added slapapi

pkg/slapshotapi/limiting.go

@@ -0,0 +1,59 @@
+package slapshotapi
+
+import (
+	"context"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/pkg/errors"
+	"golang.org/x/time/rate"
+)
+
+func (c *SlapAPI) do(ctx context.Context, req *http.Request) (*http.Response, error) {
+	for {
+		err := c.ratelimiter.Wait(ctx)
+		if err != nil {
+			return nil, errors.Wrap(err, "c.ratelimiter.Wait")
+		}
+		resp, err := c.client.Do(req)
+		if err != nil {
+			return nil, errors.Wrap(err, "c.client.Do")
+		}
+		if resp.StatusCode == http.StatusTooManyRequests {
+			resetAfter := 30 * time.Second
+			err := resp.Body.Close()
+			if err != nil {
+				return nil, errors.Wrap(err, "resp.Body.Close")
+			}
+			if resetAfter > 0 {
+				select {
+				case <-ctx.Done():
+					return nil, ctx.Err()
+				case <-time.After(resetAfter):
+					continue
+				}
+			}
+		}
+		c.updateLimiterFromHeaders(resp.Header)
+		return resp, nil
+	}
+}
+
+func (c *SlapAPI) updateLimiterFromHeaders(h http.Header) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	limit, err1 := strconv.Atoi(h.Get("RateLimit-Limit"))
+	window, err2 := strconv.Atoi(h.Get("RateLimit-Window"))
+
+	if err1 != nil || err2 != nil || limit <= 0 || window <= 0 {
+		return
+	}
+
+	if limit != c.maxTokens || time.Duration(window) != time.Duration(float64(window)/float64(limit))*time.Second {
+		c.maxTokens = limit
+		c.ratelimiter.SetBurst(limit)
+		c.ratelimiter.SetLimit(rate.Every(time.Duration(window) / time.Duration(limit)))
+	}
+}