retry more operations when accessing storage + enforcer in tests

app/lib/package/api_export/exported_api.dart

@@ -229,7 +229,7 @@ final class ExportedApi {
     required String prefix,
     required String delimiter,
   }) async {
-    var p = await _pool.withResource(() async => await _bucket.page(
+    var p = await _pool.withResource(() async => await _bucket.pageWithRetry(
           prefix: prefix,
           delimiter: delimiter,
           pageSize: 1000,
@@ -240,7 +240,8 @@ final class ExportedApi {
       }));
 
       if (p.isLast) break;
-      p = await _pool.withResource(() async => await p.next(pageSize: 1000));
+      p = await _pool
+          .withResource(() async => await p.nextWithRetry(pageSize: 1000));
     }
   }
 }
@@ -632,7 +633,7 @@ final class ExportedBlob extends ExportedObject {
         final retouchDeadline = clock.agoBy(_updateValidatedAfter);
         if (destinationInfo.metadata.validated.isBefore(retouchDeadline)) {
           try {
-            await _owner._bucket.updateMetadata(dst, _metadata());
+            await _owner._bucket.updateMetadataWithRetry(dst, _metadata());
           } catch (e, st) {
             // This shouldn't happen, but if a metadata update does fail, it's
             // hardly the end of the world.
@@ -646,7 +647,7 @@ final class ExportedBlob extends ExportedObject {
 
     // If dst or source doesn't exist, then we shall attempt to make a copy.
     // (if source doesn't exist we'll consistently get an error from here!)
-    await _owner._storage.copyObject(
+    await _owner._storage.copyObjectWithRetry(
       source.absoluteObjectName,
       _owner._bucket.absoluteObjectName(dst),
       metadata: _metadata(),
@@ -667,7 +668,7 @@ extension on Bucket {
           if (info.metadata.validated
               .isBefore(clock.agoBy(_updateValidatedAfter))) {
             try {
-              await updateMetadata(name, metadata);
+              await updateMetadataWithRetry(name, metadata);
             } catch (e, st) {
               // This shouldn't happen, but if a metadata update does fail, it's
               // hardly the end of the world.

app/lib/package/backend.dart

@@ -996,7 +996,7 @@ class PackageBackend {
       _logger.info('Removing temporary object $guid.');
 
       sw.reset();
-      await _incomingBucket.delete(tmpObjectName(guid));
+      await _incomingBucket.deleteWithRetry(tmpObjectName(guid));
       _logger.info('Temporary object removed in ${sw.elapsed}.');
       return version;
     });

app/lib/service/download_counts/backend.dart

@@ -15,6 +15,7 @@ import 'package:pub_dev/shared/cached_value.dart';
 import 'package:pub_dev/shared/configuration.dart';
 import 'package:pub_dev/shared/datastore.dart';
 import 'package:pub_dev/shared/redis_cache.dart';
+import 'package:pub_dev/shared/storage.dart';
 
 /// Sets the download counts backend service.
 void registerDownloadCountsBackend(DownloadCountsBackend backend) =>
@@ -42,7 +43,7 @@ class DownloadCountsBackend {
     try {
       final info = await storageService
           .bucket(activeConfiguration.reportsBucketName!)
-          .info(downloadCounts30DaysTotalsFileName);
+          .infoWithRetry(downloadCounts30DaysTotalsFileName);
 
       if (_lastData.etag == info.etag) {
         return _lastData.data;

app/lib/service/services.dart

@@ -9,6 +9,7 @@ import 'package:appengine/appengine.dart';
 import 'package:clock/clock.dart';
 import 'package:fake_gcloud/mem_datastore.dart';
 import 'package:fake_gcloud/mem_storage.dart';
+import 'package:fake_gcloud/retry_enforcer_storage.dart';
 import 'package:gcloud/service_scope.dart';
 import 'package:gcloud/storage.dart';
 import 'package:googleapis_auth/auth_io.dart' as auth;
@@ -148,7 +149,7 @@ Future<R> withFakeServices<R>({
   return await fork(() async {
     register(#appengine.context, FakeClientContext());
     registerDbService(DatastoreDB(datastore!));
-    registerStorageService(storage!);
+    registerStorageService(RetryEnforcerStorage(storage!));
     IOServer? frontendServer;
     IOServer? searchServer;
     if (configuration == null) {

