retry logic

internal/reddit/client.go

@@ -22,6 +22,12 @@ type Client struct {
 	statsd statsd.ClientInterface
 }
 
+var backoffSchedule = []time.Duration{
+	4 * time.Second,
+	8 * time.Second,
+	16 * time.Second,
+}
+
 func SplitID(id string) (string, string) {
 	if parts := strings.Split(id, "_"); len(parts) == 2 {
 		return parts[0], parts[1]
@@ -93,21 +99,23 @@ func (rc *Client) NewAuthenticatedClient(refreshToken, accessToken string) *Auth
 	return &AuthenticatedClient{rc, refreshToken, accessToken, nil}
 }
 
-func (rac *AuthenticatedClient) request(r *Request, rh ResponseHandler, empty interface{}) (interface{}, error) {
+func (rc *Client) doRequest(r *Request) ([]byte, error) {
 	req, err := r.HTTPRequest()
 	if err != nil {
 		return nil, err
 	}
 
-	req = req.WithContext(httptrace.WithClientTrace(req.Context(), rac.tracer))
+	req = req.WithContext(httptrace.WithClientTrace(req.Context(), rc.tracer))
 
 	start := time.Now()
-	resp, err := rac.client.Do(req)
-	_ = rac.statsd.Incr("reddit.api.calls", r.tags, 0.1)
-	_ = rac.statsd.Histogram("reddit.api.latency", float64(time.Since(start).Milliseconds()), r.tags, 0.1)
+
+	resp, err := rc.client.Do(req)
+
+	_ = rc.statsd.Incr("reddit.api.calls", r.tags, 0.1)
+	_ = rc.statsd.Histogram("reddit.api.latency", float64(time.Since(start).Milliseconds()), r.tags, 0.1)
 
 	if err != nil {
-		_ = rac.statsd.Incr("reddit.api.errors", r.tags, 0.1)
+		_ = rc.statsd.Incr("reddit.api.errors", r.tags, 0.1)
 		if strings.Contains(err.Error(), "http2: timeout awaiting response headers") {
 			return nil, ErrTimeout
 		}
@@ -115,15 +123,45 @@ func (rac *AuthenticatedClient) request(r *Request, rh ResponseHandler, empty in
 	}
 	defer resp.Body.Close()
 
-	bb, err := ioutil.ReadAll(resp.Body)
-	if err != nil {
-		_ = rac.statsd.Incr("reddit.api.errors", r.tags, 0.1)
-		return nil, err
+	if resp.StatusCode != 200 {
+		_ = rc.statsd.Incr("reddit.api.errors", r.tags, 0.1)
+		return nil, ServerError{resp.StatusCode}
 	}
 
-	if resp.StatusCode != 200 {
+	bb, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		_ = rc.statsd.Incr("reddit.api.errors", r.tags, 0.1)
+		return nil, err
+	}
+	return bb, nil
+}
+
+func (rac *AuthenticatedClient) request(r *Request, rh ResponseHandler, empty interface{}) (interface{}, error) {
+	bb, err := rac.doRequest(r)
+	if err != nil && r.retry {
+		for _, backoff := range backoffSchedule {
+			done := make(chan struct{})
+
+			time.AfterFunc(backoff, func() {
+				_ = rac.statsd.Incr("reddit.api.retries", r.tags, 0.1)
+				bb, err = rac.doRequest(r)
+				done <- struct{}{}
+			})
+
+			<-done
+
+			if err == nil {
+				break
+			}
+		}
+	}
+
+	if err != nil {
 		_ = rac.statsd.Incr("reddit.api.errors", r.tags, 0.1)
-		return nil, ServerError{resp.StatusCode}
+		if strings.Contains(err.Error(), "http2: timeout awaiting response headers") {
+			return nil, ErrTimeout
+		}
+		return nil, err
 	}
 
 	if r.emptyResponseBytes > 0 && len(bb) == r.emptyResponseBytes {

internal/reddit/request.go

@@ -19,12 +19,27 @@ type Request struct {
 	auth               string
 	tags               []string
 	emptyResponseBytes int
+	retry              bool
 }
 
 type RequestOption func(*Request)
 
 func NewRequest(opts ...RequestOption) *Request {
-	req := &Request{url.Values{}, url.Values{}, "GET", "", "", "", nil, 0}
+	req := &Request{
+		body:   url.Values{},
+		query:  url.Values{},
+		method: "GET",
+		url:    "",
+
+		token: "",
+		auth:  "",
+
+		tags: nil,
+
+		emptyResponseBytes: 0,
+		retry:              true,
+	}
+
 	for _, opt := range opts {
 		opt(req)
 	}
@@ -101,3 +116,9 @@ func WithEmptyResponseBytes(bytes int) RequestOption {
 		req.emptyResponseBytes = bytes
 	}
 }
+
+func WithRetry(retry bool) RequestOption {
+	return func(req *Request) {
+		req.retry = retry
+	}
+}