perf[time]: improve the precision of the now() method

scheduler/src/main/java/com/zfoo/scheduler/manager/SchedulerBus.java

@@ -55,7 +55,6 @@ public abstract class SchedulerBus {
     private static long lastTriggerTimestamp = 0L;
 
 
-    public static final long TRIGGER_MILLIS_INTERVAL = TimeUtils.MILLIS_PER_SECOND;
     /**
      * 在scheduler中，最小的triggerTimestamp
      */
@@ -68,7 +67,9 @@ public abstract class SchedulerBus {
             } catch (Exception e) {
                 logger.error("scheduler triggers an error.", e);
             }
-        }, 0, TRIGGER_MILLIS_INTERVAL, TimeUnit.MILLISECONDS);
+        }, 0, TimeUtils.MILLIS_PER_SECOND, TimeUnit.MILLISECONDS);
+
+        executor.scheduleAtFixedRate(TimeUtils::currentTimeMillis, 0, 20, TimeUnit.MILLISECONDS);
     }
 
     public static class SchedulerThreadFactory implements ThreadFactory {

scheduler/src/main/java/com/zfoo/scheduler/util/TimeUtils.java

@@ -31,8 +31,6 @@ import java.util.TimeZone;
  */
 public abstract class TimeUtils {
 
-    private static long timestamp = System.currentTimeMillis();
-
     // 一秒钟对应的纳秒数
     public static final long NANO_PER_SECOND = 1_000_000_000;
     // 一秒钟对应的毫秒数
@@ -85,6 +83,8 @@ public abstract class TimeUtils {
         SchedulerBus.refreshMinTriggerTimestamp();
     }
 
+    private static volatile long timestamp = System.currentTimeMillis();
+
     /**
      * 获取精确的时间戳
      */
@@ -94,7 +94,7 @@ public abstract class TimeUtils {
     }
 
     /**
-     * 获取最多只有一秒延迟的粗略时间戳，适用于对时间精度要求不高的场景，最多只有一秒误差
+     * 获取最多只有20ms延迟的粗略时间戳，适用于对时间精度要求不高的场景，最多只有20ms误差
      * <p>
      * 比System.currentTimeMillis()的性能高10倍
      */