app/lib/shared/storage.dart

@@ -44,7 +44,7 @@ extension StorageExt on Storage {
   /// local environment.
   Future<void> verifyBucketExistenceAndAccess(String bucketName) async {
     // check bucket existence
-    if (!await bucketExists(bucketName)) {
+    if (!await bucketExistsWithRetry(bucketName)) {
       final message = 'Bucket "$bucketName" does not exists!';
       _logger.shout(message);
       if (envConfig.isRunningLocally) {
@@ -69,10 +69,29 @@ extension StorageExt on Storage {
       return;
     }
   }
+
+  /// Check whether a cloud storage bucket exists with the default retry.
+  Future<bool> bucketExistsWithRetry(String bucketName) async {
+    return await _retry(() => bucketExists(bucketName));
+  }
+
+  /// Copy an object with the default retry.
+  Future<void> copyObjectWithRetry(
+    String src,
+    String dest, {
+    ObjectMetadata? metadata,
+  }) async {
+    return await _retry(() async => await copyObject(src, dest));
+  }
 }
 
 /// Additional methods on buckets.
 extension BucketExt on Bucket {
+  /// Lookup object metadata with default retry.
+  Future<ObjectInfo> infoWithRetry(String name) async {
+    return await _retry(() => info(name));
+  }
+
   /// Returns an [ObjectInfo] if [name] exists, `null` otherwise.
   Future<ObjectInfo?> tryInfo(String name) async {
     return await retry(
@@ -89,6 +108,11 @@ extension BucketExt on Bucket {
     );
   }
 
+  /// Delete an object with default retry.
+  Future<void> deleteWithRetry(String name) async {
+    return await _retry(() => delete(name));
+  }
+
   /// Deletes [name] if it exists, ignores 404 otherwise.
   Future<void> tryDelete(String name) async {
     return await retry(
@@ -159,6 +183,35 @@ extension BucketExt on Bucket {
   String objectUrl(String objectName) {
     return '${activeConfiguration.storageBaseUrl}/$bucketName/$objectName';
   }
+
+  /// Update object metadata with default retry rules.
+  Future<void> updateMetadataWithRetry(
+      String objectName, ObjectMetadata metadata) async {
+    return await _retry(() async => await updateMetadata(objectName, metadata));
+  }
+
+  /// Start paging through objects in the bucket with the default retry.
+  Future<Page<BucketEntry>> pageWithRetry(
+      {String? prefix, String? delimiter, int pageSize = 50}) async {
+    return await _retry(
+      () async => await page(
+        prefix: prefix,
+        delimiter: delimiter,
+        pageSize: pageSize,
+      ),
+    );
+  }
+}
+
+extension PageExt<T> on Page<T> {
+  /// Move to the next page with default retry.
+  Future<Page<T>> nextWithRetry({int pageSize = 50}) async {
+    return await _retry(() => next(pageSize: pageSize));
+  }
+}
+
+Future<R> _retry<R>(Future<R> Function() fn) async {
+  return await retry(fn, maxAttempts: 3, retryIf: _retryIf);
 }
 
 bool _retryIf(Exception e) {
@@ -212,7 +265,7 @@ Future<void> updateContentDispositionToAttachment(
     ObjectInfo info, Bucket bucket) async {
   if (info.metadata.contentDisposition != 'attachment') {
     try {
-      await bucket.updateMetadata(
+      await bucket.updateMetadataWithRetry(
           info.name, info.metadata.replace(contentDisposition: 'attachment'));
     } on Exception catch (e, st) {
       _logger.warning(

app/test/admin/exported_api_sync_test.dart

@@ -181,7 +181,7 @@ void main() {
         final oldData = oldRoot[path] as Map;
         final bucket =
             storageService.bucket(activeConfiguration.exportedApiBucketName!);
-        await bucket.updateMetadata(
+        await bucket.updateMetadataWithRetry(
           path,
           ObjectMetadata(
             contentType: 'text/plain',