@Override
        public void run() {
            if (pendingPings < 5) {
                if (res.tryWrite(ping)) {
                    ++pendingPings;
                    res.whenConsumed().thenRun(() -> pendingPings--);
                }
            } else {
                // Do not send a ping if the client is not reading it.
            }
        }
Extends the request timeout by the specified {@code longPollingTimeoutMillis}, because otherwise
the client will get {@code "503 Service Unavailable} due to a {@link RequestTimeoutException} before
long-polling finishes.
core/src/main/java/com/linecorp/armeria/server/healthcheck/HealthCheckService.java