// - skips t if the platform does not support os/exec,
// - sends SIGQUIT (if supported by the platform) instead of SIGKILL
// in its Cancel function
-// - adds a timeout (with an arbitrary grace period) before the test's deadline expires,
-// - sets a WaitDelay for an arbitrary grace period,
+// - if the test has a deadline, adds a Context timeout and WaitDelay
+// for an arbitrary grace period before the test's deadline expires,
// - fails the test if the command does not complete before the test's deadline, and
// - sets a Cleanup function that verifies that the test did not leak a subprocess.
func CommandContext(t testing.TB, ctx context.Context, name string, args ...string) *exec.Cmd {
MustHaveExec(t)
var (
- gracePeriod = 100 * time.Millisecond
- cancel context.CancelFunc
+ cancelCtx context.CancelFunc
+ gracePeriod time.Duration // unlimited unless the test has a deadline (to allow for interactive debugging)
)
- if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
- scale, err := strconv.Atoi(s)
- if err != nil {
- t.Fatalf("invalid GO_TEST_TIMEOUT_SCALE: %v", err)
- }
- gracePeriod *= time.Duration(scale)
- }
if t, ok := t.(interface {
testing.TB
Deadline() (time.Time, bool)
}); ok {
if td, ok := t.Deadline(); ok {
- if cd, ok := ctx.Deadline(); !ok || cd.Sub(td) > gracePeriod {
- // Either ctx doesn't have a deadline, or its deadline would expire
- // after (or too close before) the test has already timed out.
- // Compute a new timeout that will expire before the test does so that
- // we can terminate the subprocess with a more useful signal.
-
- timeout := time.Until(td)
-
- // If time allows, increase the termination grace period to 5% of the
- // remaining time.
- if gp := timeout / 20; gp > gracePeriod {
- gracePeriod = gp
+ // Start with a minimum grace period, just long enough to consume the
+ // output of a reasonable program after it terminates.
+ gracePeriod = 100 * time.Millisecond
+ if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
+ scale, err := strconv.Atoi(s)
+ if err != nil {
+ t.Fatalf("invalid GO_TEST_TIMEOUT_SCALE: %v", err)
}
+ gracePeriod *= time.Duration(scale)
+ }
+
+ // If time allows, increase the termination grace period to 5% of the
+ // test's remaining time.
+ testTimeout := time.Until(td)
+ if gp := testTimeout / 20; gp > gracePeriod {
+ gracePeriod = gp
+ }
- // When we run commands that execute subprocesses, we want to reserve two
- // grace periods to clean up. We will send the first termination signal when
- // the context expires, then wait one grace period for the process to
- // produce whatever useful output it can (such as a stack trace). After the
- // first grace period expires, we'll escalate to os.Kill, leaving the second
- // grace period for the test function to record its output before the test
- // process itself terminates.
- timeout -= 2 * gracePeriod
-
- ctx, cancel = context.WithTimeout(ctx, timeout)
- t.Cleanup(cancel)
+ // When we run commands that execute subprocesses, we want to reserve two
+ // grace periods to clean up: one for the delay between the first
+ // termination signal being sent (via the Cancel callback when the Context
+ // expires) and the process being forcibly terminated (via the WaitDelay
+ // field), and a second one for the delay becween the process being
+ // terminated and and the test logging its output for debugging.
+ //
+ // (We want to ensure that the test process itself has enough time to
+ // log the output before it is also terminated.)
+ cmdTimeout := testTimeout - 2*gracePeriod
+
+ if cd, ok := ctx.Deadline(); !ok || time.Until(cd) > cmdTimeout {
+ // Either ctx doesn't have a deadline, or its deadline would expire
+ // after (or too close before) the test has already timed out.
+ // Add a shorter timeout so that the test will produce useful output.
+ ctx, cancelCtx = context.WithTimeout(ctx, cmdTimeout)
}
}
}
cmd := exec.CommandContext(ctx, name, args...)
cmd.Cancel = func() error {
- if cancel != nil && ctx.Err() == context.DeadlineExceeded {
+ if cancelCtx != nil && ctx.Err() == context.DeadlineExceeded {
// The command timed out due to running too close to the test's deadline.
// There is no way the test did that intentionally — it's too close to the
// wire! — so mark it as a test failure. That way, if the test expects the
cmd.WaitDelay = gracePeriod
t.Cleanup(func() {
- if cancel != nil {
- cancel()
+ if cancelCtx != nil {
+ cancelCtx()
}
if cmd.Process != nil && cmd.ProcessState == nil {
t.Errorf("command was started, but test did not wait for it to complete: %v", cmd)