/// <summary>
/// Gets the personalized video suggestions for a specific user.
/// </summary>
public override async Task <GetSuggestedForUserResponse> GetSuggestedForUser(GetSuggestedForUserRequest request, ServerCallContext context)
{
// Return the output of a Spark job that runs periodically in the background to populate the video_recommendations table
// (see the /data/spark folder in the repo for more information)
PreparedStatement prepared = await _statementCache.GetOrAddAsync(
"SELECT videoid, authorid, name, added_date, preview_image_location FROM video_recommendations WHERE userid=?");
IStatement bound = prepared.Bind(request.UserId.ToGuid())
.SetAutoPage(false)
.SetPageSize(request.PageSize);
// The initial query won't have a paging state, but subsequent calls should if there are more pages
if (string.IsNullOrEmpty(request.PagingState) == false)
{
bound.SetPagingState(Convert.FromBase64String(request.PagingState));
}
RowSet rows = await _session.ExecuteAsync(bound).ConfigureAwait(false);
var response = new GetSuggestedForUserResponse
{
UserId = request.UserId,
PagingState = rows.PagingState != null && rows.PagingState.Length > 0 ? Convert.ToBase64String(rows.PagingState) : ""
};
response.Videos.Add(rows.Select(MapRowToVideoPreview));
return(response);
}
/// <summary>
/// Gets the personalized video suggestions for a specific user.
/// Based on DSL tutorial provided here, we changed the recommendation from pre-aggration
/// tables to real-time graph recommendation.
/// https://academy.datastax.com/content/gremlin-dsls-net-dse-graph
/// </summary>
public override async Task <GetSuggestedForUserResponse> GetSuggestedForUser(GetSuggestedForUserRequest request,
ServerCallContext context)
{
Logger.Information("Request suggested video(s) for user {user}", request.UserId.Value);
GraphTraversalSource g = DseGraph.Traversal(_session);
// DSL Baby !
var traversal = g.RecommendVideos(request.UserId.ToGuid().ToString(), 5, 4, 1000, 5);
GraphResultSet result = await _session.ExecuteGraphAsync(traversal);
// Building GRPC response from list of results vertices (hopefully 'numberOfVideosExpected')
var grpcResponse = new GetSuggestedForUserResponse
{
UserId = request.UserId,
PagingState = ""
};
foreach (IVertex vertex in result.To <IVertex>())
{
Logger.Information("Result " + vertex);
grpcResponse.Videos.Add(MapVertexToVideoPreview(vertex));
}
return(grpcResponse);
}
/// <summary>
/// Gets the personalized video suggestions for a specific user.
/// </summary>
public override Task <GetSuggestedForUserResponse> GetSuggestedForUser(GetSuggestedForUserRequest request, ServerCallContext context)
{
// TODO: Can we implement suggestions without DSE and Spark? (Yeah, probably not)
var response = new GetSuggestedForUserResponse {
UserId = request.UserId
};
return(Task.FromResult(response));
}