Wait for Selenium Grid to become available

WaitForSeleniumGrid.java

    /**
     * Wait for Grid to come online
     * @param url to check, e.g. http://127.0.0.1:4444/wd/hub/status
     * @param duration value
     * @param unit of duration
     */
    public static boolean waitForSeleniumGrid(String url, long duration, TemporalUnit unit) throws ExecutionException, InterruptedException {
        Instant start = Instant.now();
        Instant stopWaiting = start.plus(duration, unit);
        final ScheduledExecutorService ses = Executors.newSingleThreadScheduledExecutor();
        final CompletableFuture<Boolean> cf = new CompletableFuture<>();

        final AtomicBoolean success = new AtomicBoolean(false);
        final ScheduledFuture<?>[] m = new ScheduledFuture[] { null };
        Runnable r = () -> {
            Instant now = Instant.now();
            long timeLeft = Duration.between(now, stopWaiting).getSeconds();
            logger.warning(String.format("waiting for Selenium grid to start... time left=%d seconds", timeLeft));
            try {
                long elapsed = Duration.between(start, now).getSeconds();
                if (stopWaiting.isBefore(Instant.now())) {
                    cf.completeExceptionally(new Exception(String.format("Could not connect to Selenium Grid after %d seconds", elapsed)));
                } else {
                    URLConnection connection = new URL(url).openConnection();
                    connection.connect();
                    Reader content = new InputStreamReader(connection.getInputStream(), StandardCharsets.UTF_8);
                    WDHubStatus hubStatus = new Gson().fromJson(content, WDHubStatus.class);
                    content.close();
                    if (0 == hubStatus.status && hubStatus.value.ready) {
                        m[0].cancel(true);
                        success.set(true);
                        cf.complete(true);
                    }
                }
            } catch (MalformedURLException e) {
                cf.completeExceptionally(e);
            } catch(IOException ignored) {
            }
        };

        m[0] = ses.scheduleAtFixedRate(r, 1000, 1000, TimeUnit.MILLISECONDS);
        cf.join();
        ses.shutdown();
        return success.get();
    }

    private static class WDHubStatusValue {
        boolean ready;
        String message;
    }

    private static class WDHubStatus {
        long status;
        WDHubStatusValue value;
    }