private static RequestId nextRequestId(RoutingContext routingCtx, ServiceConfig serviceConfig) {
        try {
            final RequestId id = serviceConfig.requestIdGenerator().apply(routingCtx);
            if (id != null) {
                return id;
            }

            if (!warnedNullRequestId) {
                warnedNullRequestId = true;
                logger.warn("requestIdGenerator.apply(routingCtx) returned null; using RequestId.random()");
            }
            return RequestId.random();
        } catch (Exception e) {
            if (!warnedRequestIdGenerateFailure) {
                warnedRequestIdGenerateFailure = true;
                logger.warn("requestIdGenerator.apply(routingCtx) threw an exception; using RequestId.random()",
                            e);
            }
            return RequestId.random();
        }
    }
Sets the 'content-length' header to the response.
core/src/main/java/com/linecorp/armeria/server/HttpServerHandler.java