Add test for fix

client/internal/httpsender_test.go

@@ -0,0 +1,57 @@
+package internal
+
+import (
+	"context"
+	"net/http"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/open-telemetry/opamp-go/client/types"
+	sharedinternal "github.com/open-telemetry/opamp-go/internal"
+	"github.com/open-telemetry/opamp-go/protobufs"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestHTTPSenderRetryForStatusTooManyRequests(t *testing.T) {
+
+	var connectionAttempts int64
+	srv := StartMockServer(t)
+	srv.OnRequest = func(w http.ResponseWriter, r *http.Request) {
+		attempt := atomic.AddInt64(&connectionAttempts, 1)
+		// Return a Retry-After header with a value of 1 second for first attempt.
+		if attempt == 1 {
+			w.Header().Set("Retry-After", "1")
+			w.WriteHeader(http.StatusTooManyRequests)
+		} else {
+			w.WriteHeader(http.StatusOK)
+		}
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	url := "http://" + srv.Endpoint
+	sender := NewHTTPSender(&sharedinternal.NopLogger{})
+	sender.NextMessage().Update(func(msg *protobufs.AgentToServer) {
+		msg.AgentDescription = &protobufs.AgentDescription{
+			IdentifyingAttributes: []*protobufs.KeyValue{{
+				Key: "service.name",
+				Value: &protobufs.AnyValue{
+					Value: &protobufs.AnyValue_StringValue{StringValue: "test-service"},
+				},
+			}},
+		}
+	})
+	sender.callbacks = types.CallbacksStruct{
+		OnConnectFunc: func() {
+		},
+		OnConnectFailedFunc: func(_ error) {
+		},
+	}
+	sender.url = url
+	start := time.Now()
+	resp, err := sender.sendRequestWithRetries(ctx)
+	assert.NoError(t, err)
+	assert.Equal(t, http.StatusOK, resp.StatusCode)
+	assert.True(t, time.Since(start) > time.Second)
+	cancel()
+	srv.Close()
+}