Adding custom backoff function for API's that _can_ be excessive (#354)

Author: davidcollom

pkg/client/docker/docker.go

@@ -12,8 +12,9 @@ import (
 
 	"github.com/sirupsen/logrus"
 
-	"github.com/hashicorp/go-retryablehttp"
+	retryablehttp "github.com/hashicorp/go-retryablehttp"
 	"github.com/jetstack/version-checker/pkg/api"
+	"github.com/jetstack/version-checker/pkg/client/util"
 )
 
 const (
@@ -41,8 +42,10 @@ func New(opts Options, log *logrus.Entry) (*Client, error) {
 	}
 	retryclient.HTTPClient.Timeout = 10 * time.Second
 	retryclient.RetryMax = 10
-	retryclient.RetryWaitMax = 2 * time.Minute
+	retryclient.RetryWaitMax = 10 * time.Minute
 	retryclient.RetryWaitMin = 1 * time.Second
+	// This custom backoff will fail requests that have a max wait of the RetryWaitMax
+	retryclient.Backoff = util.HTTPBackOff
 	retryclient.Logger = log.WithField("client", "docker")
 	client := retryclient.StandardClient()
 

pkg/client/util/http_backoff.go

@@ -0,0 +1,19 @@
+package util
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/hashicorp/go-retryablehttp"
+)
+
+// This is a custom Backoff that enforces the Max wait duration.
+// If the sleep is greater we refuse to sleep at all
+func HTTPBackOff(min, max time.Duration, attemptNum int, resp *http.Response) time.Duration {
+	sleep := retryablehttp.DefaultBackoff(min, max, attemptNum, resp)
+	if sleep.Abs() <= max {
+		return sleep.Abs()
+	}
+
+	return max.Abs()
+}

pkg/client/util/http_backoff_test.go

@@ -0,0 +1,63 @@
+package util
+
+import (
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/hashicorp/go-retryablehttp"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestHTTPBackOff(t *testing.T) {
+	tests := []struct {
+		name       string
+		min        time.Duration
+		max        time.Duration
+		attemptNum int
+		resp       *http.Response
+		expSleep   time.Duration
+	}{
+		{
+			name:       "sleep within max duration",
+			min:        100 * time.Millisecond,
+			max:        1 * time.Second,
+			attemptNum: 1,
+			resp:       nil,
+			expSleep:   retryablehttp.DefaultBackoff(100*time.Millisecond, 1*time.Second, 1, nil),
+		},
+		{
+			name:       "sleep exceeds max duration (too many requests)",
+			min:        100 * time.Millisecond,
+			max:        500 * time.Millisecond,
+			attemptNum: 10,
+			resp: &http.Response{
+				StatusCode: http.StatusTooManyRequests,
+				Header:     http.Header{"Retry-After": []string{"3600"}}},
+			expSleep: 500 * time.Millisecond,
+		},
+		{
+			name:       "zero max duration",
+			min:        100 * time.Millisecond,
+			max:        0,
+			attemptNum: 1,
+			resp:       nil,
+			expSleep:   0,
+		},
+		{
+			name:       "negative max duration",
+			min:        100 * time.Millisecond,
+			max:        -1 * time.Second,
+			attemptNum: 1,
+			resp:       nil,
+			expSleep:   time.Second,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			gotSleep := HTTPBackOff(test.min, test.max, test.attemptNum, test.resp)
+			assert.Equal(t, test.expSleep, gotSleep, "unexpected sleep duration")
+		})
+	}
+}