Add a session timestamp prefix to log files (and retain 7 days of logs)

osu.Framework/Logging/Logger.cs

@@ -23,11 +23,19 @@ public class Logger
     {
         private static readonly object static_sync_lock = new object();
 
-        // separate locking object for flushing so that we don't lock too long on the staticSyncLock object, since we have to
-        // hold this lock for the entire duration of the flush (waiting for I/O etc) before we can resume scheduling logs
-        // but other operations like GetLogger(), ApplyFilters() etc. can still be executed while a flush is happening.
+        /// <summary>
+        /// Separate locking object for flushing so that we don't lock too long on the staticSyncLock object, since we have to
+        /// hold this lock for the entire duration of the flush (waiting for I/O etc) before we can resume scheduling logs
+        /// but other operations like GetLogger(), ApplyFilters() etc. can still be executed while a flush is happening.
+        /// </summary>
         private static readonly object flush_sync_lock = new object();
 
+        /// <summary>
+        /// Logs are stored with a consistent unix timestamp prefix per session (across all loggers) for logical grouping of
+        /// log files on disk.
+        /// </summary>
+        private static readonly long session_startup_timestamp = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
+
         /// <summary>
         /// Whether logging is enabled. Setting this to false will disable all logging.
         /// </summary>
@@ -60,13 +68,12 @@ public class Logger
         /// </summary>
         public static Storage Storage
         {
-            private get => storage;
+            get => storage;
             set
             {
                 storage = value ?? throw new ArgumentNullException(nameof(value));
 
-                // clear static loggers so they are correctly purged at the new storage location.
-                static_loggers.Clear();
+                cycleLogs();
             }
         }
 
@@ -83,7 +90,7 @@ public static Storage Storage
         /// <summary>
         /// Gets the name of the file that this logger is logging to.
         /// </summary>
-        public string Filename => $@"{Name}.log";
+        public string Filename { get; }
 
         public int TotalLogOperations => logCount.Value;
 
@@ -109,6 +116,7 @@ private Logger(string name, bool checkedReserved)
 
             Name = name;
             logCount = GlobalStatistics.Get<int>(nameof(Logger), Name);
+            Filename = $"{session_startup_timestamp}.{Name}.log";
         }
 
         /// <summary>
@@ -257,10 +265,7 @@ public static Logger GetLogger(string name)
                 string nameLower = name.ToLowerInvariant();
 
                 if (!static_loggers.TryGetValue(nameLower, out Logger l))
-                {
                     static_loggers[nameLower] = l = Enum.TryParse(name, true, out LoggingTarget target) ? new Logger(target) : new Logger(name, true);
-                    l.clear();
-                }
 
                 return l;
             }
@@ -409,30 +414,27 @@ private void writePendingLines()
         /// </summary>
         public static event Action<LogEntry> NewEntry;
 
-        /// <summary>
-        /// Deletes log file from disk.
-        /// </summary>
-        private void clear()
+        private bool headerAdded;
+
+        private static void cycleLogs()
         {
-            lock (flush_sync_lock)
+            try
             {
-                scheduler.Add(() =>
+                DateTime logCycleCutoff = DateTime.UtcNow.AddDays(-7);
+                var logFiles = new DirectoryInfo(storage.GetFullPath(string.Empty)).GetFiles("*.log");
+
+                foreach (var fileInfo in logFiles)
                 {
-                    try
-                    {
-                        Storage.Delete(Filename);
-                    }
-                    catch
-                    {
-                        // may fail if the file/directory was already cleaned up, ie. during test runs.
-                    }
-                });
-                writer_idle.Reset();
+                    if (fileInfo.CreationTimeUtc < logCycleCutoff)
+                        fileInfo.Delete();
+                }
+            }
+            catch (Exception e)
+            {
+                Log($"Cycling logs failed ({e})");
             }
         }
 
-        private bool headerAdded;
-
         private void ensureHeader()
         {
             if (headerAdded) return;