *exec.Cmd) *exec.Cmd {
+	attr := option.PtrValueOrDefault(cmd.SysProcAttr, syscall.SysProcAttr{})
+
+	// Creates a new session if the calling process is not a process group leader and sets the process group ID.
+	// Ensures the process has not controlling terminal.
+	// Note. A process group leader is a process whose process group ID equals its PID.
+	// https://man7.org/linux/man-pages/man2/setsid.2.html
+	attr.Setsid = true
+
+	cmd.SysProcAttr = &attr
+
+	return cmd
+}

Diff for: pkg/util/exec/windows.go

@@ -0,0 +1,16 @@
+//go:build windows
+
+package exec
+
+import (
+	"os/exec"
+)
+
+// MakeDetachable ensures command could start detachable process.
+func MakeDetachable(cmd *exec.Cmd) *exec.Cmd {
+	// We don't know right now there is or there is not the process detaching problem on Windows.
+	// Moreover, syscall.SysProcAttr for windows has not "Setsid" (linux specific) field.
+	// So we keep cross-platform compatibility do nothing.
+
+	return cmd
+}

Diff for: pkg/werf/exec/exec.go

@@ -0,0 +1,42 @@
+package exec
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/samber/lo"
+
+	"github.com/werf/logboek"
+	exec2 "github.com/werf/werf/v2/pkg/util/exec"
+	"github.com/werf/werf/v2/pkg/util/option"
+)
+
+// Detach executes werf binary in new detached process.
+// The detached process will continue to work after termination of parent process.
+func Detach(ctx context.Context, args []string) error {
+	name := option.ValueOrDefault(os.Getenv("WERF_ORIGINAL_EXECUTABLE"), os.Args[0])
+
+	env := append(os.Environ(), "_WERF_BACKGROUND_MODE_ENABLED=1")
+
+	env = lo.Filter(env, func(item string, _ int) bool {
+		return !strings.HasPrefix(item, "WERF_ENABLE_PROCESS_EXTERMINATOR=")
+	})
+
+	cmd := exec.Command(name, args...)
+	cmd.Env = env
+
+	cmd = exec2.MakeDetachable(cmd)
+
+	if err := cmd.Start(); err != nil {
+		logboek.Context(ctx).Warn().LogF("WARNING: unable to start background process: %s\n", err)
+		return nil
+	}
+
+	if err := cmd.Process.Release(); err != nil {
+		logboek.Context(ctx).Warn().LogF("WARNING: unable to detach background process: %s\n", err)
+	}
+
+	return nil
+}