Issue #5083 - Convert synchronized usages to AutoLock.

Updates after review.

Signed-off-by: Simone Bordet <simone.bordet@gmail.com>

jetty-util/src/main/java/org/eclipse/jetty/util/RolloverFileOutputStream.java

@@ -29,8 +29,10 @@
 import java.util.Date;
 import java.util.Locale;
 import java.util.TimeZone;
-import java.util.Timer;
-import java.util.TimerTask;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
 
 import org.eclipse.jetty.util.thread.AutoLock;
 
@@ -48,22 +50,26 @@
  */
 public class RolloverFileOutputStream extends OutputStream
 {
-    private static Timer __rollover;
-
     static final String YYYY_MM_DD = "yyyy_mm_dd";
     static final String ROLLOVER_FILE_DATE_FORMAT = "yyyy_MM_dd";
     static final String ROLLOVER_FILE_BACKUP_FORMAT = "HHmmssSSS";
     static final int ROLLOVER_FILE_RETAIN_DAYS = 31;
+    private static final ScheduledExecutorService __scheduler = Executors.newSingleThreadScheduledExecutor(job ->
+    {
+        Thread thread = new Thread(job, RolloverFileOutputStream.class.getName());
+        thread.setDaemon(true);
+        return thread;
+    });
 
     private final AutoLock _lock = new AutoLock();
     private OutputStream _out;
-    private RollTask _rollTask;
-    private SimpleDateFormat _fileBackupFormat;
-    private SimpleDateFormat _fileDateFormat;
+    private ScheduledFuture<?> _rollTask;
+    private final SimpleDateFormat _fileBackupFormat;
+    private final SimpleDateFormat _fileDateFormat;
     private String _filename;
     private File _file;
-    private boolean _append;
-    private int _retainDays;
+    private final boolean _append;
+    private final int _retainDays;
 
     /**
      * @param filename The filename must include the string "yyyy_mm_dd",
@@ -178,8 +184,6 @@ public RolloverFileOutputStream(String filename,
         // Calculate Today's Midnight, based on Configured TimeZone (will be in past, even if by a few milliseconds)
         setFile(now);
 
-        __rollover = new Timer(RolloverFileOutputStream.class.getName(), true);
-
         // This will schedule the rollover event to the next midnight
         scheduleNextRollover(now);
     }
@@ -197,13 +201,12 @@ public static ZonedDateTime toMidnight(ZonedDateTime now)
 
     private void scheduleNextRollover(ZonedDateTime now)
     {
-        _rollTask = new RollTask();
         // Get tomorrow's midnight based on Configured TimeZone
         ZonedDateTime midnight = toMidnight(now);
 
         // Schedule next rollover event to occur, based on local machine's Unix Epoch milliseconds
         long delay = midnight.toInstant().toEpochMilli() - now.toInstant().toEpochMilli();
-        __rollover.schedule(_rollTask, delay);
+        _rollTask = __scheduler.schedule(this::rollOver, delay, TimeUnit.MILLISECONDS);
     }
 
     public String getFilename()
@@ -394,28 +397,24 @@ public void close() throws IOException
             }
         }
 
-        RollTask rollTask = _rollTask;
+        ScheduledFuture<?> rollTask = _rollTask;
         if (rollTask != null)
-            rollTask.cancel();
+            rollTask.cancel(false);
     }
 
-    private class RollTask extends TimerTask
+    private void rollOver()
     {
-        @Override
-        public void run()
+        try
         {
-            try
-            {
-                ZonedDateTime now = ZonedDateTime.now(_fileDateFormat.getTimeZone().toZoneId());
-                RolloverFileOutputStream.this.setFile(now);
-                RolloverFileOutputStream.this.removeOldFiles(now);
-                RolloverFileOutputStream.this.scheduleNextRollover(now);
-            }
-            catch (Throwable t)
-            {
-                // Cannot log this exception to a LOG, as RolloverFOS can be used by logging
-                t.printStackTrace(System.err);
-            }
+            ZonedDateTime now = ZonedDateTime.now(_fileDateFormat.getTimeZone().toZoneId());
+            RolloverFileOutputStream.this.setFile(now);
+            RolloverFileOutputStream.this.removeOldFiles(now);
+            RolloverFileOutputStream.this.scheduleNextRollover(now);
+        }
+        catch (Throwable t)
+        {
+            // Cannot log this exception to a LOG, as RolloverFOS can be used by logging
+            t.printStackTrace(System.err);
         }
     }
 }