/// <inheritdoc />
        public Task StartClusterConfigurationUpgradeAsync(
            ClusterConfigurationUpgradeDescription clusterConfigurationUpgradeDescription,
            long?serverTimeout = 60,
            CancellationToken cancellationToken = default(CancellationToken))
        {
            clusterConfigurationUpgradeDescription.ThrowIfNull(nameof(clusterConfigurationUpgradeDescription));
            serverTimeout?.ThrowIfOutOfInclusiveRange("serverTimeout", 1, 4294967295);
            var requestId   = Guid.NewGuid().ToString();
            var url         = "$/StartClusterConfigurationUpgrade";
            var queryParams = new List <string>();

            // Append to queryParams if not null.
            serverTimeout?.AddToQueryParameters(queryParams, $"timeout={serverTimeout}");
            queryParams.Add("api-version=6.0");
            url += "?" + string.Join("&", queryParams);

            string content;

            using (var sw = new StringWriter())
            {
                ClusterConfigurationUpgradeDescriptionConverter.Serialize(new JsonTextWriter(sw), clusterConfigurationUpgradeDescription);
                content = sw.ToString();
            }

            HttpRequestMessage RequestFunc()
            {
                var request = new HttpRequestMessage()
                {
                    Method  = HttpMethod.Post,
                    Content = new StringContent(content, Encoding.UTF8)
                };

                request.Content.Headers.ContentType = System.Net.Http.Headers.MediaTypeHeaderValue.Parse("application/json; charset=utf-8");
                return(request);
            }

            return(this.httpClient.SendAsync(RequestFunc, url, requestId, cancellationToken));
        }