Use exponential backoff for polling

Introudce github.com/cenkalti/backoff/v4 library to use exponential
backoff when polling the Status API.

3 files changed, 54 insertions, 31 deletions

diff --git a/internal/source/gitlab/gitlab.go b/internal/source/gitlab/gitlab.go
index 2635d864..67c4eb6b 100644
--- a/internal/source/gitlab/gitlab.go
+++ b/internal/source/gitlab/gitlab.go
@@ -8,6 +8,8 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/cenkalti/backoff/v4"
+
 	"gitlab.com/gitlab-org/gitlab-pages/internal/domain"
 	"gitlab.com/gitlab-org/gitlab-pages/internal/request"
 	"gitlab.com/gitlab-org/gitlab-pages/internal/serving"
@@ -36,7 +38,7 @@ func New(config client.Config) (*Gitlab, error) {
 		mu:     &sync.RWMutex{},
 	}
 
-	go g.poll(defaultPollingMaxRetries, defaultPollingInterval)
+	go g.poll(backoff.DefaultInitialInterval, maxPollingTime)
 
 	// using nil for cache config will use the default values specified in internal/source/gitlab/cache/cache.go#12
 	return g, nil
diff --git a/internal/source/gitlab/gitlab_poll.go b/internal/source/gitlab/gitlab_poll.go
index 9fce7250..4e79bbf1 100644
--- a/internal/source/gitlab/gitlab_poll.go
+++ b/internal/source/gitlab/gitlab_poll.go
@@ -3,37 +3,57 @@ package gitlab
 import (
 	"time"
 
+	"github.com/cenkalti/backoff/v4"
 	log "github.com/sirupsen/logrus"
 )
 
 const (
-	// defaultPollingMaxRetries to be used by poll
-	defaultPollingMaxRetries = 30
-	// defaultPollingInterval to be used by poll
-	defaultPollingInterval = time.Minute
+	// maxPollingTime is the maximum duration to try to call the Status API
+	maxPollingTime = 60 * time.Minute
 )
 
-// poll tries to call the /internal/pages/status API endpoint once plus
-// `retries` every `interval`.
-// It updates the `isReady` value when successful.
+// Poll tries to call the /internal/pages/status API endpoint once plus
+// for `maxElapsedTime`
 // TODO: Remove in https://gitlab.com/gitlab-org/gitlab/-/issues/218357
-func (g *Gitlab) poll(retries int, interval time.Duration) {
-	var err error
-	for i := 0; i <= retries; i++ {
+func (g *Gitlab) poll(interval, maxElapsedTime time.Duration) {
+	backOff := backoff.NewExponentialBackOff()
+	backOff.InitialInterval = interval
+	backOff.MaxElapsedTime = maxElapsedTime
+
+	op := func() error {
 		log.Info("Checking GitLab internal API availability")
-		err = g.client.Status()
-		if err == nil {
-			log.Info("GitLab internal pages status API connected successfully")
-			g.mu.Lock()
-			g.isReady = true
-			g.mu.Unlock()
-
-			// return as soon as we connect to the API
-			return
-		}
-
-		time.Sleep(interval)
+
+		return g.client.Status()
+	}
+
+	err := backoff.Retry(op, backOff)
+	if err != nil {
+		// Handle error.
+		log.WithError(err).Errorf("Failed to connect to the internal GitLab API after %.2fs", interval.Seconds())
+		return
 	}
 
-	log.WithError(err).Errorf("Failed to connect to the internal GitLab API after %d tries every %.2fs", retries+1, interval.Seconds())
+	g.mu.Lock()
+	g.isReady = true
+	g.mu.Unlock()
+	log.Info("GitLab internal pages status API connected successfully")
+	//
+	// var err error
+	// for i := 0; i <= retries; i++ {
+	// 	log.Info("polling GitLab internal pages status API")
+	// 	err = g.checker.Status()
+	// 	if err == nil {
+	// 		log.Info("GitLab internal pages status API connected successfully")
+	// 		g.mu.Lock()
+	// 		g.isReady = true
+	// 		g.mu.Unlock()
+	//
+	// 		// return as soon as we connect to the API
+	// 		return
+	// 	}
+	//
+	// 	time.Sleep(interval)
+	// }
+	//
+	// log.WithError(err).Errorf("polling failed after %d tries every %.2fs", retries+1, interval.Seconds())
 }
diff --git a/internal/source/gitlab/gitlab_poll_test.go b/internal/source/gitlab/gitlab_poll_test.go
index 01f13846..9a559015 100644
--- a/internal/source/gitlab/gitlab_poll_test.go
+++ b/internal/source/gitlab/gitlab_poll_test.go
@@ -17,31 +17,31 @@ func TestClient_Poll(t *testing.T) {
 	tests := []struct {
 		name         string
 		retries      int
-		interval     time.Duration
+		maxTime      time.Duration
 		expectedFail bool
 	}{
 		{
 			name:         "success_with_no_retry",
 			retries:      0,
-			interval:     5 * time.Millisecond,
+			maxTime:      10 * time.Millisecond,
 			expectedFail: false,
 		},
 		{
 			name:         "success_after_N_retries",
 			retries:      3,
-			interval:     10 * time.Millisecond,
+			maxTime:      30 * time.Millisecond,
 			expectedFail: false,
 		},
 		{
 			name:         "fail_with_no_retries",
 			retries:      0,
-			interval:     5 * time.Millisecond,
+			maxTime:      10 * time.Millisecond,
 			expectedFail: true,
 		},
 		{
 			name:         "fail_after_N_retries",
 			retries:      3,
-			interval:     5 * time.Millisecond,
+			maxTime:      30 * time.Millisecond,
 			expectedFail: true,
 		},
 	}
@@ -64,10 +64,11 @@ func TestClient_Poll(t *testing.T) {
 
 			glClient := Gitlab{client: client, mu: &sync.RWMutex{}}
 
-			glClient.poll(tt.retries, tt.interval)
+			glClient.poll(3*time.Millisecond, tt.maxTime)
 			if tt.expectedFail {
 				require.False(t, glClient.isReady)
-				s := fmt.Sprintf("Failed to connect to the internal GitLab API after %d tries every %.2fs", tt.retries+1, tt.interval.Seconds())
+
+				s := fmt.Sprintf("\"Failed to connect to the internal GitLab API after %.2fs", tt.maxTime.Seconds())
 				require.Equal(t, s, hook.LastEntry().Message)
 				return
 			}