private async Task <IEnumerable <PackageInfo> > FindPackagesByIdAsyncCore(string id, CancellationToken cancellationToken)
        {
            for (var retry = 0; retry != 3; ++retry)
            {
                var uri = _baseUri + "FindPackagesById()?id='" + id + "'";

                try
                {
                    var results = new List <PackageInfo>();
                    var page    = 1;
                    while (true)
                    {
                        // TODO: Pages for a package Id are cached separately.
                        // So we will get inaccurate data when a page shrinks.
                        // However, (1) In most cases the pages grow rather than shrink;
                        // (2) cache for pages is valid for only 30 min.
                        // So we decide to leave current logic and observe.
                        using (var data = await _httpSource.GetAsync(
                                   uri,
                                   new[] { new MediaTypeWithQualityHeaderValue("application/atom+xml"), new MediaTypeWithQualityHeaderValue("application/xml") },
                                   $"list_{id}_page{page}",
                                   CreateCacheContext(retry),
                                   Logger,
                                   ignoreNotFounds: false,
                                   ensureValidContents: stream => HttpStreamValidation.ValidateXml(uri, stream),
                                   cancellationToken: cancellationToken))
                        {
                            if (data.Status == HttpSourceResultStatus.NoContent)
                            {
                                // Team city returns 204 when no versions of the package exist
                                // This should result in an empty list and we should not try to
                                // read the stream as xml.
                                break;
                            }

                            var doc = V2FeedParser.LoadXml(data.Stream);

                            var result = doc.Root
                                         .Elements(_xnameEntry)
                                         .Select(x => BuildModel(id, x))
                                         .Where(x => x != null);

                            results.AddRange(result);

                            // Find the next url for continuation
                            var nextUri = V2FeedParser.GetNextUrl(doc);

                            // Stop if there's nothing else to GET
                            if (string.IsNullOrEmpty(nextUri))
                            {
                                break;
                            }

                            uri = nextUri;
                            page++;
                        }
                    }

                    return(results);
                }
                catch (Exception ex) when(retry < 2)
                {
                    string message = string.Format(CultureInfo.CurrentCulture, Strings.Log_RetryingFindPackagesById, nameof(FindPackagesByIdAsyncCore), uri)
                                     + Environment.NewLine
                                     + ExceptionUtilities.DisplayMessage(ex);

                    Logger.LogMinimal(message);
                }
                catch (Exception ex) when(retry == 2)
                {
                    // Fail silently by returning empty result list
                    var message = string.Format(CultureInfo.CurrentCulture, Strings.Log_FailedToRetrievePackage, uri);

                    Logger.LogError(message + Environment.NewLine + ex.Message);

                    throw new FatalProtocolException(message, ex);
                }
            }

            return(null);
        }