Add simple polling to the GitLab client

2 files changed, 128 insertions, 0 deletions

diff --git a/internal/source/gitlab/client/client_poll.go b/internal/source/gitlab/client/client_poll.go
new file mode 100644
index 00000000..bdbfb345
--- /dev/null
+++ b/internal/source/gitlab/client/client_poll.go
@@ -0,0 +1,34 @@
+package client
+
+import (
+	"fmt"
+	"time"
+)
+
+const (
+	// DefaultPollingMaxRetries to be used by Poll
+	DefaultPollingMaxRetries = 30
+	// DefaultPollingInterval to be used by Poll
+	DefaultPollingInterval = 10 * time.Second
+)
+
+// Poll tries to call the /internal/pages/status API endpoint for
+// `retries` every `interval`.
+// TODO: should we consider using an exponential back-off approach?
+// https://pkg.go.dev/github.com/cenkalti/backoff/v4?tab=doc#pkg-examples
+func (gc *Client) Poll(retries int, interval time.Duration, errCh chan error) {
+	defer close(errCh)
+
+	var err error
+	for i := 0; i <= retries; i++ {
+		err = gc.Status()
+		if err == nil {
+			// return as soon as we connect to the API
+			errCh <- nil
+		}
+
+		time.Sleep(interval)
+	}
+
+	errCh <- fmt.Errorf("polling failed after %d tries every %fs: %w", retries, interval.Seconds(), err)
+}
diff --git a/internal/source/gitlab/client/client_poll_test.go b/internal/source/gitlab/client/client_poll_test.go
new file mode 100644
index 00000000..59da32c5
--- /dev/null
+++ b/internal/source/gitlab/client/client_poll_test.go
@@ -0,0 +1,94 @@
+package client
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestClient_Poll(t *testing.T) {
+	tests := []struct {
+		name     string
+		retries  int
+		interval time.Duration
+		timeout  time.Duration
+		status   int
+		wantErr  bool
+	}{
+		{
+			name:     "success_with_no_retry",
+			retries:  0,
+			interval: 5 * time.Millisecond,
+			timeout:  5 * time.Millisecond,
+			status:   http.StatusOK,
+			wantErr:  false,
+		},
+		{
+			name:     "success_after_N_retries",
+			retries:  3,
+			interval: 5 * time.Millisecond,
+			timeout:  20 * time.Millisecond,
+			status:   http.StatusOK,
+			wantErr:  false,
+		},
+		{
+			name:     "fail_with_no_retries",
+			retries:  0,
+			interval: 5 * time.Millisecond,
+			timeout:  100 * time.Millisecond,
+			status:   http.StatusUnauthorized,
+			wantErr:  true,
+		},
+		{
+			name:     "fail_after_N_retries",
+			retries:  3,
+			interval: 5 * time.Millisecond,
+			timeout:  100 * time.Millisecond,
+			status:   http.StatusUnauthorized,
+			wantErr:  true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var counter int
+			mux := http.NewServeMux()
+			mux.HandleFunc("/api/v4/internal/pages/status", func(w http.ResponseWriter, r *http.Request) {
+				if counter < tt.retries {
+					counter++
+					// fail on purpose until we reach the max retry
+					w.WriteHeader(http.StatusInternalServerError)
+					return
+				}
+
+				w.WriteHeader(tt.status)
+			})
+
+			server := httptest.NewServer(mux)
+			defer server.Close()
+
+			client := defaultClient(t, server.URL)
+			errCh := make(chan error)
+
+			go client.Poll(tt.retries, tt.interval, errCh)
+
+			// go func() {
+			select {
+			case err := <-errCh:
+				if tt.wantErr {
+					require.Error(t, err)
+					require.Contains(t, err.Error(), "polling failed after")
+					require.Contains(t, err.Error(), ConnectionErrorMsg)
+					return
+				}
+				require.NoError(t, err)
+			case <-time.After(tt.timeout):
+				t.Logf("%s timed out", tt.name)
+				t.FailNow()
+			}
+			// }()
+		})
+	}
+}