/// <summary>
/// Gets the first 4 videos related to the specified video. Does not support paging.
/// </summary>
public override async Task <GetRelatedVideosResponse> GetRelatedVideos(GetRelatedVideosRequest request, ServerCallContext context)
{
// Lookup the tags for the video
PreparedStatement tagsForVideoPrepared = await _statementCache.GetOrAddAsync("SELECT tags FROM videos WHERE videoid = ?");
BoundStatement tagsForVideoBound = tagsForVideoPrepared.Bind(request.VideoId.ToGuid());
RowSet tagRows = await _session.ExecuteAsync(tagsForVideoBound).ConfigureAwait(false);
// Start with an empty response
var response = new GetRelatedVideosResponse {
VideoId = request.VideoId
};
Row tagRow = tagRows.SingleOrDefault();
if (tagRow == null)
{
return(response);
}
var tagsValue = tagRow.GetValue <IEnumerable <string> >("tags");
var tags = tagsValue?.ToList() ?? new List <string>();
// If there are no tags, we can't find related videos
if (tags.Count == 0)
{
return(response);
}
var relatedVideos = new Dictionary <Uuid, SuggestedVideoPreview>();
PreparedStatement videosForTagPrepared = await _statementCache.GetOrAddAsync("SELECT * FROM videos_by_tag WHERE tag = ? LIMIT ?");
var inFlightQueries = new List <Task <RowSet> >();
for (var i = 0; i < tags.Count; i++)
{
// Use the number of results we ultimately want * 2 when querying so that we can account for potentially having to filter
// out the video Id we're using as the basis for the query as well as duplicates
const int pageSize = RelatedVideosToReturn * 2;
// Kick off a query for each tag and track them in the inflight requests list
string tag = tags[i];
IStatement query = videosForTagPrepared.Bind(tag, pageSize);
inFlightQueries.Add(_session.ExecuteAsync(query));
// Every third query, or if this is the last tag, wait on all the query results
if (inFlightQueries.Count == 3 || i == tags.Count - 1)
{
RowSet[] results = await Task.WhenAll(inFlightQueries).ConfigureAwait(false);
foreach (RowSet rowSet in results)
{
foreach (Row row in rowSet)
{
SuggestedVideoPreview preview = MapRowToVideoPreview(row);
// Skip self
if (preview.VideoId.Equals(request.VideoId))
{
continue;
}
// Skip videos we already have in the results
if (relatedVideos.ContainsKey(preview.VideoId))
{
continue;
}
// Add to results
relatedVideos.Add(preview.VideoId, preview);
// If we've got enough, no reason to continue
if (relatedVideos.Count >= RelatedVideosToReturn)
{
break;
}
}
// If we've got enough, no reason to continue
if (relatedVideos.Count >= RelatedVideosToReturn)
{
break;
}
}
// See if we've got enough results now to fulfill our requirement
if (relatedVideos.Count >= RelatedVideosToReturn)
{
break;
}
// We don't have enough yet, so reset the inflight requests to allow another batch of tags to be queried
inFlightQueries.Clear();
}
}
// Add any videos found to the response and return
response.Videos.Add(relatedVideos.Values);
return(response);
}
/// <summary>
/// Gets the first 5 videos related to the specified video.
/// </summary>
public override async Task <GetRelatedVideosResponse> GetRelatedVideos(GetRelatedVideosRequest request, ServerCallContext context)
{
// Get REST client for dse-search service
Uri searchUri = await GetDseSearchUri().ConfigureAwait(false);
IRestClient restClient = _createRestClient(searchUri);
// Example request: http://127.0.2.15:8983/solr/killrvideo.videos/mlt?q=videoid%3Asome-uuid&wt=json&indent=true&qt=mlt&mlt.fl=name&mlt.mindf=1&mlt.mintf=1
var solrRequest = new RestRequest("killrvideo.videos/mlt");
solrRequest.AddParameter("q", $"videoid:\"{request.VideoId.Value}\"");
solrRequest.AddParameter("wt", "json");
// Paging information
int start;
if (request.PagingState == null || int.TryParse(request.PagingState, out start) == false)
{
start = 0;
}
solrRequest.AddParameter("start", start);
solrRequest.AddParameter("rows", request.PageSize);
//MLT Fields to Consider
solrRequest.AddParameter("mlt.fl", "name,description,tags");
//MLT Minimum Document Frequency - the frequency at which words will be ignored which do not occur in at least this many docs.
solrRequest.AddParameter("mlt.mindf", 2);
//MLT Minimum Term Frequency - the frequency below which terms will be ignored in the source doc.
solrRequest.AddParameter("mlt.mintf", 2);
IRestResponse <MLTQueryResult> solrResponse = await restClient.ExecuteTaskAsync <MLTQueryResult>(solrRequest).ConfigureAwait(false);
// Start with an empty response
var response = new GetRelatedVideosResponse {
VideoId = request.VideoId
};
// Check for network/timeout errors
if (solrResponse.ResponseStatus != ResponseStatus.Completed)
{
// TODO: Logger.Error(response.ErrorException, "Error while querying Solr video suggestions from {host} for {query}", nodeIp, query);
return(response);
}
// Check for HTTP error codes
if (solrResponse.StatusCode != HttpStatusCode.OK)
{
// TODO: Logger.Error("HTTP status code {code} while querying Solr video suggestions from {host} for {query}", (int) response.StatusCode, nodeIp, query);
return(response);
}
// Success
int nextPageStartIndex = solrResponse.Data.Response.Start + solrResponse.Data.Response.Docs.Count;
string pagingState = nextPageStartIndex == solrResponse.Data.Response.NumFound ? "" : nextPageStartIndex.ToString();
response.PagingState = pagingState;
response.Videos.Add(solrResponse.Data.Response.Docs.Select(doc => new SuggestedVideoPreview
{
VideoId = doc.VideoId.ToUuid(),
AddedDate = doc.AddedDate.ToTimestamp(),
Name = doc.Name,
PreviewImageLocation = doc.PreviewImageLocation,
UserId = doc.UserId.ToUuid()
}));
return(response);
}