Fix buggy Last.FM by falling back to artist search

Author: dewey

api/service.go

@@ -2,6 +2,7 @@ package api
 
 import (
 	"errors"
+	"fmt"
 	"time"
 
 	"github.com/go-kit/kit/log"
@@ -138,22 +139,31 @@ func (s *service) GenerateTaste(username string, period string, limit int) ([]la
 			if err != nil {
 				// If we don't have it in our store we get the unique top tag for the first 4 artists
 				start = time.Now()
-				tt, err := s.client.GetTopTags(ta.Mbid)
+
+				// We try to get the top tags by mbid, but if this doesn't work because of the Last.FM bug we fallback to the artist name:
+				// https://www.reddit.com/r/lastfm/comments/1g9suo3/api_problem/
+				tt, err := s.client.GetTopTags(ta.Mbid, ta.Name)
 				fetchDurationHistogram.WithLabelValues(period, "get_top_tags").Observe(time.Since(start).Seconds())
 				cacheMissTotalCounter.Add(1)
 				if err != nil {
 					s.l.Log("err", err)
 					continue
 				}
+				// If we don't get any top tags, we just append the artist without tags
 				if len(tt) > 1 {
 					ta.Genre = tt[0]
 					if _, ok := m[ta.Genre]; !ok {
 						al = append(al, ta)
 						m[ta.Genre] = struct{}{}
 					}
 					// We store the newly fetched information in our storage backend so we don't have to fetch it again for the next user
-					s.storageRepository.Save(ta.Mbid, tt[0])
+					if err := s.storageRepository.Save(ta.Mbid, tt[0]); err != nil {
+						s.l.Log("msg", fmt.Sprintf("failed to save artist key: %s,", err), "backend", s.cfg.StorageBackend)
+					}
+				} else {
+					al = append(al, ta)
 				}
+
 				continue
 			}
 			cacheHitTotalCounter.Add(1)

client/lastfm/lastfm.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"net/url"
 )
 
 // Client contains everything needed for a Last.FM client
@@ -76,7 +77,8 @@ type TopArtist struct {
 
 // GetTopArtists gets the top artist of a user from Last.FM
 func (c *Client) GetTopArtists(username string, period string, limit int) ([]TopArtist, error) {
-	req, err := http.NewRequest("GET", fmt.Sprintf("http://ws.audioscrobbler.com/2.0/?method=user.gettopartists&user=%s&api_key=%s&format=json&period=%s&limit=%d", username, c.APIKey, period, limit), nil)
+	call := fmt.Sprintf("http://ws.audioscrobbler.com/2.0/?method=user.gettopartists&user=%s&api_key=%s&format=json&period=%s&limit=%d", username, c.APIKey, period, limit)
+	req, err := http.NewRequest("GET", call, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -146,9 +148,29 @@ func (c *Client) GetWeeklyArtistChart(username string, from, to int64, limit int
 	return tal, nil
 }
 
-// GetTopTags gets the top tags for an artist from the Last.FM API
-func (c *Client) GetTopTags(mbid string) ([]string, error) {
-	req, err := http.NewRequest("GET", fmt.Sprintf("http://ws.audioscrobbler.com/2.0/?method=artist.gettoptags&mbid=%s&api_key=%s&format=json", mbid, c.APIKey), nil)
+// GetTopTags gets the top tags for an artist from the Last.FM API by mbid, or artist as a fallback
+func (c *Client) GetTopTags(mbid string, artist string) ([]string, error) {
+	if mbid == "" {
+		return c.getTopTags("artist", artist)
+	}
+	return c.getTopTags("mbid", mbid)
+}
+
+func (c *Client) getTopTags(by string, value string) ([]string, error) {
+	call := fmt.Sprintf("http://ws.audioscrobbler.com/2.0/?method=artist.gettoptags&api_key=%s&format=json", c.APIKey)
+	u, err := url.Parse(call)
+	if err != nil {
+		return nil, err
+	}
+	q := u.Query()
+	switch by {
+	case "mbid":
+		q.Add("mbid", value)
+	default:
+		q.Add("artist", value)
+	}
+	u.RawQuery = q.Encode()
+	req, err := http.NewRequest("GET", u.String(), nil)
 	if err != nil {
 		return nil, err
 	}