code: public HttpHealthCheckedEndpointGroupBuilder retryInterval(Duration retryInterval) {
          requireNonNull(retryInterval, "retryInterval");
          checkArgument(!retryInterval.isNegative() && !retryInterval.isZero(),
                        "retryInterval: %s (expected > 0)", retryInterval);
          this.retryInterval = retryInterval;
          return this;
      }
docs: Sets the interval between health check requests. Must be positive.