package semaphore // Based on https://github.com/golang/sync/blob/master/semaphore/semaphore_test.go import ( "context" "math/rand" "runtime" "sync" "testing" "time" "github.com/stretchr/testify/require" ) const maxSleep = 1 * time.Millisecond func HammerDynamic(sem *Dynamic, loops int) { for i := 0; i < loops; i++ { sem.Acquire(context.Background()) time.Sleep(time.Duration(rand.Int63n(int64(maxSleep/time.Nanosecond))) * time.Nanosecond) sem.Release() } } // TestDynamic hammers the semaphore from all available cores to ensure we don't // hit a panic or race detector notice something wonky. func TestDynamic(t *testing.T) { if testing.Short() { t.Skip("too slow for testing.Short") } t.Parallel() n := runtime.GOMAXPROCS(0) loops := 10000 / n sem := NewDynamic(int64(n)) var wg sync.WaitGroup wg.Add(n) for i := 0; i < n; i++ { go func() { defer wg.Done() HammerDynamic(sem, loops) }() } wg.Wait() } func TestDynamicPanic(t *testing.T) { t.Parallel() defer func() { if recover() == nil { t.Fatal("release of an unacquired dynamic semaphore did not panic") } }() w := NewDynamic(1) w.Release() } func checkAcquire(t *testing.T, sem *Dynamic, wantAcquire bool) { t.Helper() ctx, cancel := context.WithTimeout(context.Background(), 10*time.Millisecond) defer cancel() err := sem.Acquire(ctx) if wantAcquire { require.NoErrorf(t, err, "failed to acquire when we should have") } else { require.Error(t, err, "failed to block when should be full") } } func TestDynamicAcquire(t *testing.T) { t.Parallel() ctx := context.Background() sem := NewDynamic(2) // Consume one slot [free: 1] sem.Acquire(ctx) // Should be able to consume another [free: 0] checkAcquire(t, sem, true) // Should fail to consume another [free: 0] checkAcquire(t, sem, false) // Release 2 sem.Release() sem.Release() // Should be able to consume another [free: 1] checkAcquire(t, sem, true) // Should be able to consume another [free: 0] checkAcquire(t, sem, true) // Should fail to consume another [free: 0] checkAcquire(t, sem, false) // Now expand the semaphore and we should be able to acquire again [free: 2] sem.SetSize(4) // Should be able to consume another [free: 1] checkAcquire(t, sem, true) // Should be able to consume another [free: 0] checkAcquire(t, sem, true) // Should fail to consume another [free: 0] checkAcquire(t, sem, false) // Shrinking it should work [free: 0] sem.SetSize(3) // Should fail to consume another [free: 0] checkAcquire(t, sem, false) // Release one [free: 0] (3 slots used are release, size only 3) sem.Release() // Should fail to consume another [free: 0] checkAcquire(t, sem, false) sem.Release() // Should be able to consume another [free: 1] checkAcquire(t, sem, true) }