prometheus/util/flock/flock_test.go

package flock

import (
	"os"
	"path/filepath"
	"testing"

	"github.com/prometheus/prometheus/util/testutil"
)

func TestLocking(t *testing.T) {
	dir := testutil.NewTemporaryDirectory("test_flock", t)
	defer dir.Close()

	fileName := filepath.Join(dir.Path(), "LOCK")

	if _, err := os.Stat(fileName); err == nil {
		t.Fatalf("File %q unexpectedly exists.", fileName)
	}

	lock, existed, err := New(fileName)
	if err != nil {
		t.Fatalf("Error locking file %q: %s", fileName, err)
	}
	if existed {
		t.Errorf("File %q reported as existing during locking.", fileName)
	}

	// File must now exist.
	if _, err = os.Stat(fileName); err != nil {
		t.Errorf("Could not stat file %q expected to exist: %s", fileName, err)
	}

	// Try to lock again.
	lockedAgain, existed, err := New(fileName)
	if err == nil {
		t.Fatalf("File %q locked twice.", fileName)
	}
	if lockedAgain != nil {
		t.Error("Unsuccessful locking did not return nil.")
	}
	if !existed {
		t.Errorf("Existing file %q not recognized.", fileName)
	}

	if err := lock.Release(); err != nil {
		t.Errorf("Error releasing lock for file %q: %s", fileName, err)
	}

	// File must still exist.
	if _, err = os.Stat(fileName); err != nil {
		t.Errorf("Could not stat file %q expected to exist: %s", fileName, err)
	}

	// Lock existing file.
	lock, existed, err = New(fileName)
	if err != nil {
		t.Fatalf("Error locking file %q: %s", fileName, err)
	}
	if !existed {
		t.Errorf("Existing file %q not recognized.", fileName)
	}

	if err := lock.Release(); err != nil {
		t.Errorf("Error releasing lock for file %q: %s", fileName, err)
	}
}