code: public final B healthCheckInterval(Duration healthCheckInterval) {
          requireNonNull(healthCheckInterval, "healthCheckInterval");
          checkArgument(!healthCheckInterval.isNegative(),
                        "healthCheckInterval: %s (expected: >= 0)", healthCheckInterval);
          this.healthCheckInterval = healthCheckInterval;
          return self();
      }
docs: Sets the interval between health check requests. The default value is
  {@value #DEFAULT_HEALTH_CHECK_INTERVAL_MILLIS} seconds.
  
  @param healthCheckInterval the interval between health check requests. {@link Duration#ZERO} disables
  health check requests.