ListenBrainz: Handle rate limit

backends/listenbrainz/client.go

@@ -23,6 +23,7 @@ package listenbrainz
 
 import (
 	"errors"
+	"net/http"
 	"strconv"
 	"time"
 
@@ -40,17 +41,29 @@ type Client struct {
 }
 
 func NewClient(token string) Client {
-	resty := resty.New()
-	resty.SetBaseURL(listenBrainzBaseURL)
-	resty.SetAuthScheme("Token")
-	resty.SetAuthToken(token)
-	resty.SetHeader("Accept", "application/json")
-	client := Client{
-		HttpClient: resty,
+	client := resty.New()
+	client.SetBaseURL(listenBrainzBaseURL)
+	client.SetAuthScheme("Token")
+	client.SetAuthToken(token)
+	client.SetHeader("Accept", "application/json")
+
+	// Handle rate limiting (see https://listenbrainz.readthedocs.io/en/latest/users/api/index.html#rate-limiting)
+	client.SetRetryCount(5)
+	client.AddRetryCondition(
+		func(r *resty.Response, err error) bool {
+			return r.StatusCode() == http.StatusTooManyRequests
+		},
+	)
+	client.SetRetryAfter(func(client *resty.Client, resp *resty.Response) (time.Duration, error) {
+		resetIn, err := strconv.Atoi(resp.Header().Get("X-RateLimit-Reset-In"))
+		// fmt.Printf("R %v: %v, %v\n", resp.Request.URL, resetIn, err)
+		return time.Duration(resetIn * int(time.Second)), err
+	})
+
+	return Client{
+		HttpClient: client,
 		MaxResults: DefaultItemsPerGet,
 	}
-
-	return client
 }
 
 func (c Client) GetListens(user string, maxTime time.Time, minTime time.Time) (result GetListensResult, err error) {