made stats more efficient

src/BirdsiteLive/Services/CachedStatisticsService.cs

@@ -15,7 +15,7 @@ namespace BirdsiteLive.Services
         private readonly ITwitterUserDal _twitterUserDal;
         private readonly IFollowersDal _followersDal;
 
-        private static CachedStatistics _cachedStatistics;
+        private static Task<CachedStatistics> _cachedStatistics;
         private readonly InstanceSettings _instanceSettings;
 
         #region Ctor
@@ -24,28 +24,36 @@ namespace BirdsiteLive.Services
             _twitterUserDal = twitterUserDal;
             _instanceSettings = instanceSettings;
             _followersDal = followersDal;
+            _cachedStatistics = CreateStats();
         }
         #endregion
 
         public async Task<CachedStatistics> GetStatisticsAsync()
         {
-            if (_cachedStatistics == null ||
+            var stats = await _cachedStatistics;
-                (DateTime.UtcNow - _cachedStatistics.RefreshedTime).TotalMinutes > 15)
+            if ((DateTime.UtcNow - stats.RefreshedTime).TotalMinutes > 5)
+            {
+                _cachedStatistics = CreateStats();
+            }
+
+            return stats;
+        }
+
+        private async Task<CachedStatistics> CreateStats()
         {
             var twitterUserCount = await _twitterUserDal.GetTwitterUsersCountAsync();
             var twitterSyncLag = await _twitterUserDal.GetTwitterSyncLag();
             var fediverseUsers = await _followersDal.GetFollowersCountAsync();
 
-                _cachedStatistics = new CachedStatistics
+            var stats = new CachedStatistics
             {
                 RefreshedTime = DateTime.UtcNow,
                 SyncLag = twitterSyncLag,
                 TwitterUsers = twitterUserCount,
                 FediverseUsers = fediverseUsers
             };
-            }
         
-            return _cachedStatistics;
+            return stats;
         }
     }