func waitForStartLinux()

in integration_test/gce-testing-internal/gce/gce_testing.go [2170:2231]
37 lines of code
7 McCabe index (conditional complexity)

func waitForStartLinux(ctx context.Context, logger *log.Logger, vm *VM) error {
	var backoffPolicy backoff.BackOff
	backoffPolicy = backoff.NewConstantBackOff(vmInitBackoffDuration)
	if IsSUSEImageSpec(vm.ImageSpec) {
		// Give up early on SUSE due to b/186426190. If this step times out, the
		// error will be retried with a fresh VM.
		backoffPolicy = backoff.WithMaxRetries(backoffPolicy, uint64((5*time.Minute)/vmInitBackoffDuration))
	}
	backoffPolicy = backoff.WithContext(backoffPolicy, ctx)

	// Returns an error if system startup is still ongoing.
	// Hopefully, waiting for system startup to finish will avoid some
	// hard-to-debug flaky issues like:
	// * b/180518814 (ubuntu, sles)
	// * b/148612123 (sles)
	isStartupDone := func() error {
		ctx, cancel := context.WithTimeout(ctx, vmInitPokeSSHTimeout)
		defer cancel()
		output, err := RunRemotely(ctx, logger, vm, "systemctl is-system-running")

		// There are a few cases for what is-system-running returns:
		// https://www.freedesktop.org/software/systemd/man/systemctl.html#is-system-running
		// If the command failed due to SSH issues, the stdout should be "".
		state := strings.TrimSpace(output.Stdout)
		if state == "running" {
			return nil
		}
		if state == "degraded" {
			// Even though some services failed to start, it's worth continuing
			// to run the test. There are various unnecessary services that could be
			// failing, see b/185473981 and b/185182238 for some examples.
			// But let's at least print out which services failed into the logs.
			RunRemotely(ctx, logger, vm, "systemctl --failed")
			return nil
		}
		// There are several reasons this could be failing, but usually if we get
		// here, that just means that ssh is not ready yet or the VM is in some
		// kind of non-ready state, like "starting".
		return err
	}

	if err := backoff.Retry(isStartupDone, backoffPolicy); err != nil {
		return fmt.Errorf("%v. Last err=%v", startupFailedMessage, err)
	}

	if IsSUSEImageSpec(vm.ImageSpec) {
		// TODO(b/259122953): SUSE needs additional startup time. Remove once we have more
		// sensible/deterministic workarounds for each of the individual problems.
		time.Sleep(slesStartupDelay)
		// TODO(b/259122953): wait until sudo is ready
		backoffPolicy := backoff.WithContext(backoff.WithMaxRetries(backoff.NewConstantBackOff(slesStartupSudoDelay), slesStartupSudoMaxAttempts), ctx)
		err := backoff.Retry(func() error {
			_, err := RunRemotely(ctx, logger, vm, "sudo ls /root")
			return err
		}, backoffPolicy)
		if err != nil {
			return fmt.Errorf("exceeded retries trying to get sudo: %v", err)
		}
	}

	return nil
}