Spotify: consider rate limit HTTP headers

backends/spotify/client.go

@@ -25,6 +25,7 @@ package spotify
 import (
 	"context"
 	"errors"
+	"net/http"
 	"strconv"
 	"time"
 
@@ -34,6 +35,7 @@ import (
 
 const baseURL = "https://api.spotify.com/v1/"
 const MaxItemsPerGet = 50
+const DefaultRateLimitWaitSeconds = 5
 
 type Client struct {
 	HttpClient *resty.Client
@@ -46,6 +48,24 @@ func NewClient(token oauth2.TokenSource) Client {
 	client.SetBaseURL(baseURL)
 	client.SetHeader("Accept", "application/json")
 	client.SetRetryCount(5)
+	client.AddRetryCondition(
+		func(r *resty.Response, err error) bool {
+			code := r.StatusCode()
+			return code == http.StatusTooManyRequests || code >= http.StatusInternalServerError
+		},
+	)
+	client.SetRetryMaxWaitTime(time.Duration(1 * time.Minute))
+	client.SetRetryAfter(func(client *resty.Client, resp *resty.Response) (time.Duration, error) {
+		var err error
+		var retryAfter int = DefaultRateLimitWaitSeconds
+		if resp.StatusCode() == http.StatusTooManyRequests {
+			retryAfter, err = strconv.Atoi(resp.Header().Get("Retry-After"))
+			if err != nil {
+				retryAfter = DefaultRateLimitWaitSeconds
+			}
+		}
+		return time.Duration(retryAfter * int(time.Second)), err
+	})
 	return Client{
 		HttpClient: client,
 	}